Dechirping reception method and device for multi-carrier chirp signal

Abstract

The present invention discloses a method for dechirping reception of multi-carrier linear frequency modulation signals. The method includes the following steps: Step 1, perform IQ mixing on the received multi-carrier linear frequency modulation echo signal and a reference signal; Step 2, respectively filter the high-frequency parts in the two signals generated by the IQ mixing, and then perform low-speed ADC sampling on the two obtained dechirped signals respectively; Step 3, combine the two ADC sampling signals into a complex signal, and then convert the obtained complex signal to the frequency domain to obtain the frequency-domain signal of the dechirped signal; Step 4, perform spectrum segmentation on the frequency-domain signal of the dechirped signal according to the frequency range after dechirping of each sub-carrier to obtain the frequency-domain signals of each sub-carrier after dechirping; Step 5, convert the frequency-domain signals of each sub-carrier to time-domain signals. The present invention also discloses a device for dechirping reception of multi-carrier linear frequency modulation signals. The present invention can reduce the system complexity and the ADC sampling rate requirement while ensuring the coherence between sub-carriers.

Description

Technical Field

[0001] The present invention relates to a method and device for dechirping reception of multi-carrier linear frequency modulation signals, and belongs to the technical field of radar signal processing. Background Art

[0002] As a new type of radar system, multi-carrier radar can synthesize a large bandwidth signal by transmitting multi-carrier signals to obtain high resolution. At the same time, it uses the information returned by multiple carriers for detection, which can effectively improve the target detection ability. Compared with traditional wideband frequency modulation or stepped frequency radar, multi-carrier radar is insensitive to target movement and is more suitable for detecting high-speed targets. In addition, multi-carrier radar increases the frequency dimension freedom, has stronger anti-jamming ability, and the mechanism of simultaneous transmission and reception of multiple carriers can also reduce the probability of being intercepted by electronic reconnaissance receivers. However, most of the existing multi-carrier radars adopt multi-channel reception methods, which have complex structures and poor coherence between channels, affecting the fusion detection performance of multi-carrier frequency signals. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for dechirping reception of multi-carrier linear frequency modulation signals, which can realize single-channel reception of multi-carrier signals, reduce the system complexity while ensuring the coherence between sub-carriers, and at the same time reduce the sampling rate requirement of the ADC, making it easy to realize multi-carrier radar signals with large bandwidth.

[0004] The present invention specifically adopts the following technical solutions to solve the above technical problems:

[0005] A method for dechirping reception of multi-carrier linear frequency modulation signals includes the following steps:

[0006] Step 1: Perform IQ mixing on the received multi-carrier linear frequency modulation echo signal and a reference signal. The reference signal has the same initial frequency, number of sub-carriers, time width, and sub-carrier bandwidth as the multi-carrier linear frequency modulation echo signal. The sub-carrier frequency interval of the reference signal is more than f b than that of the multi-carrier linear frequency modulation echo signal, and satisfies f b >kτ max , Δf > (N - 2)f b +kτ max , where k is the frequency modulation slope of the sub-carriers in the multi-carrier linear frequency modulation echo signal, τ max is the maximum delay of the multi-carrier linear frequency modulation echo signal, Δf is the sub-carrier frequency interval of the multi-carrier linear frequency modulation echo signal, and N is the number of sub-carriers in the multi-carrier linear frequency modulation echo signal;

[0007] Step 2: Filter out the frequencies greater than (N - 1)f b +kτ in the two signals generated by IQ mixing respectivelymax The part, and then perform low-speed ADC sampling on the two obtained dechirped signals respectively;

[0008] Step 3: Combine the two ADC sampling signals into a complex signal, and then convert the obtained complex signal to the frequency domain to obtain the frequency-domain signal of the dechirped signal;

[0009] Step 4: Perform spectrum segmentation on the frequency-domain signal of the dechirped signal according to the frequency range after dechirping of each subcarrier to obtain the frequency-domain signal of each subcarrier after dechirping; the frequency ranges after dechirping of each subcarrier from low to high are: 0~kτ max , f b ~f b +kτ max , …, (N - 1)f b ~(N - 1)f b +kτ max ;

[0010] Step 5: Convert the frequency-domain signal of each subcarrier to the time domain signal.

