Time-frequency domain time delay measurement and calibration method and system based on non-ideal factor optimization

Abstract

This application belongs to the field of wireless communication technology, specifically disclosing a time-frequency domain delay measurement and calibration method and system optimized based on non-ideal factors. This method is used for accurate delay matching in self-interference cancellation systems, improving the robustness of self-interference systems under time-varying dynamic channels. This application combines time-domain correlation and frequency-domain sweeping for wireless channel parameter measurement, achieving both high-precision measurement of the main path delay and real-time acquisition of multipath delay components. It accurately characterizes the time-frequency domain dual-dispersion characteristics of wireless channel delay and estimates multipath channel delay parameters in real time. The frequency-domain sweeping interval is designed based on the main path results of the time-domain measurement, reducing the sweeping time in the frequency-domain measurement mode. Furthermore, considering the multi-factor influence of the measurement link in actual measurement systems, the application addresses issues such as phase noise of the digital-to-analog converter, multipath effects, delay fluctuations of the analog filter, clock jitter, and frequency offset. It further improves the delay measurement accuracy through device selection design, link compensation, and calibration.

Description

Technical Field

[0001] This application belongs to the field of wireless communication technology, and more specifically, relates to a time-frequency domain delay measurement and calibration method and system optimized based on non-ideal factors. Background Technology

[0002] Wireless communication systems transmit information via radio frequency (RF) signals. A shared-platform RF system provides the hardware foundation for transmitting and receiving RF signals. It includes an RF transmitter, RF receiver, and antenna, among other components. These components work together to perform signal modulation, up-conversion, transmission, reception, down-conversion, and demodulation, thereby enabling wireless communication. With the trend towards RF integration and multi-functional integration, electromagnetic interference (EMI) problems in shared-platform RF systems are becoming increasingly complex and severe in the confined space of highly dense electronic devices. Communication equipment is severely affected by high-power self-interference. Due to the propagation of self-interference signals in free space, the multipath effect cannot be ignored. Therefore, multi-tap interference cancellation is used to suppress self-interference in multipath channels. Delay matching is crucial for multi-tap cancellation performance; improving delay matching accuracy is essential to ensure a sufficiently wide interference cancellation ratio. However, the electromagnetic environment is complex and variable. The delay parameters of self-interference channels exhibit time-varying and frequency dispersion characteristics, causing the delay parameters of multipath channels to dynamically change with time and frequency, affecting the accurate delay matching of multi-tap systems. Traditional equal / unequal interval RF multi-tap cancellation methods struggle to adaptively match the dynamic changes in channel multipath parameters over time and frequency, leading to reduced cancellation performance. There is an urgent need to develop real-time delay measurement and calibration methods to improve the robustness of interference cancellation in dynamic, time-varying channels. In dynamic channel environments, wireless channel delay parameters not only change with time but also fluctuate with frequency within the operating bandwidth; this is referred to as the channel parameters exhibiting time-frequency domain dual dispersion characteristics.

[0003] The team led by Zhang Xiaoying at the National University of Defense Technology proposed a time-domain channel measurement method based on spread spectrum sliding correlation in their paper "Channel Measurement and Modeling in Complex Urban Scenarios of the UHF Band." This method utilizes the autocorrelation characteristics of pseudo-random sequences to estimate the multipath delay of wireless channels in real time. However, the time-domain measurement method faces limitations. On the one hand, the accuracy of delay measurement is limited by the clock frequency and signal bandwidth, making it difficult to meet the accuracy requirements for main path delay measurement. On the other hand, the low frequency resolution makes it difficult to meet the requirements for fine characterization of the main path delay-frequency response. Therefore, the team led by He Fangmin at the Naval University of Engineering proposed a joint time-frequency domain channel measurement method in their paper "Multi-Tap Self-Interference Cancellation Based on Joint Time-Frequency Domain Channel Measurement in Time-Varying Channel." This method combines a frequency-domain sweep-based main path delay measurement method with a time-domain measurement method to overcome the limitations of the time-domain correlation method and achieve high measurement accuracy and high frequency resolution characterization of the main path delay in the frequency domain.

[0004] However, the aforementioned time-frequency domain joint channel measurement method is proposed under ideal conditions and does not take into account that in actual measurement systems, the accuracy and robustness of phase measurement are easily affected by the hardware performance of the measurement link, the characteristics of the wireless channel, and the signal processing algorithm. The combined effect of multiple non-ideal factors in the measurement link has a significant impact on the accuracy of time delay measurement. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this application is to provide a time-frequency domain delay measurement and calibration method and system optimized based on non-ideal factors, aiming to solve the problem of low accuracy and robustness of the frequency domain sweep method for measuring principal path delay caused by the influence of multiple factors in the measurement link.

[0006] To achieve the above objectives, in a first aspect, this application provides a time-frequency domain delay measurement and calibration system optimized based on non-ideal factors, comprising: a measurement control module, a measurement signal transmission module, a measurement signal receiving module, and a delay calibration module; The measurement control module is used to switch between time domain and frequency domain measurement modes, set the parameters of the two measurement modes, determine the frequency domain sweep interval based on the main diameter result of the time domain measurement as prior information, and generate and issue a time delay calibration command based on the main diameter delay of the frequency domain measurement and the multipath delay of the time domain measurement. The measurement signal transmission module is used to generate time-domain and frequency-domain measurement signals respectively, and obtain the radio frequency signals required for time-domain and frequency-domain measurements through carrier modulation and digital-to-analog conversion; The measurement signal receiving module is used for receiving and processing time-domain measurement signals and frequency-domain measurement signals. It estimates the number of multipaths and multipath delays in the wireless channel in real time through the sliding correlation algorithm of time-domain measurement, and measures the relationship between the main path delay and frequency through the phase calculation method of frequency-domain measurement. The time delay calibration module is used to receive time delay calibration commands from the measurement and control module, adjust the multi-stage switches of the adjustable time delay circuit, and achieve accurate time delay matching of self-interference signals.

