Ka-band DBF-SAR real-time processing system and method

Abstract

The present invention provides a Ka-band DBF-SAR real-time processing system and method, including: a data acquisition module: using different AD acquisition sub-boards to sample multi-channel intermediate frequency signals and perform framing and caching; a digital processing module: digitally down-converting the cached multi-channel intermediate frequency signals to obtain multi-channel baseband signals, and sequentially filtering, decimating and processing with an improved DBF SCORE algorithm, and synthesizing multi-channel echo data; the improved DBF-SCORE algorithm performs range-oriented multi-channel DBF after channel equalization and pulse compression, thereby reducing the amount of data downlink. The present invention has the advantages of real-time processing, multi-channel and high integration, and is expected to play an important role in the field of millimeter-wave SAR.

Description

Technical Field

[0001] The present invention relates to a radar real-time processing system, and in particular to a Ka-band DBF-SAR real-time processing system and method. Background Art

[0002] SAR is a technology that uses the principle of synthetic aperture to obtain complex data of interferometric scenes for imaging. Traditional SAR uses a single antenna to transmit and receive electromagnetic waves with a frequency of less than 10 GHz, and has been widely used in geographic surveying and mapping, wide-area detection, and ocean monitoring.

[0003] In order to achieve high-gain wide-band imaging, DBF-SAR that uses range-directed multi-channel simultaneous reception is difficult to implement in the low-frequency band due to the limited antenna volume. This is the fundamental reason why multi-channel SAR has not yet been widely used.

[0004] When using a low-band SAR system to achieve multi-channel reception, in order to achieve the same bandwidth coverage as the Ka-band SAR multi-channel system, the 1.25Ghz L-band antenna requires 28.6 times the area, the 5.6Ghz C-band antenna requires 6.4 times the area, and the 9.6Ghz X-band antenna requires 3.7 times the area, which will bring higher cost requirements and technical risks. At present, the technical approach to achieving multi-channel real-time synthesis is still mainly at the algorithm level.

[0005] Patent document CN111929682A (application number: 202010713542.9) discloses an airborne DBF-TOPS SAR imaging method based on range-based segmentation, including the following steps: S1, obtaining echo data of each receiving channel of the observation scene; S2, performing equivalent phase center processing on the echo data of each receiving channel; S3, aligning the envelopes of the echo data of each channel; S4, performing range-based segmentation on the echo data after envelope alignment; S5, processing the corresponding range blocks of each channel by range block using the DBF processing method; S6, focusing the echo data after DBF fusion processing for imaging. This patent studies the algorithm of range-based segmentation through the combined imaging algorithm of DBF-TOPS, and does not involve specific system hardware implementation.

[0006] Patent document CN101702027A (application number: 200910216504.6) discloses a method for reconstructing the non-uniform spectrum of an azimuth multi-beam synthetic aperture radar, which belongs to the synthetic aperture radar signal processing technology and solves the problems of high false rate and poor imaging quality of non-uniform sampling signal imaging in the prior art. The method includes the following steps: (1) establishing a periodic non-uniform sampling echo signal model; (2) deriving a spectrum reconstruction algorithm for the non-uniform sampling signal of an azimuth multi-beam SAR based on the FrFT spectrum reconstruction theory; (3) reconstructing the spectrum of the non-uniform sampling signal into the spectrum of the uniform sampling signal; (4) using the CS algorithm to image the spectrum of the uniform sampling signal to achieve two-dimensional focused imaging of the azimuth multi-beam SAR. This patent is an algorithm for converting uniform sampling into uniform sampling in the azimuth dimension.