[0011] Furthermore, the dechirped receiving method of the multi-carrier chirp signal further includes:

[0012] Step 6: Use the method of zero-padding splicing in the time domain to perform full-band multi-carrier fusion on the time-domain signals of each subcarrier. Even further, the dechirped receiving method of the multi-carrier chirp signal further includes:

[0013] Step 7: Extract the target information from the full-band multi-carrier fusion signal, and use the sparse reconstruction method to obtain the high-resolution range information of the target support area.

[0014] Preferably, use the fast Fourier transform to convert the complex signal to the frequency domain, and use the inverse fast Fourier transform to convert the frequency-domain signal of each subcarrier to the time domain signal.

[0015] Based on the same inventive concept, the following technical solutions can also be obtained:

[0016] A dechirped receiving device for a multi-carrier chirp signal, comprising:

[0017] An IQ mixer, configured to perform IQ mixing on the received multi-carrier chirp echo signal and a reference signal, the reference signal having the same initial frequency, number of subcarriers, time width, and subcarrier bandwidth as the multi-carrier chirp echo signal, and the subcarrier frequency interval of the reference signal being more than f b , and satisfying f b >kτ max , Δf > (N - 2)f b +kτ max, where k is the frequency modulation slope of the sub-carriers in the multi-carrier linear frequency modulation echo signal, τ max is the maximum delay of the multi-carrier linear frequency modulation echo signal, Δf is the sub-carrier frequency interval of the multi-carrier linear frequency modulation echo signal, and N is the number of sub-carriers in the multi-carrier linear frequency modulation echo signal;

[0018] A filtering and sampling module, which is used to filter out the parts with frequencies greater than (N - 1)f in the two signals generated by IQ mixing respectively b + kτ max of the two signals, and then perform low-speed ADC sampling on the two obtained de-chirped signals respectively; A time-frequency conversion module, which is used to combine the two ADC sampling signals into a complex signal, and then convert the obtained complex signal to the frequency domain to obtain the frequency domain signal of the de-chirped signal;

[0019] A spectrum splitting module, which is used to split the frequency domain signal of the de-chirped signal according to the frequency ranges after de-chirping of each sub-carrier to obtain the frequency domain signals of each sub-carrier after de-chirping; The frequency ranges after de-chirping of each sub-carrier from low to high are: 0~kτ max , f b ~f b + kτ max , …, (N - 1)f b ~(N - 1)f b + kτ max ;

[0020] A frequency-time conversion module, which is used to convert the frequency domain signals of each sub-carrier to the time domain signals.

[0021] Further, the de-chirped receiving device for the multi-carrier linear frequency modulation signal further includes:

[0022] A multi-carrier fusion module, which is used to perform full-band multi-carrier fusion on the time domain signals of each sub-carrier by using the method of zero-padding splicing in the time domain.

[0023] Even further, the de-chirped receiving device for the multi-carrier linear frequency modulation signal further includes:

[0024] A target information extraction module, which is used to extract target information from the full-band multi-carrier fusion signal and obtain high-resolution range information of the target support area by using the sparse reconstruction method.

[0025] Preferably, the time-frequency conversion module is a fast Fourier transform module, and the frequency-time conversion module is a fast inverse Fourier transform module.

[0026] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0027] The present invention realizes a single-channel dechirp receiving method for multi-carrier linear frequency modulation signals, which reduces the system complexity while ensuring the coherence between sub-carriers; the dechirp receiving method reduces the sampling rate requirement of the ADC, making it easy to realize the reception of multi-carrier radar signals with large bandwidth, and providing technical support for constructing high-performance multi-carrier radars. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic structural principle diagram of the dechirp receiving device of the present invention;

[0029] Figure 2 It is a schematic time-frequency relationship diagram of the dechirp receiving method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] Aiming at the deficiencies of the existing multi-carrier signal receiving methods, the basic idea of the present invention is to construct a corresponding reference signal based on the multi-carrier linear frequency modulation signal to realize dechirp reception, so as to realize the single-channel reception of multi-carrier signals, reduce the system complexity while ensuring the coherence between sub-carriers; in addition, the dechirp receiving method can reduce the sampling rate requirement of the ADC, facilitating the reception of multi-carrier radar signals with large bandwidth.