[0007] Preferably, the measurement control module includes a measurement mode switching unit, a measurement parameter control unit, a measurement data fusion unit, and a time delay calibration control unit; The measurement mode switching unit is used to first switch to the time domain measurement mode, and after obtaining the time domain measurement result, switch to the frequency domain measurement mode. Each measurement mode includes measurement signal generation and received signal processing. The measurement parameter control unit is used to set the number of bits of the pseudo-random code sequence, the decimation interpolation multiple, the frequency conversion frequency, and the amount of sliding window data in the time-domain measurement mode; it is also used to set the sweep frequency and sweep interval in the frequency-domain measurement mode. The measurement data fusion unit is used to determine the frequency domain sweep interval using the principal diameter result of the time domain measurement as prior information. The time delay calibration control unit is used to issue commands to control the multi-tap adjustable time delay circuit according to the main path time delay measured in the frequency domain and the multipath time delay measured in the time domain.

[0008] Preferably, the measurement signal transmission module includes a time-domain measurement mode signal generation unit, a frequency-domain measurement mode signal generation unit, a digital frequency synthesizer, a digital-to-analog converter, a power amplifier, and a transmitting antenna; The time-domain measurement mode signal generation unit is used to generate the pseudo-random sequence modulation signal required for time-domain measurement by sequentially performing framing, BPSK modulation, upsampling, and shaping filtering based on the number of bits in the pseudo-random code sequence. The frequency domain measurement mode signal generation unit is used to generate the frequency sweep single tone signal required for frequency domain measurement according to the sweep frequency and sweep interval. The digital frequency synthesizer is used to perform carrier modulation of the time-domain measurement signal and the frequency-domain measurement signal according to the frequency word information provided by the communication system, that is, up-conversion to radio frequency, and the up-conversion is the same as the local oscillator signal of the down-conversion in the time-domain measurement mode receiving signal processing unit. The digital-to-analog converter is connected to an external frequency source. The digital-to-analog converter is used to convert the time-domain / frequency-domain carrier-modulated digital radio frequency signal into an analog radio frequency signal. The frequency source meets the phase noise index of -120dBc / Hz@12.5kHz and is used to generate a clock signal to synchronize the timing of the transmitter entering the analog-to-digital converter and the receiver entering the digital-to-analog converter. The power amplifier is used to amplify the measurement signal power of the analog radio frequency signal to compensate for the power loss of wireless transmission. The transmitting antenna is used to transmit the amplified radio frequency analog signal to the wireless channel for propagation.

[0009] Preferably, the measurement signal receiving module includes a receiving antenna, a bandpass filter, an analog-to-digital converter, a time-domain measurement mode receiving signal processing unit, and a frequency-domain measurement mode receiving signal processing unit; The receiving antenna is used to receive channel measurement signals from the transmitting end; The bandpass filter is used to filter out interference and noise outside the operating frequency band in the received signal and improve the signal-to-noise ratio of the in-band measurement signal. The analog-to-digital converter is externally connected to a frequency source. The analog-to-digital converter is used to convert the filtered radio frequency analog signal into a digital radio frequency signal. The frequency source is the same as the frequency source externally connected to the digital-to-analog converter of the transmitting module. The time-domain measurement mode received signal processing unit is used for correlation processing and parameter estimation of the time-domain measurement mode received signal, including: downconverting the received measurement signal to baseband, filtering out the image frequency using a low-pass filter, entering the shaping filter and downsampling stage, and finally entering the sliding cross-correlation algorithm with the local reference signal to obtain the number of multipaths and time delay using parameter estimation; The frequency domain measurement mode received signal processing unit is used for Fourier transform and phase calculation of the received signal in the frequency domain measurement mode, including: first performing time domain filtering on the received measurement signal to suppress multipath effects, then performing Fourier transform to calculate the phase value at the maximum frequency, subtracting the phase values ​​of the transmitted and received signals at the same frequency, and then subtracting the time delay of the bandpass filter itself, and using the differential relationship between phase and time delay to calculate the time delay-frequency response.

[0010] Preferably, the time delay calibration module includes a multi-tap adjustable time delay circuit, which includes a time delay network and a switch matrix. The time delay network is formed by connecting multiple coaxial cable delay lines with a diameter of less than 2mm in series. Each delay line with a time delay of 2ns is considered as a level, and each 2ns level is equipped with a switch. The switches of multiple 2ns delay lines form a switch switching matrix. The switching matrix controls the on / off state of different level switches according to the time delay calibration command, thereby realizing the time delay adjustable function.

[0011] To achieve the above objectives, in a second aspect, this application provides a time-frequency domain delay measurement and calibration method optimized based on non-ideal factors, including: After switching to time-domain measurement mode, a pseudo-random code modulated measurement signal is generated. The measurement signal is then successively processed by carrier modulation, digital-to-analog conversion, and measurement signal power amplification, and the amplified measurement signal is transmitted by the transmitting antenna. After the receiving antenna receives the measurement signal, it passes through bandpass filtering and analog-to-digital conversion to obtain a digital radio frequency signal. A correlation peak detection algorithm based on a sliding window is used to estimate the multipath delay and the number of multipaths in real time. Based on the multipath delay measured in the time domain, the frequency sweep interval of the frequency domain measurement mode is determined. After switching to frequency domain measurement mode, single-tone sweep signals of different carrier frequencies are generated sequentially according to the sweep interval, and then sequentially undergo digital-to-analog conversion and measurement signal power amplification before being transmitted by the transmitting antenna. After the receiving antenna receives the measurement signal, it passes through bandpass filtering and analog-to-digital conversion in sequence to obtain a digital radio frequency signal. Based on the phase frequency response differential time delay calculation method, the frequency response of the principal path delay is calculated. Based on the multipath delay obtained in the time domain and the main path delay-frequency response obtained in the frequency domain, a delay calibration command is generated to control the multi-stage switching of the adjustable delay circuit, so that the multi-tap adjustable delay is set according to the multipath delay measurement results and the main tap adjustable delay is set according to the main path delay measurement results.

