CN116381689B - Unmanned aerial vehicle-mounted multi-station interference SAR detection system and method - Google Patents
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Abstract
The invention provides an unmanned aerial vehicle-mounted multi-station interference SAR detection system and method, SAR are respectively arranged on different unmanned aerial vehicles, the unmanned aerial vehicles and SAR can realize interference baseline and high-precision space, time and phase synchronization of interference SAR of ten meters to one hundred meters through formation cooperative control, the unmanned aerial vehicle-mounted multi-station interference SAR detection system has the unmanned aerial vehicle-mounted interference SAR elevation measurement capability or three-dimensional imaging capability, wherein the L-band dual-station interference SAR elevation measurement precision is better than 0.5m, the L-band multi-station interference SAR three-dimensional resolution is better than 0.5m, the P-band dual-station interference SAR elevation measurement precision is better than 1m, and the P-band multi-station interference SAR three-dimensional resolution is better than 1m; the invention provides a novel technical method and a novel technical means for application research of L or P wave band interference SAR in glaciers and frozen soil deep detection, under-forest topographic mapping, forest tree height inversion and the like.
Description
Technical Field
The invention belongs to the technical field of aerial remote sensing interferometry, and particularly relates to an unmanned aerial vehicle-mounted multi-station interferometry SAR detection system and method.
Background
The dual-station SAR is a simplest form of distributed multi-platform SAR, which refers to a SAR system in which the transceiver antennas are separated into two different platforms. In the interference application, compared with heavy rail interference of double navigation single station SAR, the double station interference SAR can avoid time decoherence so as to improve interference accuracy; compared with the interference of single-station double antennas, the double-station interference SAR can realize a long baseline which is difficult to obtain, thereby improving the accuracy of elevation measurement.
After this century, the development of the dual-station SAR technology has raised a new trend due to improvements in timing accuracy, communication technology, and navigation technology. The literature published in various aspects of dual-station SAR system design, synchronization technology, imaging processing and the like is increasing, and the international conference is also drawing more attention. The class conference (IEEE International Geoscience & Remote Sensing Symposium) has appeared in succession from 2002 on articles concerning dual-station SAR, with the "dual/distributed SAR" topic being set up annually for several years thereafter. Since 2004, the EUSAR conference (European Conference on Synthetic Aperture Radar) also specially established a double-station SAR topic, and published a series of invited reports and academic papers on double-station SAR. Moreover, some technologically developed countries have developed tests of airborne double-station SAR, ground-to-ground double-station SAR, star-to-ground double-station SAR and star-to-machine double-station SAR successively, and have obtained good images. Fig. 1 is a geometric model of a double station SAR experiment conducted in 2002 in the united kingdom and the obtained double station SAR image. The experimental wave band is an X wave band, the receiving and transmitting antennas are all in a beam-focusing mode, and the double-station angle is about 50 degrees; due to the different directions of the incident and reflected waves, the double shading of the tree (see below the image) is evident from the figure, which may provide additional information for shadow-based object height extraction. Fig. 2 is a geometric model and a double-station SAR image of an airborne double-station SAR experiment carried out by the cooperation of german DLR and french ONERA in 2003, the experiment also adopts an X-band, and the bandwidth of a transmission signal is 100 MHz. The experiment adopts three double-station SAR modes of figure 2, including a forward flight mode, a large-incidence-angle flat flight double-station mode and a small-incidence-angle flat flight double-station mode, and double-station images in the three modes are respectively obtained. Through pseudo-color synthesis of the three images, the conclusion that the classification and recognition capability of ground objects can be improved through fusion of the double-station SAR images in different modes is verified. Fig. 3 is a star-machine double station SAR image obtained by using terrsar-X as a transmitting source and its advanced airborne SAR (F-SAR) passive reception in germany 12 months 2007. In the experiment, the satellites adopt a sliding beam-focusing mode and the airplanes adopt an inverse sliding beam-focusing mode so as to prolong the cooperation time of the satellites and the airplanes, and good images prove the success of the experiment.
