Description:A RADAR SYSTEM FOR DETECTING TARGETS USING A VARIABLE PHASE DELAY AND A METHOD THEREOF
FIELD OF INVENTION
The present subject matter generally relates to radar systems, and more particularly relates to a radar system for detecting targets using a variable phase delay and a method thereof.
BACKGROUND
Each year, many people lose their lives buried in avalanches around the world. The problem has aggravated due to global climate change which has resulted in sudden and frequent triggering of avalanches. A key factor influencing the chance of survival is the burial time. If victims are not rescued within the first 15 – 30 minutes, their chance of survival drops rapidly.
FIG. 1A is a block diagram of a conventional harmonic radar system 100A, in accordance with prior art. The harmonic radar system 100A includes a transmitter 138, a receiver 140, and a transponder 136 (also known as a tag 136). The transmitter 138 is configured to generate and transmit radio wave signals or microwave signals towards a target. The transmitter 138 comprises an antenna 102, a transmission matching network 104, a power amplifier 106, an oscillator and amplitude modulator 108, and an audio signal 110. The receiver 140 is configured to process reflected waves received from a transponder 136 in response to the transmitted radio wave signals. The receiver 140 comprises an oscillator 112, a mixer, an amplifier 120, a receiver matching network 118, an antenna 106, an audio amplifier 114, and a loudspeaker 116. The transponder 136 receives and responds to an incoming signal (such as the transmitted radio wave signals) by emitting the reflected signal in response to a specific interrogation or a stimulus. The transponder 136 comprises a receiving antenna 124, a matching network 126, a non-linearity circuit 128, typically implemented as a Schottky diode, a matching network 130, and a transmitting antenna 132.
The radar transmitter 138 generates a frequency f0, which is impinged upon the transponder 136 worn by the victim (also referred herein as target) (for example, buried under snow, or any other surface). The tag 136 uses a non-linearity, typically generated by a Schottky diode 128, to generate a second (or higher) harmonic frequency N*f0, with typically N=2 corresponding to a second harmonic. The said frequency N*f0 is transmitted back to the receiver 140 which is tuned to N*f0. All other objects in the vicinity, also known as clutter, which reflect the radar signal at f0, are excluded, if the radar receiver 140 is tuned to the harmonic frequency N*f0 generated by the tag 136.
As shown in FIG. 1A, a specific harmonic radar 100A with N=2, has the transmitter 138 tuned at frequency f0, while the corresponding receiver 140 is tuned to 2*f0. In some implementations, the transmitter 138 output is modulated with an audio tone and during demodulation, the receiver 140 extracts this tone to provide an audio indication. A major drawback of the conventional harmonic radar system 100A, which are continuous wave (CW) radars, include their inability to determine a distance to the target, if a victim is buried under tens of feet of surface, such as snow. In addition, since the transceiver consisting of the transmitter 138 and receiver 140 has both the fundamental (f0) and harmonic frequency (N*f0), it is very difficult to implement this method inside a compact semiconductor chip, where the harmonics may interact through coupling. There are other drawbacks which include, the transmitted and received frequencies are widely separated causing significant attenuation through snow as only the transmitted or the received frequency may be optimally chosen while the other may be attenuated more due to propagation or antenna loss. Further, the received signal at N*f0 is still absorbed and scattered by various objects in the avalanche debris field (such as rocks, trees etc.) and in a CW radar, which is unable to extract distance separately, this makes it difficult to estimate a depth of the buried victim under the snow.
Further, the need to determine the depth of a buried person accurately while removing the impact of clutter in a debris field, has generated recent interest in frequency modulated continuous wave (FMCW) radars. FIG. 1B is a block diagram of a conventional FMCW radar system 100B, in accordance with prior art. The FMCW radar system 100b includes essential elements of the radar integrated inside an integrated circuit (semiconductor chip). The continuous wave FMCW radar system 100B comprises a microprocessor 142 including a controller 144, a signal processing unit 146, and an analog to digital converter 148. The microprocessor 142 maybe coupled to a radar on chip 172. The radar on chip 172 may include a temperature-compensated crystal oscillator (TCXO) 150, a synthesizer core 152, a Serial Peripheral Interface (SPI) 154, baseband/IF amplifiers 156 and 158, a power amplifier 160, a power splitter 164, a Receive Local Oscillator (Rx LO), a mixer 174, a low-noise amplifier (LNA) 162, and a set of antennas 166 and 168.The FMCW radar system 100b may require to be specifically enabled to support harmonic radar operation.
Some recent FMCW based harmonic radars as depicted in FIG. 1C continue to mix the fundamental frequency (f0) 182, and a second harmonic (N*f0) 180 and intermodulation frequency products 186 in a way that significantly limits their implementation in a semiconductor chip due to signal coupling.
Some other features of the prior-art harmonic radars for avalanche rescue that need to be specifically described are signal propagation and antennas. In an avalanche debris field, the presence of rocks and trees makes it more difficult to clearly predict the propagation characteristics, adding an unknown element to signal propagation. While multiple designs of wideband antennas such as the Bow-tie and Vivaldi are widely used in ground/snow penetration radars, the fixed frequencies of operation of the harmonic radar (f0 and 2*f0) are a major performance limiting factor even if wideband antennas are used.
Despite many disadvantages of a harmonic radar 100A using a tag 136, a key advantage is that the reflected signal from the tag 136 is at a harmonic frequency (say 2*f0) while all other debris (known as clutter), reflect the radar signal at the fundamental frequency (f0). By tuning the harmonic radar 100A at 2*f0, most clutter is rejected. This feature is also present in harmonic FMCW radars 100B that use harmonically related transmitter (f1 to f2) and receiver (2*f1 to 2*f2) frequencies for the transmitter and receiver, respectively.
A key aspect of advanced radar technologies (such as FMCW) which distinguishes them from older technologies such as CW, is their ability to detect both a range and a velocity of an object (also known as target). This process segregates moving targets with various velocities from static targets and allows use of a simple “static target filter” to remove the clutter. Hence, the segregation of targets based on their velocity is a very powerful technique used by radars to isolate static clutter from moving targets.
In an avalanche rescue situation, where a victim is buried under several feet of snow and debris, and has no movement, it may seem that the detection of a moving target serves no purpose.
Hence, there is a need for an improved radar system for detecting targets using a variable phase delay and a method thereof in order to address the aforementioned issues.
SUMMARY
In accordance with an embodiment of the present disclosure, a system for detecting one or more targets in an environment is disclosed. The system includes a radar system configured to detect a target based on a reflected signal received from the target. The reflected signal is received in response to a radar signal transmitted from the radar system to the target at a first frequency of operation. Further, the system includes a transponder system communicatively coupled to the radar system. The transponder system is associated with the target. The transponder system includes a receive subsystem configured for receiving an incident energy from the radar system using a receive antenna. The incident energy received corresponds to the radar signal. The transponder system further includes a bridge circuit configured for generating a rectified signal using the received incident energy. The transponder system also includes a power supply control unit configured for harvesting the received incident energy as a direct current voltage (VDD). Furthermore, the transponder system includes a configurable phase delay block communicatively coupled to the receive subsystem. The configurable phase delay block is configured for converting the received incident energy to a delayed digital signal using one or more delay line circuits. The transponder system further includes a filtering subsystem communicatively coupled to the configurable phase delay block. The filtering subsystem is configured for filtering the delayed digital signal using one or more filtering techniques and generating the reflected signal corresponding to the filtered delayed digital signal. Further, the transponder system further includes a transmitter subsystem configured for transmitting the generated reflected signal to the radar using a phase shifted frequency of operation. The generated reflected signal represents a moving target.
In accordance with another embodiment, a method for detecting one or more targets in an environment is disclosed. The method includes receiving, by a transponder system, an incident energy from a frequency modulated continuous wave (FMCW) radar system using a receive antenna. The incident energy received corresponds to a radar signal. Further, the method includes generating, by the transponder system, a rectified signal using the received incident energy. Further, the method includes harvesting, by the transponder system, the received incident energy as a direct current voltage (VDD). Furthermore, the method includes converting, by the transponder system, the received incident energy to a delayed digital signal using one or more delay line circuits. Also, the method includes filtering, by the transponder system, the delayed digital signal using one or more filtering techniques. Additionally, the method includes generating, by the transponder system, the reflected signal corresponding to the filtered delayed digital signal. Moreover, the method includes transmitting, by the transponder system, the generated reflected signal to the FMCW radar using a phase shifted frequency of operation. The generated reflected signal represents a moving target. The reflected signal is transmitted in response to the radar signal received from the FMCW radar system at a first frequency of operation.
To further clarify the advantages and features of the present disclosure, a more particular description of the disclosure will follow by reference to specific embodiments thereof, which are illustrated in the appended figures. It is to be appreciated that these figures depict only typical embodiments of the disclosure and are therefore not to be considered limiting in scope. The disclosure will be described and explained with additional specificity and detail with the appended figures.
BRIEF DESCRIPTION OF DRAWINGS
The disclosure will be described and explained with additional specificity and detail with the accompanying figures in which:
FIG. 1A is a block diagram of a conventional harmonic radar system, in accordance with prior art;
FIG. 1B is a block diagram of a conventional Frequency-Modulated Continuous Wave (FMCW) radar system, in accordance with prior art;
FIG. 1C is a block diagram of a conventional FMCW based harmonic radar, in accordance with prior art;
FIG. 2A-2B are block diagrams of an exemplary transponder system, in accordance with an embodiment of the present disclosure;
FIGs. 3A-3B are block diagrams of an exemplary FMCW radar system with a transponder system, such as those shown on FIGs. 2A-B, in accordance with an embodiment of the present disclosure;
FIG. 3C-3D are block diagrams of an exemplary front-end subsystem, such as those shown in FIGs. 3A-3B, in accordance with an embodiment of the present disclosure;
FIG. 4A-D are graphical representations of exemplary clutter rejection techniques used by FMCW radars, in accordance with an embodiment of the present disclosure;
FIG. 5 is a block diagram illustrating an exemplary apparatus for a frequency-modulated continuous wave (FMCW) radar, in accordance with an embodiment of the present disclosure;
FIG. 6 is a flow diagram illustrating an exemplary method for operating a transponder system, in accordance with embodiment of the present disclosure;
FIG. 7 is a flow diagram illustrating an exemplary method for operating a FMCW radar, in accordance with another embodiment of the present disclosure; and
FIG. 8 is a graphical representation of attenuation characteristics of radar or radio signals through snow quantified by a penetration depth, in accordance with an embodiment of the present disclosure.
Further, those skilled in the art will appreciate that elements in the figures are illustrated for simplicity and may not have necessarily been drawn to scale. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the figures by conventional symbols, and the figures may show only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the figures with details that will be readily apparent to those skilled in the art having the benefit of the description herein.

