A phased array system SAR system active pattern fast test method

Abstract

The application provides a phased array system SAR system active pattern fast testing method, the method designs interactive handshake communication mechanism of SAR system and test field control system, designs phased array antenna beam fast switching method, and substitutes amplitude and phase characteristics of the whole subsystem microwave channel in the testing process, and is closer to the final performance of the SAR subsystem. The method can greatly shorten the time of SAR subsystem joint test debugging, speeds up the progress of satellite SAR load development, and provides reference for antenna active pattern testing and system performance testing of subsequent SAR models.

Description

TECHNICAL FIELD

[0001] The application relates to a phased array system SAR system active pattern test method and belongs to the technical field of space microwave remote sensing. BACKGROUND

[0002] Synthetic aperture radar (SAR) has all-weather and all-day imaging capability and is a rapidly developing earth observation imaging radar. A spaceborne SAR has large width and high resolution index requirements, and the system has the ability to work in a large bandwidth and has flexible beam scanning capability. Unlike the traditional strip mode, the new SAR working mode includes a sliding spotlight mode, a scanning mode, a mosaic mode and a TOPS mode, and the antenna beam needs to be variable in the elevation direction and needs to be scanned in the azimuth direction. The coupling of the range and azimuth beams causes the number of beams of the system to increase significantly. According to the traditional SAR satellite antenna pattern test scheme, only the phased array antenna is brought in during the test, and the method of sending a point frequency signal for data acquisition is not included in the amplitude and phase error characteristics of the entire microwave transceiver channel of the subsystem, which deviates from the actual on-orbit application of the system active pattern. And the previous test scheme can only test one beam for one probe scan, which will greatly increase the test time of the subsystem joint test, which does not meet the needs of the satellite development schedule. At the same time, the SAR antenna based on the phased array system involves antenna deployment, array, feed line, high-integration active components, wave control, high-power power supply and radio frequency, low-frequency cable and several subsystems, plus various working modes, wide frequency band range and other factors. The active pattern test is a complex and labor-intensive work. SUMMARY

[0003] The application aims to overcome the above-mentioned deficiencies in the prior art and provide a phased array system SAR system active pattern fast test method.

[0004] The above-mentioned purpose of the application is achieved by the following technical scheme:

[0005] A phased array system SAR system active pattern fast test method, comprising:

[0006] (1) Build a test system to measure the coordinates of each TR channel radiation unit of the SAR system;

[0007] (2) Control the SAR system to work in a single channel calibration mode, and collect initial amplitude and phase data of each TR channel;

[0008] (3) Calculate the phase shift value of each TR channel;

[0009] (4) Generate a beam control code according to the coordinates, phase shift value and attenuation value of each TR channel and store it;

[0010] (5) According to the generated beam control code, the multi-frequency point and multi-beam test is completed by one scan of the antenna test system.

[0011] Preferably, the SAR system comprises a microwave transceiver channel, a data processor, a bus controller and a phased array antenna of the SAR system.

[0012] Preferably, in the step (1), the coordinates of each TR channel of the SAR system are measured in the following manner:

[0013] The theodolite is used to mechanically align the phased array antenna of the SAR system with the probe, so as to ensure that the antenna aperture plane is parallel to the probe scanning plane, and the central normal line of the antenna aperture plane is coincident with the central normal line of the probe;

[0014] The three-dimensional photogrammetry technology is used to measure the coordinates of each TR channel of the phased array antenna of the SAR system.

[0015] Preferably, in the step (2), the bus controller sends a single-channel TR calibration mode instruction to the data processor, and the data processor sends corresponding beam control information to the phased array antenna of the SAR system to control the phased array antenna of the SAR system to work in the single-channel TR calibration mode.

[0016] Preferably, in the step (3), the phase shift value ΔΨ i satisfies:

[0017]

[0018] wherein d xi is the X-direction relative coordinate distance value of the i-th TR channel, d yi is the Y-direction relative coordinate distance value of the i-th TR channel, is the initial phase matching value of the i-th TR channel, are the beam pointing pitch angle and azimuth angle respectively, and λ is the radar operating wavelength.

