Adaptive baseband signal recovery method and system

Abstract

The present invention discloses an adaptive baseband signal recovery method and system. After performing digital processing on a radio frequency signal that has undergone frequency reduction processing, a baseband signal with Doppler frequency shift is obtained; after real-time IQ decomposition, an in-phase signal and an orthogonal signal are obtained; then four-way parallel calculation is performed to obtain four sub-signals, which are respectively transmitted to a signal selector through their corresponding signal transmission channels; the Doppler phase at the current moment is obtained, the sub-signal transmitted at the current moment is determined according to the Doppler phase, and the signal selector is controlled to switch to the corresponding signal transmission channel according to the sub-signal transmitted at the current moment, and an amplitude correction coefficient is calculated according to the Doppler phase; the sub-signal transmitted at the current moment is obtained through the signal selector, and the sub-signal is corrected by using the amplitude correction coefficient to obtain a recovered baseband signal. The present invention is simple to implement, has a small amount of calculation, and has strong real-time performance, and is suitable for various signal systems requiring low delay.

Description

Technical Field

[0001] The present invention relates to the technical field of satellite communication signal processing, and in particular to an adaptive baseband signal recovery method and system. Background Art

[0002] With the increasing demand for despreading in satellite communication systems and signal processing in binary-phase coded pulse compression radar, binary-phase coded signals, due to their excellent range resolution, are widely used in pulse compression radar systems and satellite navigation communications, especially in scenarios where high-speed target signals introduce significant Doppler shift. Within a single signal cycle, in-phase and quadrature signals are extracted in real time, resulting in four sub-chips. The original signal is then restored by combining the timing relationships between the chips. This method is simple to implement, requires minimal computation, and requires few resources.

[0003] However, the high sensitivity of digitally modulated signals to Doppler shift also leads to difficulties in carrier acquisition and despreading algorithms in scenarios with large Doppler shifts. Current approaches to address these issues focus on carrier estimation, including frequency-sweep phase-locked acquisition, adaptive least squares, and maximum likelihood estimation. These methods require pre-compensation or real-time carrier frequency search, resulting in drawbacks such as long acquisition times, complex algorithms, high resource consumption, and significant processing latency. Summary of the Invention

[0004] The purpose of the present invention is to provide an adaptive baseband signal recovery method that can adaptively remove Doppler frequency shift and recover the baseband signal in real time within each cycle time. The method has low computational complexity, good real-time performance and processing delay, and consumes few resources. The method can be well applied to despreading and communication work in scenarios with large Doppler frequency shift.

[0005] To achieve the above objectives, this application provides the following solutions:

[0006] In one aspect, the present application provides an adaptive baseband signal recovery system, comprising:

[0007] The A / D sampling module is used to digitize the acquired down-converted RF signal to obtain a baseband signal with Doppler frequency shift;

[0008] The orthogonal decomposition module is used to perform real-time IQ decomposition of the baseband signal with Doppler frequency shift to obtain the in-phase signal I and the orthogonal signal Q;

[0009] The real-time IQ decomposition module includes four sub-signal calculation modules that perform four-way parallel calculations on the in-phase signal I and the quadrature signal Q to obtain four sub-signals. The four sub-signals are respectively transmitted to the signal selector through corresponding signal transmission channels;

[0010] The parameter calculation module is used to determine the sub-signal to be transmitted at the current moment based on the Doppler phase at the current moment, generate a control signal for the signal sorter and send it to the signal sorter, and calculate the amplitude correction coefficient based on the Doppler phase at the current moment and send it to the amplitude correction module;

[0011] The signal selector is used to switch to the signal transmission channel corresponding to the currently transmitted sub-signal according to the control signal, and transmit the currently transmitted sub-signal to the amplitude correction module;

[0012] The amplitude correction module is used to correct the currently transmitted sub-signal according to the amplitude correction coefficient to obtain a restored baseband signal.

[0013] In some specific implementations, the digitization processing includes:

[0014] After A / D sampling of the RF signal, a sampled signal is obtained; the sampled signal is quantized into a digital signal; and at the same time, the digital signal is down-converted in the digital domain using the signal generated by the DDS to obtain a baseband signal with Doppler frequency shift.