The research on the double-station SAR in China starts later, and related reports are increased successively after about 2003, but the follow-up development is rapid, and a plurality of units are put into the research on the double-station SAR. The institute of electronics, university of electronics technology, university of western security electronics technology, north aviation, north theory and national defense technology university and the like have developed theoretical research works in terms of synchronous technology, imaging processing and the like. The institute of electronics Shang Ziyue of the Chinese sciences is equal to the books of the first national institute of technology about the principle of the double-station SAR system published in 2003, and the university of electronics technology has performed the first national vehicle-mounted double-station SAR experiment in 2006, and subsequently developed the manned double-station SAR experiment. The institute of science and technology also carries out experiments of airplane transmitting-ground fixed station receiving and satellite transmitting-ground fixed station receiving, and verifies related technologies such as time synchronization, phase synchronization, imaging processing and the like. In addition, china has also successfully transmitted a satellite-borne double-station SAR interference system, and is carrying out global topography mapping tasks.
From the current situation, the international research on the airborne double-station SAR technology mainly stays in experimental research, the main purpose is to provide a verification platform for the spaceborne double-station SAR system, no mature airborne double-station interference SAR system exists at present, and no report on unmanned airborne double-station interference SAR system and multi-station interference SAR system exists.
Disclosure of Invention
Aiming at the technical problems that no mature airborne multi-station SAR system or an airborne multi-station interference SAR system exists at present and the requirements on time, space and phase synchronization are high, the invention provides an unmanned airborne multi-station interference SAR detection system and method.
SAR is respectively arranged on different unmanned aerial vehicles, the unmanned aerial vehicles and SAR can realize interference baseline and high-precision space, time and phase synchronization of interference SAR of ten meters to one hundred meters through formation cooperative control, and the unmanned aerial vehicle has the unmanned aerial vehicle interference SAR elevation measurement capability or three-dimensional imaging capability, wherein the L-band double-station interference SAR elevation measurement precision is better than 0.5m, the L-band multi-station interference SAR three-dimensional resolution is better than 0.5m, the P-band double-station interference SAR elevation measurement precision is better than 1m, and the P-band multi-station interference SAR three-dimensional resolution is better than 1m; the invention provides a novel technical method and a novel technical means for application research of L or P wave band interference SAR in glaciers and frozen soil deep detection, under-forest topographic mapping, forest tree height inversion and the like.
In order to achieve the above purpose, the invention adopts the following technical scheme:
an unmanned aerial vehicle-mounted multi-station interference SAR detection system comprises an unmanned aerial vehicle subsystem, a multi-station interference SAR subsystem, a data processing subsystem and a ground control subsystem;
the unmanned aerial vehicle subsystem comprises an unmanned aerial vehicle and a cooperative controller, wherein the unmanned aerial vehicle comprises an unmanned aerial vehicle power and structure platform, a satellite positioning module, a flight control computer and a task computer; the cooperative controller comprises an ad hoc network communication module and a formation cooperative control module; under the control of the cooperative controller and the task computer, the unmanned aerial vehicle subsystem has the cooperative control of 10-100 m cross-track or along-track baseline formation flight, the formation internal ad hoc network communication function, realizes double-machine or multi-machine high-precision and safe formation flight, and has the autonomous and automatic flight track planning function;
the multi-station interference SAR subsystem consists of 1 or more sets of master station SAR and 1 or more sets of slave station SAR, wherein a single set of master station SAR or slave station SAR comprises an SAR transceiver system and a bidirectional synchronous chain;
the data processing subsystem is used for processing the data acquired by the multi-station interference SAR subsystem and the position and posture measuring system; the elevation measurement precision is improved by adopting a time-varying baseline high-precision estimation and compensation processing technology, namely, residual motions corresponding to different azimuth moments are measured to obtain derivatives of the residual motions, then the derivatives are subjected to variable upper limit integration to obtain high-order residual motions, and then the high-order time-varying baselines are obtained through integration;
the ground control subsystem controls the unmanned aerial vehicle subsystem and the multi-station interference SAR subsystem through the unmanned aerial vehicle measurement and control communication link.
