Internal calibration method and device for multi-channel synthetic aperture radar

Abstract

The present invention provides a multi-channel synthetic aperture radar internal calibration method and device, belonging to the field of synthetic aperture radar internal calibration, the method comprises: designing the calibration signal as a chirp signal orthogonal to the transmission signal; realizing the calibration pulse sequence configuration by controlling the switch state inside the transceiver calibration module, and realizing the azimuth coding modulation of the calibration signal at the same time; receiving the calibration signal and the echo signal at the same time during the radar echo reception; separating the calibration signal and the echo signal in the signal processing by the waveform diversity technology; processing the calibration signal by the azimuth coherent accumulation technology, and improving the signal-to-noise ratio of the calibration signal. The present invention is realized by the transceiver calibration module, and completes the real-time calibration compensation of the radar echo amplitude and phase. The present invention improves the signal-to-noise ratio of the calibration signal in the calibration signal processing method, and optimizes the internal calibration accuracy.

Description

Technical Field

[0001] The invention belongs to the field of synthetic aperture radar internal calibration, and in particular relates to a multi-channel synthetic aperture radar internal calibration method and device. Background Art

[0002] The SweepSAR system is a special mode of synthetic aperture radar (SAR). The spaceborne SweepSAR system needs to combine real-time digital beamforming with a lightweight large-aperture reflector to achieve a new type of SAR with high resolution and wide mapping swath, and its cost is more economical than using a traditional phased array system to achieve the same goal.

[0003] The SweepSAR system has many channels, each of which includes a transceiver calibration module and a dedicated digital processor to generate independent N-channel echo data. Since the multi-channel SAR system has a large number of receiving channels and generates a large amount of data, it would be very costly or even impossible to send the radar echo data generated by all channels to the ground by the satellite data transmission subsystem. Based on the powerful processing capabilities of current digital hardware, on-orbit real-time calibration and real-time digital beamforming are feasible, which can greatly reduce the amount of downlink data.

[0004] During the radar system startup imaging process, in order to track the gain and phase fluctuations of the radar instrument, a point frequency signal outside the SAR signal working bandwidth is injected into each receiving channel of the radar system, so that the echo signal and calibration signal can be received at the same time. Using these point frequency calibration signals, calibration data can be generated synchronously during echo reception, and then the point frequency calibration signal is extracted through a digital filter to further complete the echo real-time calibration compensation and real-time digital beamforming. In addition, the point frequency can also be changed pulse by pulse to continuously characterize the characteristics of the radar instrument at different frequencies.

[0005] However, the prior art has the following disadvantages:

[0006] 1) In order to receive the point frequency signal outside the working bandwidth of the SAR signal, the receiving channel bandwidth is wider than the working bandwidth of the chirp signal, which affects the suppression effect of the out-of-band clutter signal and sacrifices the signal-to-noise ratio of the echo signal.

[0007] 2) The gain and phase characteristics of radar instruments are often related to the spectral characteristics of the excitation signal. Compared with the point frequency signal or point frequency sequence signal outside the working frequency band, choosing the chirp signal within the working frequency band as the calibration signal can better reflect the characteristics of the radar instrument.

[0008] 3) The bandwidth of the point frequency calibration signal is very small, and the distance pulse compression gain is small, which affects the signal-to-noise ratio of the calibration signal. Summary of the invention

[0009] To solve the above technical problems, the present invention provides a multi-channel synthetic aperture radar internal calibration method and device, which is a novel multi-channel SAR system internal calibration method, which solves the three deficiencies of the prior art in the calibration signal design, and improves the calibration signal-to-noise ratio in the calibration signal processing method, thereby optimizing the internal calibration accuracy.

[0010] In order to achieve the above object, the present invention adopts the following technical solution:

[0011] The multi-channel synthetic aperture radar internal calibration method comprises the following steps:

[0012] Step 1: Design the calibration signal as a chirp signal orthogonal to the transmission signal;

[0013] Step 2: configuring the calibration pulse sequence by controlling the switch state inside the transceiver calibration module, and realizing azimuth coding modulation of the calibration signal;

[0014] Step 3: During the radar echo reception, the calibration signal and the echo signal are received simultaneously;

[0015] Step 4: Separate the calibration signal and the echo signal in signal processing by using waveform diversity technology;

[0016] Step 5: Process the calibration signal through azimuth coherent accumulation technology to improve the signal-to-noise ratio of the calibration signal.

