Description:TECHNICAL FIELD
[0001] The present disclosure relates, in general, to the field of electronic circuits, and more specifically, relates to circuits used in high-speed frequency sensing of a radio frequency (RF) signal in single-channel applications.

BACKGROUND
[0002] Wideband RF systems are used in various applications such as wideband communication systems, radar applications, electronic warfare (EW) receivers for electronic intelligence (ELINT), electronic countermeasure (ECM) and electronic counter counter measure (ECCM) such as radar warning receivers. Frequency measurement of the incoming RF signal is required for different functionalities of such systems, such as channelization, gain equalization, power control, interference and jamming detection and the like.
[0003] Many wideband communication systems use switched filter banks, where the input RF signal after appropriate amplification needs to be routed to suitable filters for harmonic rejection. Such routing usually happens through the use of multiple single-pole N- throws (SPNT) switches which connect appropriate filters to the amplifier output for harmonic rejection. The selection of these filters is based on the frequency of operation. This frequency information is communicated by the system controller to the RF circuits through additional control signals. The control signals for SPNT are derived from this frequency information. High-speed automatic sensing of the frequency of input RF signal may help in filter/channel selections without the requirement of additional control lines. Thus, enabling easy system integration.
[0004] Furthermore, in cases of inter-connection issues or controller malfunctions, the amplified RF signal may not be routed to the correct filter. This may result in system malfunction and may lead to component failures in the system. This scenario may be avoided by integrating high-speed automatic frequency sensing circuits in switched filter banks to ensure proper routing of the amplified RF output in such events.
[0005] The measurement of frequency is a critical requirement in multiple EW systems where the incident RF radiation is characterised on the basis of extracted parameters. EW systems rely on measured frequency, pulse properties, modulation properties, the direction of arrival etc. to ascertain whether the incoming RF radiation is a threat. Based on such analysis the system may employ ECM or ECCM measures to counter the threat. Instantaneous Frequency Measurement (IFM) systems are widely used in these systems to measure frequency in near real-time. The disclosed frequency sensing circuit may be used to realize such IFM systems. The wideband RF systems require the use of multiple filters and multiple RF processing chains along with intelligent control to operate over the entire band of frequencies. Such systems achieve wideband performance by implementing frequency-dependent equalizations, power control, RF chain selections, sampling rates, local oscillator (LO) selections etc. Automatic frequency sensing circuits with low latency find applications in these systems.
[0006] Broadband RF tuning circuits, as used in antenna tuning modules and tunable impedance matching networks, need frequency-based control in their operation. Such systems switch and connect appropriate passive components to create a matching network. This matching network is used to match the characteristic impedance at the first port, which may be connected to an antenna to a different characteristic impedance at the second port, which may be connected to a power amplifier in order to achieve maximum RF power transfer between the ports. Such matching networks may also be utilized for impedance transformation which achieves other goals such as maximum power output, minimum noise, maximum efficiency etc. Embedding high-speed frequency measuring circuits would automate the function of these tuning networks
[0007] An example of such a system is recited in the US patent US 10,943,461 titled 'Systems, methods, and devices for automatic signal detection based on power distribution by frequency over time' discloses a system comprising an RF receiver, a generator engine, and an analyzer engine for automatic signal detection in an RF environment. Another example is recited in the US patent US 9,729,363 titled 'Frequency discriminator' describes a frequency discriminator that splits the RF input into two paths, a through path and a filtered path, without addressing reflection uncertainties or the performance of the circuit with modulated RF waveforms. Another example is recited in the US patent US 10,348,347 titled 'Apparatus for monitoring radio frequency signals' discusses an apparatus for monitoring RF signals, utilizing a splitter to divide the signal into multiple paths, each with a track-and-hold circuit and an ADC, all controlled by an FPGA, resulting in a complex circuit with significant computational overhead.
[0008] Another example is recited in US patent US 9,130,639 titled 'Frequency Resolver' reveals a frequency resolver employing multiple oscillators, mixers, and a controller to resolve the least significant bit (LSB) or the most significant bit (USB) of an incoming RF transmission, incorporating complicated circuitry with an increased number of circuit elements. Another example is recited inthe US patent US 8,116,709 titled 'Frequency measuring broadband digital receiver,' a frequency measuring microwave receiver is disclosed, employing multiple digital stages to sample the RF inputs and produce N ambiguous results. These results, along with one-bit DFTs, are analyzed in an ambiguity resolving device to determine the final frequency result. Yet another example is recited in the US patent US 8,280,328 titled 'High speed frequency detector' describes a frequency measuring device equipped with multiple filter banks and associated detectors to ascertain the frequency of the RF input signal.