[0012] Preferably, the time-domain measurement mode includes: The baseband pseudo-random code sequence is generated with normalized autocorrelation and cross-correlation functions approaching 1 and 0, respectively. Frames are assembled by adding a frame header to the initial position of the baseband pseudo-random sequence and a frame tail to the end position. The framed baseband unipolar code is converted into bipolar code by BSPK modulation. One path is upsampled and the other path is subjected to sliding cross-correlation to serve as a pseudo-random sequence for local reference. Upsampling inserts zero values ​​between baseband data to increase the sampling rate; The waveform of the baseband signal is smoothed by shaping and filtering, compressing the spectrum to the required bandwidth; The carrier frequency of the channel measurement signal is modulated to match the communication signal by up-conversion to obtain a radio frequency digital signal. After the digital-to-analog conversion is completed, the signal is amplified and used as the transmission signal of the transmitting antenna. The spectrum of the received signal is shifted to the baseband by down-conversion. The received signal is a digital signal that has been received by a receiving antenna, filtered by a bandpass filter, and sampled by an analog-to-digital converter. The local oscillator signal of up-conversion and down-conversion is the same. The image frequency of the baseband signal in the down-conversion stage is filtered out by low-pass filtering; The baseband waveform of the received signal is recovered through shaping filtering; The baseband waveform of the received signal after shaping and filtering is downsampled to reduce the sampling rate; The pseudo-random sequence of the local reference and the downsampled received signal are correlated by sliding cross-correlation. The time points that are greater than the detection threshold after sliding window correlation calculation are extracted as multipath delay.

[0013] Preferably, when generating the pseudo-random sequence for baseband, the symbol rate and code period of the pseudo-random sequence for baseband simultaneously satisfy the following constraints: (1) Symbol rate constraint: The frame time of the time-domain measurement signal should be between the maximum delay of the self-interference channel and the coherence period; (2) Constraints on code period: Multi-tap self-interference cancellation requires suppressing the power of the main path normalized and the power of the multipath components below the detection threshold; the detection threshold is required to be greater than the cross-correlation value; (3) Constraints between symbol rate and delay resolution: Calculate the theoretical upper limit of delay resolution based on the interference cancellation ratio requirement.

[0014] Preferably, the multipath parameter estimation is obtained by detecting the correlation peak of the sliding correlation, and the detection threshold is the difference between the power of the principal path normalization and the interference suppression requirement.

[0015] Preferably, the frequency domain measurement mode includes: Single-tone signals of different frequencies are generated sequentially. One path is converted into an analog radio frequency signal for measuring signal transmission, while the other path performs a Fourier transform on the transmitted signal to obtain the spectrum of the transmitted signal. Find the maximum amplitude value based on the transmitted signal spectrum, and calculate the phase of the corresponding spectral value at that frequency; The received signal is first filtered in the time domain, and then Fourier transform is performed on the received signal to obtain the spectrum of the received signal. The received signal is a digital signal that has been received by the receiving antenna, filtered by the bandpass filter, and converted by the analog-to-digital converter. Find the maximum amplitude value based on the received signal spectrum, and calculate the phase of the corresponding frequency spectrum value. Based on the frequency and phase of the transmitted signal and the frequency and phase of the received signal, the phase values ​​of the two are subtracted, and then the delay of the bandpass filter itself is subtracted to obtain the phase relationship of different frequencies. Based on the phase-delay relationship, the time delay-frequency response is calculated differentially from the phase-frequency curve.

[0016] It is understandable that the beneficial effects of the second aspect mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here.

[0017] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art: (1) This application proposes a time-frequency domain delay measurement and calibration method based on non-ideal factors optimization. By combining time-domain correlation and frequency-domain sweeping, wireless channel parameters are measured. This method can take into account both high-precision measurement of the main path delay and real-time acquisition of multipath delay components, accurately characterize the time-frequency domain dual dispersion characteristics of wireless channel delay, and estimate the delay parameters of multipath channels in real time. Considering the influence of multiple factors on the measurement link in the actual measurement system, the frequency-domain sweeping interval is designed based on the main path results of the time-domain measurement, reducing the sweeping time in the frequency-domain measurement mode. Therefore, the measurement time is reduced, making the self-interference cancellation converge faster and improving the ability to quickly adapt to time-varying dynamic channels.

[0018] (2) This application proposes a time-frequency domain delay measurement and calibration method based on non-ideal factors. For the two non-ideal factors of phase noise and clock jitter of digital-to-analog converter, a frequency source is connected to the digital-to-analog converter. The same low phase noise frequency source is connected to the digital-to-analog converter. The frequency source meets the phase noise index of -120dBc / Hz@12.5kHz and is used to generate a clock signal to synchronize the timing of the transmitter entering the analog-to-digital converter and the receiver entering the digital-to-analog converter, thereby improving the accuracy of delay measurement and avoiding fluctuation variance.

[0019] (3) This application proposes a time-frequency domain delay measurement and calibration method based on non-ideal factors. For the non-ideal factor of multipath effect, the received signal is first filtered in the time domain by the frequency domain measurement mode receiving signal processing unit to suppress the multipath effect, and then Fourier transform is performed to reduce its impact on the high-precision delay measurement of the main path.

[0020] (4) This application proposes a time-frequency domain delay measurement and calibration method based on non-ideal factors. For the non-ideal factor of delay fluctuation of analog filter, the receiving signal processing unit of frequency domain measurement mode calculates the phase value of the transmitting and receiving signals at the same frequency, and then subtracts the delay of the bandpass filter itself, thereby calibrating the nonlinear delay introduced by the analog filter and improving the accuracy of delay measurement.

[0021] (5) This application proposes a time-frequency domain delay measurement and calibration method based on non-ideal factors. For the non-ideal factor of frequency shift, the local oscillator signals of up-conversion and down-conversion are the same. The synchronous design of common local oscillator is adopted to reduce its impact on high-precision delay measurement of main diameter. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the time-frequency domain delay measurement and calibration system optimized based on non-ideal factors provided in the embodiments of this application.

[0023] Figure 2 This is a flowchart of the time-domain measurement mode provided in the embodiments of this application.

[0024] Figure 3 This is a schematic diagram of the normalized time delay power spectrum provided in the embodiments of this application.