DETAILED DESCRIPTION OF THE DISCLOSURE
For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiment illustrated in the figures and specific language will be used to describe them. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Such alterations and further modifications in the illustrated system, and such further applications of the principles of the disclosure as would normally occur to those skilled in the art are to be construed as being within the scope of the present disclosure. It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the disclosure and are not intended to be restrictive thereof.
In the present document, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.
The terms "comprise", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that one or more devices or sub-systems or elements or structures or components preceded by "comprises... a" does not, without more constraints, preclude the existence of other devices, sub-systems, additional sub-modules. Appearances of the phrase "in an embodiment", "in another embodiment" and similar language throughout this specification may, but not necessarily do, all refer to the same embodiment.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this disclosure belongs. The system, methods, and examples provided herein are only illustrative and not intended to be limiting.
Accordingly, the term “module” or “subsystem” should be understood to encompass a tangible entity, be that an entity that is physically constructed permanently configured (hardwired) or temporarily configured (programmed) to operate in a certain manner and/or to perform certain operations described herein.
Embodiments of the present disclosure provides a frequency modulated continuous wave (FMCW) radar system with a transponder (tag), which utilizes in-built delay elements in the transponder to generate phase delays and create artificial movement as detected by the radar. The present system uses modifications to a conventional FMCW radar architecture using a front-end module (FEM) to perform optimum frequency selection. The present system further uses a combination of energy harvesting, configurable phase delay generation, amplification, and filtering in the transponder to create artificial movement as extracted by a radar. Some movement detection techniques may be used to detect the target and separate them from background clutter, enabling the rescue of people buried under avalanches in a debris field with a mixture of dry and wet snow, rocks, and uprooted trees.
Referring now to the drawings, and more particularly to FIG. 2A through FIG. 8, where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments, and these embodiments are described in the context of the following exemplary system and/or method.
FIG.s 2A-2B are block diagrams illustrating an exemplary transponder system 200, in accordance with an embodiment of the present disclosure. In an exemplary embodiment, the transponder system 200A (also referred herein as tag 200) comprises a receive antenna 202, a receiver matching network 204, a diode bridge 206, a power supply control 208, a reserve battery 210, a system power supply 212, a configurable phase delay 214, a radio-frequency filter 216, a radio-frequency amplifier 218, a transmit matching network 220, and a transmitter antenna 222.
The transponder system 200A comprises a receive subsystem comprising the receive antenna 202, and the receiver matching network 204. The receive subsystem is configured for receiving an incident energy from the FMCW radar system using a receive antenna. The incident energy received corresponds to the radar signal.
The diode bridge 206 (also referred herein as a bridge circuit 206) is configured for generating a rectified signal using the received incident energy. Further, the transponder system 200 comprises a power supply control unit 208 configured for harvesting the received incident energy as a direct current voltage (VDD). Furthermore, the transponder system 200 comprises a configurable phase delay block 214 communicatively coupled to the receive subsystem. The configurable phase delay block 214 is configured for converting the received incident energy to a delayed digital signal using one or more delay line circuits. Further, the configurable phase delay block 214 is configured for creating an artificial movement for the target by generating a delayed reflected signal. The delayed reflected signal represents the created artificial movement of the target.
Further, the transponder system 200 comprises a filtering subsystem 216 (also referred herein as radio-frequency filter 216) communicatively coupled to the configurable phase delay block 214. The filtering subsystem 216 is configured for filtering the delayed digital signal using one or more filtering techniques. Further, the filtering subsystem 216 is configured for generating the reflected signal corresponding to the filtered delayed digital signal. Additionally, the transponder system 200A comprises a transmitter subsystem. The transmitter subsystem comprises the transmit matching network 220, and the transmitter antenna 222. The transmitter subsystem is configured for transmitting the generated reflected signal to the FMCW radar using a phase shifted frequency of operation . The generated reflected signal represents a moving target.
The reserve battery 210 is configured for back up operation if energy harvested is determined to be insufficient.
The power supply control 208 (or also referred herein as a power supply control network) is configured for determining an optimal power source to be used for generating the reflected signal based on a status of the reserve battery 210. The optimal power source is selected between one of the reserve battery 210 and an incident energy source corresponding to the received output offset frequency .
When the incident energy is received, it is full wave rectified with a diode bridge circuit 206. The bridge’s output is low pass filtered (with a capacitor) to harvest the RF energy as a DC voltage, VDD 212. In one embodiment, the tag 200 also uses the reserve battery 210 for back up operation in case the energy harvesting is not sufficient. The power supply control block 208 determines its use, if needed.
The incident RF signal is passed through a configurable phase delay block 214. The configurable delay block 214 uses an RF amplifier to amplify the input signal and passes it through a thresholding circuit, such as, for example, a comparator (not shown in FIG. 2A) to convert the input signal to a digital signal. Thereafter, a variable digital delay block (also known as a delay line), is used to add delays to the signal.
Subsequently, the delayed digital signal at the output of the configurable delay block 214 is filtered by an RF low pass filter (LPF) or band pass filter (BPF) 216 and amplified by an RF amplifier 218 as shown, before the signal is transmitted back to a frequency-modulated continuous wave (FMCW) radar.
As a specific example, if a target is at a distance of 20m from the FMCW radar, then a round-trip delay time for a radar signal is given by 2d/c and equal to 133.33ns, where d is a distance of the target and c is a speed of light. If additional delays of 10, 20 and 30ns are added by the delay lines in the tag 200, the “calculated distance” of the target changes by 1.5, 3 and 4.5 meters respectively. This implies that although the target wearing the tag 200 is stationary, and possibly buried under 20m of snow, by changing the delay as a function of time, the variable delay lines give the radar an illusion of movement for the target. Using the movement detection techniques, such as for example, but not limited to, an MTI and a range-Doppler filtering, this target may now easily be separated from static targets (known as clutter). Hence, by using the variable delays embedded in the tag 200, a static target is converted into a dynamic target in the eyes of the radar and made easily detectable by the FMCW radar capable of MTI or range-Doppler (velocity) extraction.
The components used in the tag 200 may be both discrete commercial off the shelf (COTS) or can be implemented in a semiconductor chip specifically designed for this purpose.
FIG. 2B is a block diagram of an exemplary configurable phase delay block 214, such as those shown in FIG. 2A, in accordance with an embodiment of the present disclosure. The configurable phase delay block 214 includes an RF amplifier 224, a thresholding circuit 226, and a delay line circuit 228. The delay line circuit 228 further comprises one or more inverter chain with delay lines 230-1, 230-2 communicatively coupled to a multiplexer 232.
The RF amplifier 224 is configured for amplifying the received incident energy. The thresholding circuit 226 is configured for converting the amplified signal to a digital signal. The delay line circuit 228 is configured for generating the delayed digital signal by applying a phase delay in time to the converted digital signal.
The one or more inverter chain with delay lines 230-1, 230-2 are also referred herein as a first delay line circuit 230-1 and a second delay line circuit 230-2. The first delay line circuit 230-1 is configured for generating a first delayed digital signal by applying a first phase delay in time to the converted digital signal. The second delay line circuit 230-2 is configured for generating a second delayed digital signal by applying a second phase delay in time to the converted digital signal. The multiplexer unit 232 is driven by a timer unit 234. The multiplexer unit 232 is configured for receiving the first delayed digital signal and the second delayed digital signal as inputs from the first delay line circuit 230-1 and the second delay line circuit 230-2. Further, the multiplexer unit 232 is configured for generating a time varying delayed digital signal by selecting at least one of the first delayed digital signal and the second delayed digital signal based on an alternate selection of the output of the first delay line circuit 230-1 and the second delay line circuit 230-2.
The configurable delay block 214 uses an RF amplifier 224 to amplify the input signal and passes it through a thresholding circuit 226, such as, for example, a comparator to convert the input signal to a digital signal. Thereafter, a variable digital delay block 228 (also known as a delay line), is used to add delays to the signal. In one embodiment, the delay line 228 may be, for example, two identical sets of inverters introducing delays of D1 and 2*D1 using a multiplexing arrangement 232 driven by a timer 234. This implies that the output of the delay line 228 is the digital version of the RF input with a configurable delay of D1 or 2*D1 added.
FIGs. 3A-3B are block diagrams of an exemplary FMCW radar system 300 with a transponder system 200, such as those shown on FIGs. 2A-B, in accordance with an embodiment of the present disclosure. In an exemplary embodiment, the FMCW radar 300 may be one of, for example, but not limited to a harmonic FMCW radar system or a frequency-modulated continuous wave (FMCW) radar system or a continuous wave (CW) radar system. In FIGs. 3A-3B, the FMCW radar system 300 comprises a control unit 142 including a controller 144, a signal processing unit 146, and an analog to digital converter 148. The control unit 142 may be coupled to a radar on chip subsystem 172 (also referred as radar subsystem 172, herein). In one example embodiment, the radar on chip subsystem 172 may be, for example, the FMCW radar on chip subsystem or a CW radar on chip subsystem. In a preferred embodiment, a FMCW radar system 300 with a FMCW radar-on-chip subsystem 172 is considered. However, a person skilled in the art may apply the same description in case the CW radar subsystem may be used in addition to or in place of the FMCW radar sub-system 300. The radar subsystem 172 may include, for example, but not limited to, a synthesizer core 152, a Serial Peripheral Interface (SPI) 154, a baseband/IF amplifier 156, 158, a power amplifier 160, a power splitter 164, a mixer 174, and a low-noise amplifier (LNA) 162. The synthesizer core 152 may further include, but not limited to, a temperature-compensated crystal oscillator (TCXO) 150, and a local oscillator (not shown in FIG. 3A). The radar subsystem 172 is further communicatively coupled to a front-end subsystem. In the mixer circuit 174, a part of the frequency-modulated transmitted signal is mixed with the received signal, producing a new signal, which may be used to determine the distance (d) and/or velocity of the moving target 170. The frequency of the new signal is the difference between the frequency of the transmitted and received (reflected) signal.
The front-end subsystem may include front-end module (FEM) 302, a transmitter matching network 304, a receiver matching network 306, a transmitter antenna 308 for RF out, and a receiver antenna 310 for RF in. In an embodiment the transmitter subsystem comprises the transmitter matching network 304 and the transmitter antenna 308. The receiver subsystem comprises the receiver matching network 306 and the receiver antenna 310. The FMCW radar system 300 may further include target 170 comprising a tag 200.
FIG. 3B is a block diagram illustrating an exemplary FMCW radar system 300b, in accordance with an embodiment of the present disclosure. Further, the control unit 142 may be configured to generate a second set of control signals for controlling a frequency of operation based on a set of signal parameters. Furthermore, the control unit 142 transmits the generated first set of control signals to a FMCW radar-on-chip subsystem 172. The control unit 142 may be configured to transmit the generated second set of control signals to a front-end subsystem 316.
The FMCW radar on chip subsystem 172 comprises a local oscillator 314 configured to operate at a base frequency of operation required for transmission of the chirp signal based on the first set of control signals. The base frequency of operation ranges between a first frequency and a second frequency based on the first set of control signals. The front-end subsystem 316 may be communicatively coupled to the FMCW radar on chip subsystem 172 and the control unit 142. The front-end subsystem 316 comprises a front-end module 302 configured to generate at least one output offset frequency based on the base frequency of operation and the generated second set of control signals. The at least one output offset frequency comprises a third frequency value and a fourth frequency value. The first frequency and the second frequency are shifted to the third frequency value and the fourth frequency value. In case the radar on chip subsystem 172 is a CW radar subsystem, then the first frequency of operation may be equal to the second frequency of operation and the fourth frequency of operation may be equal to the third frequency of operation, wherein this system 300 can also support the continuous wave (CW) mode of operation in addition to the FMCW mode of operation.
The transmitter subsystem 318 is communicatively coupled to the front-end module 302 and configured for transmitting the output offset frequency as a transmit signal to at least one target 170 via a transmit antenna 308. The receiver subsystem 320 may be configured for receiving the at least one input offset frequency as the reflected signal from the target 170 via a receive antenna 310. The received at least one input offset frequency comprises the third frequency value and the fourth frequency value. The receiver subsystem 320 may be further configured for transmitting the received at least one input offset frequency to a receiver port of the front-end module 302 as an input signal.
The front-end module 302 may be configured to generate a first frequency of operation based on the received at least one input offset frequency from the receiver subsystem 320 and the generated second set of control signals. The first frequency of operation ranges between the first frequency and the second frequency, and the third frequency value and the fourth frequency value are shifted to the first frequency and the second frequency. In case the radar on chip subsystem 172 is a CW radar subsystem, then the second frequency may be equal to the first frequency and the fourth frequency may be equal to the third frequency, wherein this system 300 can also support the continuous wave (CW) mode of operation in addition to the FMCW mode of operation.
In an exemplary embodiment, during the transmission phase, the base frequency of operation may include f1’ to f2’, where first frequency may be f1’ and a second frequency may be f2’. The output offset frequency may be f1 to f2, where f1 may be third frequency and f2 may be fourth frequency.
Similarly, during the reception phase, the at least one input offset frequency may be f1 to f2, and the first frequency of operation may include f1’ to f2’, where first frequency may be f1’ and a second frequency may be f2’.
In an exemplary embodiment, in case the radar subsystem 172 corresponds to the CW radar subsystem, the first frequency may be equal to the second frequency and the fourth frequency may be equal to the third frequency.