[0017] Furthermore, the step 1 comprises:

[0018] The bandwidth of the calibration signal is the same as that of the transmitted signal; the pulse width of the calibration signal reaches the width of the echo receiving window, achieving a higher range-direction pulse compression gain and optimizing the calibration signal-to-noise ratio.

[0019] Furthermore, in the step 2, the calibration signal is coded and modulated in azimuth by switching the switch inside the transceiver calibration module;

[0020] The total gain of the range signal processing and azimuth signal processing of the calibration signal The formula is:

[0021] (1)

[0022] in, is the calibration signal pulse width, is the calibration signal bandwidth, is the azimuth integration interval, and PRF is the pulse repetition frequency when the synthetic aperture radar is working.

[0023] Furthermore, the step three comprises:

[0024] In the receiving window, the received calibration signal or the reference calibration signal and the echo signal have an orthogonal relationship, so the calibration signal and the echo signal or the reference calibration signal and the echo signal are received simultaneously and separated during signal processing.

[0025] Furthermore, the step 4 includes the following steps:

[0026] Step 4.1: Establish a matched filter for the calibration signal;

[0027] Step 4.2: Perform range pulse compression processing on the radar receiving signal; the radar receiving signal includes a calibration signal and an echo signal;

[0028] Step 4.3: Perform azimuth fast Fourier transform on the radar receiving signal after pulse compression;

[0029] Step 4.4: Extract the calibration signal in the frequency domain through a high-pass filter.

[0030] Furthermore, the step five comprises the following steps:

[0031] Step 5.1: Perform an inverse fast Fourier transform on the filtered calibration signal in azimuth, multiply it by the complex conjugate of the azimuth coding term, and then perform azimuth coherent accumulation;

[0032] Step 5.2: Obtain the calibration signal and obtain the compensation item;

[0033] Step 5.3: Compensate the amplitude and phase of the echo data.

[0034] The present invention also provides a device for implementing the above-mentioned multi-channel synthetic aperture radar internal calibration method, including a transceiver calibration module, the transceiver calibration module includes a calibration submodule, the calibration submodule is composed of a switch group and an attenuator, and the switching of multiple internal calibration loops is achieved by controlling the state of each switch of the switch group, and the calibration signal level is adjusted to a value suitable for processing by controlling the attenuation value of the attenuator.

[0035] Furthermore, the transmission calibration, reception calibration and reference calibration are combined in order and quantity to form a calibration pulse sequence of the synthetic aperture radar system; during the imaging of the multi-channel synthetic aperture radar system, the flexible configuration of the calibration pulse sequence is achieved by controlling the state switching of the switch group.

[0036] Furthermore, the circuit of the transceiver calibration module includes a digitally controlled phase shifter, a power amplifier, a circulator, a limiter, a low noise amplifier, a gain controller, a bandpass filter, a first coupler, a second coupler and a calibration submodule; within the transmission window, the transmission signal enters the transmission port, passes through the first port to the second port of the calibration submodule, the digitally controlled phase shifter, the power amplifier, the circulator, the first coupler, and then is radiated by the antenna; within the transmission window, the calibration signal sampled by the first coupler passes through the third port to the fourth port of the calibration submodule, and is coupled to the main path by the second coupler to form a transmission calibration signal.

[0037] Furthermore, within the receiving window, the echo signal received by the antenna is output from the receiving port to the digital electronic module via the first coupler, the circulator, the limiter, the low noise amplifier, the gain controller, the second coupler and the bandpass filter; within the receiving window, one of the following two situations is taken: situation one, the calibration signal enters the transmitting port, passes through the first port to the third port of the calibration submodule, and then is coupled to the main path via the first coupler to form a received calibration signal; situation two, the calibration signal enters the transmitting port, passes through the first port to the fourth port of the calibration submodule, and is coupled to the main path by the second coupler to form a reference calibration signal.

[0038] Beneficial effects:

[0039] 1. The calibration signal is designed as a chirp signal that is orthogonal to the transmitted signal. Compared with the point frequency signal, the chirp signal can reflect the gain and phase fluctuations of the radar instrument under actual working conditions, and the calibration accuracy is higher.