[0025] Figure 4 This is a flowchart of the frequency domain measurement mode provided in the embodiments of this application. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0027] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. In this application, the symbol " / " indicates that the related objects are in an "or" relationship, for example, A / B means A or B.

[0028] In this application, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order of objects. For example, "first response message" and "second response message," etc., are used to distinguish different response messages, not to describe a specific order of response messages.

[0029] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0030] In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more, for example, multiple processing units means two or more processing units, multiple elements means two or more elements, etc.

[0031] For ease of understanding, the English abbreviations and related technical terms used in the embodiments of this application will be explained and described below.

[0032] Multipath propagation refers to the phenomenon where, during transmission, communication signals travel through multiple different paths to the receiver due to the complexity of the propagation environment. These paths may include direct paths, reflected paths, refracted paths, and scattered paths. Because the lengths of these different paths vary, the arrival times of the signals at the receiver also differ, resulting in multipath propagation.

[0033] Delay matching refers to the process in a multi-tap interference cancellation system where the time delay of each tap is precisely adjusted to align the generated cancellation signal with the actual self-interference signal in time, thereby achieving effective interference cancellation.

[0034] The main path delay refers to the propagation delay of the signal along the first and strongest path from the transmitter to the receiver.

[0035] Multipath delay components refer to the relative delay of each propagation path relative to a reference path (usually the main path, i.e. the path that arrives first) when a signal reaches the receiver through different paths.

[0036] Main path power refers to the power of the strongest path (i.e., the main path) in a multipath propagation environment.

[0037] BPSK modulation, or Binary Phase Shift Keying, is a basic digital signal modulation technique that uses phase changes in a carrier signal to represent binary data "0" and "1".

[0038] The embodiments of this application are described below with reference to the accompanying drawings.

[0039] like Figure 1 As shown, this application provides a time-frequency domain delay measurement and calibration system optimized based on non-ideal factors, including: a measurement control module 10, a measurement signal transmission module 20, a measurement signal receiving module 30, and a delay calibration module 40. The measurement signal transmission module 20 is located at the transmitting end, and the measurement signal receiving module 30 and the delay calibration module 40 are located at the receiving end. The measurement control module 10 connects the functions of the entire system, can perform parameter configuration and data loading, and is independent of the transmitting and receiving ends.

[0040] The measurement control module 10 is used to switch between time-domain and frequency-domain measurement modes, adjust the parameter settings of the two measurement modes, fuse the time delay measurement data of the two measurement methods, and generate time delay calibration commands to control the time delay calibration module.

[0041] The measurement signal transmission module 20 is used to generate time-domain and frequency-domain measurement signals, and convert them into radio frequency signals through a digital frequency synthesizer and a digital-to-analog converter. These include pseudo-random sequence modulation signals required for time-domain measurements and single-tone sweep signals of different frequencies required for frequency-domain measurements.

[0042] The measurement signal receiving module 30 is used for receiving and processing time-domain and frequency-domain measurement signals. It estimates the number of multipath paths and multipath delays in the wireless channel in real time using a sliding correlation algorithm in the time domain, and measures the main path delay as a function of frequency using a phase calculation method in the frequency domain. The measurement data is uploaded to the measurement control module, which then fuses the delay measurement results from the time-domain and frequency-domain methods.

[0043] The time delay calibration module 40 is used to receive the time delay calibration command transmitted from the measurement control module, adjust the multi-stage switches of the adjustable time delay circuit, and achieve accurate time delay matching of self-interference signals.

[0044] The measurement control module 10 includes a measurement mode switching unit 11, a measurement parameter control unit 12, a measurement data fusion unit 13, and a time delay calibration control unit 14.

[0045] The measurement mode switching unit 11 is used to switch between time-domain measurement mode and frequency-domain measurement mode. The measurement mode includes the entire process of measurement signal generation and received signal processing. When the measurement system is turned on, it first switches to time-domain measurement mode. The time-domain measurement results can be used to assist in the parameter adjustment of the measurement parameter control unit. The frequency sweep interval of the frequency-domain measurement mode can be designed to shorten the measurement time. Then, it switches to frequency-domain measurement mode.

[0046] The measurement parameter control unit 12 is used to adjust parameters such as the number of bits in the pseudo-random code sequence, the decimation interpolation multiple, the frequency conversion frequency, and the amount of sliding window data in the time-domain measurement mode. It is also used to adjust parameters such as the sweep frequency and sweep interval in the frequency-domain measurement mode.

[0047] The measurement data fusion unit 13 is used to fuse the multipath delay and number of multipaths obtained by the time-domain measurement method and the principal path-frequency response obtained by the frequency-domain measurement method.

[0048] The time delay calibration control unit 14 is used to transmit time delay control commands to regulate the time delay calibration module based on the multipath time delay and main path time delay obtained by the measurement data fusion unit.

[0049] The fusion of time-domain and frequency-domain results is used to guide the setting of adjustable delay for multi-tap measurement. The time-domain results include multipath delay and main diameter delay. However, the main diameter delay obtained from the time-domain measurement mode has low accuracy. Therefore, the frequency-domain method is used to measure the main diameter to improve its accuracy, and the frequency-domain result is the main diameter delay. The fusion process involves issuing commands to the multi-tap adjustable delay circuit using both the main diameter delay measured in the frequency domain and the multipath delay measured in the time domain. Specifically, the fusion method is as follows: First, based on the main diameter delay obtained from the time-domain measurement (which has lower accuracy), the initial (coarse) range of the main diameter can be obtained. Then, using the main diameter from the time-domain method as prior information, adjusting the frequency sweep interval measurement parameter in the frequency domain method can reduce the measurement time.

[0050] The measurement signal transmission module 20 includes a time-domain measurement mode signal generation unit 21, a frequency-domain measurement mode signal generation unit 22, a digital frequency synthesizer 23, a digital-to-analog converter 24, a power amplifier 25, and a transmitting antenna 26.

[0051] The time-domain measurement mode signal generation unit 21 is used to generate the pseudo-random sequence modulation signal required for the time-domain measurement method. It includes a pseudo-random code generator to generate a baseband pseudo-random code sequence, designing frame headers and tails to frame the pseudo-random sequence, performing bipolar conversion through modulation, and then obtaining the baseband time-domain measurement signal through upsampling and shaping filtering.