[0007] Patent document CN101236247A (application number: 200810101522.5) discloses a satellite-borne multi-channel antenna SAR data channel amplitude and phase error correction platform. By selecting the amplitude and phase characteristics of a channel as a standard, the amplitude and phase characteristics of other channels are subjected to complex division operation, and the ratio between the amplitude and phase characteristics of other channels and the amplitude and phase characteristics of the selected standard channel can be obtained. When processing actual data, it is only necessary to divide the amplitude and phase characteristics of other channels except the standard channel by the corresponding ratio result, thereby avoiding the error introduced by the signal generator itself; on the other hand, although the amplitude and phase characteristics of the selected standard channel are not completely ideal, since the data of each channel has the same amplitude and phase characteristics after the amplitude and phase error correction, the appearance of false targets can be effectively suppressed in the azimuth direction, and the ideal azimuth image performance index can be obtained. At the same time, from the perspective of imaging, the error compensation effect is evaluated and adjusted adaptively, thereby obtaining a satisfactory compensation effect. This patent focuses on the amplitude and phase correction of spaceborne SAR channels, and completes channel equalization through an amplitude and phase correction method based on frequency domain data. It does not overlap with the research content of this achievement. It is applied to DPCA of azimuth multi-channels, while this achievement is applied to distance multi-channels; it is applied to inter-channel error extraction in the frequency domain, and this patent completes inter-channel error extraction in the time domain after completing distance compression in the frequency domain. The two belong to different levels.

[0008] The frequency range of millimeter wave is usually defined as 30-300GHz, and the corresponding wavelength is 1mm-10mm. The Ka-band real-time processing system involved in this patent is in the millimeter wave band. Compared with the lower frequency band processing system, the Ka-band DBF-SAR real-time processing system has the following technical innovations: 1. The wavelength of millimeter wave is short, which greatly reduces the actual size of the device under the condition that the electrical length remains unchanged, and can realize the integrated design of single-platform multi-antenna DBF; 2. Under the same antenna size, a larger width can be achieved to obtain an ideal mapping range; 3. Multi-channel reception synthesis realizes DBF-SCORE and reduces the transmission power requirement; 4. From the perspective of platform composition, FPGA is used to realize multi-channel echo data processing in the distance direction, and multiple processing platforms can be combined to realize data processing in different azimuth directions. In the future, the function can be expanded according to the requirements of different Ka-band DBF-SAR systems to improve the adaptability of the digital processing platform.

[0009] Compared with the low-frequency band signal processing structure, the Ka-band real-time processing system adopted by the present invention has the advantages of multi-channel, high gain, and lightweight equipment. Therefore, the real-time processing system involved in this patent has better engineering value. Summary of the invention

[0010] In view of the defects in the prior art, the object of the present invention is to provide a Ka-band DBF-SAR real-time processing system and method.

[0011] A Ka-band DBF-SAR real-time processing system provided by the present invention comprises:

[0012] Data acquisition module: Use different AD acquisition sub-boards to sample multi-channel intermediate frequency signals and perform framing and buffering;

[0013] Digital processing module: digitally down-converts the cached multi-channel intermediate frequency signal to obtain a multi-channel baseband signal, and performs filtering, extraction, and improved DBF SCORE algorithm processing in turn, and synthesizes multi-channel echo data;

[0014] The improved DBF-SCORE algorithm performs distance multi-channel DBF after channel equalization and pulse compression, thereby reducing the amount of data transmitted downstream.

[0015] Preferably, in the data acquisition module, different AD acquisition sub-boards are selected according to the number of antenna apertures to implement digital echo processing of N apertures.

[0016] Preferably, the data acquisition module can communicate directly with the backend device bypassing the data processing module.

[0017] Preferably, the improved DBF-SCORE algorithm adopts: multi-channel baseband signal data is first subjected to matched filtering to obtain high resolution in the range direction, and then DBF weighting, frequency domain interference filtering, multi-channel synthesis and time domain data recovery processing are sequentially performed.

[0018] Preferably, the improved DBF-SCORE algorithm adopts: firstly, the baseband echoes of each channel after channel consistency compensation are respectively subjected to FFT transformation, then multiplied by the range-pulse-compression function, and then the obtained results are restored to the time domain through IFFT transformation to obtain the high-resolution signal s after pulse compression. n (t); Each channel signal in the time domain and the generated DBF weighting coefficient w n (t) FFT transformation after multiplication; each channel data is interfered with the reference channel in the frequency domain, and the low-frequency component after interference phase filtering is restored to the original channel; finally, the data of each channel are summed and IFFT transformation is performed to obtain the time domain synthetic signal.

