Radio frequency link and probe device for passive wireless probe device

Abstract

This invention relates to a radio frequency (RF) link and detection device for passive wireless detection equipment, belonging to the field of wireless detection technology. The RF link includes: a tracking local oscillator link, comprising: an instantaneous frequency measurement receiver and a fast frequency hopping synthesizer connected to it; the instantaneous frequency measurement receiver is used to evaluate the frequency of the incoming signal and determine the instantaneous estimated frequency; the fast frequency hopping synthesizer is used to determine the local oscillator frequency based on the instantaneous estimated frequency and perform local oscillator frequency hopping to generate the local oscillator signal; a receiving link is used to mix the incoming signal and the local oscillator signal, down-converting it to an intermediate frequency (IF) signal; and a processing unit connected to the receiving link is used to sample and process the IF signal to track agile wireless detection equipment. Through the above method, the frequency hopping of agile signals can be effectively addressed, avoiding problems such as IF signal distortion, clutter interference, and signal filtering caused by frequency mismatch in traditional ordinary local oscillators.

Description

Technical Field

[0001] This invention relates to the field of wireless detection technology, and in particular to a radio frequency link and detection device for passive wireless detection equipment. Background Technology

[0002] Passive wireless detection devices are a type of electronic equipment that does not actively emit electromagnetic signals but receives radio frequency signals radiated by targets (such as radar and communication equipment) to detect, identify, and track them. Their core principle is to receive and process the target's radiated signals via a radio frequency link, extracting characteristic information such as frequency, pulse, and azimuth to support subsequent analysis and decision-making.

[0003] However, the research found that frequency-agile wireless detection devices, especially pulse-to-pulse frequency-agile wireless detection devices, are difficult to track using passive wireless detection devices because each pulse operates at a different frequency. Existing passive wireless detection devices cannot effectively and accurately track frequency-agile wireless detection devices. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides a radio frequency link and a detection device for passive wireless detection devices.

[0005] In a first aspect, this application provides a radio frequency link for a passive wireless detection device, comprising: a tracking local oscillator link, including: an instantaneous frequency measurement receiver and a fast frequency hopping synthesizer connected to it; the instantaneous frequency measurement receiver is used to evaluate the frequency of the incoming signal and determine an instantaneous estimated frequency; the fast frequency hopping synthesizer is used to determine the local oscillator frequency based on the instantaneous estimated frequency and perform local oscillator frequency hopping to generate a local oscillator signal; a receiving link is used to mix the incoming signal and the local oscillator signal and down-convert it to an intermediate frequency signal; a processing unit is connected to the receiving link and is used to sample and process the intermediate frequency signal to track the agile wireless detection device.

[0006] Optionally, the instantaneous frequency measurement receiver includes: a channelization filter circuit, a power divider delay circuit, a phase detector circuit, and an FPGA circuit connected in sequence; wherein, the channelization filter circuit is used to perform coarse frequency localization on the incoming signal to determine a first frequency; the power divider delay circuit is used to perform signal power division, one path of which is directly connected to the phase detector circuit, and the other path introduces a time delay; the phase detector circuit is used to combine the two signals to obtain the phase difference, thereby refining the frequency and generating a second frequency; the FPGA circuit is used to calculate the instantaneous estimated frequency based on the first frequency and the second frequency.

[0007] Optionally, the instantaneous frequency measurement receiver further includes: a limiter, a limiting amplifier circuit, and a detector circuit connected in sequence; the detector circuit is also connected to the channelization filter circuit; the incoming signal passes through the limiter, the limiting amplifier circuit, and the detector circuit in sequence; the limiter is used to limit the amplitude of the incoming signal to a controllable window; the limiting amplifier circuit is used to perform amplitude fixing processing on the incoming signal; and the detector circuit is used to perform pulse detection and threshold control.

[0008] Optionally, the instantaneous frequency measurement receiver further includes: a frequency conversion circuit; the frequency conversion circuit is disposed between the detection circuit and the channelization filter circuit; the frequency conversion circuit is used to shift the incoming wave signal to an intermediate frequency.

