Claims:1. A device for estimating phase noise for slow-moving targets, the device comprising:
a transmitter (202) that transmits radio frequency (RF) signal illuminating target and surrounding clutter objects disposed in a predetermined coverage area;
a receiver (204) receives the RF signal reflected from the target and the clutter objects;
a heterodyne conversion unit (208) receives the reflected RF signal and down-converts the reflected RF signal to intermediate frequency (IF) signal, the heterodyne conversion unit receives an oscillator signal from a local oscillator (302), which effects phase noise characteristics of the down-converted IF signal in processing, along with time delay effect helps in accurate modelling of device phase noise requirement;
a processor (212) operatively coupled to the heterodyne conversion unit, the processor configured to:
receive, from the heterodyne conversion unit, the IF signal; and
process the IF signal to extract doppler information of the target effected by the phase noise characteristics of the IF signal to improve detection capability of slow-moving targets.

2. The device as claimed in claim 1, wherein said local oscillator is coherent local oscillator (302).

3. The device as claimed in claim 1, wherein said heterodyne conversion unit (208) coupled to the receiver to down-convert the incident reflected RF signal.
4. The device as claimed in claim 1, wherein the phase noise measurement of the IF signal normalized with respect to phase noise of RF input signal using synchronous coherent mechanism.

5. The device as claimed in claim 1, wherein the phase noise improvement in lower doppler offsets for detection of slow-moving targets is obtained by incorporating synchronous coherence based heterodyne detection mechanism.

6. The device as claimed in claim 1, wherein the time delay (206) between transmission and reception of the signals is 2 /c.

7. The device as claimed in claim 1, wherein the effect of time delay to estimate phase noise signal at frequency offset for the reflected RF signal from the target along with presence of stationary clutter objects leads to cancellation phases with improvement factor.

8. A method (500) for estimating phase noise for slow-moving targets, the method comprising:
transmitting (502), by a transmitter, RF signal illuminating target and surrounding clutter objects disposed in a predetermined coverage area;
receiving (504), by a receiver, the RF signal reflections from the target and the clutter objects;
receiving (506), by a heterodyne conversion unit, the reflected RF signal as input and down-converting the received RF input signal to intermediate frequency (IF) signal, the heterodyne conversion unit receives an oscillator signal from a coherent local oscillator, which effects the phase noise characteristics of the down converted IF signal in processing, along with time delay effect helps in accurate modelling of device phase noise requirement;
receiving (508), at a processor, the IF signal from the heterodyne conversion unit; and
processing (510) the IF signal to extract doppler information of the target effected by the phase noise characteristics of the IF signal to improve detection capability of slow-moving targets.
, Description:TECHNICAL FIELD
[0001] The present disclosure relates, in general, to a radar sensor, and more specifically, relates to a method of modelling phase noise estimation for heterodyne based RF sensors for slow-moving targets.

BACKGROUND
[0002] The role of high accuracy tracking is a prime requirement in modern sensors meant for target interception and detection. There are many uncertainties, which limits the detection capability and provide incorrect results in the modern era of Doppler based RF sensors. In general, any RF sensor performance is improved as the signal to noise ratio (SNR) becomes larger. It is also known that in the presence of clutter, the sensor performance may degrade beyond the impact of thermal noise alone, and in this case, the signal-to-clutter ratio (SCR) becomes more critical than the SNR. In heterodyne based RF sensor operation, another source of noise that greatly limits slow-moving target detection is phase noise. The phase noise is random in nature and is caused by instabilities within any local oscillator in the transmitter and its effects in the heterodyne receiver for target detection. Hence phase noise may limit, depending on its actual value, the RF sensor ability to detect very slow-moving targets whose RCS is relatively small. The phase noise is a random frequency perturbation (relatively small in nature) occurring around the signal carrier frequency, thus causing a new instantaneous signal frequency that is slightly different from the original value.