[0009] Further, FIG. 1 shows the implementation of an existing frequency detector circuit. The frequency detector circuit discloses a circuit 100 consisting of a buffer amplifier 104, a coarse band selection band pass filter 106, a local oscillator 108, a mixer 110, a filter bank (112-1 to 112-4) and associated RF power detectors(114-1 to 114-4). The incident RF signal 102 is provided gain and filtered using the buffer amplifier and the bandpass filter. The local oscillator frequency is selected such that the down converted output falls within the passband of one of the filters (112-1 to 112-4). Each filter is associated with a peak RF power detector, which provides a voltage output whenever RF is present at the output of the associated filter. Using multiple filter banks and multiple local oscillators and mixers, the prior art is able to provide wide-band high-speed RF detection. However, the use of calibrated local oscillators and filter banks makes the implementation costly and bulky. Furthermore, the resolution offered by the existing disclosure is poor.
[0010] Therefore, it is desired to overcome the drawbacks, shortcomings, and limitations associated with existing solutions, and develop a means for a high-speed frequency sensing circuit having low complexity.

OBJECTS OF THE PRESENT DISCLOSURE
[0011] An object of the present disclosure provides fast frequency measurement of the input RF signal with low latency, enabling near real-time analysis and control functions.
[0012] Another object of the present disclosure provides a circuit that is relatively simple, which reduces manufacturing costs and increases overall efficiency.
[0013] Another object of the present disclosure provides a circuit utilized for control function integration improving overall signal quality.
[0014] Another object of the present disclosure provides a circuit that can be used in different systems, including electronic warfare (EW) systems, where incident RF radiation is characterized based on extracted parameters. This enables the realization of Instantaneous Frequency Measurement (IFM) systems.
[0015] Another object of the present disclosure provides a circuit that includes a reflection less equalizer that minimizes measurement uncertainties caused by reflections from the equalizer in a 50-ohm chain. This ensures accurate and reliable frequency measurement.
[0016] Another object of the present disclosure provides a circuit that can handle various types of RF signals, including continuous wave (CW) signals and modulated waveforms, making it versatile in its applications.
[0017] Yet another object of the present disclosure provides a circuit that incorporates dual-channel RMS RF power detector with two power detectors having identical electrical characteristics. This enables accurate power measurement and enhances the overall performance of the circuit.
SUMMARY
[0018] The present disclosure relates in general, to the field of electronic circuits, and more specifically, relates to circuits used in high-speed frequency sensing of a radio frequency (RF) signal in single-channel applications. The main objective of the present disclosure is to overcome the drawback, limitations, and shortcomings of the existing system and solution, by providing a low-latency circuit for measuring the frequency of radio frequency signals in single carrier applications designed to meet system requirements of different applications. The disclosed circuit includes a wide band splitter, a wideband equalizer with optimal frequency response, dual-channel root mean-square (RMS) responding RF power detector and a differential amplifier circuit. The generated output results in the determination of the frequency of the RF signal after necessary post-processing in analog and digital domain. This frequency information may be further used for channelizations and filter selections as is common in wideband RF systems. The circuit thus circumvents the requirement of accurate time bases.
[0019] The wideband splitter splits the input RF signal into two RF signals with equal amplitudes and phase delays, wherein the two such split RF signals are routed to two different paths. The input RF signal comprises one single channel FM signal, AM signal, frequency shift keying (FSK) signal, phase shift keying (PSK) signal, quadrature amplitude modulated (QAM) signal or any such single carrier analog or digitally modulated signal.
[0020] The wideband passive equalizer with optimal frequency response provides controlled attenuation with low reflections to the input RF signal, wherein the attenuation provided is a function of the frequency of the input radio frequency signal. The wideband equalizer has a low coefficient of reflection to minimize mismatch errors. The equalizer is designed to have an optimally shaped frequency response which is selected from linear positive sloped, linear negative sloped, or some other optimal shapes for providing controlled attenuation as per the frequency of the input RF signal.