[0040] 2. The calibration signal has the same operating frequency band as the transmitting signal, and the receiving channel bandwidth is the same as the transmitting channel bandwidth, which effectively suppresses the influence of out-of-band clutter signals.

[0041] 3. Compared with the point frequency signal, the chirp signal with a certain bandwidth can obtain a higher range pulse compression gain in signal processing, which is beneficial to improving the signal-to-noise ratio of the calibration signal.

[0042] 4. In signal processing, azimuth coherent accumulation of the azimuth modulated calibration signal can obtain azimuth gain, further optimize the calibration signal-to-noise ratio and improve the internal calibration accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is the schematic diagram of the composition of the multi-channel SAR system;

[0044] Figure 2 This is the composition schematic diagram of the transceiver calibration module;

[0045] Figure 3 It is a working timing diagram of the multi-channel synthetic aperture radar internal calibration method of the present invention;

[0046] Figure 4 Flowchart for the real-time digital calibration process. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0048] In the description of the present invention, it should be understood that the terms "upper", "lower", "top", "bottom", "inner", "outer", etc. used in the present invention to indicate the orientation or position relationship is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0049] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0050] like Figure 1 As shown in the figure, the multi-channel SAR system mainly includes antennas, transceiver calibration modules, digital electronic modules, radar signal sources and power division networks, which constitute radar transmission links and radar reception links. In the radar transmission link, the radar signal source outputs one chirp signal, which is divided into N channels by power division networks, and then transmitted to the transmission ports of N transceiver calibration modules, and then stimulates N antennas to radiate signals into space; in the radar reception link, the echo signal is received by the antenna, amplified and filtered by N transceiver calibration modules, and then output from the receiving port to the digital electronic module, in which analog-to-digital conversion (ADC), real-time digital calibration and real-time digital beamforming are completed.

[0051] The antennas include a first antenna, a second antenna, a third antenna, ... an Nth antenna.

[0052] The radar signal source is used to generate a radar signal and a calibration signal.

[0053] The power division network is used to distribute one signal output by the radar signal source into N signals with equal power.

[0054] The transceiver calibration module is used to amplify the power of the radar signal and excite the antenna, and output the received echo signal after amplification and filtering, and complete the internal calibration during the imaging of the multi-channel SAR system.

[0055] The digital electronic module internally comprises an N-channel analog-to-digital converter, a real-time digital calibration submodule and a digital beamforming submodule.

[0056] The N-channel analog-to-digital converter converts analog signals into digital values ​​for use in signal processing in the real-time digital scaling submodule and the digital beamforming submodule.

[0057] The real-time digital calibration submodule uses a digital domain algorithm to complete the real-time calibration compensation of the amplitude and phase of N-channel echo data.

[0058] The digital beam forming submodule uses a digital domain algorithm to synthesize a plurality of echo signals after real-time calibration and compensation to form a range beam scanning reception.

[0059] Figure 1 In the figure, TX is the transmitting port of the transceiver calibration module; RX is the receiving port of the transceiver calibration module; the power division network includes the first port, the second port, the third port ... the Nth port, which are respectively connected to the N transceiver calibration modules. Figure 1 The 1, 2, 3, and N in the figure represent the channel numbers of the multi-channel SAR system, and N is an integer greater than or equal to 2.

[0060] During radar transmission, N transceiver calibration modules transmit radar signals in phase at the same time, and a wide beam can be formed through the parabolic reflector to illuminate the ground target; the echo signal scattered by the ground target is received by the transceiver calibration module and collected by the analog-to-digital converter to form echo data. In the echo data processing flow, the N-channel echo data is first calibrated and compensated in real time, and then the digital domain algorithm is used to synthesize several echo data to form range beam scanning reception.

[0061] The schematic diagram of the transceiver calibration module is as follows: Figure 2 As shown, compared with the traditional transceiver module, the principle design of the transceiver calibration module adds a calibration sub-module. The calibration sub-module is composed of a switch group and an attenuator. By controlling the state of each switch in the switch group, the switching of multiple internal calibration loops can be achieved. By controlling the attenuation value of the attenuator, the calibration signal level can be adjusted to a value suitable for subsequent processing.

