CN117518167B - Wide SAR scanning mode system design method based on multichannel system - Google Patents
Wide SAR scanning mode system design method based on multichannel system Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 39
- 238000005457 optimization Methods 0.000 claims abstract description 10
- 230000035945 sensitivity Effects 0.000 claims abstract description 10
- 238000003384 imaging method Methods 0.000 claims abstract description 5
- 239000011159 matrix material Substances 0.000 claims description 8
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- 230000017105 transposition Effects 0.000 claims description 2
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Abstract
The invention discloses a wide SAR scanning mode system design method based on a multichannel system, which relates to the field of radar system design and comprises the following steps: determining the subband width in a multichannel system SAR scanning mode according to the distance ambiguity ratio index of the wide SAR system; determining the number of scanned sub-bands, resolution improvement factors, equivalent azimuth resolution and equivalent azimuth antenna length according to the breadth/resolution index and the sub-band breadth; determining the length of a transmitting antenna and an equivalent antenna pattern according to the length of the equivalent azimuth antenna and the length of a receiving sub-antenna; under a multichannel system, carrying out azimuth multichannel signal reconstruction by taking sensitivity factors as constraint conditions and azimuth ambiguity as an optimization target, and realizing a wide SAR system. The invention can design and obtain a wide SAR scanning mode system based on a multichannel system, and realize wide SAR imaging.
Description
Technical Field
The invention relates to the field of radar system design, in particular to a wide SAR scanning mode system design method based on a multichannel system.
Background
Synthetic aperture radar (Synthetic Aperture Radar, SAR) is a microwave remote sensing technology that enables the monitoring of the earth's surface at any time and in any weather condition. In the SAR scanning mode, the antenna periodically scans on adjacent sub mapping bands along the distance direction, so that the limitation of the mapping bandwidth of the strip mode distance direction can be broken through, and wide mapping can be realized. The azimuth multichannel technology reduces the requirement on azimuth time sampling through azimuth space dimension sampling, thereby reducing the pulse repetition frequency of the system and further widening the imaging breadth.
Under the azimuth multichannel system, a wide SAR system can be realized through a scanning mode. However, the wide SAR system relates to multi-channel reconstruction, scanning sub-band switching and the like, so that the system is complex, has multiple parameters, multiple constraints and high design difficulty, and is difficult to meet the system index requirement. How to design a SAR scan mode system based on a multi-channel regime is therefore a key issue for wide-range SAR system design.
Disclosure of Invention
In order to solve the technical problems, the invention provides a wide SAR scanning mode system design method based on a multichannel system, so as to meet the system index requirements and realize wide mapping.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a design method of a wide SAR scanning mode system based on a multichannel system comprises the following steps:
step 101, determining the sub-band width of a multi-channel system under a scanning mode of a wide SAR system according to a distance ambiguity ratio index of the wide SAR system;
step 102, determining the number of scanning sub-bands, resolution improvement factors, equivalent azimuth resolution and equivalent azimuth antenna length according to the breadth/resolution index and the sub-band breadth;
step 103, determining the length of a transmitting antenna and an equivalent antenna pattern according to the length of the equivalent azimuth antenna and the length of a receiving sub-antenna;
and 104, under a multichannel system, carrying out azimuth multichannel signal reconstruction by taking sensitivity factors as constraint conditions and azimuth ambiguity as an optimization target, so as to realize a wide SAR system.
The beneficial effects are that:
the SAR scanning mode system based on the multichannel system can be designed and obtained, and wide SAR imaging is achieved.
Drawings
FIG. 1 is a schematic flow chart of a wide SAR scanning mode system design method based on a multi-channel system;
FIG. 2 is a timing diagram of a multi-channel scanning SAR system;
FIG. 3 is a range-to-blur ratio (RASR) diagram of a multi-channel scanning SAR system;
FIG. 4 is an azimuth ambiguity ratio (AASR) diagram of a multi-channel scanning SAR system;
fig. 5 is a signal-to-noise ratio scale factor graph for a multi-channel scanning SAR system.