[0009] Optionally, the formula for calculating the instantaneous estimated frequency is:

[0010] ;

[0011] in, This represents the instantaneous estimated frequency. Indicates the first frequency. Indicates the second frequency. , Indicates phase difference, Indicates time delay. Represents the residual.

[0012] Optionally, the total delay of the tracking local oscillator link satisfies the following relationship:

[0013] ;

[0014] in, Indicates the total delay; Indicates multiples, The value ranges from 0.1 to 0.3.

[0015] Optionally, the formula for calculating the total delay is:

[0016] ;

[0017] in, Indicates the arrival detection time. Indicates the instantaneous frequency measurement processing time. Indicates the control transmission and command processing time. This indicates the switching time of the fast frequency hopping synthesizer. This indicates the local oscillator locking and phase settling time. This indicates the latency of the chain group.

[0018] Optionally, the receiving link includes: a limiter, a digitally controlled attenuator, a low-noise amplifier, a mixer, a low-pass filter, and an intermediate frequency amplifier connected in sequence; the incoming signal passes sequentially through the limiter, the digitally controlled attenuator, the low-noise amplifier, the mixer, the low-pass filter, and the intermediate frequency amplifier; the limiter is used to limit the amplitude of the incoming signal to a controllable window; the digitally controlled attenuator is used to adjust the channel gain according to the strength of the incoming signal; the low-noise amplifier is used to amplify the incoming signal; the mixer is used to mix the incoming signal with the local oscillator signal and down-convert it to an intermediate frequency signal; the low-pass filter is used to filter out high-frequency components and local oscillator leakage after mixing; and the intermediate frequency amplifier is used to amplify the power and shape the amplitude of the intermediate frequency signal.

[0019] Optionally, the low-pass filter further defines an equivalent noise bandwidth, and the sensitivity is controlled based on the equivalent noise bandwidth. The formula for calculating the sensitivity is:

[0020] ;

[0021] in, -174 indicates sensitivity; -174 indicates thermal noise power reference. This represents the equivalent noise bandwidth. Represents the noise figure. This represents the minimum signal-to-noise ratio required for demodulation.

[0022] In a second aspect, this application provides a passive wireless detection device, including a radio frequency link for a passive wireless detection device as described in any of the first aspects above.

[0023] The beneficial effects of this invention include: the tracking local oscillator link provided in this application has an instantaneous frequency measurement receiver and a fast frequency hopping synthesizer. The instantaneous frequency measurement receiver can perform frequency evaluation based on the incoming signal to determine the instantaneous estimated frequency. Then, the fast frequency hopping synthesizer performs local oscillator frequency hopping based on the instantaneous estimated frequency, enabling the receiving link to stably output the intermediate frequency (IF) signal. Through this method, the frequency hopping of agile signals can be effectively addressed, avoiding problems such as IF signal distortion, noise interference, and signal filtering caused by frequency mismatch in traditional ordinary local oscillators.

[0024] In other words, research has found that traditional local oscillators cannot dynamically adapt to agile signals and can only process fixed / slowly varying frequency signals. When faced with agile wireless detection devices, they cannot be tracked due to signal reception failure. Therefore, this application achieves rapid and dynamic matching between the incoming wave frequency and the local oscillator frequency by tracking the local oscillator link. Combined with the mixing and processing unit of the receiving link for sampling and processing the intermediate frequency signal, this achieves the core objective of tracking agile wireless detection devices. This expands the passive wireless detection device from only being able to process fixed frequency signals to being able to track agile frequency signals, adapting to the detection needs of targets such as agile radar and agile communication equipment, and improving the applicability and practical value of the device. Attached Figure Description

[0025] Figure 1 This is a block diagram of a radio frequency link provided in an embodiment of the present invention;

[0026] Figure 2 This is a block diagram of a first instantaneous frequency measurement receiver provided in an embodiment of the present invention;

[0027] Figure 3 This is a block diagram of a second instantaneous frequency measurement receiver provided in an embodiment of the present invention;

[0028] Figure 4 This is a block diagram of a receiving link provided in an embodiment of the present invention. Detailed Implementation

[0029] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application can also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0030] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0031] Currently, research has revealed that frequency-agile wireless detection devices, especially pulse-to-pulse frequency-agile wireless detection devices, present certain challenges when tracked by passive wireless detection devices because each pulse operates at a different frequency. Existing passive wireless detection devices are unable to effectively and accurately track frequency-agile wireless detection devices.