[0062] In the embodiment, the internal switch group of the calibration submodule includes the first switch, the second switch, the third switch, and the fourth switch. The truth table of the internal switch group switching each calibration loop is shown in Table 1 (the truth table of the switch group for switching the internal working state of the transceiver calibration module).

[0063] Table 1

[0064]

[0065] The transmission calibration, reception calibration and reference calibration are combined in a certain order and quantity to form the calibration pulse sequence of the SAR system. During the imaging of the multi-channel SAR system, the calibration pulse sequence can be flexibly configured by controlling the state switching of the switch group.

[0066] like Figure 2 As shown, the circuit composition of the transceiver calibration module includes a digitally controlled phase shifter, a power amplifier, a circulator, a limiter, a low noise amplifier, a gain controller, a bandpass filter, a first coupler, a second coupler and a calibration submodule.

[0067] In the transmission window, the transmission signal enters the transmission port, passes through the first port to the second port of the calibration submodule, the digitally controlled phase shifter, the power amplifier, the circulator, the first coupler, and then is radiated by the antenna.

[0068] In the multi-channel SAR system, the signal flow direction of the calibration signal is designed as: radar signal source, power division network, transceiver calibration module, and digital electronic module.

[0069] Inside the transceiver calibration module, the signal flow of the transmit calibration loop, receive calibration loop, and reference calibration loop is designed as follows:

[0070] The signal flow direction of the transmit calibration loop is designed as:

[0071] Transmitting port, first switch, digitally controlled phase shifter, power amplifier, circulator, first coupler, third switch, calibration submodule fixed attenuator, second switch, second coupler, bandpass filter, receiving port;

[0072] The signal flow direction of the receiving calibration loop is designed as:

[0073] Transmitting port, first switch, fourth switch, variable attenuator of calibration submodule, third switch, first coupler, circulator, limiter, low noise amplifier, gain controller, second coupler, bandpass filter, receiving port;

[0074] The reference calibration loop signal flow direction is designed as:

[0075] Transmitting port, first switch, second switch, second coupler, bandpass filter, receiving port.

[0076] In the transmission window, the calibration signal sampled by the first coupler passes through the third port to the fourth port of the calibration submodule, and is coupled to the main path by the second coupler to form a transmission calibration signal (i.e. Figure 2 (emission calibration in ).

[0077] In the receiving window, the antenna (i.e. Figure 2 The echo signal received at the antenna port) passes through the first coupler, circulator, limiter, low noise amplifier, gain controller, second coupler and bandpass filter, and is output from the receiving port to the digital electronic module, and then forms the echo data. In the receiving window, one of the following two situations is taken: Situation 1, the calibration signal enters the transmitting port, passes through the first port to the third port of the calibration submodule, and then is coupled to the main path through the first coupler to form the received calibration signal (i.e. Figure 2 In case 2, the calibration signal enters the transmitting port, passes through the first port to the fourth port of the calibration submodule, and is coupled to the main path by the second coupler to form a reference calibration signal (i.e. Figure 2 By controlling the switch state inside the calibration submodule, the path switching between the internal ports can be realized.

[0078] The present invention also provides a multi-channel synthetic aperture radar internal calibration method, which can synchronously complete the internal calibration during echo reception, comprising:

[0079] Step 1: Design the calibration signal as a chirp signal orthogonal to the transmission signal;

[0080] Step 2: configuring the calibration pulse sequence by controlling the switch state inside the transceiver calibration module, and realizing azimuth coding modulation of the calibration signal;

[0081] Step 3: During the radar echo reception, the calibration signal and the echo signal are received simultaneously;

[0082] Step 4: Separate the calibration signal and the echo signal in signal processing by using waveform diversity technology;

[0083] Step 5: Process the calibration signal through azimuth coherent accumulation technology to improve the signal-to-noise ratio of the calibration signal.

[0084] Specifically, the step one includes:

[0085] In order to improve the calibration signal processing gain, the calibration signal is designed as a chirp signal orthogonal to the transmitted signal, and the bandwidth of the calibration signal is the same as that of the transmitted signal; the calibration signal pulse width is large and can reach the echo receiving window width, so a higher range pulse compression gain can be achieved and the calibration signal-to-noise ratio can be optimized.

[0086] Specifically, the step 2 includes:

[0087] The azimuth coding modulation of the calibration signal is realized by switching the internal switch of the transceiver calibration module.