[0031] Specifically, the dechirp receiving method for multi-carrier linear frequency modulation signals of the present invention includes the following steps:

[0032] Step 1, perform IQ mixing on the received multi-carrier linear frequency modulation echo signal and the reference signal. The reference signal has the same initial frequency, number of sub-carriers, time width, and sub-carrier bandwidth as the multi-carrier linear frequency modulation echo signal. The sub-carrier frequency interval of the reference signal is more than the sub-carrier frequency interval of the multi-carrier linear frequency modulation echo signal by f b , and satisfies f b >kτ max , Δf > (N - 2)f b +kτ max , where k is the frequency modulation slope of the sub-carriers in the multi-carrier linear frequency modulation echo signal, τ max is the maximum delay of the multi-carrier linear frequency modulation echo signal, Δf is the sub-carrier frequency interval of the multi-carrier linear frequency modulation echo signal, and N is the number of sub-carriers in the multi-carrier linear frequency modulation echo signal;

[0033] Step 2, respectively filter out the parts with frequencies greater than (N - 1)f b +kτ max in the two signals generated by IQ mixing, and then perform low-speed ADC sampling on the two obtained dechirp signals respectively;

[0034] Step 3, combine the two ADC sampling signals into a complex signal, and then convert the obtained complex signal to the frequency domain to obtain the frequency domain signal of the dechirp signal;

[0035] Step 4: Perform spectrum segmentation on the frequency-domain signal of the dechirped signal according to the frequency ranges after dechirping of each subcarrier, to obtain the frequency-domain signals after dechirping of each subcarrier; the frequency ranges after dechirping of each subcarrier from low to high are successively: 0 to kτ max , f b to f b + kτ max , …, (N - 1)f b to (N - 1)f b + kτ max ;

[0036] Step 5: Convert the frequency-domain signals of each subcarrier into time-domain signals.

[0037] Furthermore, the dechirping receiving method of the multi-carrier linear frequency modulation signal further includes:

[0038] Step 6: Use the method of zero-padding splicing in the time domain to perform full-band multi-carrier fusion on the time-domain signals of each subcarrier.

[0039] Even further, the dechirping receiving method of the multi-carrier linear frequency modulation signal further includes:

[0040] Step 7: Extract target information from the full-band multi-carrier fusion signal, and use the sparse reconstruction method to obtain the high-resolution range information of the target support area.

[0041] For the convenience of public understanding, the technical solution of the present invention will be described in detail below with reference to the accompanying drawings:

[0042] The basic structure of the dechirping receiving device of the present invention is as Figure 1 shown. First, a reference signal with a different subcarrier frequency interval from the multi-carrier linear frequency modulation echo signal is generated, and this reference signal and the multi-carrier linear frequency modulation echo signal are input into the IQ mixer together; for the two dechirped signals output by the IQ mixer, two low-pass filters are respectively used to filter out the low-frequency signals corresponding to the dechirping of each subcarrier, and the two dechirped signals are collected by two low-speed ADCs; the two ADC sampling signals are combined into a complex signal in the form of I + jQ, and then the obtained complex signal is subjected to a fast Fourier transform (FFT) to obtain the frequency-domain signal of the dechirped signal; spectrum segmentation is performed according to the frequency ranges after dechirping of different subcarriers, and inverse fast Fourier transforms (IFFT) are respectively performed on the segmented different spectrum signals to obtain the dechirped time-domain signals of the corresponding subcarriers, that is, the separation and time-domain reconstruction of the subcarrier dechirped signals are completed, and the target information therein can be extracted based on the reconstructed subcarrier dechirped signals.

[0043] The multi-carrier linear frequency modulation echo signal input into the IQ mixer is S rx (t), and its expression is:

[0044]

[0045] Among them, T, f c , Δf, and k are the time width, initial frequency, sub - carrier frequency interval, and sub - carrier frequency modulation slope of the multi - carrier linear frequency - modulated echo signal respectively, R is the distance where the target is located, and N is the number of sub - carriers of the echo signal.