[0019] A Ka-band DBF-SAR real-time processing method provided by the present invention comprises:

[0020] Step S1: The data acquisition module uses different AD acquisition sub-boards to sample the intermediate frequency signals of multiple channels and perform framing and buffering;

[0021] Step S2: the data processing module digitally down-converts the cached multi-channel intermediate frequency signal to obtain a multi-channel baseband signal, and sequentially performs filtering, extraction, and improved DBF-SCORE algorithm processing, and synthesizes the multi-channel echo data;

[0022] The improved DBF-SCORE algorithm performs distance multi-channel DBF after channel equalization and pulse compression, thereby reducing the amount of data transmitted downstream.

[0023] Preferably, the step S1 adopts: selecting different AD acquisition sub-boards according to the number of antenna apertures to realize N aperture digital echo processing.

[0024] Preferably, the step S1 adopts: the data acquisition module can directly communicate with the back-end device across the data processing module.

[0025] Preferably, the improved DBF-SCORE algorithm adopts: multi-channel baseband signal data is first subjected to matched filtering to obtain high resolution in the range direction, and then DBF weighting, frequency domain interference filtering, multi-channel synthesis and time domain data recovery processing are sequentially performed.

[0026] Preferably, the improved DBF-SCORE algorithm adopts: firstly, the baseband echoes of each channel after channel consistency compensation are respectively subjected to FFT transformation, then multiplied by the range-pulse-compression function, and then the obtained results are restored to the time domain through IFFT transformation to obtain the high-resolution signal s after pulse compression. n (t); Each channel signal in the time domain and the generated DBF weighting coefficient w n (t) FFT transformation after multiplication; each channel data is interfered with the reference channel in the frequency domain, and the low-frequency component after interference phase filtering is restored to the original channel; finally, the data of each channel are summed and IFFT transformation is performed to obtain the time domain synthetic signal.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention adopts the integrated design of multiple receiving channels under millimeter wave, which effectively reduces the cost and equipment size;

[0029] 2. The present invention improves the signal-to-noise ratio by synthesizing multiple channels of echoes;

[0030] 3. The present invention is implemented by FPGA and has extremely high scalability in terms of the number of channels;

[0031] 4. The present invention has the advantages of real-time processing, multi-channel and high integration, and is expected to play an important role in the field of millimeter wave SAR. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0033] Figure 1 This is a schematic diagram of the DBF principle of the present invention.

[0034] Figure 2 This is a flow chart of the improved DBF-SCORE processing method of the present invention.

[0035] Figure 3 This is a simulation diagram of the signal-to-noise ratio improvement of the present invention.

[0036] Figure 4 This is a schematic diagram of the FPGA system implementation of the present invention.

[0037] Figure 5 This is a processing flow chart of the FPGA acquisition module of the present invention.

[0038] Figure 6 This is a processing flow chart of the FPGA data processing module of the present invention. DETAILED DESCRIPTION

[0039] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0040] The object of the present invention is to provide a multi-channel, integrated, high-resolution Ka-band DBF-SAR real-time processing system.

[0041] Example 1

[0042] A Ka-band DBF-SAR real-time processing system provided by the present invention comprises:

[0043] Data acquisition module: Use different AD acquisition sub-boards to sample multi-channel intermediate frequency signals and perform framing and buffering;

[0044] Digital processing module: digitally down-convert the cached multi-channel intermediate frequency signal to obtain a multi-channel baseband signal, and perform filtering, extraction, and improved DBF-SCORE algorithm processing in turn, and synthesize multi-channel echo data;

[0045] The improved DBF-SCORE algorithm performs distance multi-channel DBF after channel equalization and pulse compression, thereby reducing the amount of data transmitted downstream.

[0046] Specifically, in the data acquisition module, different AD acquisition sub-boards are selected according to the number of antenna apertures to implement N-aperture digital echo processing, which has extremely high scalability.

[0047] Specifically, the data acquisition module can communicate directly with the backend device across the data processing module.

[0048] Specifically, the improved DBF-SCORE algorithm adopts: multi-channel baseband signal data is first matched filtered to obtain high resolution in the range direction, and then DBF weighting, frequency domain interference filtering, multi-channel synthesis and time domain data recovery are performed in sequence. The purpose of implementing multi-channel DBF weighted superposition in the digital domain is to achieve signal-to-noise ratio enhancement, while the purpose of implementing it through hardware is to reduce the output data rate and the total amount of stored data.