[0019] Preferably, the step (5) is implemented in the following manner:

[0020] a. The antenna test system controls the probe to move to a set scan point, and sends a position pulse to the data processor;

[0021] b. The data processor pulls the enable signal LE in the synchronous serial port to low level, transmits the beam control code to the phased array antenna of the SAR system through the data and clock interface, and pulls the LE to high level after the transmission is completed;

[0022] c. After the SAR system phased array antenna detects the rising edge of the LE, the received beam control code is latched to the TR channel;

[0023] d. The data processor sends a beam switching completion signal to the antenna test system, and at the same time pulls the LE to low level, starting the transmission of the next beam control code;

[0024] e. The antenna test system sends a modulation pulse to the data processor, which forwards the modulation pulse to the microwave transceiver channel and the SAR system phased array antenna TR channel. After the probe receives the antenna signal, it is sent to the vector network analyzer, which completes the single-beam, multi-frequency point signal acquisition. After the signal acquisition is completed, the data processor pulls the LE to high level;

[0025] f. Repeat steps c-e to complete multi-beam, multi-frequency point signal acquisition;

[0026] g. The antenna test system controls the probe to move to the next set scan point, and sends a position pulse to the data processor; repeat steps b-f to complete signal acquisition at all positions of the scanning frame.

[0027] Preferably, in step a, the position pulse width is 1us, and the high level is effective.

[0028] Preferably, in step d, the beam switching completion signal has a pulse width of 1us, and the rising edge is effective.

[0029] The advantages of the present application compared with the prior art are:

[0030] a. The present application designs a simple and practical handshake communication protocol between the radar system and the test field control system, which can quickly complete beam switching and realize multi-frequency point testing in one scan through three synchronization signals, i.e. the position pulse, the completion pulse and the modulation pulse (see Figure 3 and Figure 4 ), and the enable signal in the radar wave control protocol (see Figure 5 ), greatly improving the efficiency of the directional diagram test. The interaction mode of the SAR system designed by the present application with the antenna test system is not limited to the planar near-field antenna test system, and can be used in general antenna test systems.

[0031] b. The active directional diagram test method designed by the present application integrates the SAR entire subsystem (including electronic equipment and phased array antenna) together during testing, which can consider the influence factors of the SAR microwave transceiver channel amplitude and phase characteristics on the active directional diagram, and is closer to the satellite on-orbit load state, and at the same time, the functions and performances of the entire SAR system under high-power wireless state can be verified. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is the system architecture block diagram of the present application;

[0033] Figure 2 is the test flowchart of the present application;

[0034] Figure 3 is a handshake communication protocol flow chart of the test field control system and the SAR system of the application;

[0035] Figure 4 is a test timing diagram of the application;

[0036] Figure 5 is a measured result of the phased array antenna pattern of the application. DETAILED DESCRIPTION

[0037] The detailed process of the implementation method of the application is given below in combination with the drawings:

[0038] The Ku-band phased array SAR radar active pattern with a working center frequency of 15 GHz and a bandwidth of 600 MHz is tested by using the method of the application. According to the test system shown in the figure, the test system is built. Figure 1 The test system is composed of a radar system, a test field control system, a netted array, a probe and the like. Figure 1 The overall test system is composed of Figure 1 the right test field control system, the netted array and the probe.

[0039] The SAR radar system includes a microwave transceiving channel, a data processor, a bus controller and a phased array antenna of the SAR system. The bus controller sends test instructions, beam switching strategies, gain and channel parameters and working mode instructions to the data processor through the CAN bus. The data processor sends the gain and channel parameters to the microwave transceiving channel. According to the beam switching strategy, the antenna beam is controlled. According to the in-place pulse and the pulse modulation signal sent by the test field control system, the antenna modulation pulse is controlled, and the beam switching completion pulse is sent to the test field control system after the beam switching is completed.

[0040] The antenna pattern darkroom calibration mode is designed in the SAR system, which has an in-place pulse, a completion pulse and a modulation pulse transceiving interface. The netted array has a frequency conversion function. The test is completed according to the working process shown in the figure. Figure 2 As shown in the figure, Figure 3 Figure 4 The antenna test system controls the probe scanning and the netted array. The radar system communicates with the test field control system through three TTL signals of the in-place pulse, the completion pulse and the modulation pulse, and cooperates with the antenna test system to quickly complete the active pattern test. As shown in the figure, Figure 5 The radar system completes the wave control code transmission in a two-stage wave control mode. The radar processor sends the wave control code to the antenna sub-wave control machine through a three-wire RS422 synchronous interface. The sub-wave control machine completes the beam switching. The specific implementation process is as follows:

[0041] (1) Accurately measure the coordinates of each TR radiating unit; ​

[0042] The radar system is built, the theodolite is used to carry out antenna and probe mechanical alignment, ensure that the antenna mouth surface and probe scanning plane are parallel, and the antenna mouth surface center normal line and probe center normal line are coincident. Utilize three-dimensional photogrammetry technique, accurately measure each radiation unit coordinate d xi ,d yi .