[0088] Specifically, in order to achieve high-precision calibration within the system, the signal-to-noise ratio of the calibration signal should be optimized as much as possible. The effective way to achieve this is to increase the gain of the calibration signal as much as possible during signal processing. The formula is:

[0089] (1)

[0090] in, is the calibration signal pulse width, is the calibration signal bandwidth, is the azimuth integration interval, and PRF is the pulse repetition frequency when SAR is working.

[0091] The calibration pulse sequence configuration is taken as an example of a working sequence design of a calibration method in a multi-channel SAR system. Figure 3 As shown, the workflow is as follows:

[0092] Step 3.1: Perform emission calibration within the emission window of the first PRT (pulse repetition time);

[0093] Step 3.2: Perform receiving calibration within the receiving window of the first PRT;

[0094] Step 3.3: Perform transmit calibration within the transmit window of the second PRT;

[0095] Step 3.4: Perform reference calibration within the receiving window of the second PRT; jump to step 3.1 and repeat the process.

[0096] In the transmission window, while the radar transmits the signal, the first coupler of the transceiver calibration module takes samples to complete the transmission calibration.

[0097] As shown in Table 1, any order and number of combinations of receiving calibration and reference calibration can be achieved by switching the switch group state. In the receiving window, the azimuth modulation of the receiving calibration signal and the reference calibration signal can be achieved by controlling the periodic switching of the switch group. The azimuth coding modulation of the calibration signal can be achieved by switching the switch group inside the transceiver calibration module, and different azimuth coding modulation schemes can be obtained by changing the switch group control signal. An example table of achieving azimuth coding modulation of the calibration signal by switch group control is shown in Table 2.

[0098] Table 2

[0099]

[0100] Specifically, the step three includes:

[0101] In the receiving window, the received calibration signal or reference calibration signal has an orthogonal relationship with the echo signal, so they can be received simultaneously and separated during signal processing. In this calibration pulse sequence design, calibration data acquisition of three calibration loops can be completed within two PRTs without interrupting SAR imaging.

[0102] In addition, considering that the reference calibration loop has a short path, simple passive circuit composition, and slow system drift, while the receiving channel of the transceiver calibration module is composed of active devices such as low-noise amplifiers, the system gain is high, and the drift characteristics are more obvious. Therefore, the calibration pulse sequence design should be optimized, and the receiving calibration should be appropriately increased and the reference calibration should be reduced within the receiving window.

[0103] Specifically, the step 4 includes:

[0104] Based on different azimuth coding modulation schemes, a flexible design of the calibration sequence in the multi-channel SAR system is formed. Figure 3 , several internal calibration working timing diagrams can be designed.

[0105] The calibration signal is designed to be a chirp signal orthogonal to the transmitted signal. The calibration signal output by the transceiver calibration module is collected by the analog-to-digital converter and processed in the digital domain, such as Figure 4 As shown, the specific processing steps are as follows:

[0106] Step 4.1: Establish a matched filter for the calibration signal;

[0107] Step 4.2: Perform range pulse compression processing on the radar receiving signal; the radar receiving signal includes a calibration signal and an echo signal;

[0108] Step 4.3: Perform azimuth fast Fourier transform (FFT) on the radar received signal after pulse compression (i.e. Figure 4 Azimuth FFT transform in ( );

[0109] Step 4.4: Extract the calibration signal in the frequency domain through a high-pass filter.

[0110] Specifically, the step five includes:

[0111] During signal processing, the azimuth gain can be obtained through azimuth coherent accumulation, which further optimizes the signal-to-noise ratio of the calibration signal. After the digital domain processing in step 4, real-time calibration compensation is achieved, such as Figure 4 As shown, including:

[0112] Step 5.1: Perform an inverse fast Fourier transform (IFFT) on the filtered calibration signal (i.e. Figure 4The azimuth IFFT in the image is multiplied by the complex conjugate of the azimuth coding term and then azimuth coherent accumulation is performed;

[0113] Step 5.2: Obtain the calibration signal and obtain the compensation item;

[0114] Step 5.3: Compensate the amplitude and phase of the echo data.