[0049] Specifically, the improved DBF-SCORE algorithm adopts: firstly, the baseband echo of each channel after channel consistency compensation is subjected to FFT transformation, then multiplied by the range-pulse-compression function, and then the obtained result is restored to the time domain through IFFT transformation to obtain the high-resolution signal s after pulse compression. n (t); Each channel signal in the time domain and the generated DBF weighting coefficient wn (t) FFT transformation after multiplication; each channel data is interfered with the reference channel in the frequency domain, and the low-frequency component after interference phase filtering is restored to the original channel; finally, the data of each channel is summed and IFFT transformation is performed to obtain the time domain synthetic signal. The signal-to-noise ratio of the target obtained by the DBF weighted algorithm is significantly improved compared with the signal-to-noise ratio of the signal obtained by single-channel data.

[0050] The present invention reduces the requirements for antenna power density and radio frequency link, which is conducive to reducing costs, shortening the development cycle, and realizing system miniaturization. The theoretical gain (noise suppression capability) obtained by N channels is 10log10(N) (dB), while the main way to increase the gain of traditional single-channel SAR systems is to increase the antenna transmission power, which will put forward great requirements on the antenna power density and radio frequency link.

[0051] A Ka-band DBF-SAR real-time processing method provided by the present invention comprises:

[0052] Step S1: The data acquisition module uses different AD acquisition sub-boards to sample the intermediate frequency signals of multiple channels and perform framing and buffering;

[0053] Step S2: the digital processing module digitally down-converts the cached multi-channel intermediate frequency signal to obtain a multi-channel baseband signal, and sequentially performs filtering, extraction, and improved DBF-SCORE algorithm processing, and multi-channel echo data synthesis;

[0054] The improved DBF-SCORE algorithm performs distance multi-channel DBF after channel equalization and pulse compression, thereby reducing the amount of data transmitted downstream.

[0055] Specifically, the step S1 adopts: selecting different AD acquisition sub-boards according to the number of antenna apertures to realize N aperture digital echo processing, which has extremely high scalability.

[0056] Specifically, the data acquisition module can communicate directly with the backend device across the data processing module.

[0057] Specifically, the improved DBF-SCORE algorithm adopts: multi-channel baseband signal data is first matched filtered to obtain high resolution in the range direction, and then DBF weighting, frequency domain interference filtering, multi-channel synthesis and time domain data recovery are performed in sequence. The purpose of implementing multi-channel DBF weighted superposition in the digital domain is to achieve signal-to-noise ratio enhancement, while the purpose of implementing it through hardware is to reduce the output data rate and the total amount of stored data.

[0058] Specifically, the improved DBF-SCORE algorithm adopts: firstly, the baseband echo of each channel after channel consistency compensation is subjected to FFT transformation, then multiplied by the range-pulse-compression function, and then the obtained result is restored to the time domain through IFFT transformation to obtain the high-resolution signal s after pulse compression. n (t); Each channel signal in the time domain and the generated DBF weighting coefficient w n (t) FFT transformation after multiplication; each channel data is interfered with the reference channel in the frequency domain, and the low-frequency component after interference phase filtering is restored to the original channel; finally, the data of each channel is summed and IFFT transformation is performed to obtain the time domain synthetic signal. The signal-to-noise ratio of the target obtained by the DBF weighted algorithm is significantly improved compared with the signal-to-noise ratio of the signal obtained by single-channel data.

[0059] The present invention reduces the requirements for antenna power density and radio frequency link, which is conducive to reducing costs, shortening the development cycle, and realizing system miniaturization. The theoretical gain (noise suppression capability) obtained by N channels is 10log10(N) (dB), while the main way to increase the gain of traditional single-channel SAR systems is to increase the antenna transmission power, which will put forward great requirements on the antenna power density and radio frequency link.

[0060] Example 2

[0061] Embodiment 2 is a preferred embodiment of Embodiment 1

[0062] The invention discloses a novel Ka-band DBF-SAR real-time processing system, which has the characteristics of miniaturization, lightness and strong expansibility.