[0046] The radar receiving end generates a reference signal whose sub - carrier frequency interval differs from that of the multi - carrier linear frequency - modulated echo signal by f b . Its expression is:

[0047]

[0048] The reference signal and the multi - carrier linear frequency - modulated echo signal have the same initial frequency, number of sub - carriers, time width, and sub - carrier bandwidth. Only the sub - carrier frequency interval of the reference signal is f b more than that of the echo signal.

[0049] The reference signal and the echo signal are input into the IQ mixer together. Two low - pass filters are used to filter out the low - frequency signals after de - chirping of the corresponding sub - carriers of the two signals from the two output signals, that is, to filter out the parts with frequencies greater than (N - 1)f b +kτ max in the two signals generated by the IQ mixing respectively; the expression of the signal after de - chirping is:

[0050]

[0051] Figure 2 is a schematic diagram of the time - frequency relationship for de - chirping reception of the multi - carrier linear frequency - modulated radar echo. Assume that the maximum delay of the multi - carrier linear frequency - modulated echo signal is τ max = 2R / c (which can be achieved by controlling the transmit signal power, etc.). From equation (3), it can be known that the frequency range of the de - chirped signal of the first sub - carrier is 0~kτ max , the frequency range of the de - chirped signal of the second sub - carrier is f b ~f b +kτ max , and the frequency range of the de - chirped signal of the Nth sub - carrier is (N - 1)f b ~(N - 1)f b +kτ max . When the condition:

[0052] f b >kτ max (4)

[0053] When there is no overlap in the spectra of different subcarrier dechirped signals. To avoid interference caused by the beat frequency between the echo signal of the higher-order subcarrier and the reference signal of the lower-order subcarrier, it is required that the instantaneous frequency of the echo signal of the Nth subcarrier is greater than the instantaneous frequency of the reference signal of the (N - 1)th subcarrier, that is, (N - 1)Δf - kτ max >(N - 2)(Δf + f b ), which simplifies to:

[0054] Δf > (N - 2)f b + kτ max (5)

[0055] When the condition of equation (5) is satisfied, it can be ensured that the beat frequency signal between the reference signal of the higher-order subcarrier and the echo signal of the lower-order subcarrier will not introduce interference to the dechirped signal. Therefore, when equations (4) and (5) are satisfied simultaneously, there is no mutual interference between different subcarrier dechirped signals in the positive frequency range after the two signals are mixed, so they can be separated in the frequency domain.

[0056] The separation of different subcarrier dechirped signals is specifically described in Figure 1 the signal processing part. The two-channel ADC sampling data are combined into a complex signal in the form of I + jQ, and the fast Fourier transform (FFT) is performed on the complex signal to obtain the frequency-domain signal. According to the frequency range of different subcarrier dechirped signals, the obtained signal spectrum is segmented, and the inverse fast Fourier transform (IFFT) is performed respectively to obtain the time-domain signals of the corresponding subcarrier dechirping, that is, the separation of the subcarrier dechirped signals and the reconstruction of the time-domain signals are completed. Subsequently, zero-padding splicing in the time domain can be used to achieve full-band multi-carrier fusion in the case of discontinuous spectra; for the problem that the range image may have high sidelobes caused by zero-padding splicing in the time domain, while extracting the target information from the full-band multi-carrier fusion signal, a sparse reconstruction method can be further used to obtain the high-resolution range information of the target support area.