[0043] (2) the SAR system works in single-channel calibration mode, and completes the acquisition of initial amplitude and phase data of each channel in cooperation with the antenna test system;

[0044] Through the CAN bus controller, the SAR system works in single-channel TR calibration mode, and completes the acquisition of single-channel TR amplitude and phase data in cooperation with the antenna test system, and the test phase data is recorded as The amplitude data is recorded as A i

[0045] (3) according to the phased array antenna theory, the TR channel phase shift value is calculated;

[0046] According to the phased array antenna theory, the mathematical model of the active phased array antenna pattern is established, and the total phase shift value of each TR channel is calculated:

[0047]

[0048] Wherein, d xi is the relative coordinate distance value of the i-th channel X direction to the coordinate origin, d yi is the relative coordinate distance value of the i-th channel Y direction to the coordinate origin, is the initial phase matching value of the i-th channel, respectively, the beam pointing pitch angle and azimuth angle. λ is the radar working wavelength.

[0049] (4) the test coordinates, phase shift value, attenuator generated beam control code and storage;

[0050] According to the pointing of the to-be-measured beam, the total phase shift value ΔΨ i of the TR channel, the attenuation value A i , the calculation of the amplitude and phase coefficients of the N beams to be measured is completed, and the beam control data is uploaded to the storage FLASH of the radar processor through the CAN bus controller;

[0051] (5) in the near-field test system, through one-time scanning, multi-frequency point and multi-beam test are completed;

[0052] The SAR subsystem is controlled by the CAN bus controller to work in the multi-beam test mode. In the planar near-field test system environment, the antenna test system and the SAR system are communicated by handshake. The multi-beam and multi-frequency point system active pattern test is completed in one scanning process. The detailed process is as follows:

[0053] a. The antenna test system controls the probe scanning, and sends a to-position pulse (width 1us, high level effective) to the data processor after moving to the preset position

[0054] b. After the data processor receives the to-position pulse, the enable signal LE in the synchronous serial port is pulled to low level, and 600 component control code information containing check code, a total of 15,600 bits, is transmitted to 5 antenna sub-wave controls at a clock rate of 4MHz through the data and clock interface, which needs t1=780us. After the transmission is completed, LE is pulled to high level;

[0055] c. After the antenna sub-wave control machine detects the rising edge of LE, the received wave control code data is latched to the TR component through the 8-way data interface and 5-way clock signal at a clock rate of 2MHz, which needs t2=65us to complete the beam switching;

[0056] d. The data processor sends a beam switching completion signal (pulse width 1us, rising edge effective) to the antenna test system, and at the same time, LE is pulled to low level to start the transmission of the next beam control code.

[0057] e. The antenna test system sends a modulation pulse (width 30us, repetition frequency 200us) to the data processor, which forwards the modulation pulse to the SAR system microwave transceiver channel and the phased array antenna TR component. The net completes the signal acquisition of multiple frequency points within t3=1ms; after the signal acquisition is completed, the data processor pulls LE to high level.

[0058] f. Repeat steps c-e to complete the signal acquisition of multiple beams and multiple frequency points;

[0059] g. The data processor receives the next to-position pulse, and repeats steps b-f to complete the signal acquisition of all positions of the scanning frame. The measured results of the SAR subsystem active antenna pattern are shown in Figure 5 . The measured results of 16 beams are given, which verify the effectiveness of the method.

[0060] The antenna near-field test system generally comprises a scanning frame, a test probe, a vector network analyzer, a control system and the like. The application controls the SAR subsystem to work in a multi-beam test mode through a CAN bus controller, in the environment of a planar near-field test system, utilizes interactive handshake communication between a test field control system and the SAR system, through a scanning process, the test field control system informs the SAR system to switch beams through a position pulse signal, the SAR system informs antenna testing to collect data through a completed switching pulse signal, and meanwhile the test field control system synchronizes the pulse signal of radio frequency emission with the pulse working state of the SAR system through a pulse modulation signal, so as to ensure that data collection is in the effective signal of a pulse. Thus, the SAR system active pattern test of multi-beam and multi-frequency points is realized in one antenna test scanning process.