[0003] In cases, where a Doppler of slow-moving target echo is close to zero, it may likely be masked by the phase noise caused by a noisy local oscillator and information become ambiguous. Close to the carrier, the noise indicates slow fluctuations sometimes crystal drift in temperature or time and flicker noise of active devices. These slowly varying noise components usually can be tracked by the receiver. As we move away from the center frequency, noise components become faster and add to the additive noise that always exists in any communication. Since the overall dynamic range of RF sensor is influenced by the noise of the transmitted signal, it is not only important to know the absolute noise of the individual oscillators but to know the residual or additive noise caused by the modules in sensors like power amplifier, pulse modulator, mixers, signal processor along with the effects of time delay. The modelling exact requirements of phase noise is a quite tedious task as additional factors like time delay, receiver topology, components selection and the likes need to be considered while calculation.
[0004] An existing method includes estimating the phase noise of an RF oscillator signal in a frequency-modulated continuous-wave (FMCW) radar system and related radar devices. Another existing method generates a model of the effect of phase noise in the Doppler radar system which includes calculating, using a processing unit, an initial signal-to-clutter ratio (SCR) representing a ratio of power received from echoes from a target by the radar system to power resulting from received clutter reflection. Yet another accurate system simulation has proven to be a valuable aid during the development process and help to decrease the time-to-market and the amount of design iterations, thus keeping development costs at a moderate level.
[0005] However, a complex and sophisticated mechanism based on the cancellation methods mentioned above makes the system not feasible for applications having size constraints and does not include all the aspects of modelling which influence the phase noise requirement of the system.
[0006] Therefore, there is a need for compact, non-complex, complete modelling techniques and methods for phase noise estimation for selecting suitable architecture for RF sensor for slow-moving targets.

OBJECTS OF THE PRESENT DISCLOSURE
[0007] An object of the present disclosure relates, in general, to a radar sensor, and more specifically, relates to a method of modelling phase noise estimation for heterodyne based RF sensor for slow-moving targets.
[0008] Another object of the present disclosure is to provide a method that obtains a better detection capability by accurately estimating phase noise requirement for slow moving targets.
[0009] Another object of the present disclosure is to provide a compact sensor.
[0010] Another object of the present disclosure is to provide a method that do not required sophisticated mechanism to operate.
[0011] Another object of the present disclosure is to provide a method that is feasible for applications having size constraints.
[0012] Another object of the present disclosure is to provide a method that enhance the performance.
[0013] Another object of the present disclosure is to provide a method that provides better accuracy.
[0014] Another object of the present disclosure is to provide a method that reduces additional complex circuitry for mitigation of phase noise degradation in close vicinity of fundamental signal for processing low frequency doppler through improvement factor.
[0015] Yet another object of the present disclosure is to provide a method that is cost-effective.

SUMMARY
[0016] The present disclosure relates, in general, to a radar sensor, and more specifically, relates to a method of modelling phase noise estimation for heterodyne based RF sensor for slow-moving targets.
[0017] In an aspect, the present disclosure relates to a device for estimating phase noise for slow moving targets, the device comprising a transmitter that transmits RF signal illuminating target and surrounding clutter objects disposed in a predetermined coverage area, a receiver receives the RF signal reflected from the target and the clutter objects, a heterodyne conversion unit receives the reflected RF signal and down-converts the reflected RF signal to intermediate frequency (IF) signal, the heterodyne conversion unit receives an oscillator signal from a local oscillator, which effects the phase noise characteristics of the down-converted IF signal in processing, along with time delay effect helps in accurate modelling of device phase noise requirement, a processor operatively coupled to the heterodyne conversion unit, the processor configured to receive, from the heterodyne conversion unit, the IF signal; and process the IF signal to extract doppler information of the target effected by phase noise characteristics of the IF signal to improve detection capability of slow-moving targets.
[0018] According to an embodiment, the local oscillator is any or a combination of coherent local oscillator.
[0019] According to an embodiment, the heterodyne conversion unit coupled to the receiver to down-convert the incident reflected RF signal.
[0020] According to an embodiment, the phase noise measurement of the IF signal normalized with respect to phase noise of RF input signal using synchronous coherent mechanism.