The control unit 142 is configured to receive a baseband signal corresponding to the generated first frequency of operation from the FMCW radar on chip subsystem 172. The control unit 142 is configured to evaluate signal strength of the received baseband signal strength using one or more signal processing techniques. The one or more signal processing techniques may include, for example, but not limited to: a Pulse Compression, a Moving Target Indication (MTI), a Clutter Rejection, a Synthetic Aperture Radar (SAR), and the like.
Further, the control unit 142 is configured to detect the at least one target 170 based on received baseband signal and the evaluated signal strength. The control unit 142 is configured to determine whether a signal quality of the baseband signal meets a pre-defined signal quality criteria based on the detected at least one target and using at least one of a data driven model and predefined rules. In an example embodiment, the data driven model may be any artificial intelligence based or machine learning based model. The pre-defined signal criteria may include, for example, but not limited to, at least one of validating number of targets detected, validating a type of targets detected and validating environmental requirements. The control unit 142 may be configured with a pre-defined criteria for the minimum and maximum number of targets expected to be detected in a given scenario. Thus, helps in verifying that the radar 300 in detecting the expected number of targets and may alert operators, if there are any discrepancies.
The control unit 142 detects specific types of targets based on their radar cross-section (RCS), size, speed, and other characteristics. A pre-defined criteria may be used to validate that the detected targets match the expected types based on these characteristics. Further, performance may be affected by various environmental factors such as weather conditions, terrain, and electromagnetic interference. The pre-defined criteria may be used by the control unit 142 to validate that the received signal which meets the required performance specifications under different environmental conditions.
The control unit 142 is configured to determine an updated set of frequency of operation for operating the FMCW radar on chip subsystem 172, if the determined signal quality does not meet the pre-defined signal quality criteria. Further, the control unit 142 is configured to generate an updated first set of control signals for the chirp signal to be transmitted based on determined updated set of frequency of operation. Furthermore, the control unit 142 is configured to generate an updated second set of control signals for controlling the updated set of frequency of operation. The control unit 142 is further configured to tune the FMCW radar on chip subsystem 172 and the front-end subsystem 316 to the updated set of frequency of operation using the corresponding generated updated first set of control signals and the updated second set of control signals.
Further, the control unit 142 is configured to transmit the generated plurality of control signals to the radar subsystem 172.
Further, in detecting the at least one target 170 based on received baseband signal and the evaluated signal strength, the control unit 142 is further configured for determining that the signal strength of the received baseband signal matches with a predefined threshold value. Further, the control unit 142 is configured for extracting properties associated with a set of targets from the received baseband signal using movement detection techniques. The control unit 142 is configured for filtering a set of static targets from among the set of targets by performing a static clutter rejection on the set of targets based on the extracted properties. Furthermore, the control unit 142 is configured for identifying a moving target among the set of targets upon filtering the set of static targets. Also, the control unit 142 is configured for determining one or more properties associated with the identified moving target. Also, the control unit 142 is configured for generating an alarm indicating presence of the identified moving target based on the determined one or more properties. Additionally, the control unit 142 is configured for outputting the generated alarm using an output unit of the radar system 300.
In an embodiment, the radar subsystem 172 is communicatively coupled to the control unit 142 via a communication network (not shown ). The communication network may be wired or wireless network. The radar subsystem 172 is tuned to operate in the frequency range of f1’ to f2’ and does not generate any undesirable harmonics. Thus, such FMCW radar systems 300 may be suitable for a semiconductor chip implementation, where multiple harmonics do not circulate and interact with each other inside the chip, degrading performance. The input frequency range of f1’ to f2’ is applied at the radar-on-chip side 172, and the FEM 302 may be configured to shift the frequency range to f1 to f2. The input frequencies applied to the receiver end are in the range of f1 to f2 and shifted to f1’ to f2’. The output frequency of the FEM 302, existing between f1 and f2 may be next transmitted using the transmitter subsystem 318, and the transmission antenna 308 with some implementations requiring additional power amplification. The signal impinges upon the tag 200 worn by the target 170. The tag 200 generates the reflected signal and transmits it back to the FMCW radar system 300.
The FEM 302 together with the control unit 142, may use, for example, artificial intelligence (AI) algorithms to perform tasks such as signal preprocessing, target detection, and the like. In signal preprocessing, the frontend module 302 and control unit 142 may apply techniques which include, but not limited to: noise reduction, clutter suppression, signal enhancement, and the like to improve the quality of the radar signals. Thus, facilitates extracting information from the received signals and reduces the impact of environmental factors or interference. For target detection, AI algorithms may be used to identify potential targets in the radar data. This may involve detecting peaks in the signal that indicate the presence of a target or using machine learning algorithms to classify radar returns as either targets or clutter.
In an embodiment, the ability to tune the frequency of operation using fTXLO and fRXLO as offsets in the FEM 302, allows the radar subsystem 172 to operate at a suitable frequency where the propagation due to a type of snow (dry vs. wet) and debris is optimal. The determination is made by the control unit 142, which evaluates the signal quality (after digitization by the ADC 148) and tunes the radar system 300 operational frequency to an optimal value using the FMCW radar on the chip 172 and the Frequency control instruction given to the FEM module 302.
The transmit subsystem 318 comprises a transmit antenna 308 configured to transmit the output offset frequency as a transmit signal to at least one target 170 via a transmit antenna 308. The receiver subsystem 320 may receive the at least one input offset frequency as a received signal from the at least one target 170 via a receive antenna 310. The received at least one input offset frequency comprises the third frequency value and the fourth frequency value. The output offset frequency may be f1 to f2, where f1 may be third frequency and f2 may be fourth frequency.
Further, the receiver subsystem 320 may transmit the received at least one input offset frequency to a receiver port of the front-end module 302 as an input signal to generate a first frequency of operation based on the received at least one input offset frequency from the receiver subsystem 320 and the generated second set of control signal. The first frequency of operation ranges between the first frequency and the second frequency, and where the third frequency value and the fourth frequency value are shifted to the first frequency and the second frequency. In case the radar on chip subsystem 172 is a CW radar subsystem, then the second frequency may be equal to the first frequency and the fourth frequency may be equal to the third frequency, wherein this system 300 can also support the continuous wave (CW) mode of operation in addition to the FMCW mode of operation.
At the FMCW radar-on-chip’s transmitter output, a front-end module 302 (FEM) is connected. On the radar-on-chip side, the frequency range of f1’ to f2’ applied at its input, which is shifted by the FEM 302 to f1 to f2. On the receiver side, the input frequencies are in the range of f1 to f2 and are shifted by the FEM 302 to f1’ to f2’.
FIG. 3C-3D are block diagrams of an exemplary front-end subsystem 316, such as those shown in FIGs. 3A-3B, in accordance with an embodiment of the present disclosure. In an embodiment, when this signal “RF in” is received by the receiving antenna 310 along with the receiving subsystem 320, it may be filtered (optionally) using the bandpass filter 330-2. Further, the FEM 302 may be configured to shift the received signal from f1-f2 to f1’-f2’. Any mixing products, are rejected due to the tuned nature of the FMCW radar-on-chip 172.The front-end module 302 may be configured for processing incoming radar signals.
The FMCW radar system 300 comprises a control unit 142 (similar to those shown in FIG.3A). At the transmitter side, the front-end subsystem 316 comprises a first transmit signal received from the radar subsystem 172 as an input signal, a first transmit filter 322-1, a first intermediate frequency (IF) amplifier 324-1, a transmitter side mixer module 326-1, a power amplifier 328-1, a second transmit filter 330-1, and a transmit antenna. At the receiver side, the front-end subsystem 316 comprises a first receive output signal, a first receive filter 322-2, a second intermediate frequency (IF) amplifier 324-2, a receiver side mixer module 326-2, a low-noise amplifier (LNA) 328-2, a fourth filter 330-2, and a receive antenna.
The front-end module 302 further comprises a frequency generation module 332 configured to generate a transmit frequency control signal (TXLO) and a receive frequency control signal (RXLO) based on the generated second set of control signals. The transmitter side mixer module 326-1 is configured to generate the at least one output offset frequency by mixing the generated transmit frequency control signal (TXLO) with the base frequency of operation. The receiver side mixer module 326-2 is configured to generate the first frequency of operation by mixing the receive frequency control signal (RXLO) with the received at least one input offset frequency.
In one embodiment, the transmitter side mixer module 326-1 multiplies a signal TXLO with the input signals (f1’ to f2’) to generate the offset output (f1 to f2).
Specifically, f1 = f1’ +fTXLO -------- Equation (1), and
f2=f2’+fTXLO -------- Equation (2)
Where, fTXLO is the frequency of the signal TXLO. Since several additional frequency components may be produced during multiplication, the amplifiers and filters shown in FIG. 3A, may help in selecting the desired signals that exists between f1 to f2. Similarly, the receiver side mixer module 326-2, which uses fRXLO to shift the frequency of the received input signal (f1-f2) to a new frequency (f1’-f2’) which is the operating range of the FMCW radar-on-chip 172 and cleans up the spectrum using amplifiers and filters. Both TXLO and RXLO signals are generated using the frequency generation module 332 such as for example, but not limited to, a phase locked loop (PLL) which obtains the frequency control instruction from the control unit 142.
In another embodiment, the FEM 302, or parts of the front-end subsystem 316, may be implemented inside the FMCW radar-on-chip 172 without impacting coupling between signals as it will be an interface (peripheral) block which may be segregated from the rest of the chip.
In another embodiment, the entire FEM block 302 or parts of it, may be implemented inside the FMCW radar-on-chip 172 without impacting coupling between signals as it will be an interface (peripheral) block which may be segregated from the rest of the chip.
The ability to tune the frequency of operation using fTXLO and fRXLO as offsets in the FEM block 302, allows the radar 300 to operate at a suitable frequency where the propagation due to the type of snow (dry vs. wet) and debris is optimal. As shown in the flow chart in FIG. 7, this determination is made by the control unit 142, which evaluates the signal quality (after digitization by the ADC) and tunes the radar’s operational frequency to an optimal value using the FMCW radar on chip 172 and the Frequency control instruction given to the FEM 302. Additionally, once an optimal frequency range has been selected, the artificial movement created by the tag 200 may be used to separate the target from the static clutter in an avalanche debris field using techniques such as MTI or Range-Doppler filtering and generate an alarm once an avalanche victim has been located.
Both the above developed techniques, i.e., optimal frequency selection and the creation of artificial movement signature using phase delays may be used by themselves in specific embodiments, although a combination of both has been shown in FIG. 7.
This invention is specifically distinct from a harmonic CW or a harmonic FMCW radar, where in that it does not require the use of a frequency and its harmonic (e.g. f0 and 2*f0) spanning a wide range of possible attenuation values in a debris field. Hence, the selected frequency range for the FMCW radar 300 may be narrow and it will see almost the same attenuation in the transmit and received signals.
While this radar architecture, along with the developed tag 200 improves the performance of avalanche rescue radars, the same architecture has applications in other areas such as, for example, (but not limited to) foliage penetration and search and rescue under earthquake debris, with some customization. As such, this invention is not limited only to the avalanche rescue application.
FIG. 4A-D are graphical representations of an exemplary clutter rejection techniques used by FMCW radars, in accordance with an embodiment of the present disclosure. A specific application, known as moving target indication (MTI), is illustrated in FIG. 4A. A person moving behind a clump of trees (part (i)) is imaged by an FMCW radar 300 from a distance. As shown in FIG. 4B and 4C, parts (ii) and (iii), the received radar signal is plotted as a “range vs. time” spectrogram. The time evolution is plotted on the y-axis, while the distances of various targets are plotted on the x-axis. The color indicates the strength of the return from the target 170 with red and orange representing strong returns while greens and blues represent weak ones. In part (ii), FIG. 4B, we observe that strong static targets or clutter (represented by red vertical lines) which are the trees surrounding the moving person, completely hide the moving person from the radar 300. In part (iii), FIG. 4C, the MTI algorithm is applied by subtracting subsequent time samples, which removes the static clutter due to the trees and clearly shows the moving person. In FIG. 4D, we show a more advanced clutter rejection technique used by FMCW radars 300, where the range and the velocity of a moving target are simultaneously plotted. This process segregates moving targets with various velocities from static targets and allows the use of a simple “static target filter” to remove the clutter. Hence, the segregation of targets based on their velocity is a very powerful technique used by radars 300 to isolate static clutter from moving targets.
FIG. 5 is a block diagram illustrating an exemplary apparatus for a frequency-modulated continuous wave (FMCW) radar 300, in accordance with an embodiment of the present disclosure. In an example embodiment, the apparatus 500 may be one of a control unit 142, or a radar subsystem 172 or a front-end subsystem 316 or a combination of the control unit 142, the radar subsystem 172 and the front-end subsystem 316. The apparatus 500 comprises one or more hardware processors 502, a memory 504 and a storage unit 506. The one or more hardware processors 502, the memory 504 and the storage unit 506 are communicatively coupled through a system bus 508 or any similar mechanism. The memory 504 comprises the plurality of modules 510 in the form of programmable instructions executable by the one or more hardware processors 502.
The one or more hardware processors 502, as used herein, means any type of computational circuit, such as, but not limited to, a microprocessor unit, microcontroller, complex instruction set computing microprocessor unit, reduced instruction set computing microprocessor unit, very long instruction word microprocessor unit, explicitly parallel instruction computing microprocessor unit, graphics processing unit, digital signal processing unit, or any other type of processing circuit. The one or more hardware processors 502 may also include embedded controllers, such as generic or programmable logic devices or arrays, application specific integrated circuits, single-chip computers, and the like.