[0021] The dual-channel root-mean-square (RMS) responding wideband RF power detector has two individual electrically identical RMS RF power detectors, wherein each individual RMS RF power detector provides a first analog output voltage signal and a second analog output voltage signal which is proportional to the RMS power of the input RF signal and differential amplifier 208 for amplifying the difference between the first analog output voltage signal and the second analog output voltage signal with a pre-determined gain. The dual-channel root-mean-square responding wideband RF detector provides an RF power measurement of the input signal which does not vary with input signal modulation.
[0022] The wideband splitter splits the input RF signal into two parts with equal power, with the first split RF signal being input to a first channel of the power detector generating a first analog output voltage signal. The second split RF signal is input to the wideband equalizer, attenuating the second split RF signal as per the frequency of the signal, wherein the output of the wideband equalizer is fed to the second channel of the power detector generating a second analog output voltage. The differential amplifier computes the difference between the first analog output voltage signal and the second analog output voltage signal, generating a third analog output voltage signal which is further processed, in analog or digital domain along with window comparators or look-up tables (LUT), to calculate the frequency of the input RF signal. The wideband splitter, the wideband passive equalizer, the dual-channel root-mean-square (RMS) responding wideband RF power detector, and the differential amplifier realized on an RF integrated chip (RFIC).
[0023] 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
[0024] 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.
[0025] FIG. 1 shows the implementation of an existing frequency detector circuit.
[0026] FIG. 2 illustrates an exemplary block diagram of the low-complexity circuit, in accordance with an embodiment of the present disclosure.
[0027] FIG. 3 illustrates the dual-channel root-mean-square (RMS) responding power detector, in accordance with an embodiment of the present disclosure.
[0028] FIG. 4 illustrates RF mismatch errors and measurement uncertainties in a typical RF measurement system, in accordance with an embodiment of the present disclosure.
[0029] FIG. 5 illustrates an exemplary performance of any filter, not particularly as implemented in an embodiment of present disclosure.
[0030] FIG. 6 illustrates an exemplary frequency response of an equalizer, in accordance with an embodiment of the present disclosure.
[0031] FIG.7 illustrates the block diagram of the low-complexity circuit, in accordance with an embodiment of the present disclosure.
[0032] FIG. 8 illustrates the disclosed circuits use in switched filter bank, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0033] 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.
[0034] 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.
[0035] The present disclosure relates, in general, to the field of electronic circuits, and more specifically, relates to circuits used in high-speed frequency sensing of a Radio Frequency (RF) signal in single channel applications. The disclosed frequency sensing circuit provides frequency measurement of the input RF signal with low latency. The frequency measurement may be used for different control functions. In an aspect, the measurement result selects appropriate filters to be connected to amplifier output for the purpose of harmonic rejection. Such control may be realized through the use of single pole N- throws (SPNT) switches at input and output, where the path selection signals are derived from the frequency measurement.
[0036] In another aspect, the circuit is used in EW systems where the incident RF radiation is characterised on the basis of extracted parameters. Instantaneous Frequency Measurement (IFM) systems are widely used in these systems to measure frequency in near real-time. The disclosed frequency sensing circuit may be used to realize such IFM systems. The circuit can include wideband splitter, an equalizer with a shaped frequency response, the dual-channel RMS RF power detector having two power detectors with identical electrical characteristics, and the differential amplifier. The equalizer is a reflection less equalizer which minimizes measurement uncertainties caused by reflection from the equalizer in a 50 ohm chain. The input RF signal can be CW or modulated waveform. The present disclosure can be described in enabling detail in the following examples, which may represent more than one embodiment of the present disclosure.
[0037] The advantages achieved by the frequency sensing circuit of the present disclosure can be clear from the embodiments provided herein. The frequency sensing circuit offers the advantages of high-speed frequency measurement, low complexity, control function integration, wide applicability, accurate measurement with a reflection less equalizer, compatibility with different RF signals, and enhanced performance through the dual-channel power detector.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.
[0038] FIG. 2 illustrates an exemplary block diagram of the low-complexity circuit, in accordance with an embodiment of the present disclosure.