[0032] In view of the above problems, this application proposes the following embodiments to solve the above technical problems.

[0033] Please see Figure 1This application provides a radio frequency link 1 for a passive wireless detection device, which includes a tracking local oscillator link 10, a receiving link 20, and a processing unit 30.

[0034] The tracking local oscillator link 10 includes a connected instantaneous frequency measurement receiver 11 and a fast frequency hopping synthesizer 12.

[0035] Functionally, the instantaneous frequency measurement receiver 11 is used to evaluate the frequency of the incoming wave signal and determine the instantaneous estimated frequency.

[0036] The fast frequency hopping synthesizer 12 is used to determine the local oscillator frequency based on the instantaneously estimated frequency, and to perform local oscillator frequency hopping to generate the local oscillator signal.

[0037] It should be noted that the fast frequency hopping synthesizer 12 uses a high-speed frequency hopping source as the local oscillator, which can complete the local oscillator frequency hopping in a very short time. The instantaneous frequency measurement receiver 11 uses the measured and evaluated instantaneous estimated frequency as the basis for controlling the fast frequency hopping synthesizer 12, thereby enabling the tracking local oscillator link 10 to complete frequency estimation and local oscillator hopping in a very short time.

[0038] The receiving link 20 is used to mix the incoming wave signal with the local oscillator signal and down-convert it to an intermediate frequency signal.

[0039] The processing unit 30, connected to the receiving link 20, is used to sample and process the intermediate frequency signal in order to track the agile wireless detection device.

[0040] The following is a specific example illustrating the RF link 1 for a passive wireless detection device provided in this application embodiment. Assume the incoming signal is an RF signal (9.2 GHz) from an X-band pulse-agile radar. After the incoming signal is detected by the RF link 1 provided in this application embodiment, it first enters the instantaneous frequency measurement receiver 11 for rapid frequency estimation, outputting the instantaneous estimated frequency (e.g., estimated to be 9.2 GHz). Then, it enters the fast frequency hopping synthesizer 12 for processing. For example, based on a preset intermediate frequency (IF) (500 MHz), the required local oscillator frequency (9.2 GHz - 500 MHz = 8.7 GHz) can be calculated, and the local oscillator frequency hopping can be quickly completed to stabilize and generate the local oscillator signal. Next, the incoming signal (9.2 GHz) and the local oscillator signal (8.7 GHz) can simultaneously enter the receiving link 20, where the incoming signal and the local oscillator signal are mixed and down-converted to generate an intermediate frequency signal (500 MHz). Finally, the processing unit 30 performs sampling processing on the generated intermediate frequency signal (including but not limited to analog-to-digital conversion, digital filtering, parameter extraction, and tracking algorithm processing) to achieve tracking and sensing of the radio frequency signal of a certain X-band pulse agile radar.

[0041] In summary, the radio frequency link 1 for a passive wireless detection device provided in this application has the following beneficial effects: The tracking local oscillator link 10 provided in this application has an instantaneous frequency measurement receiver 11 and a fast frequency hopping synthesizer 12. The instantaneous frequency measurement receiver 11 can perform frequency evaluation based on the incoming wave signal to determine the instantaneous estimated frequency. Then, the fast frequency hopping synthesizer 12 performs local oscillator frequency hopping based on the instantaneous estimated frequency, enabling the receiving link 20 to stably output the intermediate frequency signal. Through the above method, the frequency hopping of agile signals can be effectively dealt with, avoiding problems such as intermediate frequency signal distortion, clutter interference, and signal filtering caused by frequency mismatch in traditional ordinary local oscillators.