The memory 504 may be non-transitory volatile memory and non-volatile memory. The memory 504 may be coupled for communication with the one or more hardware processors 502, such as being a computer-readable storage medium. The one or more hardware processors 502 may execute machine-readable instructions and/or source code stored in the memory 504. A variety of machine-readable instructions may be stored in and accessed from the memory 504. The memory 504 may include any suitable elements for storing data and machine-readable instructions, such as read only memory, random access memory, erasable programmable read only memory, electrically erasable programmable read only memory, a hard drive, a removable media drive for handling compact disks, digital video disks, diskettes, magnetic tape cartridges, memory cards, and the like. In the present embodiment, the memory 504 includes the plurality of modules 510 stored in the form of machine-readable instructions on any of the above-mentioned storage media and may be in communication with and executed by the one or more hardware processors 502.
The storage unit 506 may be a cloud storage or a local file directory within a remote server. The storage unit 506 may store the set of radar parameters, the first set of control signals, the second set of control signals, a chirp signal, the output offset frequency, the base frequency and the like.
In an example embodiment, the control unit 142 is configured to determine a set of radar parameters corresponding to a chirp signal to be transmitted through a user interface where the user selects such parameters to determine specific characteristics of the target 170 such as range and velocity to a certain accuracy and resolution. In some embodiments, the set of radar parameters may be automatically determined by the control unit 142. The set of radar parameters may include at least one of the start frequency (fstart) and stop frequency (fstop) of the chirp signal, a ramp rate of the chirp signal, bandwidth information of the chirp signal and the like. In an embodiment, the start frequency (fstart) of the chirp signal corresponds to initial frequency of the chirp signal at the beginning of the transmission. This parameter determines starting point of the "chirp." The bandwidth information of the chirp signal specifies a total range of frequencies covered by the chirp. A wider bandwidth allows the FMCW radar system 300 to detect the one or more targets 170 with a better resolution of speeds and distances.
Further, the processor 502 is configured to generate a first set of control signals for a chirp signal to be transmitted based on a set of radar parameters. Furthermore, the processor 502 is configured to generate a second set of control signals for controlling a frequency of operation based on a set of signal parameters. The processor 502 is further configured to transmit the generated first set of control signals to a FMCW radar-on-chip subsystem 172. Further, processor 502 is configured to transmit the generated second set of control signals to a front-end subsystem 316. The FMCW radar on chip subsystem 172, communicatively coupled to the control unit 142, comprises a local oscillator 314 configured to operate at a base frequency of operation required for transmission of the chirp signal based on the first set of control signals. The base frequency of operation ranges between a first frequency and a second frequency. The base frequency of operation is set based on the first set of control signals.
Further, the front-end subsystem 316 is communicatively coupled to the FMCW radar on chip subsystem 172 and the control unit 142. The front-end subsystem 316 comprises a front-end module 302 configured to generate at least one output offset frequency based on the base frequency of operation and the generated second set of control signals. The at least one output offset frequency comprises a third frequency value and a fourth frequency value, and where the first frequency and the second frequency are shifted to the third frequency value and the fourth frequency value.
The transmitter subsystem 318 is configured to transmit the output offset frequency as a transmit signal to at least one target 170 via a transmit antenna 308. The receiver subsystem 320is configured to receive the at least one input offset frequency as a received signal from the at least one target 170 via a receive antenna 310. Further, the received at least one input offset frequency comprises the third frequency value and the fourth frequency value. The receiver subsystem 320 transmits the received at least one input offset frequency to a receiver port of the front-end module 302 as an input signal.
The front-end module 302 is configured to generate a first frequency of operation based on the received at least one input offset frequency from the receiver subsystem 320 and the generated second set of control signals. The first frequency of operation ranges between the first frequency and the second frequency, and where the third frequency value and the fourth frequency value are shifted to the first frequency and the second frequency.
FIG. 6 is a flow diagram illustrating an exemplary method 600 for operating a transponder system 200, in accordance with embodiment of the present disclosure. At step 602, the method 600 includes receiving, by a transponder system 200, an incident energy from a frequency modulated continuous wave (FMCW) radar system using a receive antenna. The incident energy received corresponds to a radar signal. At step 604, the method 600 includes generating, by the transponder system 200, a rectified signal using the received incident energy. At step 606, the method 600 includes harvesting, by the transponder system 200, the received incident energy as a direct current voltage (VDD). At step 608, the method 600 includes converting, by the transponder system 200, the received incident energy to a delayed digital signal using one or more delay line circuits 228. At step 610, the method 600 includes filtering, by the transponder system 200, the delayed digital signal using one or more filtering techniques. At step 612, the method 600 includes generating, by the transponder system 200, the reflected signal corresponding to the filtered delayed digital signal. At step 614, the method 600 includes transmitting, by the transponder system 200, the generated reflected signal to the FMCW radar using a phase shifted frequency of operation , wherein the generated reflected signal represents a moving target. The reflected signal is transmitted in response to the radar signal received from the FMCW radar system 300 at a first frequency of operation.
Further, the method 600 includes creating, by the transponder system 200, an artificial movement for the target by generating a time varying delayed reflected signal, wherein the time varying delayed reflected signal represents the created artificial movement of the target.
In converting, by the transponder system 200, the received incident energy to the delayed digital signal using the one or more delay line circuits 228, the method 600 includes amplifying, by the transponder system, the received incident energy; converting, by the transponder system, the amplified signal to a digital signal; and generating, by the transponder system, the time varying delayed digital signal by applying a phase delay in time to the converted digital signal.
In generating, by the transponder system, the delayed digital signal by applying a phase delay in time to the converted digital signal, the method 600 includes generating, by the transponder system 200, a first delayed digital signal by applying a first phase delay in time to the converted digital signal; generating, by the transponder system 200, a second delayed digital signal by applying a second phase delay in time to the converted digital signal; receiving, by the transponder system 200, the first delayed digital signal and the second delayed digital signal as inputs; and generating, by the transponder system 200, a time varying delayed digital signal by selecting at least one of the first delayed digital signal and the second delayed digital signal based on an alternate selection of the output of the first delay line circuit and the second delay line circuit.
FIG. 7 is a flow diagram illustrating an exemplary method 700 for operating a FMCW radar 300, in accordance with embodiment of the present disclosure. At, step 702, the method 700 includes setting, by the processor 502, the frequency of operation (f1’ to f2’) and the first set of radar parameters and translating, by the processor 502, the operational frequency range to f1-f2 using the FEM 302. At step 704, the method 700 includes transmitting, by the processor 502, a FMCW radar signal. At step 706, the method 700 includes evaluating, by the processor 502, a signal strength of the received baseband signal using one or more signal processing techniques. Specifically, a baseband signal quality is analyzed using the A/D converter 148 and the control unit 142 with Fast Fourier Transform (FFT) or other signal processing techniques. At step 708, the method 700 incudes determining, by the processor 502, whether a signal quality of the baseband signal meets a pre-defined signal quality criteria based on the detected at least one target and using at least one of a data driven model and predefined rules. The pre-defined signal criteria comprise at least one of validating number of targets detected, validating type of targets detected and validating environmental requirements.
At step 712, if the signal quality does not meet the pre-defined signal criteria, then, the method 700 includes determining, by the processor 502, new frequencies of operation based on either or combination of: signal processing models based on snow/debris characteristics and/or machine learning models based on training on data collected from deployment scenarios. In order to determine whether the received baseband signal meets the pre-defined signal criteria, the processor 502 may determine whether the received baseband signal has low signal to noise ratio and hence, low signal quality caused by attenuation due to propagation, interference, or deliberate jamming from other radio frequency sources. Further, the method 700 includes determining, by the processor 502, an updated set of frequency of operation for operating the FMCW radar on chip subsystem 172, if the determined signal quality does not meet the pre-defined signal quality criteria.
Further, the method 700 includes generating, by the processor 502, an updated first set of control signals for the chirp signal to be transmitted based on determined updated set of frequency of operation. Further, the method 700 includes generating, by the processor 502, an updated second set of control signals for controlling the updated set of frequency of operation. Finally, at step 714, the method 700 includes tuning, by the processor 502, the FMCW radar on chip subsystem 172 and the front-end subsystem 316 to the updated set of frequency of operation using the corresponding generated updated first set of control signals and the updated second set of control signals.
At step 710, the method 700 includes extracting, by the processor 502, properties associated with a set of targets from the received baseband signal using movement detection techniques. In an exemplary embodiment, the properties may include, for example, but are not limited to radar cross section, range, velocity, range resolution, velocity resolution, micro-Doppler signature and the like. At step 716, the method 700 includes filtering, by the processor 502, a set of static targets from among the set of targets by performing a static clutter rejection on the set of targets based on the extracted properties. Further, the method 700 includes identifying, by the processor 502, a moving target among the set of targets upon filtering the set of static targets. Further, the method 700 includes determining, by the processor 502, one or more properties associated with the identified moving target. At step 718, the method 700 incudes generating, by the processor 502, an alarm indicating presence of the identified moving target based on the determined one or more properties and outputting the generated alarm using an output unit. In an exemplary embodiment, the alarm may be an audio signal, a vibration or the like.
The FMCW radar 300 of the present disclosure provides better range resolution by using frequency modulation to encode the transmitted signal, allowing for more precise distance measurements. The FMCW radar 300 of the present system may achieve better interference rejection compared to other radar systems, by using frequency modulation. The FMCW radar 300 may distinguish between signals reflected from the target and those from other sources, such as clutter or noise.
FIG. 8 is an exemplary graphical representation of attenuation characteristics of radio or radar signals through snow quantified by the penetration depth in, accordance with an embodiment of the present disclosure.
As shown in FIG. 8, the penetration depth of radar signals under snow, which is critical to the rescue of a trapped person, is a strong function of frequency and the type of snow (dry or wet). In general, higher frequencies and wetter snow, both reduce the penetration depth. In an avalanche debris field, the presence of rocks and trees makes it more difficult to clearly predict the propagation characteristics, adding an unknown element to signal propagation.
Thus, penetration depth of radar signals under snow depends on several factors, including the frequency of the radar signal, the type of snow, and the properties of the underlying material (such as soil or ice). For example, in dry snow conditions, radar signals with frequencies in the range of 100 MHz to 1 GHz may penetrate several meters or more. However, in wet snow or near the melting point, the penetration depth may be significantly reduced.
The radars implementing FMCW radar technology along with harmonics are used in such a way that the harmonics may be segregated inside a semiconductor chip, inhibiting signal coupling. Additionally, a method to enable optimal propagation through snow under varying conditions of weather, snow type (dry or wet) and the composition of debris (rocks, snow and the like.) is disclosed.
The radar signals may penetrate deeper into dense materials such as ice or compacted or dry snow compared to loose, dry or wet snow. Additionally, the presence of air gaps, ice layers, or water pockets within the snowpack may affect the penetration depth. The radar system 300 is used to estimate the thickness and density of the snowpack based on the penetration depth of the radar signals.
In summary, compared to conventional above mentioned harmonic and CW radars, the present system 200 and 300 has a significant advantage in terms of accuracy and semiconductor chip operation leading to low power and portable operation, while making the best of the limitations of antennas and propagation through snow and debris.
The present disclosure may also be applicable to automotive sector. The FMCW radar sensors are integral to advanced driver assistance systems (ADAS) in modern cars. Radar sensors for cars are typically deployed for blind spot detection (BSD), lane change assistance (LCA), collision mitigation (CM), parking aid (PA), and rear cross-traffic alert (RCTA) features. There are numerous other applications in ground and foliage penetrating radars, avalanche rescue radars, biomedical radars, weather radars, and the like, to which the present system may be applicable.
The embodiments herein may comprise hardware and software elements. The embodiments that are implemented in software include but are not limited to, firmware, resident software, microcode. The functions performed by various modules described herein may be implemented in other modules or combinations of other modules. For the purposes of this description, a computer-usable or computer readable medium may be any apparatus that may comprise, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.
The illustrated steps are set out to explain the exemplary embodiments shown, and it should be anticipated that ongoing technological development will change the manner in which particular functions are performed. These examples are presented herein for purposes of illustration, and not limitation. Further, the boundaries of the functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternative boundaries may be defined so long as the specified functions and relationships thereof are appropriately performed. Alternatives (including equivalents, extensions, variations, deviations, and the like, of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the disclosed embodiments. Also, the words “comprising,” “having,” “containing,” and “including,” and other similar forms are intended to be equivalent in meaning and be open-ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.
Finally, the language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based here on. Accordingly, the embodiments of the present invention are intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.