[0039] Referring to FIG. 2, low-complexity circuit200 can include a wideband splitter 202, an equalizer 204 with a shaped transmission frequency response, a dual-channel power detector with two electrically identical channels, where the two electrically identical channels can include first channel206-1 and second channel206-2 and a differential amplifier 208. One or more components may be realized on an RF integrated chip (RFIC) for space and cost savings.
[0040] The wideband splitter 202 splits the input RF signal into two RF signals with equal amplitudes and phase delays, wherein the two such split RF signals being routed to two different paths. The input RF signal comprises one single channel FM signal, AM signal, frequency shift keying (FSK) signal, phase shift keying (PSK) signal, quadrature amplitude modulated (QAM) signal or any such single carrier analog or digitally modulated signal.
[0041] The wideband passive equalizer 204 with optimal frequency response provides controlled attenuation with low reflections to the input RF signal, wherein the attenuation provided is a function of the frequency of input radio frequency signal. The wideband equalizer 204 has a low coefficient of reflection to minimize mismatch errors. The equalizer 204 is designed to have an optimally shaped frequency response which is selected from linear positive sloped, linear negative sloped, parabolic and inverse parabolic for providing controlled attenuation as per the frequency of the input RF signal.
[0042] The dual-channel root-mean-square (RMS) responding wideband RF power detector having two individual electrically identical RMS RF power detectors(206-1, 206-2), wherein each individual RMS RF power detector provides a first analog output voltage signal and a second analog output voltage signal which is proportional to the RMS power of the input RF signal and differential amplifier 208 for amplifying the difference between the first analog output voltage signal and the second analog output voltage signal with a pre-determined gain. The dual-channel root-mean-square responding wideband RF detector provides a RF power measurement of the input signal which does not vary with input signal modulation.
[0043] The wideband splitter 202 splits the input RF signal into two parts with equal power, with the first split RF signal being input to a first channel of the power detector generating the first analog output voltage signal. The second split RF signal is input to the wideband equalizer 204, attenuating the second split RF signal as per the frequency of the signal, wherein the output of the wideband equalizer 204 is fed to the second channel of the power detector generating the second analog output voltage. The differential amplifier 208 computes the difference between the first analog output voltage signal and the second analog output voltage signal, generating a third analog output voltage signal which is further processed, in analog or digital domain along with window comparators or look-up tables (LUT), to calculate the frequency of the input RF signal. The wideband splitter, the wideband passive equalizer, dual-channel root-mean-square (RMS) responding wideband RF power detector, and differential amplifier realized on an RF integrated chip (RFIC).
[0044] The present invention discloses the low-latency frequency sensing circuit for high-speed measurement of the frequency of RF signals. The circuit is aimed at single-channel applications and may be used in wide band systems. Frequency sensing is critical to systems relying on frequency data for their operation. One such system includes wideband RF systems such as EW receivers. EW receivers are used to characterize incident RF radiation to identify and track signals of interest. Such signals may include RF emissions from radars, jammers, broadcasting stations, civilian and tactical communication systems. The RF emissions from the sources of interest may be pulsed, CW, periodic, intermittent, modulated, fixed frequency or swept over frequency. EW systems extract measured frequency, pulse properties, modulation properties, the direction of arrival etc. of these emissions and classify them accordingly. Based on the EW system’s output, the user then decides whether to monitor, track, employ electronic countermeasures or electronic counter countermeasures or record for reconnaissance purposes. Due to the wide band width of analysis and the pulsed nature of emissions, a high-speed frequency sensing technique is required. Such measurements provide essential intelligence about the nature of emissions.
[0045] One of the embodiments of the present disclosure pertains to wideband RF systems. Such systems contain multiple RF filters and RF processing chains to cover the wide frequency bandwidths of operations ranging from 1GHz to 40GHz. In order to achieve functional specifications over these wide bandwidths, wideband RF systems perform frequency-dependent power control, gain equalization, sampling rate changes, local oscillator frequency tuning, filter selection and other configuration changes. This frequency-dependent control is enabled by frequency sensing circuits which generate suitable control signals based on the frequency of the input RF signal.