Detailed Description
The present invention will be described in further detail with reference to examples.
Example 1
As shown in fig. 1, the method for designing a broad-width SAR scanning mode system based on a multi-channel system according to the present embodiment includes the following steps:
step 101, determining the subband width in a multichannel SAR scanning mode according to a distance ambiguity ratio index of a wide SAR system;
step 102, determining the number of scanning sub-bands, resolution improvement factors, equivalent azimuth resolution and equivalent azimuth antenna length according to the breadth/resolution index and the sub-band breadth;
step 103, determining the length of a transmitting antenna and an equivalent antenna pattern according to the length of the equivalent azimuth antenna and the length of a receiving sub-antenna;
and 104, under a multichannel system, carrying out azimuth multichannel signal reconstruction by taking sensitivity factors as constraint conditions and azimuth ambiguity as an optimization target, so as to realize a wide SAR system.
Specifically, the step 101 includes:
in the case of the scan mode, the pulse repetition frequency is set to PRF, and the subband width of each subband is. And calculating the distance blur ratio of each sub-band according to a distance blur ratio formula obtained by the SAR system. Then the sub-band width is +.>And (5) performing optimization selection to enable the distance ambiguity index to meet the distance ambiguity index of the SAR system.
Specifically, the step 102 includes:
to meet the whole space-borne SAR breadthNumber of scanning sub-bands +.>The following conditions are satisfied (integers):
（1）
wherein,for the overlap ratio between sub-bands, +.>Representing an upward rounding function;
in order to ensure continuity of SAR imaging along azimuth direction in scanning mode, the following needs to be satisfied:
（2）
in the above-mentioned method, the step of,to sum function, +.>For azimuth overlap rate, ++>For resolution improvement factor, +.>For azimuth antenna beam width, +.>Is->The slant distance of the sub-band; according to the above formula, resolution improvement factor +.>The method meets the following conditions:
（3）
in the above-mentioned method, the step of,representing a maximum function;
according to the resolution index requirementAnd resolution improvement factor->Obtaining equivalent azimuth resolutionAnd its corresponding equivalent azimuth antenna length +.>Wherein->The spreading factor introduced for the treatment of windowing, +.>For satellite speed>The speed of the beam along the ground; in the case of satellite vehiclesAt this time->。
Specifically, the step 103 includes:
according toEquivalent azimuth antenna lengthObtaining the beam width of the antenna with equivalent azimuthWherein->Is wavelength; according to azimuth antenna length->And channel number->Determining the gain of the receiving sub-antenna in the beam width of the equivalent azimuth antenna>Wherein->Normalized antenna pattern at a certain azimuth angle for the receiving sub-antenna;
according to equivalent azimuth antenna beam widthAnd gain of the receiving sub-antenna in equivalent azimuth antenna beam width +.>Determining the transmit antenna length +.>The method comprises the steps of carrying out a first treatment on the surface of the Then, an equivalent azimuth antenna pattern is obtained according to the length of the receiving sub-antenna and the length of the transmitting antenna>The method comprises the following steps:
（4）
in the above-mentioned method, the step of,representing sinc function>Is azimuth.
Specifically, the step 104 includes:
according to Doppler frequencyAnd azimuth->Relation of (i.e.)>Determining the equivalent azimuth antenna pattern +.>Function about Doppler frequency->：
Let the multi-channel reconstruction filter be（/>Indicate->Individual channels), the sensitivity factor is +.>Azimuth blur power +.>The method comprises the following steps:
（5）
wherein the superscript H represents the conjugate transpose of the matrix;is an integer>As a channel vector, expressed as:
（6）
in the above-mentioned method, the step of,j is an imaginary number and d is a spacing between the sub-antennas for matrix transposition operation; 0d represents a spacing between 0 sub-antennas, 1d represents a spacing between 1 sub-antenna, (M-1) d represents a spacing between (M-1) sub-antennas;
by a sensitivity factorThe multichannel reconstruction optimization model for the constraint condition is:
（7）
wherein,is a sensitivity factor constraint;
solving the above method by using a convex optimization method to obtain a reconstruction filter matrix of the multi-channel scanning SARThe method comprises the following steps:
（8）
wherein,a reconstruction filter representing M channels;
thereby obtaining the signal-to-noise ratio scale factorThe method comprises the following steps:
（9）
wherein,representing the desired function. And carrying out multichannel reconstruction according to the reconstruction filter matrix, realizing a wide SAR system, and determining the azimuth ambiguity ratio AASR of the multichannel scanning SAR.