[0052] The frequency domain measurement mode signal generation unit 22 is used to generate the swept-frequency single-tone signal required for the frequency domain measurement method. This includes directly generating single-tone signals of different frequencies using a digital frequency synthesizer based on parameters such as the operating frequency band and sweep interval provided by the measurement control module, and calculating the phase value of the frequency measurement signal using Fourier transform.

[0053] The digital frequency synthesizer 23 is used to perform carrier modulation of the time-domain measurement signal and the frequency-domain measurement signal according to the frequency word information provided by the communication system, that is, up-conversion to radio frequency.

[0054] The digital-to-analog converter 24 is used to convert digital radio frequency signals into analog radio frequency signals.

[0055] The power amplifier 25 is used to amplify the power of the measurement signal and compensate for the power loss of wireless transmission.

[0056] The transmitting antenna 26 is used to transmit radio frequency analog signals to a wireless channel for propagation.

[0057] The measurement signal receiving module 30 includes a receiving antenna 31, a bandpass filter 32, an analog-to-digital converter 33, a time-domain measurement mode receiving signal processing unit 34, and a frequency-domain measurement mode receiving signal processing unit 35.

[0058] The receiving antenna 31 is used to receive channel measurement signals from the transmitting end.

[0059] The bandpass filter 32 is used to filter out interference and noise outside the operating frequency band and improve the signal-to-noise ratio of the in-band measurement signal.

[0060] The analog-to-digital converter 33 is used to convert radio frequency analog signals into digital radio frequency signals, which facilitates digital algorithm processing.

[0061] The time-domain measurement mode received signal processing unit 34 is used for correlation processing and parameter estimation of the received signal in the time domain method. This includes down-converting the received measurement signal to baseband, filtering out image frequencies using a low-pass filter, proceeding to shaping filtering and downsampling stages, and finally inputting it with a local reference signal into a sliding cross-correlation algorithm to obtain parameters such as the number of multipath paths and time delay through parameter estimation.

[0062] The frequency domain measurement mode received signal processing unit 35 is used for Fourier transform and phase calculation of the received signal in the frequency domain. This includes directly Fourier transforming the received measurement signal, calculating the phase value at the maximum frequency, subtracting the phase values ​​of the transmitted and received signals at the same frequency, and using the differential relationship between phase and time delay to calculate the time delay-frequency response.

[0063] The time delay calibration module 40 includes a multi-tap adjustable time delay circuit 41. The adjustable time delay circuit 41 includes a time delay network and a switch matrix. The time delay network is formed by connecting multiple levels of coaxial cable delay lines with diameters within 2mm. Each delay line with a time delay of 2ns represents a position, and each 2ns position is equipped with a switch. The switches of multiple 2ns delay lines form a switch switching matrix. The switching matrix controls the on / off state of different positions according to the time delay calibration command, thereby achieving the adjustable time delay function.

[0064] This application provides a systematic optimization method for non-ideal factors in a time delay measurement link, the method comprising the following steps: First, after the system is turned on, the measurement mode switching unit 11 switches the measurement signal transmission module 20 to the time domain measurement mode. The time domain measurement mode signal generation unit 21 generates a measurement signal modulated by a pseudo-random code. After carrier modulation by the digital frequency synthesizer 23, the digital radio frequency signal is converted into an analog radio frequency signal by the digital-to-analog converter 24. The power amplifier 25 amplifies the measurement signal power, and the transmitting antenna 26 transmits the measurement signal.

[0065] Secondly, the receiving antenna 31 of the measurement signal receiving module 30 receives the measurement signal, which is filtered out by the bandpass filter 32 to remove out-of-band interference and noise. The analog radio frequency signal is converted into a digital radio frequency signal by the analog-to-digital converter 33 and enters the time-domain measurement mode receiving signal processing unit 34 to estimate the multipath delay and the number of multipaths in real time. The main path delay measured by the time-domain method is uploaded to the measurement data fusion unit 13 of the measurement control module 10, which then calculates the optimal range of the frequency domain method measurement parameters and inputs them to the measurement parameter control unit 12. This unit controls the frequency sweep interval parameters of the frequency domain measurement mode signal generation unit 22.

[0066] Then, the measurement mode switching unit 11 switches the measurement signal transmission module 20 to the frequency domain measurement mode. The frequency domain measurement mode signal generation unit 22 uses the digital frequency synthesizer 23 to generate single-tone sweep signals of different carrier frequencies in sequence. Then, the digital radio frequency signal is converted into an analog radio frequency signal through the digital-to-analog converter 24. The power amplifier 25 amplifies the measurement signal power, and the transmitting antenna 26 transmits the measurement signal.

[0067] Subsequently, the receiving antenna 31 of the measurement signal receiving module 30 receives the measurement signal, which is filtered out by the bandpass filter 32 to remove out-of-band interference and noise. The analog radio frequency signal is converted into a digital radio frequency signal by the analog-to-digital converter 33 and enters the frequency domain measurement mode. The receiving signal processing unit 35 calculates the frequency response of the principal diameter delay, and the measurement result of the frequency domain method is uploaded to the measurement data fusion unit 13 of the measurement control module 10.

[0068] Finally, the measurement data fusion unit 13 inputs the multipath delay obtained by the time domain method and the main path delay-frequency response obtained by the frequency domain method to the delay calibration control unit 14, thereby generating a delay calibration command to control the adjustable delay circuit 41 in the delay calibration module 40, so that the multi-tap adjustable delay is set according to the multipath delay measurement result and the main tap adjustable delay is set according to the main path delay measurement result.

[0069] In the time-domain measurement mode, a correlation peak detection algorithm based on a sliding window is used to estimate multipath in real time. This method belongs to the existing technology.

[0070] The optimal range for frequency domain measurement parameters is calculated as follows: According to this formula, given the principal path delay measured by the time-domain method, the range of values ​​for the sweep frequency interval can be calculated, and the maximum value is generally adopted.