[0015] In some specific implementation schemes, the orthogonal decomposition module uses the CORDIC algorithm to perform real-time IQ decomposition on the baseband signal with Doppler frequency shift to obtain the in-phase signal and the in-phase signal I and the orthogonal signal Q, where the I-path signal is I=sin(x+θ), the Q-path signal is Q=cos(x+θ), θ represents the phase modulation information, x represents the phase difference between the transmitted and received signals, and the frequency value of x is the Doppler frequency shift.

[0016] In some specific implementations, the four sub-signal calculation modules respectively perform the following calculation process to obtain four sub-signals:

[0017] Sig1=I+Q=sin(x+θ)+cos(x+θ)=sin(x+θ+0.25π)

[0018] Sig2=IQ=sin(x+θ)-cos(x+θ)=sin(x+θ-0.25π)

[0019] Sig3=-IQ=-sin(x+θ)-cos(x+θ)=sin(x+θ-0.75π)

[0020] Sig4=QI=cos(x+θ)-sin(x+θ)=sin(x+θ-1.25π);

[0021] In some specific implementations, the parameter calculation module obtains the Doppler phase at the current moment The calculation process is:

[0022]

[0023] in, Indicates the preset initial phase, ft indicates the current moment, and unwrap indicates the The calculated phase is subjected to unwrapping calculation.

[0024] In some specific implementations, the parameter calculation module pre-stores the numbers of the signal transmission channels in the real-time IQ decomposition module and the quadrants corresponding to the sub-signals transmitted by the signal transmission channels. The process of determining the sub-signal transmitted at the current moment is as follows:

[0025] Determine the quadrant position of the Doppler phase at the current moment according to the Doppler phase at the current moment, and determine the number of the signal transmission channel according to the comparison between the quadrant position and the quadrant corresponding to each sub-signal channel;

[0026] A control signal for controlling the signal selector to switch to the corresponding signal transmission channel is generated according to the number of the signal transmission channel.

[0027] In some specific implementations, the amplitude correction coefficient A C The calculation process is:

[0028]

[0029] Where abs represents the absolute value function.

[0030] In a second aspect, the present application provides an adaptive baseband signal recovery method, which specifically includes the following steps:

[0031] S1. Obtain a down-converted radio frequency signal, and digitize the radio frequency signal to obtain a baseband signal with Doppler frequency shift;

[0032] S2, performing real-time IQ decomposition on the baseband signal with Doppler frequency shift to obtain an in-phase signal and a quadrature signal;

[0033] S3, performing four-way parallel calculation on the in-phase signal and the quadrature signal to obtain four sub-signals and transmitting them to the signal selector through their corresponding signal transmission channels;

[0034] S4. Obtain the Doppler phase at the current moment, determine the sub-signal transmitted at the current moment according to the Doppler phase, control the signal sorter to switch to the corresponding signal transmission channel according to the sub-signal transmitted at the current moment, and calculate the amplitude correction coefficient according to the Doppler phase;

[0035] S5. Obtain the sub-signal currently transmitted through the signal selector, and correct the sub-signal using the amplitude correction coefficient to obtain a restored baseband signal.

[0036] In some specific implementations, the parameter calculation module obtains the Doppler phase at the current moment The calculation process is:

[0037]

[0038] in, Indicates the preset initial phase, ft indicates the current moment, and unwrap indicates the The calculated phase is subjected to unwrapping calculation.

[0039] In some specific implementations, the amplitude correction coefficient A C The calculation process is:

[0040]

[0041] Where abs represents the absolute value function.

[0042] The inventive concept of the present invention is:

[0043] Currently, the problems of difficult carrier capture and demodulation algorithms in Doppler frequency shift scenarios mostly revolve around carrier estimation. This process requires pre-compensation or real-time search for the carrier frequency, resulting in long capture time, difficult algorithms, high resource consumption, and large processing delays.