[0063] The present invention is described in more detail below in conjunction with the accompanying drawings:

[0064] like Figure 1 As shown, the Ka-band DBF-SAR real-time processing system of the present invention has N apertures in the range direction and correspondingly has N channels. A middle aperture or part of the apertures is used to transmit a wide beam to illuminate a wide mapping area, and each aperture receives separately. The angle between the center of the receiving beam and the vertical direction at any moment is determined by the estimation of the echo direction.

[0065] like Figure 2 As shown, the Ka-band DBF-SAR real-time processing system of the present invention first performs FFT transformation on the baseband echo signals of each channel after channel consistency compensation, and then uses the range-direction pulse compression function H(f) to perform complex multiplication. The result of multiplying each channel with the corresponding pulse compression function is subjected to IFFT to obtain the pulse compressed signal s n (t); data of each channel s n (t) and weighting function w n(t) After complex multiplication, FFT transformation is performed to the frequency domain; the frequency domain signals of each channel are interfered with the reference channel respectively, and the interference results are compensated to the original channel after interference phase filtering; finally, the data of each channel are summed and IFFT transformed to obtain the time domain data after DBF synthesis.

[0066] like Figure 3 As shown, in the Ka-band DBF-SAR real-time processing system of the present invention, the DBF synthetic time domain signal obtains a signal-to-noise ratio gain compared with the single-channel time domain signal.

[0067] like Figure 4 As shown, the Ka-band DBF-SAR real-time processing system of the present invention has an acquisition module located at the front end of the real-time processing system, which uses different AD acquisition sub-boards to sample multi-channel intermediate frequency signals and perform framing and buffering; it can also assist in data processing, including low-pass filtering, data extraction and other functions. The main components are 1 acquisition FPGA chip and two external FMC sub-boards.

[0068] like Figure 5 As shown, the Ka-band DBF-SAR real-time processing system of the present invention adopts the XC7VX485T 2FFG1761I chip of XILINX for acquisition FPGA, which is connected to the AD acquisition sub-board through the standard FMC interface. Different AD acquisition sub-boards are used to sample the intermediate frequency signals of multiple channels and perform framing and caching, so that the acquisition of 8-channel DBF echo data from two acquisition sub-boards can be realized. After the data is transmitted to the data processing module, the conversion from the intermediate frequency signal to the baseband signal is completed. Two external FMC interfaces are used to install the AD acquisition sub-board, and two groups of DDR3 chips are used for cache speed reduction processing. Each group of high-speed memory has a total of 4 chips / 64 bits, which completes the cache of 4-way analog echo data. The cascade can realize the cache of 25.6Gbps data.

[0069] The acquisition module can communicate directly with the back-end equipment across the processing module, so that the Ka-band DBF-SAR real-time processing system can be applied to other specific use environments. For example, when the front end is a zero intermediate frequency receiver output, since the output signal is a baseband signal, the data acquisition and processing volume is small, and the acquisition module can be used as an independent processing platform to complete the relevant processing of the echo data.

[0070] like Figure 6As shown, the Ka-band DBF-SAR real-time processing system of the present invention adopts a data processing module designed with 3 FPGAs, which mainly completes digital orthogonal demodulation (mixing, filtering, extraction) of multi-channel data, extraction and compensation of consistency errors of each channel, matched filtering, DBF weighted calculation and compensation, inter-channel interference filtering processing, synthesis, BAQ compression processing, and sends the synthesized data to the storage unit. FPGA1 and FPGA2 adopt a symmetrical design, mainly including an SRIO receiving module, a data separation and merging module, a DDC_DBF algorithm module, and an SRIO sending module. The SRIO receiving module stores the auxiliary data and the collected data sent by the acquisition FPGA into a high-speed cache; the data separation and merging module realizes the separation of auxiliary data and effective collected data, wherein the effective collected data is input into the DDC_DBF algorithm module; the DDC_DBF algorithm module realizes the down-conversion of the intermediate frequency echo data, DBF weighted compensation, interference filtering and cache in the FIFO; the SRIO sending module transfers the cached data to the processing FPGA3. The processing FPGA3 mainly includes an SRIO receiving module, a data combining module, a BAQ compression module, an SRIO sending module, etc. The processing FPGA 3 receives input data through the SRIO high-speed transmission interface and performs multi-channel synthesis into one-channel processing; the combined data is compressed by the BAQ compression module and sent to the back-end storage device.