[0021] According to an embodiment, phase noise improvement in lower doppler offsets for detection of slow-moving targets is obtained by incorporating synchronous coherence mechanism.
[0022] According to an embodiment, time delay between transmission and reception of the signals is 2Rt/c.
[0023] According to an embodiment, the effect of time delay in phase noise signal at frequency offset f0 for the reflected RF signal from the target along with presence of stationary clutter objects leads to cancellation phases with improvement factor.
[0024] In an aspect of the present disclosure relates to a method for estimating phase noise for slow moving targets, the method comprising transmitting, by a transmitter, RF signal illuminating target and surrounding clutter objects disposed in a predetermined coverage area; receiving, by a receiver, the RF signal reflections from the target and the clutter objects; receiving, by a heterodyne conversion unit, the reflected RF signal as input and down-converting the received RF input signal to intermediate frequency (IF) signal, the heterodyne conversion unit receives the oscillator signal from a local oscillator, which effects the phase noise characteristics of the down converted IF signal in processing, along with time delay effect helps in accurate modelling of device phase noise requirement; receiving, at a processor, the IF signal from the heterodyne conversion unit; and processing the IF signal to extract doppler information of the target effected by phase noise characteristics of the IF signal to improve detection capability of slow-moving targets.
[0025] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The following drawings form part of the present specification and are included to further illustrate aspects of the present disclosure. The disclosure may be better understood by reference to the drawings in combination with the detailed description of the specific embodiments presented herein.
[0027] FIG. 1A illustrates exemplary schematic view of tracking scenario with RF sensor and low speed moving targets considered for development of phase noise estimation model, in accordance with an embodiment of the present disclosure.
[0028] FIG. 1B is a graphical view illustrating measured transmitted RF signal power measurement of RF sensor on a spectrum analyser (SA), in accordance with an embodiment of the present disclosure.
[0029] FIG. 2A illustrates a schematic view of non-coherent detection and processing with the representation of time delay between transmitter and receiver along with clutter environment, in accordance with an embodiment of the present disclosure.
[0030] FIG. 2B is a graphical view illustrating the measured phase noise of reflected RF signal from desired target and undesired interferences within confined area of illumination, in accordance with an embodiment of the present disclosure.
[0031] FIGs. 2C to 2D illustrate graphical views of measured phase noise of processed IF signal using non-coherent heterodyne based detection mechanism, in accordance with an embodiment of the present disclosure.
[0032] FIG. 3A illustrates a schematic view of coherent detection and processing with representation of time delay between transmitter and receiver along with clutter environment, in accordance with an embodiment of the present disclosure.
[0033] FIG. 3B is a graphical view illustrating the effect of time delay on phase noise characteristics between transmitted and received echo in presence of clutter, in accordance with an embodiment of the present disclosure.
[0034] FIG. 3C illustrates a graphical view of the measured spectrum of processed IF signal of heterodyne based synchronous coherent detection mechanism, in accordance with an embodiment of the present disclosure.
[0035] FIGs. 3D to 3E illustrates graphical views of the measured phase noise of processed IF signal of heterodyne based synchronous coherent detection mechanism, in accordance with an embodiment of the present disclosure.
[0036] FIG. 4 is a high-level flow diagram illustrating the working of the method, in accordance with an embodiment of the present disclosure.
[0037] FIG. 5 illustrates a flow chart of method for estimating phase noise for slow moving targets, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0038] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. If the specification states a component or feature “may”, “can”, “could”, or “might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.
[0039] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0040] The present disclosure relates, in general, to a radar sensor, and more specifically, relates to a method of modelling phase noise estimation for heterodyne based RF sensors for slow-moving targets. The present disclosure relates to an improved method of modelling phase noise estimation for low-speed targets in heterodyne principle-based RF sensors. The proposed method estimates phase noise requirement for a synchronous, coherent detection and processing based RF sensor. The effects of time delay between transmitted and received RF signal from the desired target along with the presence of stationary clutter on phase noise characteristics. The method of the present disclosure enables to overcome the limitations of the prior art by obtaining better accuracy with help of enhanced phase noise using synchronous coherent LO based heterodyne conversion for slow-moving target detection. The present disclosure can be applicable to bi-static radars, monostatic radars and any combination thereof.