Further, the data processing subsystem divides single-view complex image data of the multi-station interference SAR subsystem into a plurality of sub-view images in an azimuth frequency domain, respectively processes adjacent sub-view images to obtain a plurality of groups of differential interference phase diagrams, and obtains a time-varying baseline derivative at each pixel point by weighting and averaging the differential interference phase diagrams according to a coherence coefficient; estimating a horizontal baseline and a vertical baseline according to the projection result of the three-dimensional baseline on a plurality of distance gates, and establishing an air-borne variable model of the three-dimensional baseline along with the change of the distance; solving the distance space-variant model by using a random sampling consistency test method to obtain optimal horizontal and vertical baseline derivative values; and compensating the estimated time-varying baseline error into an auxiliary image, firstly performing azimuth decompression on single-view complex image data, adopting a motion error compensation method based on an inertial measurement unit/a differential global positioning system, then estimating the time-varying baseline, and further optimizing an estimation result through loop iteration for a plurality of times.
Further, the L-band dual-station interference SAR elevation measurement precision is better than 0.5m, the L-band multi-station interference SAR three-dimensional resolution is better than 0.5m, the P-band dual-station interference SAR elevation measurement precision is better than 1m, and the P-band multi-station interference SAR three-dimensional resolution is better than 1m.
The invention also provides an unmanned aerial vehicle multi-station interference SAR detection method, which comprises the following steps:
step 1, when an unmanned aerial vehicle-mounted multi-station interference SAR detection system enters a route to start working, a digital module of an SAR receiving and transmitting system of a master station SAR generates digital/analog signals and transmits the digital/analog signals to a radio frequency module of the SAR receiving and transmitting system, the radio frequency module carries out primary amplification and multi-stage amplification on the signals and then transmits the signals to a radar antenna of the SAR receiving and transmitting system, and the radar antenna transmits radar microwave signals;
step 2, radar microwave signals irradiate a target area to generate echo signals, radar antennas of SAR receiving and transmitting systems of a master station SAR and a slave station SAR both receive the echo signals and transmit the echo signals to radio frequency modules of the respective SAR receiving and transmitting systems to amplify and filter, the processed signals are transmitted to digital modules of the respective SAR receiving and transmitting systems, the digital modules acquire the signals and combine GNSS time information to time the echo data and finish storage of radar echo data, and simultaneously, the digital modules of the SAR receiving and transmitting systems of the master station SAR and the slave station SAR receive IMU data, GNSS data and POS data transmitted by a POS measuring and processing module and finish storage of the data;
step 3, a digital module of a bidirectional synchronous chain of a master station SAR firstly generates a baseband synchronous signal when each pulse sampling period starts, the baseband synchronous signal is sent to a radio frequency module, the radio frequency module carries out frequency conversion and grading amplification on the baseband synchronous signal, and the baseband synchronous signal is sent to an antenna of the bidirectional synchronous chain and radiated after being generated;
step 4, the microwave signals of the bidirectional synchronous chain of the master station SAR are directly received by the antennas of the bidirectional synchronous chain of the slave station SAR, and are sent to the radio frequency module of the bidirectional synchronous chain of the slave station SAR, the radio frequency module of the bidirectional synchronous chain of the slave station SAR amplifies, filters and mixes the signals and then sends the signals to the digital module of the bidirectional synchronous chain of the slave station SAR, the digital module of the bidirectional synchronous chain of the slave station SAR starts time sequence detection at the beginning of each pulse sampling period, receives the signals sent by the radio frequency module of the bidirectional synchronous chain of the slave station SAR, detects the position of the synchronous signals after analog-to-digital conversion acquisition of the signals, establishes the system working time sequence of the whole slave station SAR, combines GNSS time information, and carries out time service on synchronous data and data packing and storage;
step 5, after fixed delay, the digital module of the bidirectional synchronous chain of the slave station SAR carries out digital-to-analog conversion on the time-service synchronous data and then sends the digital-to-analog conversion to the radio frequency module of the bidirectional synchronous chain of the slave station SAR, and the radio frequency module of the bidirectional synchronous chain of the slave station SAR carries out hierarchical amplification on signals to generate synchronous microwave signals which are sent to the bidirectional synchronous chain antenna of the slave station SAR and radiated;
step 6, microwave signals of a bidirectional synchronous chain of a slave station SAR are directly received by an antenna of the bidirectional synchronous chain of a master station SAR and are sent to a radio frequency module of the bidirectional synchronous chain of the master station SAR, the radio frequency module of the bidirectional synchronous chain of the master station SAR amplifies, filters and mixes the signals and then sends the signals to a digital module of the bidirectional synchronous chain of the master station SAR, the digital module of the bidirectional synchronous chain of the master station SAR carries out analog-to-digital conversion on the signals in a synchronous acquisition period, then the position of the synchronous signals is detected, a system working time sequence of the whole master station SAR is established, and synchronous data are time-shared and are packed and stored in combination with GNSS time information;
and 7, during the operation of the unmanned aerial vehicle-mounted multi-station interference SAR detection system entering the route, the POS measurement and processing modules of the master station SAR and the slave station SAR process the IMU data and the GNSS data, generate POS data, and send the POS data to the digital modules of the respective SAR receiving and transmitting systems for storage.