[0042] In other words, research has found that traditional local oscillators cannot dynamically adapt to agile signals and can only process fixed / slowly varying frequency signals. When faced with agile wireless detection devices, they will fail to track due to signal reception failure. Therefore, this application achieves rapid and dynamic matching of the incoming wave frequency and the local oscillator frequency through the tracking local oscillator link 10. Combined with the mixing and processing unit 30 of the receiving link 20 for sampling and processing the intermediate frequency signal, the core objective of tracking agile wireless detection devices is achieved. This expands the passive wireless detection device from only being able to process fixed frequency signals to being able to track agile frequency signals, adapting to the detection needs of targets such as agile radar and agile communication equipment, and improving the applicability and practical value of the device.

[0043] Please see Figure 2 Optionally, the instantaneous frequency measurement receiver 11 includes a channelization filter circuit 110, a power divider delay circuit 111, a phase detector circuit 112, and an FPGA circuit 113 connected in sequence.

[0044] Functionally, the channelization filter circuit 110 is used to perform coarse frequency localization on the incoming wave signal and determine the first frequency.

[0045] The power divider delay circuit 111 is used to divide the signal power, one path of which is directly connected to the phase detector circuit 112, and the other path introduces a time delay.

[0046] The phase detector circuit 112 is used to combine two signals to obtain the phase difference, thereby refining the frequency and generating a second frequency.

[0047] FPGA circuit 113 is used to calculate the instantaneous estimated frequency based on a first frequency and a second frequency.

[0048] Specifically, the channelization filter circuit 110 can be designed with a set of parallel narrowband filters, selectively passing through sub-bands. The distribution of output power in each sub-band provides coarse frequency localization, which can be recorded as the weighted result of hitting the center of the sub-band and adjacent bands. The sub-band bandwidth determines the upper limit of resolution and boundary degradation characteristics of the coarse measurement. That is, the channelization filter circuit 110 divides the entire operating frequency band into several continuous sub-bands through multiple parallel narrowband filters. After the incoming signal is incident, it will be captured by the sub-band filter of the corresponding frequency band. By identifying the signal in the sub-band, the approximate frequency range (i.e., the first frequency) of the incoming signal can be quickly determined.

[0049] While completing the coarse positioning, the main path enters the power divider and delay circuit 111 after power division (one path is direct, and the other path introduces a strictly controlled time delay). That is, the channelized filtered signal is processed by power division and delay, and two signals are output to the phase detector circuit 112.

[0050] It should be noted that the power divider splits the signal after coarse frequency localization into two signals with the same amplitude and phase; the delay introduces a fixed and controllable time delay into one of the signals (the amount of delay is matched with the signal frequency and fine measurement accuracy). The core purpose of this design is to provide the phase detector circuit 112 with two co-originating signals with a phase difference. Due to the time difference between the two signals, a fixed phase difference will be generated at the same frequency.

[0051] The two paths are combined in the phase detector circuit 112 to obtain the phase difference. Under the single-frequency narrowband approximation, the frequency is refined to generate a second frequency, which can be understood as the fine-measured frequency.

[0052] It should be noted that the phase detection circuit 112 can capture the phase difference between two signals through the phase detection unit. Based on the frequency-phase relationship of the electromagnetic signals, it can then calculate the fine frequency offset of the signal, i.e., the second frequency, in reverse using the known time delay and the detected phase difference.

[0053] Finally, all channel data enters the FPGA circuit 113, which can perform pulse gating, subband energy normalization and coarse-fine fusion (such as using the subband center as the base point, adding phase detection refinement and amplitude / phase / group delay compensation of the calibration LUT) to obtain the instantaneous frequency estimate.

[0054] Here, the FPGA circuit 113 can fuse the first frequency and the second frequency to obtain an instantaneous frequency estimate.