[0044] To address this issue, the present application proposes a system that does not require pre-compensation and carrier search, does not require carrier estimation, and does not use other devices such as discriminators or phase-locked loops. In scenarios where high-speed target signals bring about large Doppler shifts, in a single signal cycle, after A / D processing is completed, a field programmable gate array is used to complete a digital down-conversion module in the digital domain to obtain a baseband signal with Doppler shift; then, through an orthogonal decomposition module, an in-phase signal I and an orthogonal signal Q are obtained; then, in a real-time IQ decomposition module, four sub-signals are calculated; finally, a parameter calculation module is used to obtain the quadrature in which the current Doppler phase is located, and a four-selection module is used to correctly output the current corresponding sub-signal. After amplitude correction, a baseband signal with Doppler shift removed can be obtained at the output port. This method is simple to implement, has a small amount of computation, and is implemented using a field programmable gate array (FPGA), has strong real-time performance, and is suitable for various signal systems requiring low latency. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A block diagram of an adaptive baseband signal recovery system provided by an embodiment of the present invention;

[0046] Figure 2 It is a time domain diagram of the baseband signal when there is no Doppler frequency shift;

[0047] Figure 3 Schematic diagram of baseband signal demodulation measurement results when there is no Doppler frequency shift, where (a) is the measurement time diagram, (b) is the spectrum diagram, and (c) is the output result diagram;

[0048] Figure 4 It is the time domain waveform of the echo signal with Doppler frequency shift;

[0049] Figure 5 Figure 1 shows the demodulation test of a baseband signal with Doppler frequency shift, where (a) shows the measurement time diagram, (b) shows the spectrum diagram, and (c) shows the output result diagram.

[0050] Figure 6 Schematic diagram of time domain test results of four sub-signals in a sub-signal calculation module provided in an embodiment of the present invention; wherein (a) is a schematic diagram of the time domain test results of sig1, (b) is a schematic diagram of the time domain test results of sig2; (c) is a schematic diagram of the time domain test results of sig3; and (d) is a schematic diagram of the time domain test results of sig4;

[0051] Figure 7 A time domain diagram of a recovered baseband signal provided by an embodiment of the present invention;

[0052] Figure 8 Schematic diagram of the demodulation test results of the recovered baseband signal provided by an embodiment of the present invention, wherein (a) is a measurement time diagram, (b) is a spectrum diagram, and (c) is a schematic diagram of the output results. DETAILED DESCRIPTION

[0053] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0054] Unless otherwise specifically stated, the relative arrangement of components and steps, the numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention.

[0055] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0056] Additionally, descriptions of well-known structures, functions, and configurations may be omitted for clarity and conciseness. Those skilled in the art will recognize that various changes and modifications can be made to the examples described herein without departing from the spirit and scope of the present disclosure.

[0057] Technologies, methods, and apparatus known to ordinary technicians in the relevant field may not be discussed in detail, but where appropriate, such technologies, methods, and apparatus should be considered part of the authorization specification.

[0058] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0059] Before introducing the specific implementation methods of this application, the following concepts are explained:

[0060] Example 1

[0061] like Figure 1 As shown, this embodiment provides an adaptive baseband signal recovery system, including:

[0062] The A / D sampling module is used to digitize the acquired down-converted RF signal to obtain a baseband signal with Doppler frequency shift;

[0063] The orthogonal decomposition module is used to perform real-time IQ decomposition of the baseband signal with Doppler frequency shift to obtain the in-phase signal I and the orthogonal signal Q;

[0064] The real-time IQ decomposition module includes four sub-signal calculation modules that perform four-way parallel calculations on the in-phase signal I and the quadrature signal Q to obtain four sub-signals. The four sub-signals are respectively transmitted to the signal selector through corresponding signal transmission channels;

[0065] The parameter calculation module is used to determine the sub-signal to be transmitted at the current moment based on the Doppler phase at the current moment, generate a control signal for the signal sorter and send it to the signal sorter, and calculate the amplitude correction coefficient based on the Doppler phase at the current moment and send it to the amplitude correction module;

[0066] The signal selector is used to switch to the signal transmission channel corresponding to the currently transmitted sub-signal according to the control signal, and transmit the currently transmitted sub-signal to the amplitude correction module;

[0067] The amplitude correction module is used to correct the currently transmitted sub-signal according to the amplitude correction coefficient to obtain a restored baseband signal.

[0068] In digital modulation communication scenarios, if the signal is compressed to find the pulse pressure peak, the amplitude error of the recovered signal will be particularly large. In order to avoid this situation, this application performs amplitude correction on the signal, expanding the applicable scenarios.

[0069] Based on Figure 1 The specific processing process in each module of the system is as follows:

[0070] In the A / D sampling module, the digital processing includes:

[0071] After A / D sampling of the RF signal, a sampled signal is obtained; the sampled signal is quantized into a digital signal; and at the same time, the digital signal is down-converted in the digital domain using the signal generated by the DDS to obtain a baseband signal with Doppler frequency shift.