, Claims:We claim:
1. A system for detecting one or more targets in an environment comprising:
a radar system (300, 500) configured to detect a target (170) based on a reflected signal received from the target (170), wherein the reflected signal is received in response to a radar signal transmitted from the radar system (300, 500) to the target (170) at a first frequency of operation; and
a transponder system (200) communicatively coupled to the radar system (300, 500), wherein the transponder system (200) is associated with the target (170), and wherein the transponder system (200) comprises:
a receive subsystem configured for receiving an incident energy from the radar system (300, 500) using a receive antenna (202), wherein the incident energy received corresponds to the radar signal;
a bridge circuit (206) configured for generating a rectified signal using the received incident energy;
a power supply control unit (208) configured for harvesting the received incident energy as a direct current voltage (VDD);
a configurable phase delay block (214) communicatively coupled to the receive subsystem, wherein the configurable phase delay block (214) is configured for:
converting the received incident energy to a delayed digital signal using one or more delay line circuits (228);
a filtering subsystem (216) communicatively coupled to the configurable phase delay block (214), wherein the filtering subsystem (216) is configured for:
filtering the delayed digital signal using one or more filtering techniques; and
generating the reflected signal corresponding to the filtered delayed digital signal; and
a transmitter subsystem configured for transmitting the generated reflected signal to the radar (300, 500) using a phase-shifted frequency of operation, wherein the generated reflected signal represents a moving target.