[0055] Research has shown that traditional instantaneous frequency measurement using only a single phase detection path is susceptible to periodic and amplitude-dependent errors. While the pure channelization scheme is robust, its accuracy degrades at subband boundaries and only provides coarse resolution, often requiring subsequent finer estimation and calibration. Therefore, the instantaneous frequency measurement receiver 11 in this application employs a channelization filter circuit 110, a power divider delay circuit 111, a phase detection circuit 112, and an FPGA circuit 113 connected in sequence. The parallel coarse measurement design of the channelization filter circuit 110 ensures rapid completion of coarse frequency localization (without frequency sweeping waiting). The fine frequency refinement design of the phase detection circuit 112 improves frequency accuracy based on coarse measurement. The real-time fusion processing of the FPGA circuit 113 avoids the connection delay between coarse and fine measurement, thereby achieving fast and accurate frequency measurement.

[0056] In this embodiment of the application, the formula for calculating the instantaneous estimated frequency can be expressed as:

[0057] ;

[0058] in, Indicates the instantaneous estimated frequency. This indicates the first frequency (corresponding to the sub-band center in the aforementioned description). Indicates the second frequency. , Indicates phase difference, Indicates time delay. This represents the residual; that is, the residual introduced by noise, amplitude-phase inconsistency, quantization and temperature drift, which can be minimized through power-on calibration and temperature drift tracking.

[0059] In this embodiment, the formula for calculating the local oscillator frequency by the fast frequency hopping synthesizer 12 can be expressed as:

[0060] ;

[0061] in, This represents the calculated local oscillator frequency. Indicates the instantaneous estimated frequency. This represents the desired intermediate frequency, where the sign depends on the direction of frequency conversion.

[0062] Optionally, please refer to Figure 3 The instantaneous frequency measurement receiver 11 also includes a first limiter 114, a limiting amplifier circuit 115, and a detector circuit 116 connected in sequence.

[0063] The detector circuit 116 is also connected to the channelization filter circuit 110.

[0064] In the above connection relationship, the incoming wave signal passes through the first limiter 114, the limiting amplifier circuit 115 and the detector circuit 116 in sequence.

[0065] Functionally, the first limiter 114 is used to limit the amplitude of the future wave signal to a controllable window.

[0066] The limiting amplifier circuit 115 is used to perform amplitude limiting processing on the incoming wave signal.

[0067] The detection circuit 116 is used for pulse detection and threshold control.

[0068] Specifically, in the instantaneous frequency measurement branch, the incoming wave first enters the first limiter 114, whose task is to compress the input amplitude into a controllable window, reduce the impact of amplitude fluctuations on the subsequent phase and power decisions, and protect the subsequent devices from breakdown in the event of strong pulses or strong nearby interference. Then, it undergoes amplitude fixing processing through the limiting amplifier circuit 115, making the subsequent phase comparison and channel power estimation as independent of amplitude as possible.

[0069] It should be noted that the first limiter 114 can only suppress over-amplitude signals and cannot completely eliminate small-amplitude fluctuations, and the signal power after limiting may be too low. The limiting amplifier circuit 115 has both limiting and amplification characteristics; it locks the signal amplitude at a fixed level through a negative feedback mechanism to achieve fixed-amplitude processing; at the same time, it supplements the signal power to ensure that the subsequent detection circuit and channelization filter circuit have sufficient signal energy to support detection and filtering. Its core is to ensure that all subsequent processing links (detection, channelization filtering, phase detection) operate based on a signal with stable amplitude, avoiding interference from amplitude fluctuations on pulse detection and frequency determination.

[0070] The pulse detection circuit 116 then enters the detection circuit to complete pulse detection and threshold control. It converts the envelope energy of the high-frequency carrier into a low-frequency criterion to generate an effective frequency measurement time window and a rough power estimate, thus avoiding false triggering of the channel and phase detection process due to noise or spurious signals.

[0071] It should be noted that all components of the front-end preprocessing link (first limiter 114, limiting amplifier circuit 115, and detector circuit 116) are high-speed response devices, and the processing delay can be controlled in the nanosecond range, which will not affect the instantaneous characteristics of the instantaneous frequency measurement receiver 11. At the same time, the preprocessed signal has better quality and higher effectiveness, making the frequency measurement and local oscillator switching of the tracking local oscillator link 10 more coordinated, further shortening the total closed-loop delay of the system, and ensuring real-time tracking of the agile wireless detection device.