[0115] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-channel synthetic aperture radar internal calibration method, characterized in that: The steps include: Step 1: Design the calibration signal as a chirp signal orthogonal to the transmission signal, including: The bandwidth of the calibration signal is the same as that of the transmitted signal; the pulse width of the calibration signal reaches the width of the echo receiving window, achieving a higher range-direction pulse compression gain and optimizing the calibration signal-to-noise ratio; Step 2: configuring the calibration pulse sequence by controlling the switch state inside the transceiver calibration module, and realizing azimuth coding modulation of the calibration signal; Step 3: During the radar echo reception, the calibration signal and the echo signal are received simultaneously; Step 4: Separating the calibration signal and the echo signal in signal processing by waveform diversity technology, including the following steps: Step 4.1: Establish a matched filter for the calibration signal; Step 4.2: Perform range pulse compression processing on the radar receiving signal; the radar receiving signal includes a calibration signal and an echo signal; Step 4.3: Perform azimuth fast Fourier transform on the radar receiving signal after pulse compression; Step 4.4: Extract the calibration signal in the frequency domain through a high-pass filter; Step 5: Processing the calibration signal by using the azimuth coherent accumulation technology to improve the signal-to-noise ratio of the calibration signal, including the following steps: Step 5.1: Perform an inverse fast Fourier transform on the filtered calibration signal in azimuth, multiply it by the complex conjugate of the azimuth coding term, and then perform azimuth coherent accumulation; Step 5.2: Obtain the calibration signal and obtain the compensation item; Step 5.3: Compensate the amplitude and phase of the echo data.

2. The multi-channel synthetic aperture radar internal calibration method according to claim 1, characterized in that: In the step 2, the calibration signal is coded and modulated in azimuth by switching the switch inside the transceiver calibration module; The total gain of the range signal processing and azimuth signal processing of the calibration signal The formula is: (1) in, is the calibration signal pulse width, is the calibration signal bandwidth, is the azimuth integration interval, and PRF is the pulse repetition frequency when the synthetic aperture radar is working.

3. The multi-channel synthetic aperture radar internal calibration method according to claim 1, characterized in that: The step three comprises: In the receiving window, the received calibration signal or the reference calibration signal and the echo signal have an orthogonal relationship, so the received calibration signal and the echo signal or the reference calibration signal and the echo signal are received simultaneously and separated during signal processing.

4. A device for implementing the multi-channel synthetic aperture radar internal calibration method according to any one of claims 1 to 3, characterized in that: It includes a transceiver calibration module, which includes a calibration submodule. The calibration submodule consists of a switch group and an attenuator. The switching of multiple internal calibration loops is achieved by controlling the states of the switches of the switch group, and the calibration signal level is adjusted to a value suitable for processing by controlling the attenuation value of the attenuator.

5. The device according to claim 4, characterized in that Transmit calibration, receive calibration and reference calibration are combined in order and quantity to form a calibration pulse sequence of a synthetic aperture radar system. During imaging of a multi-channel synthetic aperture radar system, the calibration pulse sequence is flexibly configured by controlling the state switching of a switch group.

6. The device according to claim 4, characterized in that The circuit of the transceiver calibration module includes a digitally controlled phase shifter, a power amplifier, a circulator, a limiter, a low noise amplifier, a gain controller, a bandpass filter, a first coupler, a second coupler and a calibration submodule; within the transmission window, the transmission signal enters the transmission port, passes through the first port to the second port of the calibration submodule, the digitally controlled phase shifter, the power amplifier, the circulator, the first coupler, and then is radiated by the antenna; within the transmission window, the calibration signal sampled by the first coupler passes through the third port to the fourth port of the calibration submodule, and is coupled to the main path by the second coupler to form a transmission calibration signal.

7. The device according to claim 4, characterized in that In the receiving window, the echo signal received by the antenna is output from the receiving port to the digital electronic module through the first coupler, circulator, limiter, low noise amplifier, gain controller, second coupler and bandpass filter; in the receiving window, one of the following two situations is taken: situation 1, the calibration signal enters the transmitting port, passes through the first port to the third port of the calibration submodule, and then is coupled to the main path through the first coupler to form a receiving calibration signal; situation 2, the calibration signal enters the transmitting port, passes through the first port to the fourth port of the calibration submodule, and is coupled to the main path by the second coupler to form a reference calibration signal.

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