Further, for the subsequent airlines, the monitoring software on the ground control subsystem is used for controlling the parameters and start and stop of all radar systems, and monitoring the working states of the multi-station interference SAR subsystem in real time.
The beneficial effects are that:
the detection system is an international first-set multi-station interference SAR system, is also an unmanned airborne P/L wave band interference SAR detection system with the first-set elevation measurement precision superior to 0.5m and the three-dimensional resolution superior to 0.5m, has 10-100 m cross-track interference baseline and high-precision space, time and phase synchronization, provides new technical methods and technical means in the aspects of glacier and frozen soil deep detection, under-forest topography mapping, forest tree height inversion and other application research, and provides new technical exploration and technical accumulation for chromatographic SAR technology and application research, perspective earth multi-aviation platform collaborative observation research and the like.
Drawings
FIG. 1 is a geometric model and experimental image of a double station SAR experiment conducted in 2002 in England;
FIG. 2 is a pseudo color composite image of three dual station modes of the DLR-ONERA experiment in 2003;
FIG. 3 is a star-machine double station SAR experimental image of Terra SAR-X and F-SAR at 11 months of 2007;
FIG. 4 is a block diagram of an unmanned airborne multi-station interferometric SAR detection system of the present subject matter;
fig. 5 is a flow chart of the unmanned aerial vehicle multi-station interference SAR detection method.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
As shown in fig. 4, the unmanned aerial vehicle-mounted multi-station interference SAR detection system of the present invention includes an unmanned aerial vehicle subsystem, a multi-station interference SAR subsystem, a data processing subsystem, and a ground control subsystem.
The unmanned aerial vehicle subsystem comprises an unmanned aerial vehicle and a cooperative controller, wherein the unmanned aerial vehicle comprises an unmanned aerial vehicle power and structure platform, a satellite positioning module, a flight control computer and a task computer; the cooperative controller comprises an ad hoc network communication module and a formation cooperative control module; under the control of the cooperative controller and the task computer, the unmanned aerial vehicle subsystem has the cooperative control of 10-100 m cross-track or along-track baseline formation flight, the formation internal ad hoc network communication function, realizes double-machine or multi-machine high-precision and safe formation flight, and has the autonomous and automatic flight track planning function.
The multi-station interference SAR subsystem consists of 1 or more sets of master station SAR and 1 or more sets of slave station SAR, and a single set of master station SAR or slave station SAR comprises an SAR transceiver system and a bidirectional synchronous chain.