[0041] The present disclosure relates the aspect of phase noise effects in synchronous coherent LO heterodyne conversion for slow-moving target detection to enhance overall sensor performance. The method enables to overcome the limitations of the prior art by generating an improved model of phase noise which include the effects of time delay, detection and processing technique for slow-moving target detections. The present disclosure exhibits a technique of modelling RF sensor phase noise requirement for accurate detection of slow-moving targets.
[0042] A technical advantage of the present disclosure relates to obtaining a better detection capability by accurately estimating phase noise requirement for slow-moving targets. The description of terms and features related to the present disclosure shall be clear from the embodiments that are illustrated and described; however, the invention is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents of the embodiments are possible within the scope of the present disclosure. Additionally, the invention can include other embodiments that are within the scope of the claims but are not described in detail with respect to the following description. The present disclosure can be described in enabling detail in the following examples, which may represent more than one embodiment of the present disclosure.
[0043] FIG. 1A illustrates exemplary schematic view of tracking scenario with RF sensor and low speed moving targets considered for development of phase noise estimation model, in accordance with an embodiment of the present disclosure.
[0044] Referring to FIG. 1A, radio frequency sensor 100 (also referred to as device 100, herein) for estimating phase noise for slow-moving targets. The device 100 can include a transmitter and a receiver, the transmitter continuously radiates a RF signal, the transmitted RF signal illuminates moving target and surrounding clutter environment and is received by the receiver. The received signal (also referred to as return echo) can include desired target information mixed with undesired interference from clutters and multipath reflections. The present disclosure provides analysis with a feasible solution to address these challenges for 4D radar operation with the importance of phase noise and realistic solution for reliable detection ability and its performance repeatability.
[0045] The term “phase noise” as used herein is one of the critical and demanding parameters in modern radar for flawless operation. The present disclosure aids to build a heterodyne based system architecture for enhanced detection capability by modelling and estimating phase noise requirements in a heterodyne based coherent receiver. The total integrated phase noise, primarily contributed by the waveforms of exciters in the transmitter and local oscillators in receivers play a major role to suppress the clutter effects in the RF sensor to detect the targets. The device 100 can be employed, for example, on-board an aircraft, ship or other vehicle or vessel.
[0046] FIG. 1B is a graphical view illustrating measured transmitted RF signal power measurement of RF sensor on a spectrum analyser (SA), in accordance with an embodiment of the present disclosure. FIG. 1B indicates transmitted RF signal power measurement of RF sensor on the spectrum analyser (SA), which illuminates the desired target and undesired interferences within the confined area. The power of the transmitted RF signal is governed by operational range, sensor parameters along with operating environment.
[0047] FIG. 2A illustrates a schematic view of non-coherent detection and processing with the representation of time delay between transmitter and receiver along with clutter environment, in accordance with an embodiment of the present disclosure.
[0048] Referring to FIG. 2A, the non-coherent detection and processing approach 200 of the RF sensor 100 can include transmitter 202, receiver 204, time delay 206, heterodyne conversion unit 208, non-coherent local oscillator 210 and a processor 212. The transmitter 202 can transmit the RF signal illuminating the target 214 and surrounding clutter environment/objects 216 in a predetermined coverage area. The receiver 204 can receive the RF signal reflections from the target and the clutter objects. The time delay 206 between transmission and reception play a role in system phase noise requirements. The heterodyne conversion unit 208 is configured to receive the RF signal reflected from the target and the clutter objects as input and down-convert the RF input signal to intermediate frequency (IF) signal. The non-coherent local oscillator 210 generates an oscillator signal, which effects on phase noise characteristics of down-converted IF signal. The intermediate frequency (IF) signal is received by the processor 212 for detection and processing. The processor 212 process the IF signal to extract doppler information of the target effected by phase noise characteristics of the IF signal to improve detection capability of slow-moving targets. The digital signal processing may be performed in a digital signal processing unit, which may include, e.g., a digital signal processor (DSP) executing appropriate software instructions.