[0061] The method designs interactive handshake communication mechanism of the SAR system and the test field control system, designs a phased array antenna beam switching method based on a synchronous 422 interface, and substitutes the amplitude and phase characteristics of the whole subsystem microwave channel in the test process, which is closer to the final performance of the SAR subsystem. The method can greatly shorten the SAR subsystem joint test debugging time, accelerate the progress of satellite SAR load development, and provide a reference for subsequent SAR type antenna active pattern test.

[0062] The application can test the high-power emission pattern and the receiving pattern of the whole SAR system (including the subsystem electronic equipment and the phased array antenna) in the integrated state, provide measured data for on-orbit application, and verify the function and performance of the whole SAR system in the high-power wireless state.

[0063] The above-described embodiments are only the preferred specific embodiments of the application, and the common changes and replacements made by those skilled in the art within the technical scheme range of the application should be included in the protection range of the application.

[0064] The contents not described in detail in the specification of the application belong to the common technology of the skilled in the art.

Claims

1. A method for fast testing of active pattern of a phased array SAR system, characterized in that, The method comprises the following steps: (1) setting up a test system to measure the coordinates of the radiation units of each TR channel of the SAR system; (2) controlling the SAR system to work in a single-channel calibration mode to collect initial amplitude and phase data of each TR channel; (3) calculating the phase shift values of each TR channel; (4) generating a beam control code according to the coordinates, phase shift values and attenuation values of each TR channel and storing the beam control code; (5) using the antenna test system to complete multi-frequency point and multi-beam testing through one-time scanning according to the generated beam control code; The step (5) is implemented in the following manner: a. The antenna test system controls the probe to move to a set scanning point and sends a to-position pulse to the data processor; b. The data processor pulls the enable signal LE in the synchronous serial port to a low level, transmits the beam control code to the SAR system phased array antenna through the data and clock interface, and pulls the LE to a high level after the transmission is completed; c. The SAR system phased array antenna latches the received beam control code to the TR channel after detecting the rising edge of the LE; d. The data processor sends a beam switching completion signal to the antenna test system and pulls the LE to a low level to start transmission of the next beam control code; e. The antenna test system sends a modulated pulse to the data processor, which forwards the modulated pulse to the microwave transceiver channel and the SAR system phased array antenna TR channel, and the probe sends the antenna signal to the net after receiving the antenna signal, and the net completes single-beam and multi-frequency point signal collection, and the data processor pulls the LE to a high level after the signal collection is completed; f. Repeat steps c-e to complete multi-beam and multi-frequency point signal collection; g. The antenna test system controls the probe to move to the next set scanning point and sends a to-position pulse to the data processor, and repeats steps b-f until signal collection at all positions of the scanning frame is completed.

2. The method of claim 1, wherein the method is used for fast testing of the active pattern of a phased array SAR system. The SAR system comprises a microwave transceiver channel, a data processor, a bus controller and a SAR system phased array antenna.

3. The method of claim 2, wherein the method is characterized by: In the step (1), the coordinates of each TR channel of the SAR system are measured in the following manner: A theodolite is used to mechanically align the SAR system phased array antenna with the probe, to ensure that the antenna aperture plane is parallel to the probe scanning plane and the center normal line of the antenna aperture plane coincides with the center normal line of the probe; Three-dimensional photogrammetry technology is used to measure the coordinates of each TR channel of the SAR system phased array antenna.

4. The method of claim 2, wherein the method is characterized by: In the step (2), the bus controller sends a single-channel TR calibration mode instruction to the data processor, and the data processor sends corresponding beam control information to the SAR system phased array antenna to control the SAR system phased array antenna to work in a single-channel TR calibration mode.

5. The method of claim 2, wherein the method is characterized by: In the step (3), the phase shift value ΔΨ of the i-th TR channel i satisfies: wherein d xi is the relative coordinate origin distance value of the i-th TR channel in the X direction, d yi is the relative coordinate origin distance value of the i-th TR channel in the Y direction, is the initial phase alignment value of the i-th TR channel, are the beam pointing elevation and azimuth angles, respectively, and λ is the radar operating wavelength.

6. The method of claim 1, wherein the method is a fast test method for the active pattern of a phased array SAR system. In the step a, the to-position pulse has a pulse width of 1us and a high level is effective.

7. The method of claim 1, wherein the method is a fast test method for the active pattern of a phased array SAR system. In the step d, the beam switching completion signal has a pulse width of 1us and a rising edge is effective.

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