The data processing subsystem is used for processing the data acquired by the multi-station interference SAR and the position and posture measurement system; the method comprises the steps of adopting a time-varying baseline high-precision estimation compensation processing technology to improve elevation measurement precision, namely measuring residual motions corresponding to different azimuth moments to obtain derivatives of the residual motions, then carrying out variable upper limit integration on the derivatives to obtain high-order residual motions, and obtaining a high-order time-varying baseline through integration, and comprises the following steps:
a. dividing single-view complex image data of the multi-station interference SAR into a plurality of sub-view images in an azimuth frequency domain, respectively processing adjacent sub-view images to obtain a plurality of groups of differential interference phase diagrams, and obtaining a time-varying baseline derivative at each pixel point by weighting and averaging the differential interference phase diagrams according to a coherence coefficient;
b. estimating a horizontal baseline and a vertical baseline according to the projection result of the three-dimensional baseline on a plurality of distance gates, and establishing an air-borne variable model of the three-dimensional baseline along with the change of the distance;
c. solving the distance space-variant model by using a random sampling consistency test method to obtain optimal horizontal and vertical baseline derivative values;
d. compensating the estimated time-varying baseline error into an auxiliary image, firstly performing azimuth decompression on single-view complex image data, adopting a motion error compensation method based on an IMU/DGPS (inertial measurement unit/differential global positioning system), then estimating the time-varying baseline, and further optimizing an estimation result through loop iteration for a plurality of times;
the ground control subsystem controls the unmanned aerial vehicle subsystem and the multi-station interference SAR subsystem through the unmanned aerial vehicle measurement and control communication link.
As shown in fig. 5, the unmanned aerial vehicle-mounted multi-station interference SAR detection method of the present invention includes the following steps:
step 1, when an unmanned aerial vehicle-mounted multi-station interference SAR detection system enters a route to start working, a digital module of an SAR receiving and transmitting system of a master station SAR generates digital/analog signals and transmits the digital/analog signals to a radio frequency module of the SAR receiving and transmitting system, the radio frequency module carries out primary amplification and multi-stage amplification on the signals and then transmits the signals to a radar antenna of the SAR receiving and transmitting system, and the radar antenna transmits radar microwave signals;
step 2, radar microwave signals irradiate a target area to generate echo signals, radar antennas of SAR receiving and transmitting systems of a master station SAR and a slave station SAR both receive the echo signals and transmit the echo signals to radio frequency modules of the respective SAR receiving and transmitting systems to amplify and filter, the processed signals are transmitted to digital modules of the respective SAR receiving and transmitting systems, the digital modules acquire the signals and combine GNSS time information to time the echo data and finish storage of radar echo data, and simultaneously, the digital modules of the SAR receiving and transmitting systems of the master station SAR and the slave station SAR receive IMU data, GNSS data and POS data transmitted by a POS measuring and processing module and finish storage of the data;
step 3, a digital module of a bidirectional synchronous chain of a master station SAR firstly generates a baseband synchronous signal when each pulse sampling period starts, the baseband synchronous signal is sent to a radio frequency module, the radio frequency module carries out frequency conversion and grading amplification on the baseband synchronous signal, and the baseband synchronous signal is sent to a bidirectional synchronous chain antenna and radiated after being generated;
step 4, the bidirectional synchronous chain microwave signals of the master station SAR are directly received by a bidirectional synchronous chain antenna of the slave station SAR, and are sent to a radio frequency module of the slave station SAR bidirectional synchronous chain, the radio frequency module of the slave station SAR bidirectional synchronous chain amplifies, filters and mixes the signals and then sends the signals to a digital module of the slave station SAR bidirectional synchronous chain, the digital module of the slave station SAR bidirectional synchronous chain starts time sequence detection at the beginning of each pulse sampling period, receives the signals sent by the radio frequency module of the slave station SAR bidirectional synchronous chain, detects the position of the synchronous signals after analog-digital conversion acquisition of the signals, establishes the system working time sequence of the whole slave station SAR, and combines GNSS time information to time service synchronous data and package and store the data;
step 5, after the digital module of the secondary station SAR bidirectional synchronous chain is subjected to fixed delay, digital-to-analog conversion is carried out on time-service synchronous data, the time-service synchronous data are sent to the radio frequency module of the secondary station SAR bidirectional synchronous chain, the radio frequency module of the secondary station SAR bidirectional synchronous chain carries out hierarchical amplification on signals, and synchronous microwave signals are generated and sent to a secondary station SAR bidirectional synchronous chain antenna and radiated;
step 6, the bidirectional synchronous chain microwave signals of the slave station SAR are directly received by a bidirectional synchronous chain antenna of the master station SAR and are sent to a radio frequency module of the master station SAR bidirectional synchronous chain, the radio frequency module of the master station SAR bidirectional synchronous chain amplifies, filters and mixes the signals and then sends the signals to a digital module of the master station SAR bidirectional synchronous chain, the digital module of the master station SAR bidirectional synchronous chain carries out analog-to-digital conversion on the signals in a synchronous acquisition period, then detects the positions of the synchronous signals, establishes a system working time sequence of the whole master station SAR, and carries out time service on synchronous data and data packaging and storage in combination with GNSS time information;
and 7, during the operation of the unmanned aerial vehicle-mounted multi-station interference SAR detection system entering the route, the POS measurement and processing modules of the master station SAR and the slave station SAR process the IMU data and the GNSS data, generate POS data, and send the POS data to the digital modules of the respective SAR receiving and transmitting systems for storage.