[0071] The frequency domain method measures the sweep frequency band and the sweep interval, generating single-tone sweep signals with different carrier frequencies. For example, if the sweep frequency band is 100MHz~120MHz and the sweep interval is 1MHz, then the digital frequency synthesizer will generate single-tone signals of 100MHz, 101MHz, 102MHz, ..., 119MHz and 120MHz in sequence.

[0072] like Figure 2As shown, the time-domain measurement mode includes: baseband pseudo-random code generation 101, framing 102, modulation 103, upsampling 104, shaping filtering 105, upconversion 106, downconversion 107, low-pass filtering 108, shaping filtering 109, downsampling 110, sliding correlation algorithm 111, and multipath parameter estimation 112. Specifically, framing is used to add a frame header to the initial position of the baseband pseudo-random sequence and a frame tail to the end position to protect the interval and prevent mutual interference between pseudo-random codes of consecutive cycles. Modulation is used to convert the baseband unipolar code into bipolar modulation. Upsampling is used to insert zero values ​​between baseband data to increase the sampling rate and achieve a higher resolution signal. Shaping filtering is used to smooth the waveform of the baseband signal, compress the spectrum to the required bandwidth, and reduce the code size. Inter-channel interference; the up-conversion is used to modulate the carrier frequency of the channel measurement signal to match that of the communication signal, and then send the resulting radio frequency digital signal to the digital-to-analog converter to convert it into a radio frequency analog signal; the down-conversion is used to shift the spectrum of the radio frequency signal to the baseband, and the radio frequency signal is the radio frequency digital signal sampled by the analog-to-digital converter; the low-pass filter is used to filter out the image frequency of the baseband signal in the down-conversion stage; the shaping filter is used to recover the baseband waveform of the transmitted signal; the downsampling is used to downsample the baseband waveform of the transmitted signal after shaping filtering to reduce the sampling rate; the sliding correlation algorithm is used to perform sliding window correlation calculation between the pseudo-random sequence of the local reference and the signal received by the receiver; the multipath estimation is used to extract the time points greater than the threshold after sliding window calculation as the multipath delay.

[0073] The sliding correlation algorithm yields the time delay frequency spectrum. Correlation peaks in this spectrum that are greater than the detection threshold can be considered as multipath components. Therefore, the number of multipath components can also be estimated.

[0074] Normalized time delay power spectrum as follows Figure 3 As shown, the horizontal axis represents time delay, and the vertical axis represents normalized power. Each peak in the graph represents a correlation peak. Peaks greater than the red dashed line (detection threshold) are considered main path and multipath components, while those less than are considered noise. The normalized power of the main path is 0 dB, and the power of other multipath components is less than that of the main path, while their time delay is greater than that of the main path. The detection threshold is determined based on the cancellation ratio requirement. For example, if the interference cancellation ratio requirement is 40 dB, then the detection threshold on the normalized power spectrum is 0 - 40 dB = -40 dB. The baseband pseudo-random code generation is used to generate pseudo-random sequences in the baseband whose normalized autocorrelation and cross-correlation functions approach 1 and 0, respectively.

[0075] like Figure 4As shown, the frequency domain measurement mode includes: a digital frequency synthesizer 201, a transmit signal Fourier transform 202, a transmit signal phase value calculation 203, saving the frequency and phase values ​​of the transmit signal 204, a receive signal Fourier transform 205, a receive signal phase value calculation 206, saving the frequency and phase values ​​of the receive signal 207, calculating the phase-frequency curve 208, and calculating the time delay-frequency response 209. Specifically, the digital frequency synthesizer 201 is used to sequentially generate single-tone signals of different frequencies, one path of which is sent to a digital-to-analog converter to convert into an analog radio frequency signal for measuring signal transmission, and the other path is sent to a Fourier transform; the transmit signal Fourier transform 202 is used to obtain the spectrum of the transmit signal through Fourier transform; the transmit signal phase value calculation 203 is used to find the maximum amplitude value based on the single-tone signal spectrum and calculate the phase of the corresponding spectral value; the receive signal Fourier transform 205 is used to obtain the spectrum of the received signal through Fourier transform, and the receive signal... The signal is received by a receiving antenna, filtered by a bandpass filter, and sampled by an analog-to-digital converter before being converted into a digital signal; the received signal phase value calculation 206 is used to find the maximum amplitude value based on the spectrum of the received signal and calculate the phase of the corresponding spectral value at that frequency; the phase frequency curve calculation 208 is used to obtain the phase relationship of different frequencies by subtracting the phase values ​​of the stored transmitted signal frequency and phase value and the stored received signal frequency and phase value; the time delay-frequency response calculation 209 is used to calculate the time delay-frequency response differentially based on the phase and time delay relationship formula and the phase frequency curve.

[0076] In frequency domain measurement mode, the calculation method for the principal path delay is as follows: assuming the sweep frequency signal's... The frequency is The phase value calculated by the transmitter is The phase value calculated by the receiver is Then the phase difference between the transmitted and received signals calculated by the receiving end is: The first frequency sweep signal The frequency is The phase value calculated by the transmitter is The phase value calculated by the receiver is Then the phase difference between the transmitted and received signals calculated by the receiving end is: This yields the phase frequency response, i.e. , Finally, based on the relationship between phase and time delay, the frequency is calculated. Time delay :

[0077] It is understood that the detailed functional implementation of each of the above units / modules can be found in the description in the aforementioned method embodiments, and will not be repeated here.

[0078] It should be understood that the above-described device is used to execute the methods in the above embodiments. The implementation principle and technical effect of the corresponding program modules in the device are similar to those described in the above methods. The working process of the device can be referred to the corresponding process in the above methods, and will not be repeated here.

[0079] Based on the methods in the above embodiments, this application provides an electronic device that may include a processor, a communications interface, a memory, and a communication bus, wherein the processor, communications interface, and memory communicate with each other via the communication bus. The processor may invoke logical instructions stored in the memory to execute the methods in the above embodiments.

[0080] Furthermore, the logical instructions in the aforementioned memory can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application.