[0072] Optionally, the instantaneous frequency measurement receiver 11 also includes a frequency conversion circuit.

[0073] In terms of connection, the frequency conversion circuit is set between the detector circuit 116 and the channelization filter circuit 110.

[0074] Functionally, the frequency conversion circuit is used to shift the incoming radio frequency signal to the intermediate frequency (IF). That is, through frequency shifting technology, the effective radio frequency incoming signal after detection and screening is converted into a lower frequency, more easily processed IF signal.

[0075] It should be noted that the incoming wave is first moved to a more easily implemented intermediate frequency (IF) via a frequency conversion circuit to reduce the size of the filter and delay line and improve insertion loss and group delay consistency. At this time, the bandwidth and center frequency of the IF need to be balanced with the channelization bandwidth to take into account both instantaneous coverage and group delay flatness.

[0076] In one embodiment, the total delay of the tracking local oscillator link 10 satisfies the following relationship:

[0077] ;

[0078] in, This represents the total delay, that is, the time taken from the detection of the incoming wave signal to the generation and stable output of the local oscillator signal by the fast frequency hopping synthesizer 12. Indicates multiples, The value ranges from 0.1 to 0.3.

[0079] In the embodiments of this application, Take 0.3.

[0080] By ensuring that the total delay is less than 0.1 to 0.3 times the pulse duration, the response speed of the tracking local oscillator link 10 is constrained in the time domain, ensuring that the entire process of frequency measurement, local oscillator switching, and stable output is completed within a single pulse duration.

[0081] In one embodiment, total delay The calculation formula is:

[0082] ;

[0083] in, Indicates the arrival detection time. Indicates the instantaneous frequency measurement processing time. Indicates the control transmission and command processing time. This indicates the transition time of the fast frequency hopping synthesizer 12. This indicates the local oscillator locking and phase settling time. This represents the link group delay, the total delay of signal transmission across the links. + The switching and locking characteristics are dominated by the fast frequency hopping synthesizer 12.

[0084] Optionally, please refer to Figure 4The entire receiving link 20 adopts a broadband frequency conversion structure, which specifically includes: a second limiter 201, a digitally controlled attenuator 202, a low-noise amplifier 203, a mixer 204, a low-pass filter 205, and an intermediate frequency amplifier 206 connected in sequence.

[0085] The incoming signal passes sequentially through the second limiter 201, the digitally controlled attenuator 202, the low-noise amplifier 203, the mixer 204, the low-pass filter 205, and the intermediate frequency amplifier 206.

[0086] Functionally, the second limiter 201 is used to limit the amplitude of the future wave signal to a controllable window.

[0087] The numerically controlled attenuator 202 is used to adjust the channel gain according to the strength of the incoming wave signal.

[0088] The low-noise amplifier 203 is used to amplify the incoming signal.

[0089] Mixer 204 is used to mix the incoming wave signal with the local oscillator signal and down-convert it to an intermediate frequency signal.

[0090] Low-pass filter 205 is used to filter out high-frequency components and local oscillator leakage after mixing.

[0091] Intermediate frequency amplifier 206 is used to amplify the power and shape the amplitude of intermediate frequency signals.

[0092] Specifically, the incoming signal first passes through the second limiter 201, which prevents high-power pulses or strong interference from damaging subsequent circuits and reduces frequency measurement errors caused by input amplitude variations. Subsequently, the digitally controlled attenuator 202 automatically adjusts the channel gain based on signal strength, thereby dynamically controlling the linear operating range of the receiving link. The low-noise amplifier 203 determines the lower limit of the overall noise figure, and its high gain and low noise characteristics ensure the system's sensitivity. Next, the incoming signal and the local oscillator signal generated by the fast frequency hopping synthesizer 12 are down-converted to the intermediate frequency (IF) in the mixer 204, achieving spectrum shifting. The mixing performance directly affects the system's image rejection and spurious characteristics. The low-pass filter 205 is used to filter out high-frequency components and local oscillator leakage after mixing. The intermediate frequency amplifier 206 completes the final power amplification and amplitude shaping, ensuring that the IF signal amplitude matches the full-scale range of the downstream digital-to-analog converter, thus improving the signal-to-noise ratio.