For the subsequent airlines, the monitoring software on the ground control subsystem is used for controlling the parameters and start and stop of all radar systems and monitoring the working states of the multi-station interference SAR subsystem in real time.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (5)
1. The unmanned aerial vehicle-mounted multi-station interference SAR detection system is characterized by comprising an unmanned aerial vehicle subsystem, a multi-station interference SAR subsystem, a data processing subsystem and a ground control subsystem;
the unmanned aerial vehicle subsystem comprises an unmanned aerial vehicle and a cooperative controller, wherein the unmanned aerial vehicle comprises an unmanned aerial vehicle power and structure platform, a satellite positioning module, a flight control computer and a task computer; the cooperative controller comprises an ad hoc network communication module and a formation cooperative control module; under the control of the cooperative controller and the task computer, the unmanned aerial vehicle subsystem has the cooperative control of 10-100 m cross-track or along-track baseline formation flight, the formation internal ad hoc network communication function, realizes double-machine or multi-machine high-precision and safe formation flight, and has the autonomous and automatic flight track planning function;
the multi-station interference SAR subsystem consists of 1 or more sets of master station SAR and 1 or more sets of slave station SAR, wherein a single set of master station SAR or slave station SAR comprises an SAR transceiver system and a bidirectional synchronous chain;
the data processing subsystem is used for processing the data acquired by the multi-station interference SAR subsystem and the position and posture measuring system; the elevation measurement precision is improved by adopting a time-varying baseline high-precision estimation and compensation processing technology, namely, residual motions corresponding to different azimuth moments are measured to obtain derivatives of the residual motions, then the derivatives are subjected to variable upper limit integration to obtain high-order residual motions, and then the high-order time-varying baselines are obtained through integration;
the ground control subsystem controls the unmanned aerial vehicle subsystem and the multi-station interference SAR subsystem through the unmanned aerial vehicle measurement and control communication link.
2. The unmanned airborne multi-station interference SAR detection system of claim 1, wherein the data processing subsystem divides single-view complex image data of the multi-station interference SAR subsystem into a plurality of sub-view images in an azimuth frequency domain, respectively processes adjacent sub-view images to obtain a plurality of groups of differential interference phase maps, and obtains a time-varying baseline derivative at each pixel point by weighting and averaging the differential interference phase maps according to a coherence coefficient; estimating a horizontal baseline and a vertical baseline according to the projection result of the three-dimensional baseline on a plurality of distance gates, and establishing an air-borne variable model of the three-dimensional baseline along with the change of the distance; solving the distance space-variant model by using a random sampling consistency test method to obtain optimal horizontal and vertical baseline derivative values; and compensating the estimated time-varying baseline error into an auxiliary image, firstly performing azimuth decompression on single-view complex image data, adopting a motion error compensation method based on an inertial measurement unit/a differential global positioning system, then estimating the time-varying baseline, and further optimizing an estimation result through loop iteration for a plurality of times.
3. The unmanned airborne multi-station interferometric SAR detection system of claim 1, wherein the L-band dual-station interferometric SAR has an elevation measurement accuracy better than 0.5m, the L-band multi-station interferometric SAR has a three-dimensional resolution better than 0.5m, the p-band dual-station interferometric SAR has an elevation measurement accuracy better than 1m, and the p-band multi-station interferometric SAR has a three-dimensional resolution better than 1m.