[0046] In the present disclosure, circuit 200comprises the wideband splitter202, the equalizer204with shaped transmission response, the dual-channel root-mean-square (RMS) responding RF power detector (206-1, 206-2), and the differential amplifier208. An RF signal is input to the disclosed circuit 200which is necessarily a single carrier excitation within a wide frequency bandwidth. The input RF signal may be pulsed or continuous waves. It may contain message signals which have been encoded through analog or digital modulations such as single channel FM signal, AM signal, frequency shift keying (FSK) signal, phase shift keying (PSK) signal, quadrature amplitude modulated (QAM) signal or any such single carrier modulated signal.
[0047] The input RF signal is split into two parts by the wideband splitter202. The two parts are equal in amplitude and phase. The first split RF signal is made available at a first port and the second split RF signal is made available at a second port. The circuit of the present disclosure includes the dual channel wideband RMS responding RF power detectors (206-1, 206-2) which have two individual RMS RF power detectors. The two individual RMS power detectors are identical in electrical characteristics. The first RF input signal at the first channel of the power detector 206-1 leads to a first analog output voltage signal at the first output of the power detector and a second RF input signal at the second channel of the power detector 206-2 leads to a second analog output voltage signal at the second output of the power detector.
[0048] Peak and Schottky diode-based detectors without post-processing are not able to provide correct power measurements for modulations with amplitude variations. The variable envelope due to the use of advanced modulations results in variations in the power detector output voltage. Therefore, for the same average power level of the input RF signal, the analog output voltage from the detector keeps on varying. This makes accurate power measurements difficult. To solve this problem, the root-mean-square responding power detector extracts the power of the input RF signal irrespective of the modulation in the RF signal.
[0049] The first split RF signal, as mentioned above, is input to the first channel 206-1of the power detector, resulting in the first analog output voltage signal at the first output of the power detector, where the analog output voltage signal is dependent on the RMS power of the first split RF signal. The second split RF signal, as obtained from the wideband splitter202, is fed to the wideband equalizer, which attenuates the second split RF signal as per the signal’s frequency and results in a third output RF signal. The third output RF signal is input to the second channel206-2 of the power detector resulting in the second analog output voltage signal at the second output of the power detector.
[0050] The present disclosure contains the wideband equalizer 204, which has been designed to have an optimally shaped frequency response which may be linear, parabolic, inverse parabolic, ramp, saw tooth and the likes for providing controlled attenuation as per the frequency of the input RF signal. Equalizers are designed to provide the transmission coefficient which varies with frequency. Such controlled variation in transmission coefficient is designed to complement the variation of other components in the RF chain thus resulting in a flat gain profile in the frequency domain.
[0051] In the present disclosure, the equalizer 204 is used to impart frequency-dependent attenuation to the input RF signal. As thus the frequency of the input signal gets converted into amplitude information. This enables a power domain measurement resulting in the extraction of frequency information. The equalizers 204 have low reflection coefficients over their design bands. This facilitates easy cascading of equalizers with other systems while ensuring low mismatch errors. In an RF chain comprising multiple RF devices, mismatch loss and mismatch uncertainty play an important role. Multiple impedance interfaces are created in an RF chain. At each interface, the RF signal may be reflected with the magnitude of reflection being dependent on the impedances at the interface. The reflection coefficient is a measure of the amount of RF power reflected at the interface formed by the device. Lower reflection coefficients result in less reflection. In a chain, reflected RF energy affects forward transmission, coupling, isolation and gain parameters. The presence of such interfaces leads to mismatch-related uncertainties. These need to be accounted for in any measurement of RF parameters.
[0052] The circuit herein disclosed contains the differential amplifier208. The differential amplifier 208computes the difference between the first analog output voltage signal and the second analog output voltage signal, while also providing an optimal gain to the difference thus computed, to generate the third analog output voltage signal. The third analog output voltage signal is dependent on the frequency of the input RF signal and may be further processed in analog or digital domain along with window comparators or look-up tables (LUT) to calculate the frequency of the input RF signal. Further, the components of the disclosure may be realized as discrete devices or may be integrated into an RF integrated chip (RFIC).
[0053] FIG. 3 illustrates the dual-channel root-mean-square (RMS) responding power detector, in accordance with an embodiment of the present disclosure. FIG. 3 depicts the dual-channel RMS responding RF power detector with the first channel 206-1 and second channel 206-2. Each channel can include an input buffer amplifier, a square law detector followed by a configurable low pass filter. The output of the filter is again buffered using a voltage amplifier to provide a linear–in - dB output voltage 302 as shown.