[0081] Based on the methods in the above embodiments, this application provides a computer-readable storage medium storing a computer program that, when run on a processor, causes the processor to execute the methods in the above embodiments.

[0082] Based on the methods in the above embodiments, this application provides a computer program product that, when run on a processor, causes the processor to execute the methods in the above embodiments.

[0083] It is understood that the processor in the embodiments of this application can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. A general-purpose processor can be a microprocessor or any conventional processor.

[0084] The method steps in this application embodiment can be implemented in hardware or by a processor executing software instructions. The software instructions can consist of corresponding software modules, which can be stored in random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, portable hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can reside in an ASIC.

[0085] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially as a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted through the computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state disk (SSD)).

[0086] It is understood that the various numerical designations used in the embodiments of this application are merely for the convenience of description and are not intended to limit the scope of the embodiments of this application.

[0087] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A time-frequency domain delay measurement and calibration system optimized based on non-ideal factors, characterized in that, include: Measurement control module (10), measurement signal transmission module (20), measurement signal receiving module (30), and time delay calibration module (40); The measurement control module (10) is used to switch between time domain and frequency domain measurement modes, set the parameters of the two measurement modes, determine the frequency domain sweep interval based on the main diameter result of time domain measurement as prior information, and generate and issue a time delay calibration command based on the main diameter delay of frequency domain measurement and the multipath delay of time domain measurement. The measurement signal transmission module (20) is used to generate time-domain and frequency-domain measurement signals respectively, and obtain the radio frequency signals required for time-domain and frequency-domain measurements through carrier modulation and digital-to-analog conversion; The measurement signal receiving module (30) is used for receiving and processing time-domain measurement signals / frequency-domain measurement signals. It estimates the number of multipaths and multipath delays in the wireless channel in real time through the sliding correlation algorithm of time-domain measurement, and measures the relationship between the main path delay and frequency through the phase calculation method of frequency-domain measurement. The time delay calibration module (40) is used to receive the time delay calibration command issued by the measurement control module, adjust the multi-stage switch of the adjustable time delay circuit, and realize the accurate time delay matching of the self-interference signal. The measurement signal receiving module (30) includes a receiving antenna (31), a bandpass filter (32), an analog-to-digital converter (33), a time-domain measurement mode receiving signal processing unit (34), and a frequency-domain measurement mode receiving signal processing unit (35). The receiving antenna (31) is used to receive channel measurement signals from the transmitting end; The bandpass filter (32) is used to filter out interference and noise outside the operating frequency band in the received signal and improve the signal-to-noise ratio of the in-band measurement signal; The analog-to-digital converter (33) is externally connected to a frequency source. The analog-to-digital converter is used to convert the filtered radio frequency analog signal into a digital radio frequency signal. The frequency source is the same as the frequency source externally connected to the digital-to-analog converter of the transmitting module. The time-domain measurement mode received signal processing unit is used for correlation processing and parameter estimation of the time-domain measurement mode received signal, including: downconverting the received measurement signal to baseband, filtering out the image frequency using a low-pass filter, entering the shaping filter and downsampling stage, and finally entering the sliding cross-correlation algorithm with the local reference signal to obtain the number of multipaths and time delay using parameter estimation; The frequency domain measurement mode received signal processing unit is used for Fourier transform and phase calculation of the received signal in the frequency domain measurement mode, including: first performing time domain filtering on the received measurement signal to suppress multipath effects, then performing Fourier transform to calculate the phase value at the maximum frequency, subtracting the phase values ​​of the transmitted and received signals at the same frequency, and then subtracting the time delay of the bandpass filter itself, and using the differential relationship between phase and time delay to calculate the time delay-frequency response. The measurement signal transmission module (20) includes a time-domain measurement mode signal generation unit (21), a frequency-domain measurement mode signal generation unit (22), a digital frequency synthesizer (23), a digital-to-analog converter (24), a power amplifier (25), and a transmitting antenna (26). The time-domain measurement mode signal generation unit (21) is used to generate the pseudo-random sequence modulation signal required for time-domain measurement by sequentially performing framing, BPSK modulation, upsampling and shaping filtering based on the number of bits of the pseudo-random code sequence. The frequency domain measurement mode signal generation unit (22) is used to generate the frequency sweep single tone signal required for frequency domain measurement according to the sweep frequency and sweep interval; The digital frequency synthesizer (23) is used to realize carrier modulation of time-domain measurement signal and frequency-domain measurement signal according to the frequency word information provided by the communication system, that is, up-conversion to radio frequency, and the up-conversion is the same as the local oscillator signal of down-conversion in the time-domain measurement mode receiving signal processing unit. The digital-to-analog converter (24) is connected to an external frequency source. The digital-to-analog converter is used to convert the digital radio frequency signal after time-domain / frequency-domain carrier modulation into an analog radio frequency signal. The frequency source meets the phase noise index of -120dBc / Hz@12.5kHz and is used to generate a clock signal to synchronize the timing of the transmitter entering the analog-to-digital converter and the receiver entering the digital-to-analog converter. The power amplifier (25) is used to amplify the measurement signal power of the analog radio frequency signal to compensate for the power loss of wireless transmission. The transmitting antenna (26) is used to transmit the amplified radio frequency analog signal to the wireless channel for propagation.

2. The system as described in claim 1, characterized in that, The measurement control module (10) includes a measurement mode switching unit (11), a measurement parameter control unit (12), a measurement data fusion unit (13), and a time delay calibration control unit (14). The measurement mode switching unit (11) is used to first switch to the time domain measurement mode, and after obtaining the time domain measurement result, switch to the frequency domain measurement mode. Each measurement mode includes measurement signal generation and received signal processing. The measurement parameter control unit (12) is used to set the number of bits of the pseudo-random code sequence, the decimation interpolation multiple, the frequency conversion frequency and the amount of sliding window data in the time domain measurement mode, and is also used to set the sweep frequency and sweep interval in the frequency domain measurement mode. The measurement data fusion unit (13) is used to determine the frequency domain sweep interval using the principal diameter result of the time domain measurement as prior information; The time delay calibration control unit (14) is used to issue commands to control the multi-tap adjustable time delay circuit according to the main path time delay measured in the frequency domain and the multipath time delay measured in the time domain.