[0072] It should be noted that A / D sampling conversion and digital down-conversion processing are both commonly used methods and will not be described in detail in this application.

[0073] The orthogonal decomposition module uses the CORDIC algorithm to perform real-time IQ decomposition on the baseband signal with Doppler frequency shift to obtain the in-phase signal and the orthogonal signal Q. Among them, the I-path signal is I = sin(x + θ), and the Q-path signal is Q = cos(x + θ). θ represents the phase modulation information, x represents the phase difference between the transmitted and received signals, and x is in one of the four quadrants between 0 and 2π. The frequency value of x is the Doppler frequency shift.

[0074] The four sub-signal calculation modules perform the following calculation process respectively, and the four sub-signals obtained are:

[0075] Sig1=I+Q=sin(x+θ)+cos(x+θ)=sin(x+θ+0.25π)

[0076] Sig2=IQ=sin(x+θ)-cos(x+θ)=sin(x+θ-0.25π)

[0077] Sig3=-IQ=-sin(x+θ)-cos(x+θ)=sin(x+θ-0.75π)

[0078] Sig4=QI=cos(x+θ)-sin(x+θ)=sin(x+θ-1.25π);

[0079] The four sub-signals are located in four quadrants, where Sig1 corresponds to the first quadrant, Sig2 corresponds to the second quadrant, Sig3 corresponds to the third quadrant, and Sig4 corresponds to the fourth quadrant. The above formula normalizes the amplitude in the simplified calculation.

[0080] The Doppler phase at the current moment is obtained in the parameter calculation module The calculation process is:

[0081]

[0082] in, Indicates the preset initial phase, ft indicates the current moment, and unwrap indicates the The calculated phase is subjected to unwrapping calculation.

[0083] Specifically, in order to switch the signal sorter to the corresponding transmission channel, each sub-signal calculation module can be defined, and the calculation formulas of the four sub-signal calculation modules are fixed as follows:

[0084] Sig1=I+Q

[0085] Sig2=IQ

[0086] Sig3=-IQ

[0087] Sig4=QI

[0088] Therefore, the four sub-signal calculation modules are numbered respectively, and the parameter calculation module pre-stores the number of each signal transmission channel in the real-time IQ decomposition module and the quadrant corresponding to the sub-signal transmitted by each signal transmission channel. In this way, the corresponding transmission channel can be located according to the quadrant determined by the Doppler phase. The process of determining the sub-signal transmitted at the current moment is as follows:

[0089] Determine the quadrant position of the Doppler phase at the current moment according to the Doppler phase at the current moment, and determine the number of the signal transmission channel according to the comparison between the quadrant position and the quadrant corresponding to each sub-signal channel;

[0090] A control signal for controlling the signal selector to switch to the corresponding signal transmission channel is generated according to the number of the signal transmission channel.

[0091] Amplitude correction coefficient A C The calculation process is:

[0092]

[0093] Where abs represents the absolute value function.

[0094] Example 2

[0095] Based on the system of Example 1, this embodiment provides an adaptive baseband signal recovery method and is described in conjunction with specific data. This embodiment takes the communication digital modulation signal transmission wavelength of 0.04 meters, the symbol rate of 1 Msps, and the use of a raised cosine filter with a roll-off coefficient of 0.35 for shaping filtering as an example. Figure 2 It can be seen that when there is no Doppler frequency shift in the signal time domain, the demodulation situation is as follows Figure 3 As shown in (a)-(c), it can be seen that the demodulated EVM is about 0.8% rms. When the source speed is 3000m / s, the time domain waveform of the echo signal is as follows: Figure 4 As shown, in the case of Doppler frequency shift, the demodulation Figure 5 As shown in (a)-(c), it can be seen that the demodulation EVM is about 25% rms. Compared with the case without Doppler frequency shift, the demodulation quality is greatly affected. The system involved in the present invention can be used to recover the baseband signal and obtain the correct demodulation result. The specific implementation process is as follows:

[0096] S1. Obtain a down-converted radio frequency signal, and digitize the radio frequency signal to obtain a baseband signal with Doppler frequency shift;

[0097] The A / D sampling module performs A / D sampling on the down-converted RF signal and quantizes it into a digital signal. At the same time, the signal generated by the DDS is down-converted in the digital domain to obtain a baseband signal with Doppler frequency shift.