[0054] FIG. 4 illustrates RF mismatch errors and measurement uncertainties in a typical RF measurement system, in accordance with an embodiment of the present disclosure. In any RF system, multiple RF components are connected in series to achieve system design goals. Such a series connection constructs an RF chain, where individual component properties affect the performance of other components in the chain. One aspect of this coupling between components is the measurement uncertainty due to port mismatches. Each component may have a different port mismatch compared to the system characteristic impedance of 50 ohms. This mismatch leads to reflections in between components as shown in the figure. This in turn affects the transmission coefficients and isolation between components leading to increased measurement uncertainties. The problem of port mismatch reduces with the decrease in the reflection coefficient. The measurement uncertainties may increase when the constituting components do not have a low reflection coefficient.
[0055] FIG. 5 illustrates an exemplary frequency response of a filter, in accordance with an embodiment of the present disclosure. FIG. 5 shows the variation of reflection coefficient 504 and transmission coefficient 502 for a typical low-pass filter. It is evident that beyond cut off frequency the transmission coefficient varies linearly with frequency. However, the reflection coefficient degrades rapidly as the frequency of operation increases beyond the cut off. In such cases, the filter may introduce measurement errors and uncertainties which would need to be removed by the proper calibration process.
[0056] FIG. 6 illustrates an exemplary frequency response of an equalizer, in accordance with an embodiment of the present disclosure. FIG. 6shows the variation of the reflection coefficient and transmission coefficient for one of the possible equalizer configurations. From the figure the transmission coefficient 602 of the equalizer varies in early with frequency while the reflection coefficient 604 is lower than -10dB.
[0057] FIG.7 illustrates the block diagram of the low-complexity circuit, in accordance with an embodiment of the present disclosure. The input RF signal 700 is split by the wide-band splitter 202 into two RF paths (702-1, 702-2). The two split RF signals are equal in amplitude and phase. The first split RF signal 702-1 is input to the first channel206-1 of the dual-channel RMS power detector. The first channel power detector 206-1 generates the first analog output voltage 704-1 which is proportional to the RMS power of the first split RF signal. This analog output voltage serves as the reference for the subsequent comparison function. The second split RF signal 702-2 is input to the wideband equalizer 204. The wideband passive equalizer is realized through lumped components such as resistor, inductor and capacitor. The equalizer 204 is having an optimally designed frequency domain transmission profile. This profile provides a frequency-dependent attenuation to the input RF signal. Therefore, the power of the second split RF signal 702-2 gets reduced as per the frequency of input resulting in the third output RF signal 706. The second channel of the RMS power detector 206-2 receives the third output RF signal 706 to generate the second analog output voltage 704-2 proportional to the power of third output RF signal 706. The differential amplifier 208 computes the difference between the first analog output voltage704-1 and the second analog output voltage 704-2. The difference is provided with an optimal gain to increase the sensitivity of the circuit. The third analog output voltage signal 708 at the output of the differential amplifier 208 is dependent on the frequency of the input RF signal and may be further processed in analog or digital domain along with window comparators or look-up tables (LUT) to calculate the frequency of the input RF signal.
[0058] FIG. 8 illustrates the disclosed circuits used in switched filter banks, as one of the embodiments of present disclosure. The filter bank is used for suppressing the harmonics emanating from the amplifier output.
[0059] The present disclosure targets wideband communication systems using switched filter banks, where the input RF signal after appropriate amplification needs to be routed to suitable filters for harmonic rejection. Such routing usually happens through the use of multiple single-pole N- throws (SPNT) switches which connect appropriate filters to the amplifier output for harmonic rejection. The selection of these filters is based on the frequency of operation. This frequency information is communicated by the system controller to the RF circuits through additional control signals. The control signals for SPNT are derived from this frequency information. High-speed automatic sensing of the frequency of input RF signal may help in filter/channel selections without the requirement of additional control lines. Thus, enabling easy system integration.
[0060] Furthermore, in cases of inter-connection issues or controller malfunctions, the amplified RF signal may not be routed to the correct filter. This may result in system malfunction and may lead to component failures in the system. This scenario may be avoided by integrating high-speed automatic frequency sensing circuits 200 in switched filter banks to ensure proper routing of the amplified RF output in such events.