2. The system as claimed in claim 1, wherein the configurable phase delay block (214) is configured for creating an artificial movement for the target (170) by generating a delayed reflected signal, wherein the delayed reflected signal represents the created artificial movement of the target (170).

3. The system as claimed in claim 1, wherein a configurable phase delay block (214) comprises:
an amplifier unit (224) configured for amplifying the received incident energy;
a threshold circuit (226) configured for converting the amplified signal to a digital signal; and
a delay circuit (228) configured for generating the delayed digital signal by applying a phase delay in time to the converted digital signal.

4. The system as claimed in claim 3, wherein the delay circuit (228) comprises:
a first delay line circuit (230-1) configured for generating a first delayed digital signal by applying a first phase delay in time to the converted digital signal;
a second delay line circuit (230-2) configured for generating a second delayed digital signal by applying a second phase delay in time to the converted digital signal;
a multiplexer unit (232) driven by a timer unit (234), wherein the multiplexer unit (232) configured for:
receiving the first delayed digital signal and the second delayed digital signal as inputs from the first delay line circuit (230-1) and the second delay line circuit (230-2); and
generating a time varying delayed digital signal by selecting at least one of the first delayed digital signal and the second delayed digital signal based on an alternate selection of the output of the first delay line circuit (230-1) and the second delay line circuit (230-2).