[0093] It should be noted that the receiving link 20 adopts a broadband frequency conversion scheme and has sufficient instantaneous bandwidth, which can cover the operating bandwidth of most wireless detection devices, thereby further improving the tracking capability of pulse-to-pulse frequency conversion wireless detection devices.

[0094] In other words, the receiving link 20 of this application has a large dynamic range (achieved through the coordinated operation of the numerically controlled attenuator 202 and the low-noise amplifier 203) and high anti-interference capability (achieved through the coordinated operation of the second limiter 201 and the low-pass filter 205), making it adaptable to agile devices in different scenarios. Whether it is a short-range high-power agile radar, a long-range low-power agile communication device, or a cluttered environment with multiple targets, it can accurately capture target signals, avoid tracking interruptions caused by interference or amplitude fluctuations, and enhance the practical value of passive wireless detection devices.

[0095] Optionally, the low-pass filter 205 further defines an equivalent noise bandwidth, and controls the sensitivity based on the equivalent noise bandwidth. The sensitivity is calculated using the following formula:

[0096] ;

[0097] in, -174 indicates sensitivity; -174 indicates thermal noise power reference. Indicates the equivalent noise bandwidth. Represents the noise figure. This represents the minimum signal-to-noise ratio required for demodulation.

[0098] Here, the low-pass filter 205 is used to filter out high-frequency components and local oscillator leakage after mixing, while limiting the equivalent noise bandwidth, thus affecting the system's sensitivity. If the bandwidth is increased, the sensitivity will decrease; therefore, a trade-off must be made between broadband coverage and noise control. That is, if the frequency measurement accuracy of the tracking local oscillator link 10 is high and the local oscillator stabilizes quickly, the receiving link 20 can be appropriately increased to expand the bandwidth, using the accuracy of the tracking local oscillator link 10 to compensate for the slight decrease in sensitivity; if the time delay of the tracking local oscillator link 10 is slightly large, the receiving link 20 can be reduced to improve sensitivity, ensuring that even weak signals can be captured in time. Through the above cross-link collaborative optimization, the overall tracking capability of the entire RF link 1 for agile targets can be improved.

[0099] In summary, the entire receiving link achieves adaptive response to both strong and weak signals through amplitude limiting protection, automatic gain control, and low-noise amplification, ensuring high linearity and anti-interference capability while maintaining sensitivity. When working in conjunction with the tracking local oscillator link 10, this link can provide a stable intermediate frequency output immediately after the rapid transition of the local oscillator, thereby achieving intra-pulse tracking when the pulse width is sufficiently large and maintaining continuous recognition and tracking performance under inter-pulse agility conditions.

[0100] Based on the same inventive concept, this application also provides a passive wireless detection device, which includes a housing and a radio frequency link 1 as provided in the foregoing embodiments.

[0101] It should be noted that the radio frequency link 1 can be partially located inside the housing, or partially located outside the housing or on the surface; this application does not impose any limitation on this.

[0102] Furthermore, the description of RF link 1 can be referred to the foregoing embodiments, and the same parts can be referred to each other.

[0103] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0104] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "assembly" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0105] In the description of the embodiments of this application, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0106] In the description of the embodiments of this application, it should be understood that "-" and "~" represent a range between two numerical values, and this range includes the endpoints. For example, "AB" represents a range greater than or equal to A and less than or equal to B. "A~B" represents a range greater than or equal to A and less than or equal to B.