[0061] Thus, the present invention overcomes the drawbacks, shortcomings, and limitations associated with existing solutions, and provides the frequency sensing circuit that offers the advantages of high-speed frequency measurement, low complexity, control function integration, wide applicability, accurate measurement with a reflection less equalizer, compatibility with different RF signals, and enhanced performance through a dual-channel power detector.
[0062] It will be apparent to those skilled in the art that the frequency sensing circuit 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 INVENTION
[0063] The present invention provides a circuit that provides fast frequency measurement of the input RF signal with low latency, enabling near real-time analysis and control functions.
[0064] The present invention provides a relatively simple circuit, which reduces manufacturing costs and increases overall efficiency.
[0065] The present invention provides a circuit utilized for control function integration improving overall signal quality.
[0066] The present invention provides a circuit that can be used in different systems, including electronic warfare (EW) systems, where incident RF radiation is characterized based on extracted parameters. This enables the realization of Instantaneous Frequency Measurement (IFM) systems.
[0067] The present invention provides a circuit that includes a reflection less equalizer that minimizes measurement uncertainties caused by reflections from the equalizer in a 50-ohm chain. This ensures accurate and reliable frequency measurement.
[0068] The present invention provides a circuit that can handle various types of RF signals, including continuous wave (CW) signals and modulated waveforms, making it versatile in its applications.
[0069] The present invention provides a circuit that incorporates dual-channel RMS RF power detector with two power detectors having identical electrical characteristics. This enables accurate power measurement and enhances the overall performance of the circuit.
, Claims:
1. A circuit (200) for sensing the frequency of an input radio frequency (RF) signal in wideband single channel applications, the circuit comprising:
a wideband splitter (202) splits an input RF signal into two RF signals with equal amplitudes and phase delays, wherein the two such split RF signals are routed to two different paths;
a wideband passive equalizer (204) with optimal frequency response which provides controlled attenuation with low reflections to the input RF signal, wherein the attenuation provided is a function of the frequency of input radio frequency signal;
a dual-channel root-mean-square (RMS) responding wideband RF power detector having two individual electrically identical RMS RF power detectors (206-1, 206-2), wherein each individual RMS RF power detector provides a first analog output voltage signal and a second analog output voltage signal which is proportional to the RMS power of the input RF signal; and
a differential amplifier (208) for amplifying the difference between the first analog output voltage signal and the second analog output voltage signal with a pre-determined gain.
2. The circuit as claimed in claim 1, wherein the wideband equalizer (204) has a low coefficient of reflection to minimize mismatch errors.
3. The circuit as claimed in claim 1, wherein the dual-channel root-mean-square responding wideband RF detector that provides an RF power measurement of the input signal which does not vary with input signal modulation.
4. The circuit as claimed in claim 1, wherein the input RF signal comprises one single channel frequency modulation (FM)signal, amplitude modulation (AM) signal, frequency shift keying (FSK) signal, phase shift keying (PSK) signal, quadrature amplitude modulated (QAM) signal or any such single carrier analog or digitally modulated signal.
5. The circuit as claimed in claim 1, wherein the wideband splitter (202) splits the input RF signal into two parts with equal power, with the first split RF signal being input to a first channel of the power detector (206-1) generating the first analog output voltage signal.
6. The circuit as claimed in claim 1, wherein the second split RF signal is input to the wideband equalizer, attenuating the second split RF signal as per the frequency of the signal, wherein the output of the wideband equalizer is fed to the second channel of the power detector (206-2) generating the second analog output voltage.
7. The circuit as claimed in claim 1, wherein the differential amplifier (208) computes the difference between the first analog output voltage signal and the second analog output voltage signal, generating a third analog output voltage signal which is further processed, in analog or digital domain along with window comparators or look-up tables (LUT), to calculate the frequency of the input RF signal.
8. The circuit as claimed in claim 1, wherein the equalizer (204) is designed to have an optimally shaped frequency response which is selected from linear positive sloped, linear negative sloped, parabolic and inverse parabolic for providing controlled attenuation as per the frequency of the input RF signal.
9. The circuit as claimed in claim 1, wherein the wideband splitter, the wideband passive equalizer, dual-channel root-mean-square (RMS) responding wideband RF power detector, and differential amplifier, with the flexibility to be realized on or excluded from an RF integrated chip (RFIC).