Claims

1. A dechirping reception method for multi-carrier chirp signals, characterized in that, Including the following steps: Step 1, perform IQ mixing on the received multi-carrier chirp echo signal and the reference signal. The reference signal has the same initial frequency, number of sub-carriers, time width, and sub-carrier bandwidth as the multi-carrier chirp echo signal. The sub-carrier frequency interval of the reference signal is more than that of the multi-carrier chirp echo signal by f b , and it satisfies f b >kτ max , Δf > (N - 2)f b +kτ max , where k is the chirp slope of the sub-carriers in the multi-carrier chirp echo signal, τ max is the maximum delay of the multi-carrier chirp echo signal, Δf is the sub-carrier frequency interval of the multi-carrier chirp echo signal, and N is the number of sub-carriers in the multi-carrier chirp echo signal; Step 2: Filter out the parts with frequencies greater than (N - 1)f in the two signals generated by IQ mixing respectively, and then perform low-speed ADC sampling on the two obtained de-chipped signals respectively; b +kτ max ​ Step 3: Combine the two-channel ADC sampling signals into a complex signal, and then convert the obtained complex signal to the frequency domain to obtain the frequency-domain signal of the dechirped signal; Step 4: Perform spectral segmentation on the frequency-domain signal of the dechirped signal according to the frequency ranges after dechirping of each subcarrier, to obtain the frequency-domain signals after dechirping of each subcarrier; the frequency ranges after dechirping of each subcarrier from low to high are successively: 0 to kτ max , f b to f b + kτ max , …, (N - 1)f b to (N - 1)f b + kτ max ; Step 5: Convert the frequency-domain signals of each subcarrier to the time domain signals.

2. The method for dechirping reception of multi-carrier chirp signals according to claim 1, wherein It also includes: Step 6: Use the time-domain zero-padding splicing method to perform full-band multi-carrier fusion on the time-domain signals of each subcarrier.

3. The dechirping reception method of the multi-carrier chirp signal according to claim 2, characterized in that, It also includes: Step 7: Extract the target information from the full-band multi-carrier fusion signal, and use the sparse reconstruction method to obtain the high-resolution range information of the target support area.

4. The method for dechirping reception of multi-carrier chirp signals according to any one of claims 1 to 3, characterized in that, Use the fast Fourier transform to convert the complex signal to the frequency domain, and use the inverse fast Fourier transform to convert the frequency-domain signals of each subcarrier to the time domain signals.

5. A dechirping receiving device for multi-carrier chirp signals, characterized in that, Including: An IQ mixer is used to perform IQ mixing on the received multi-carrier chirp echo signal and a reference signal. The reference signal has the same initial frequency, number of sub-carriers, time width, and sub-carrier bandwidth as the multi-carrier chirp echo signal. The sub-carrier frequency interval of the reference signal is more than that of the multi-carrier chirp echo signal by f b , and satisfies f b >kτ max , Δf > (N - 2)f b +kτ max , where k is the chirp slope of the sub-carriers in the multi-carrier chirp echo signal, τ max is the maximum delay of the multi-carrier chirp echo signal, Δf is the sub-carrier frequency interval of the multi-carrier chirp echo signal, and N is the number of sub-carriers in the multi-carrier chirp echo signal; A filtering and sampling module, which is used to respectively filter out the parts with frequencies greater than (N - 1)f b +kτ max in the two signals generated by IQ mixing, and then perform low-speed ADC sampling on the two obtained de-angled signals respectively; A time-frequency conversion module, which is used to combine the two-channel ADC sampling signals into a complex signal, and then convert the obtained complex signal to the frequency domain to obtain the frequency-domain signal of the dechirped signal; A spectrum splitting module, which is used to split the frequency-domain signal of the dechirped signal according to the frequency ranges of the dechirped subcarriers, so as to obtain the frequency-domain signals of the dechirped subcarriers; the frequency ranges of the dechirped subcarriers from low to high are successively: 0 to kτ max , f b ~f b +kτ max , …, (N - 1)f b ~(N - 1)f b +kτ max ; A frequency-time conversion module, which is used to convert the frequency-domain signals of each subcarrier to the time domain signals.

6. The dechirping receiving device for multi-carrier chirp signals according to claim 5, characterized in that, It also includes: A multi-carrier fusion module, which is used to perform full-band multi-carrier fusion on the time-domain signals of each subcarrier by using the time-domain zero-padding splicing method.

7. The dechirping receiving device for multi-carrier chirp signals according to claim 6, characterized in that, It also includes: A target information extraction module, which is used to extract the target information from the full-band multi-carrier fusion signal, and use the sparse reconstruction method to obtain the high-resolution range information of the target support area.

8. The dechirping receiving device for multi-carrier chirp signals according to any one of claims 5 to 7, characterized in that The time-frequency conversion module is a fast Fourier transform module, and the frequency-time conversion module is an inverse fast Fourier transform module.

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