[0107] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0108] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0109] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0110] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0111] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A radio frequency link for a passive wireless detection device, characterized in that, include: The local oscillator link includes: a connected instantaneous frequency measurement receiver and a fast frequency hopping synthesizer; the instantaneous frequency measurement receiver is used to evaluate the frequency of the incoming wave signal and determine the instantaneous estimated frequency; the fast frequency hopping synthesizer is used to determine the local oscillator frequency based on the instantaneous estimated frequency, and perform local oscillator frequency hopping to generate the local oscillator signal. A receiving link is used to mix the incoming signal with the local oscillator signal and down-convert it to an intermediate frequency signal; A processing unit, connected to the receiving link, is used to sample and process the intermediate frequency signal in order to track the agile wireless detection device; The instantaneous frequency measurement receiver includes: a channelization filter circuit, a power divider delay circuit, a phase detector circuit, and an FPGA circuit connected in sequence; wherein, the channelization filter circuit is used to coarsely locate the incoming signal and determine a first frequency; the power divider delay circuit is used to perform signal power division, one path of which is directly connected to the phase detector circuit, and the other path introduces a time delay; the phase detector circuit is used to combine the two signals to obtain the phase difference, thereby refining the frequency and generating a second frequency; the FPGA circuit is used to calculate the instantaneous estimated frequency based on the first frequency and the second frequency; The formula for calculating the instantaneous estimated frequency is as follows: ； in, This represents the instantaneous estimated frequency. Indicates the first frequency. Indicates the second frequency. , Indicates phase difference, Indicates time delay. Represents the residual.

2. The radio frequency link for a passive wireless detection device according to claim 1, characterized in that, The instantaneous frequency measurement receiver further includes: a first limiter, a limiter amplifier circuit, and a detector circuit connected in sequence; the detector circuit is also connected to the channelization filter circuit. The incoming wave signal passes sequentially through the first limiter, the limiting amplifier circuit, and the detector circuit; The first limiter is used to limit the amplitude of the incoming wave signal to a controllable window; The amplitude limiting amplifier circuit is used to perform amplitude limiting processing on the incoming wave signal; The detection circuit is used for pulse detection and threshold control.

3. The radio frequency link for a passive wireless detection device according to claim 2, characterized in that, The instantaneous frequency measurement receiver also includes: a frequency conversion circuit; The frequency conversion circuit is disposed between the detector circuit and the channelization filter circuit; The frequency conversion circuit is used to shift the incoming wave signal to an intermediate frequency.

4. The radio frequency link for a passive wireless detection device according to claim 1, characterized in that, The total delay of the tracking local oscillator link satisfies the following relationship: ； in, Indicates the total delay; Indicates multiples, The value ranges from 0.1 to 0.

3.

5. The radio frequency link for a passive wireless detection device according to claim 4, characterized in that, The formula for calculating the total delay is: ； in, Indicates the arrival detection time. Indicates the instantaneous frequency measurement processing time. Indicates the control transmission and command processing time. This indicates the switching time of the fast frequency hopping synthesizer. This indicates the local oscillator locking and phase settling time. This indicates the latency of the chain group.

6. The radio frequency link for a passive wireless detection device according to claim 1, characterized in that, The receiving link includes: a second limiter, a digitally controlled attenuator, a low-noise amplifier, a mixer, a low-pass filter, and an intermediate frequency amplifier connected in sequence; The incoming signal passes sequentially through the second limiter, the digitally controlled attenuator, the low-noise amplifier, the mixer, the low-pass filter, and the intermediate frequency amplifier; The second limiter is used to limit the amplitude of the incoming wave signal to a controllable window; The digitally controlled attenuator is used to adjust the channel gain according to the strength of the incoming wave signal; The low-noise amplifier is used to amplify the incoming signal; The mixer is used to mix the incoming signal with the local oscillator signal and down-convert it to an intermediate frequency signal; The low-pass filter is used to filter out high-frequency components and local oscillator leakage after mixing; The intermediate frequency amplifier is used to amplify the power and shape the amplitude of the intermediate frequency signal.

7. The radio frequency link for a passive wireless detection device according to claim 6, characterized in that, The low-pass filter further defines an equivalent noise bandwidth, and the sensitivity is controlled based on this equivalent noise bandwidth. The formula for calculating the sensitivity is as follows: ； in, -174 indicates sensitivity; -174 indicates thermal noise power reference. This represents the equivalent noise bandwidth. Represents the noise figure. This represents the minimum signal-to-noise ratio required for demodulation.

8. A passive wireless detection device, characterized in that, Includes a radio frequency link for a passive wireless detection device as described in any one of claims 1-7.

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