4. A detection method of an unmanned airborne multi-station interferometric SAR detection system according to any of claims 1-3, comprising the steps of:
step 1, when an unmanned aerial vehicle-mounted multi-station interference SAR detection system enters a route to start working, a digital module of an SAR receiving and transmitting system of a master station SAR generates digital/analog signals and transmits the digital/analog signals to a radio frequency module of the SAR receiving and transmitting system, the radio frequency module carries out primary amplification and multi-stage amplification on the signals and then transmits the signals to a radar antenna of the SAR receiving and transmitting system, and the radar antenna transmits radar microwave signals;
step 2, radar microwave signals irradiate a target area to generate echo signals, radar antennas of SAR receiving and transmitting systems of a master station SAR and a slave station SAR both receive the echo signals and transmit the echo signals to radio frequency modules of the respective SAR receiving and transmitting systems to amplify and filter, the processed signals are transmitted to digital modules of the respective SAR receiving and transmitting systems, the digital modules acquire the signals and combine GNSS time information to time the echo data and finish storage of radar echo data, and simultaneously, the digital modules of the SAR receiving and transmitting systems of the master station SAR and the slave station SAR receive IMU data, GNSS data and POS data transmitted by a POS measuring and processing module and finish storage of the data;
step 3, a digital module of a bidirectional synchronous chain of a master station SAR firstly generates a baseband synchronous signal when each pulse sampling period starts, the baseband synchronous signal is sent to a radio frequency module, the radio frequency module carries out frequency conversion and grading amplification on the baseband synchronous signal, and the baseband synchronous signal is sent to an antenna of the bidirectional synchronous chain and radiated after being generated;
step 4, the microwave signals of the bidirectional synchronous chain of the master station SAR are directly received by the antennas of the bidirectional synchronous chain of the slave station SAR, and are sent to the radio frequency module of the bidirectional synchronous chain of the slave station SAR, the radio frequency module of the bidirectional synchronous chain of the slave station SAR amplifies, filters and mixes the signals and then sends the signals to the digital module of the bidirectional synchronous chain of the slave station SAR, the digital module of the bidirectional synchronous chain of the slave station SAR starts time sequence detection at the beginning of each pulse sampling period, receives the signals sent by the radio frequency module of the bidirectional synchronous chain of the slave station SAR, detects the position of the synchronous signals after analog-to-digital conversion acquisition of the signals, establishes the system working time sequence of the whole slave station SAR, combines GNSS time information, and carries out time service on synchronous data and data packing and storage;
step 5, after fixed delay, the digital module of the bidirectional synchronous chain of the slave station SAR carries out digital-to-analog conversion on the time-service synchronous data and then sends the digital-to-analog conversion to the radio frequency module of the bidirectional synchronous chain of the slave station SAR, and the radio frequency module of the bidirectional synchronous chain of the slave station SAR carries out hierarchical amplification on signals to generate synchronous microwave signals which are sent to the bidirectional synchronous chain antenna of the slave station SAR and radiated;
step 6, microwave signals of a bidirectional synchronous chain of a slave station SAR are directly received by an antenna of the bidirectional synchronous chain of a master station SAR and are sent to a radio frequency module of the bidirectional synchronous chain of the master station SAR, the radio frequency module of the bidirectional synchronous chain of the master station SAR amplifies, filters and mixes the signals and then sends the signals to a digital module of the bidirectional synchronous chain of the master station SAR, the digital module of the bidirectional synchronous chain of the master station SAR carries out analog-to-digital conversion on the signals in a synchronous acquisition period, then the position of the synchronous signals is detected, a system working time sequence of the whole master station SAR is established, and synchronous data are time-shared and are packed and stored in combination with GNSS time information;
and 7, during the operation of the unmanned aerial vehicle-mounted multi-station interference SAR detection system entering the route, the POS measurement and processing modules of the master station SAR and the slave station SAR process the IMU data and the GNSS data, generate POS data, and send the POS data to the digital modules of the respective SAR receiving and transmitting systems for storage.
5. The method of claim 4, wherein the monitoring software on the ground control subsystem performs all radar system parameters and start-stop control on the subsequent course, and monitors the operating state of the multi-station interference SAR subsystem in real time.
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