[0071] The Ka-band DBF-SAR real-time processing system has been verified by airborne multi-channel project tests and is capable of collecting and processing stable measured data in real time, with good performance.

[0072] The undisclosed technologies in the present invention are common knowledge to those skilled in the art.

[0073] Those skilled in the art know that, in addition to implementing the system, device and its various modules provided by the present invention in a purely computer-readable program code, it is entirely possible to implement the same program in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers and embedded microcontrollers by logically programming the method steps. Therefore, the system, device and its various modules provided by the present invention can be considered as a hardware component, and the modules included therein for implementing various programs can also be considered as structures within the hardware component; the modules for implementing various functions can also be considered as both software programs for implementing the method and structures within the hardware component.

[0074] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A Ka-band DBF-SAR real-time processing system, characterized in that: include: Data acquisition module: Use different AD acquisition sub-boards to sample multi-channel intermediate frequency signals and perform framing and buffering; Digital processing module: digitally down-convert the cached multi-channel intermediate frequency signal to obtain a multi-channel baseband signal, and perform filtering, extraction, and improved DBF-SCORE algorithm processing in turn, and synthesize multi-channel echo data; The improved DBF-SCORE algorithm performs distance multi-channel DBF after channel equalization and pulse compression, thereby reducing the amount of data transmitted; In the data acquisition module, different AD acquisition sub-boards are selected according to the number of antenna apertures to realize N aperture digital echo processing; The data acquisition module can communicate directly with the back-end device across the data processing module; The improved DBF-SCORE algorithm adopts: multi-channel baseband signal data is first subjected to matched filtering to obtain high resolution in the range direction, and then DBF weighting, frequency domain interference filtering, multi-channel synthesis and time domain data recovery processing are performed in sequence; The improved DBF-SCORE algorithm adopts: firstly, the baseband echo of each channel after channel consistency compensation is subjected to FFT transformation, then multiplied by the range-pulse-compression function, and then the obtained result is restored to the time domain through IFFT transformation to obtain the high-resolution signal s after pulse compression. n (t); Each channel signal in the time domain and the generated DBF weighting coefficient w n (t) FFT transformation after multiplication; each channel data is interfered with the reference channel in the frequency domain, and the low-frequency component after interference phase filtering is restored to the original channel; finally, the data of each channel are summed and IFFT transformation is performed to obtain the time domain synthetic signal.

2. A Ka-band DBF-SAR real-time processing method, characterized in that: include: Step S1: The data acquisition module uses different AD acquisition sub-boards to sample the intermediate frequency signals of multiple channels and perform framing and buffering; Step S2: the data processing module digitally down-converts the cached multi-channel intermediate frequency signal to obtain a multi-channel baseband signal, and sequentially performs filtering, extraction, and improved DBF-SCORE algorithm processing, and synthesizes the multi-channel echo data; The improved DBF-SCORE algorithm performs distance multi-channel DBF after channel equalization and pulse compression, thereby reducing the amount of data transmitted; The step S1 adopts: selecting different AD acquisition sub-boards according to the number of antenna apertures to realize N aperture digital echo processing; The step S1 adopts: the data acquisition module can directly communicate with the back-end device across the data processing module; The improved DBF-SCORE algorithm adopts: multi-channel baseband signal data is first subjected to matched filtering to obtain high resolution in the range direction, and then DBF weighting, frequency domain interference filtering, multi-channel synthesis and time domain data recovery processing are performed in sequence; The improved DBF-SCORE algorithm adopts: firstly, the baseband echo of each channel after channel consistency compensation is subjected to FFT transformation, then multiplied by the range-pulse-compression function, and then the obtained result is restored to the time domain through IFFT transformation to obtain the high-resolution signal s after pulse compression. n (t); Each channel signal in the time domain and the generated DBF weighting coefficient w n (t) FFT transformation after multiplication; each channel data is interfered with the reference channel in the frequency domain, and the low-frequency component after interference phase filtering is restored to the original channel; finally, the data of each channel are summed and IFFT transformation is performed to obtain the time domain synthetic signal.

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