[0098] S2, performing real-time IQ decomposition on the baseband signal with Doppler frequency shift to obtain an in-phase signal and a quadrature signal;

[0099] In the digital domain, the CORDIC algorithm is used to perform real-time IQ decomposition on the baseband signal with Doppler frequency shift obtained in step 1 to obtain a pair of orthogonal signals I and Q, as shown in the following example: Figure 4 shown.

[0100] S3, performing four-way parallel calculation on the in-phase signal and the quadrature signal to obtain four sub-signals and transmitting them to the signal selector through their corresponding signal transmission channels;

[0101] The in-phase signal and the orthogonal signal are calculated in four parallel ways to obtain four sub-signals as follows: Figure 6 Sig1=I+Q shown in (a), as Figure 6 Sig2 = IQ as shown in (b), Figure 6 Sig3 = -IQ as shown in (c), Figure 6 Sig4 = QI shown in (d);

[0102] S4. Obtain the Doppler phase at the current moment, determine the sub-signal transmitted at the current moment according to the Doppler phase, control the signal sorter to switch to the corresponding signal transmission channel according to the sub-signal transmitted at the current moment, and calculate the amplitude correction coefficient according to the Doppler phase;

[0103] In the parameter calculation module, the quadrant corresponding to the current moment, that is, the phase of the Doppler frequency shift signal, is calculated. The first quadrant corresponds to 0 to 0.5π, the second quadrant corresponds to 0.5π to π, the third quadrant corresponds to -0.5π to 0, and the fourth quadrant corresponds to -π to 0.5π. The calculated quadrant is then used to generate the corresponding control signal, that is, sub-signal Sig1 is selected in the first quadrant, sub-signal Sig2 is selected in the second quadrant, sub-signal Sig3 is selected in the third quadrant, and sub-signal Sig4 is selected in the fourth quadrant. This sub-signal is always in phase with the baseband signal.

[0104] For example, at time 5555.75us, the phase of the Doppler frequency shift is 2.2777rad, then it is determined to be in the second-phase quadrant, and the parameter calculation module outputs a control signal for selecting the sub-signal Sig2;

[0105] The amplitude correction factor at the current moment can be calculated as follows:

[0106]

[0107] S5. Obtain the sub-signal currently transmitted through the signal selector, and correct the sub-signal using the amplitude correction coefficient to obtain a restored baseband signal.

[0108] The signal selector is a four-to-one signal selector. Based on the control signal from the parameter calculation module, the four-to-one signal selector selects the corresponding branched sub-signal for output, generating the recovered baseband signal. For example, at time 5555.75µs, the parameter calculation module outputs a control signal selecting sub-signal Sig2, and the four-to-one signal selector selects sub-signal Sig2.

[0109] In the amplitude correction module, the signal is amplitude corrected, that is, multiplied by the amplitude correction coefficient A C And output to obtain the restored baseband signal.

[0110] For example, at time 5555.75us, the amplitude correction module will perform amplitude correction before the signal is output, and the correction coefficient is 0.753. This coefficient is calculated and given in the parameter calculation module.

[0111] like Figure 7-Figure 8 The experimental results obtained based on the above example show that this embodiment can successfully recover the digital modulation baseband signal from the signal with Doppler frequency shift. The waveform of the recovered baseband digital modulation signal is as follows: Figure 7 As shown, the demodulation result of the restored baseband digital modulation signal is as follows Figure 8As shown in Figures (a)-(c), the demodulation EVM is around 1.7% rms, which is significantly lower than the demodulation results of the baseband signal with Doppler frequency shift. This result shows that the method proposed in this application can be used as a baseband signal recovery method to adaptively eliminate Doppler frequency shift.