[0049] FIG. 2B is a graphical view illustrating the measured phase noise of reflected RF signal from desired target and undesired interferences within the confined area of illumination, in accordance with an embodiment of the present disclosure. The intended return signal from desired target has to compete with strong stationary clutters or undesired moving targets by a factor of R4 due to two-way transmission.
[0050] FIGs. 2C to 2D illustrate graphical views of measured phase noise of processed IF signal using non-coherent heterodyne based detection mechanism, in accordance with an embodiment of the present disclosure. As indicated in 2C to 2D, the measured phase noise of heterodyne principle based IF signal normalized with respect to RF input signal (also referred to as RF In signal) phase noise using non-coherent mechanism. Not much improvement is observed at lower offsets in IF signal. In the mechanism of non-coherent mixing, the phase noise of down-converted signal is governed by the worst phase noise characteristics among RF In and LO signal.
[0051] FIG. 3A illustrates a schematic view of coherent detection and processing with representation of time delay between transmitter and receiver along with clutter environment, in accordance with an embodiment of the present disclosure.
[0052] Referring to FIG. 3A, the coherent detection and processing approach 300 of the RF sensor 100 can include transmitter 202, receiver 204, time delay 206, heterodyne conversion unit 208, coherent local oscillator 302 and the processor 212. In the coherent detection and processing approach, the transmitter 202 can transmit the RF signal illuminating the target 214 and surrounding clutter environment/objects 216. The receiver 204 can receive the RF signal reflections from the target 214 and clutter objects 216. The time delay 206 between transmission and reception play a role in system phase noise requirements. The heterodyne conversion unit 208 configured to receive the RF signal reflected from the target and the clutter objects as input and down-convert the RF input signal to intermediate frequency (IF) signal. The intermediate frequency (IF) signal is received by the processor 212 for detection and processing. The coherent local oscillator 302 generates an oscillator signal that effect on phase noise characteristics of the down-converted IF signal in processing, along with time delay effect helps in accurate modelling of device phase noise requirement.
[0053] FIG. 3B is a graphical view illustrating the effect of time delay on phase noise characteristics between transmitted and received echo in presence of clutter, in accordance with an embodiment of the present disclosure. The effect of time delay on phase noise characteristics between the transmitted signal and received signal from the desired target along with the presence of stationary clutter is shown in FIG. 3B. The effect of time delay in phase noise component at frequency offset leads to cancellation phases with improvement factor. In practical scenarios, the target returns in form of electromagnetic wave energy reflection that is delayed in time and therefore phase change occur on reception in respect with transmitted signal and only partial cancellation of the phase noise occurs. It signifies more the range of the target, the lesser may be cancellation of phase noise. For mathematical expression, considered two phasors with equal amplitude but with phase difference Ꝋ. The relative power of this difference component is
= +
=2(1-cosꝊ)
[0054] For a target at range at specific instant of electromagnetic wave energy reflection from target, the time delay between transmitter and receiver is 2 /c (in monostatic/ bistatic) configuration. For a phase noise component at particular frequency offset for this means there is a phase change of 2 2π/c radians. Putting this as the value of theta and expression of cancellation factor is
Cancellation=10 [2-2cos(2 2π/c)]
[0055] It also indicates phase noise characteristics of the local oscillator used in both coherent/non-coherent detection techniques. It also shows the processed down-converted signal with Doppler information along with undesired clutter signal, which guide to determine the phase noise requirement of system to have higher detection probability. The term “Doppler effect” used herein relates to the apparent change in the frequency of a signal as the source of the signal moves relative to an observer.
[0056] FIG. 3C illustrates a graphical view of the measured spectrum of processed IF signal of heterodyne based synchronous coherent detection mechanism, in accordance with an embodiment of the present disclosure. The power measurement of heterodyne principle based received and processed IF signal using synchronous coherent LO mechanism is shown in FIG. 3C. IF signal is further processed for extracting target Doppler information effected by phase noise characteristics of received and processed IF signal.