5. The system as claimed in claim 1, wherein the transponder system (200) comprises a reserve battery (210) for back up operation if energy harvested is determined to be insufficient.

6. The system as claimed in claim 1, wherein the transponder system (200) comprises a power supply control network (208) configured for:
determining an optimal power source to be used for generating the reflected signal based on a status of the reserve battery (210), wherein the optimal power source is selected between one of the reserve battery (210) and an incident energy source corresponding to the received output offset frequency.

7. The system as claimed in claim 1, wherein the radar system (300, 500) comprises:
a control unit (142) configured for:
generating a first set of control signals for a chirp signal to be transmitted based on a set of radar parameters;
generating a second set of control signals for controlling a frequency of operation based on a set of signal parameters;
transmitting the generated first set of control signals to a radar-on-chip subsystem (172); and
transmitting the generated second set of control signals to a front-end module (302);
the radar on chip subsystem (172), communicatively coupled to the control unit (142), comprises:
a local oscillator (314) configured for:
operating at a base frequency of operation required for transmission of the chirp signal based on the first set of control signals, wherein the base frequency of operation ranges between a first frequency and a second frequency based on the first set of control signals;
the front-end module (302) communicatively coupled to the radar on chip subsystem (172) and the control unit (142), wherein the front-end module (302) is configured for generating at least one output offset frequency based on the base frequency of operation and the generated second set of control signals, wherein the at least one output offset frequency comprises a third frequency value and a fourth frequency value, and wherein the first frequency and the second frequency are shifted to the third frequency value and the fourth frequency value;
a transmitter subsystem (318) communicatively coupled to the front-end module (302), wherein the transmitter subsystem (318) is configured for transmitting the output offset frequency as a transmit signal to at least one target (170) via a transmit antenna (308); and
a receiver subsystem (320) configured for:
receiving the at least one input offset frequency as the reflected signal from the target (170) via a receive antenna (310), wherein the received at least one input offset frequency comprises the third frequency value and the fourth frequency value; and
transmitting the received at least one input offset frequency to a receiver port of the front-end module (302) as an input signal; and
wherein the front-end module (302) is configured for generating the first frequency of operation based on the received at least one input offset frequency from the receiver subsystem (320) and the generated second set of control signals, and wherein the first frequency of operation ranges between the first frequency and the second frequency, and wherein the third frequency value and the fourth frequency value are shifted to the first frequency and the second frequency.

8. The system as claimed in claim 7, wherein the control unit (142) is further configured for:
receiving a baseband signal corresponding to the generated first frequency of operation from the radar on chip subsystem (172);
evaluating signal strength of the received baseband signal strength using one or more signal processing techniques;
detecting at least one target (170) based on received baseband signal and the evaluated signal strength;
determining whether a signal quality of the baseband signal meets a pre-defined signal quality criteria based on the detected at least one target (170) and using at least one of a data driven model and predefined rules, wherein the pre-defined signal criteria comprise at least one of validating number of targets detected, validating a type of targets detected and validating environmental requirements;
determining an updated set of frequency of operation for operating the radar on chip subsystem (172) if the determined signal quality meets the pre-defined signal quality criteria;
generating an updated first set of control signals for the chirp signal to be transmitted based on determined updated set of frequency of operation;
generating an updated second set of control signals for controlling the updated set of frequency of operation; and
tuning the radar on chip subsystem (172) and the front-end module (302) to the updated set of frequency of operation using the corresponding generated updated first set of control signals and the updated second set of control signals.