[0112] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Based on the technical essence of the present invention and within the spirit and principles of the present invention, any simple modification, equivalent replacement and improvement of the above embodiment shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. An adaptive baseband signal recovery system, characterized in that: include: The A / D sampling module is used to digitize the acquired down-converted RF signal to obtain a baseband signal with Doppler frequency shift; The orthogonal decomposition module is used to perform real-time IQ decomposition of the baseband signal with Doppler frequency shift to obtain the in-phase signal I and the orthogonal signal Q; A real-time IQ decomposition module includes four sub-signal calculation modules that perform four-way parallel calculations on the in-phase signal I and the quadrature signal Q. The four sub-signal calculation modules are used to obtain four sub-signals and transmit the four sub-signals to the signal sorter through corresponding signal transmission channels; The parameter calculation module is used to determine the sub-signal to be transmitted at the current moment based on the Doppler phase at the current moment, generate a control signal for the signal sorter and send it to the signal sorter, and calculate the amplitude correction coefficient based on the Doppler phase at the current moment and send it to the amplitude correction module; The Doppler phase at the current moment is obtained in the parameter calculation module φ d The calculation process is: φ d =unwrap(φ_init+2π*ft); Where φ_init represents the preset initial phase, ft represents the current moment, and unwrap represents the unwrapping calculation of the phase calculated by φ_init+2π*ft; The signal selector is used to switch to the signal transmission channel corresponding to the currently transmitted sub-signal according to the control signal, and transmit the currently transmitted sub-signal to the amplitude correction module; An amplitude correction module is used to correct the currently transmitted sub-signal according to the amplitude correction coefficient to obtain a restored baseband signal; Amplitude correction factor A C The calculation process is: A C =-abs(sin(2 φ d ))*0.25)+1 Where abs represents the absolute value function.

2. The adaptive baseband signal recovery system according to claim 1, characterized in that: Digital processing includes: After A / D sampling of the RF signal, a sampled signal is obtained; the sampled signal is quantized into a digital signal; and at the same time, the digital signal is down-converted in the digital domain using the signal generated by the DDS to obtain a baseband signal with Doppler frequency shift.

3. The adaptive baseband signal recovery system according to claim 1, wherein: The orthogonal decomposition module uses the CORDIC algorithm to perform real-time IQ decomposition on the baseband signal with Doppler frequency shift to obtain the in-phase signal I and the orthogonal signal Q, where the in-phase signal I is: I=sin( x + θ ), the orthogonal signal Q is: Q = cos ( x + θ ), θ Indicates phase modulation information, x Represents the phase difference between the transmitted and received signals. x The frequency value of is the Doppler shift.

4. The adaptive baseband signal recovery system according to claim 3, wherein: The four sub-signal calculation modules perform the following calculation process respectively, and the four sub-signals obtained are: 。 5. The adaptive baseband signal recovery system according to claim 1, wherein: The parameter calculation module pre-stores the numbers of each signal transmission channel in the real-time IQ decomposition module and the quadrants corresponding to the sub-signals transmitted by each signal transmission channel. The process of determining the sub-signal transmitted at the current moment is as follows: Determine the quadrant position of the Doppler phase at the current moment according to the Doppler phase at the current moment, and determine the number of the signal transmission channel according to the quadrant position and the quadrant corresponding to each sub-signal; A control signal for controlling the signal selector to switch to the corresponding signal transmission channel is generated according to the number of the signal transmission channel.

6. An adaptive baseband signal recovery method, characterized in that: The specific steps include: S1. Obtain a down-converted radio frequency signal, and digitize the radio frequency signal to obtain a baseband signal with Doppler frequency shift; S2, performing real-time IQ decomposition on the baseband signal with Doppler frequency shift to obtain an in-phase signal and a quadrature signal; S3, performing four-way parallel calculation on the in-phase signal and the quadrature signal to obtain four sub-signals and transmitting them to the signal selector through their corresponding signal transmission channels; S4. Obtain the Doppler phase at the current moment, determine the sub-signal transmitted at the current moment according to the Doppler phase, control the signal sorter to switch to the corresponding signal transmission channel according to the sub-signal transmitted at the current moment, and calculate the amplitude correction coefficient according to the Doppler phase; Get the Doppler phase at the current moment φ d The calculation process is: φ d =unwrap(φ_init+2π*ft); Where φ_init represents the preset initial phase, ft represents the current moment, and unwrap represents the unwrapping calculation of the phase calculated by φ_init+2π*ft; Amplitude correction factor A C The calculation process is: A C =-abs(sin(2 φ d ))*0.25)+1 Among them, abs represents the absolute value function; S5. Obtain the sub-signal currently transmitted through the signal selector, and correct the sub-signal using the amplitude correction coefficient to obtain a restored baseband signal.

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