[0057] FIGs. 3D to 3E illustrates graphical views of the measured phase noise of processed IF signal of heterodyne based synchronous coherent detection mechanism, in accordance with an embodiment of the present disclosure. The phase noise measurement of heterodyne principle based processed IF signal normalized with respect to phase noise of the RF input signal (also referred to as RF In signal) using synchronous coherent mechanism. Significant improvement is shown at lower offsets in IF signal (or slow moving targets) which plays vital role in defining overall system phase noise requirements for improved detection. This improvement helps in defining RF sensor phase noise requirements by using developed model as shown in FIG.4.
[0058] FIG.4 is a high-level flow diagram illustrating the working of the method, in accordance with an embodiment of the present disclosure.
[0059] Referring to FIG. 4, method 400 includes a sequence of activities, linked parameters and computational actions to form a model to estimate the phase noise requirement for coherent heterodyne based RF sensor. The model maps the effects of time delay, receiver operating topology, non-coherent LO effects, synchronous coherent LO effects and its implication in the improvement of phase noise at closer offsets to re-calculate modified phase noise requirements of RF sensor for improved detection.
[0060] The method 400 includes at block 402, enter the properties, target and operation environment parameters of the RF sensor to derive initial level phase noise requirement. At block 404, calculate the basic phase noise requirements of the RF sensor. At block 406, modify the phase noise requirement based on the time delay effect. At block 408, perform the operation of the receiver using non-coherent LO effects and synchronous coherent LO effects. At block 410, non-coherent LO effects and synchronous coherent LO effects are implied in the improvement of phase noise at closer offsets to re-calculate modified phase noise requirements of RF sensor for improved detection. The proposed method helps in defining specifications of frequency source used in RF sensors for detecting slow-moving targets.
[0061] The embodiments of the present disclosure described above provide several advantages. The device 100 obtains a better detection capability by accurately estimating phase noise requirement for slow-moving targets. The proposed method is cost-effective, feasible for applications having size constraints and do not require sophisticated mechanism to operate. The proposed device and method reduces additional complex circuitry for mitigation of phase noise degradation in close vicinity of fundamental signal for processing low frequency doppler through improvement factor.
[0062] FIG. 5 illustrates a flow chart of method for estimating phase noise for slow moving targets, in accordance with an embodiment of the present disclosure.
[0063] Referring to FIG. 5, the method 500 include at block 502, the transmitter that transmits RF signal illuminating target and surrounding clutter objects. At bock 504, the receiver receives the RF signal reflections from the target and the clutter objects. At block 506, the heterodyne conversion unit receives the reflected RF signal as input and down-converts the received RF input signal to intermediate frequency (IF) signal. The local oscillator generates RF oscillator signal, which effects the phase noise characteristics of down converted IF signal. At block 508, a processor operatively coupled to the heterodyne conversion unit, the processor configured to receive, from the heterodyne conversion unit, the IF signal and at block 510, the processor configured to process the IF signal to extract doppler information of the target effected by phase noise characteristics of the IF signal to improve detection capability of slow-moving targets.
[0064] It will be apparent to those skilled in the art that the proposed method of the disclosure may be provided using some or all of the mentioned features and components without departing from the scope of the present disclosure. While various embodiments of the present disclosure have been illustrated and described herein, it will be clear that the disclosure is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents will be apparent to those skilled in the art, without departing from the spirit and scope of the disclosure, as described in the claims.

ADVANTAGES OF THE PRESENT DISCLOSURE
[0065] The present disclosure provides a method that obtains a better detection capability by accurately estimating phase noise requirement for slow moving targets.
[0066] The present disclosure provides a compact sensor.
[0067] The present disclosure provides a method that do not required sophisticated mechanism to operate.
[0068] The present disclosure provides a method that is feasible for applications having size constraints.
[0069] The present disclosure provides a method that enhances the performance.
[0070] The present disclosure provides a method that provides better accuracy.
[0071] The present disclosure provides a method that reduces additional complex circuitry for mitigation of phase noise degradation in close vicinity of fundamental signal for processing low frequency doppler through improvement factor.
[0072] The present disclosure provides a method that is cost-effective.