9. The system as claimed in claim 8, wherein in detecting the at least one target (170) based on received baseband signal and the evaluated signal strength, the control unit (142) is further configured for:
determining that the signal strength of the received baseband signal strength matches with a predefined threshold value;
extracting properties associated with a set of targets from the received baseband signal using movement detection techniques;
filtering a set of static targets from among the set of targets by performing a static clutter rejection on the set of targets based on the extracted properties;
identifying a moving target among the set of targets upon filtering the set of static targets;
determining one or more properties associated with the identified moving target;
generating an alarm indicating presence of the identified moving target based on the determined one or more properties; and
outputting the generated alarm using an output unit of the radar system (300, 500).

10. The system as claimed in claim 7, wherein the front-end module (302) comprises:
a frequency generation module (332) configured to generate a transmit frequency control signal (TXLO) and a receive frequency control signal (RXLO) based on the generated second set of control signals;
a transmitter side mixer module (326-1) configured to generate the at least one output offset frequency by mixing the generated transmit frequency control signal (TXLO) with the base frequency of operation; and
a receiver side mixer module (326-2) configured to generate the first frequency of operation by mixing the receive frequency control signal (RXLO) with the received at least one input offset frequency.

11. The system as claimed in claim 7, wherein the radar on chip subsystem (172) corresponds to one of a frequency-modulated continuous wave (FMCW) radar subsystem (172) and a continuous wave (CW) radar subsystem, and wherein if radar on chip subsystem (172) corresponds to the CW radar subsystem, then the second frequency may be equal to the first frequency and the fourth frequency may be equal to the third frequency.

12. A method (600, 700) for detecting one or more targets (170) in an environment comprising:
receiving, by a transponder system (200), an incident energy from a radar system (300, 500) using a receive antenna (202), wherein the incident energy received corresponds to a radar signal;
generating, by the transponder system (200), a rectified signal using the received incident energy;
harvesting, by the transponder system (200), the received incident energy as a direct current voltage (VDD);
converting, by the transponder system (200), the received incident energy to a delayed digital signal using one or more delay line circuits (228);
filtering, by the transponder system (200), the delayed digital signal using one or more filtering techniques;
generating, by the transponder system (200), the reflected signal corresponding to the filtered delayed digital signal; and
transmitting, by the transponder system (200), the generated reflected signal to the radar (300, 400) using a phase-shifted frequency of operation, wherein the generated reflected signal represents a moving target, wherein the reflected signal is transmitted in response to the radar signal received from the radar system (300, 500) at a first frequency of operation.

13. The method (600, 700) as claimed in claim 12, further comprising:
creating, by the transponder system (200), an artificial movement for the target (170) by generating a time varying delayed reflected signal, wherein the time varying delayed reflected signal represents the created artificial movement of the target (170).

14. The method (600, 700) as claimed in claim 12, wherein converting, by the transponder system (200), the received incident energy to the delayed digital signal using the one or more delay line circuits (228) comprises:
amplifying, by the transponder system (200), the received incident energy;
converting, by the transponder system (200), the amplified signal to a digital signal; and
generating, by the transponder system (200), the time varying delayed digital signal by applying a phase delay in time to the converted digital signal.

15. The method (600, 700) as claimed in claim 14, wherein generating, by the transponder system (200), the delayed digital signal by applying a phase delay in time to the converted digital signal comprises:
generating, by the transponder system (200), a first delayed digital signal by applying a first phase delay in time to the converted digital signal;
generating, by the transponder system (200), a second delayed digital signal by applying a second phase delay in time to the converted digital signal;
receiving, by the transponder system (200), the first delayed digital signal and the second delayed digital signal as inputs; and
generating, by the transponder system (200), a time varying delayed digital signal by selecting at least one of the first delayed digital signal and the second delayed digital signal based on an alternate selection of the output of the first delay line circuit (230-1) and the second delay line circuit (230-2).

16. The method (600, 700) as claimed in claim 12, further comprising:
generating, by a radar (300, 500), a first set of control signals for a chirp signal to be transmitted based on a set of radar parameters;
generating, by the radar (300, 500), a second set of control signals for controlling a frequency of operation based on a set of signal parameters;
operating, by the radar (300, 500), at a base frequency of operation required for transmission of the chirp signal based on the first set of control signals, wherein the base frequency of operation ranges between a first frequency and a second frequency based on the first set of control signals;
generating, by the radar (300, 500), at least one output offset frequency based on the base frequency of operation and the generated second set of control signals, wherein the at least one output offset frequency comprises a third frequency value and a fourth frequency value, and wherein the first frequency and the second frequency are shifted to the third frequency value and the fourth frequency value;
transmitting, by the radar (300, 500), the output offset frequency as a transmit signal to at least one target (170) via a transmit antenna (308); and
receiving, by the radar (300, 500), the at least one input offset frequency as the reflected signal from the target (170) via a receive antenna (310), wherein the received at least one input offset frequency comprises the third frequency value and the fourth frequency value; and
wherein the first frequency of operation is generated based on the received at least one input offset frequency and the generated second set of control signals, and wherein the first frequency of operation ranges between the first frequency and the second frequency, and wherein the third frequency value and the fourth frequency value are shifted to the first frequency and the second frequency.

17. The method (600, 700) as claimed in claim 16, further comprising:
receiving, by the radar (300, 500), a baseband signal corresponding to the generated first frequency of operation;
evaluating, by the radar (300, 500), signal strength of the received baseband signal strength using one or more signal processing techniques;
detecting, by the radar (300, 500), at least one target (170) based on received baseband signal and the evaluated signal strength;
determining, by the radar (300, 500), whether a signal quality of the baseband signal meets a pre-defined signal quality criteria based on the detected at least one target and using at least one of a data driven model and predefined rules, wherein the pre-defined signal criteria comprise at least one of validating number of targets detected, validating type of targets detected and validating environmental requirements;
determining, by the radar (300, 500), an updated set of frequency of operation for operating the radar on chip subsystem (172) if the determined signal quality meets the pre-defined signal quality criteria;
generating, by the radar (300, 500), an updated first set of control signals for the chirp signal to be transmitted based on determined updated set of frequency of operation;
generating, by the radar (300, 500), an updated second set of control signals for controlling the updated set of frequency of operation; and
tuning, by the radar (300, 500), a radar on chip subsystem (172) and a front-end module (302) to the updated set of frequency of operation using the corresponding generated updated first set of control signals and the updated second set of control signals.

18. The method (600, 700) as claimed in claim 17, wherein detecting the at least one target (170) based on received baseband signal and the evaluated signal strength comprises:
determining, by the radar (300, 500), that the signal strength of the received baseband signal strength matches with a predefined threshold value;
extracting, by the radar (300, 500), properties associated with a set of targets from the received baseband signal using movement detection techniques;
filtering, by the radar (300, 500), a set of static targets from among the set of targets by performing a static clutter rejection on the set of targets based on the extracted properties;
identifying, by the radar (300, 500), a moving target among the set of targets upon filtering the set of static targets;
determining, by the radar (300, 500), one or more properties associated with the identified moving target;
generating, by the radar (300, 500), an alarm indicating presence of the identified moving target based on the determined one or more properties; and
outputting, by the radar (300, 500), the generated alarm using an output unit.

19. The method (600, 700) as claimed in claim 12, further comprising:
generating, by the radar (300, 500), a transmit frequency control signal (TXLO) and a receive frequency control signal (RXLO) based on the generated second set of control signals;
generating, by the radar (300, 500), the at least one output offset frequency by mixing the generated transmit frequency control signal (TXLO) with the base frequency of operation; and
generating, by the radar (300, 500), the first frequency of operation by mixing the receive frequency control signal (RXLO) with the received at least one input offset frequency.

Dated this 16th day of April 2024

Name: Sanath MV
Prasa IP
Patent Agent (IN/PA-5004)
Agent for the Applicant