3. The system as described in claim 1, characterized in that, The time delay calibration module (40) includes a multi-tap adjustable time delay circuit (41), which includes a time delay network and a switching matrix; A time delay network is formed by connecting multiple levels of coaxial cable delay lines with a diameter of less than 2mm in series. Each delay line with a delay of 2ns is considered a level, and each 2ns level is equipped with a primary switch. The switches of multiple 2ns delay lines form a switch switching matrix. The system controls the on / off state of different switches in the switch matrix according to the time delay calibration command, thereby realizing the time delay adjustable function.

4. A time-frequency domain delay measurement and calibration method optimized based on non-ideal factors, characterized in that, include: After switching to time-domain measurement mode, a pseudo-random code modulated measurement signal is generated. The measurement signal is then successively processed by carrier modulation, digital-to-analog conversion, and measurement signal power amplification, and the amplified measurement signal is transmitted by the transmitting antenna. After the receiving antenna receives the measurement signal, it passes through bandpass filtering and analog-to-digital conversion to obtain a digital radio frequency signal. A correlation peak detection algorithm based on a sliding window is used to estimate the multipath delay and the number of multipaths in real time. Based on the multipath delay measured in the time domain, the frequency sweep interval of the frequency domain measurement mode is determined. After switching to frequency domain measurement mode, single-tone sweep signals of different carrier frequencies are generated sequentially according to the sweep interval, and then sequentially undergo digital-to-analog conversion and measurement signal power amplification before being transmitted by the transmitting antenna. After receiving the measurement signal, the receiving antenna first performs time-domain filtering to suppress multipath effects, then performs a Fourier transform to calculate the phase value at the maximum frequency. The phase values ​​of the transmitted and received signals at the same frequency are then subtracted from the time delay of the bandpass filter itself. Using the difference between phase and time delay, the time delay-frequency response is calculated. Based on the multipath delay obtained in the time domain and the main path delay-frequency response obtained in the frequency domain, a delay calibration command is generated to control the multi-stage switching of the adjustable delay circuit, so that the multi-tap adjustable delay is set according to the multipath delay measurement results and the main tap adjustable delay is set according to the main path delay measurement results. The digital radio frequency signal after time-domain / frequency-domain carrier modulation is converted into an analog radio frequency signal. The frequency source meets the phase noise index of -120dBc / Hz@12.5kHz and is used to generate a clock signal to synchronize the timing of the transmitter entering the analog-to-digital converter and the receiver entering the digital-to-analog converter.

5. The method as described in claim 4, characterized in that, The time-domain measurement mode includes: The baseband pseudo-random code sequence is generated with normalized autocorrelation and cross-correlation functions approaching 1 and 0, respectively. Frames are assembled by adding a frame header to the initial position of the baseband pseudo-random sequence and a frame tail to the end position. The framed baseband unipolar code is converted into bipolar code by BSPK modulation. One path is upsampled and the other path is subjected to sliding cross-correlation to serve as a pseudo-random sequence for local reference. Upsampling inserts zero values ​​between baseband data to increase the sampling rate; The waveform of the baseband signal is smoothed by shaping and filtering, compressing the spectrum to the required bandwidth; The carrier frequency of the channel measurement signal is modulated to match the communication signal by up-conversion to obtain a radio frequency digital signal. After the digital-to-analog conversion is completed, the signal is amplified and used as the transmission signal of the transmitting antenna. The spectrum of the received signal is shifted to the baseband by down-conversion. The received signal is a digital signal that has been received by a receiving antenna, filtered by a bandpass filter, and sampled by an analog-to-digital converter. The local oscillator signal of up-conversion and down-conversion is the same. The image frequency of the baseband signal in the down-conversion stage is filtered out by low-pass filtering; The baseband waveform of the received signal is recovered through shaping filtering; The baseband waveform of the received signal after shaping and filtering is downsampled to reduce the sampling rate; The pseudo-random sequence of the local reference and the downsampled received signal are correlated by sliding cross-correlation. The time points that are greater than the detection threshold after sliding window correlation calculation are extracted as multipath delay.

6. The method as described in claim 5, characterized in that, When generating a pseudo-random sequence for baseband, the symbol rate and code period of the pseudo-random sequence for baseband must simultaneously satisfy the following constraints: (1) Symbol rate constraint: The frame time of the time-domain measurement signal should be between the maximum delay of the self-interference channel and the coherence period; (2) Code period constraint: Multi-tap self-interference cancellation requires suppressing the power of the main path normalized and the power of the multipath component below the detection threshold; The detection threshold must be greater than the cross-correlation value; (3) Constraints between symbol rate and delay resolution: Calculate the theoretical upper limit of delay resolution based on the interference cancellation ratio requirement.

7. The method as described in claim 5, characterized in that, Multipath parameter estimation is obtained by detecting correlation peaks through sliding correlation, with the detection threshold being the difference between the power of the principal path normalized and the interference suppression requirement.

8. The method as described in claim 4, characterized in that, The frequency domain measurement modes include: Single-tone signals of different frequencies are generated sequentially. One path is converted into an analog radio frequency signal for measuring signal transmission, while the other path performs a Fourier transform on the transmitted signal to obtain the spectrum of the transmitted signal. Find the maximum amplitude value based on the transmitted signal spectrum, and calculate the phase of the corresponding spectral value at that frequency; The received signal is first filtered in the time domain, and then Fourier transform is performed on the received signal to obtain the spectrum of the received signal. The received signal is a digital signal that has been received by the receiving antenna, filtered by the bandpass filter, and converted by the analog-to-digital converter. Find the maximum amplitude value based on the received signal spectrum, and calculate the phase of the corresponding frequency spectrum value. Based on the frequency and phase of the transmitted signal and the frequency and phase of the received signal, the phase values ​​of the two are subtracted, and then the delay of the bandpass filter itself is subtracted to obtain the phase relationship of different frequencies. Based on the phase-delay relationship, the time delay-frequency response is calculated differentially from the phase-frequency curve.

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