The system parameters used in this example are shown in table 1:
TABLE 1
，
Fig. 2 is a timing diagram of a multi-channel scanning SAR system. Fig. 3 is a range-to-ambiguity ratio result for a multi-channel scanning SAR system. FIG. 4 is an azimuth ambiguity ratio result of a multi-channel scanning SAR system. Fig. 5 is a signal-to-noise ratio scale factor result of a multi-channel scanning SAR system.
As can be seen from the above description, the method provided by the invention can realize the width/resolution requirement of 240km/5m, and has AASR lower than-22 dB, RASR lower than-20 dB and signal to noise ratio scale factor lower than 3 dB.
The foregoing is merely exemplary embodiments of the present invention and is not intended to limit the scope of the present invention.
Claims (4)
1. A design method of a wide SAR scanning mode system based on a multichannel system is characterized by comprising the following steps:
step 101, determining the sub-band width of a multi-channel system under a scanning mode of a wide SAR system according to a distance ambiguity ratio index of the wide SAR system;
step 102, determining the number of scanning sub-bands, resolution improvement factors, equivalent azimuth resolution and equivalent azimuth antenna length according to the breadth/resolution index and the sub-band breadth;
step 103, determining the length of a transmitting antenna and an equivalent antenna pattern according to the length of the equivalent azimuth antenna and the length of a receiving sub-antenna;
104, under a multichannel system, carrying out azimuth multichannel signal reconstruction by taking sensitivity factors as constraint conditions and azimuth ambiguity as an optimization target, and realizing a wide SAR system, wherein the method comprises the following steps:
according to Doppler frequencyAnd azimuth->Relation of (i.e.)>，/>Determining an equivalent azimuth antenna pattern for a wavelength +.>Function about Doppler frequency->：
Let the multi-channel reconstruction filter be，/>Indicate->The number of channels, M, represents the number of channels, the sensitivity factor +.>The superscript H denotes the conjugate transpose of the matrix, azimuth ambiguity power +.>The method comprises the following steps:
（5）
wherein,PRF is the pulse repetition frequency, +.>As a channel vector, expressed as:
（6）
in the above-mentioned method, the step of,j is an imaginary number and d is a spacing between the sub-antennas for matrix transposition operation; 0d represents a spacing between 0 sub-antennas, 1d represents a spacing between 1 sub-antenna, (M-1) d represents a spacing between (M-1) sub-antennas;
by a sensitivity factorThe multichannel reconstruction optimization model for the constraint condition is:
（7）
wherein,for sensitivity factor constraint, +.>As a function of the minimum value; />Representing an mth channel vector;
solving the above method by using a convex optimization method to obtain a reconstruction filter matrixThe method comprises the following steps:
（8）
wherein,a reconstruction filter representing M channels;
thereby obtaining the signal-to-noise ratio scale factorThe method comprises the following steps:
（9）
wherein,representing a desired function;
from reconstructed filter matrixAnd carrying out multichannel reconstruction, realizing a wide SAR system, and determining an azimuth ambiguity ratio AASR.
2. The method for designing a broad SAR scan mode system based on a multi-channel system according to claim 1, wherein said step 101 comprises:
in the scanning mode, the subband width of each subband isThe method comprises the steps of carrying out a first treatment on the surface of the Calculating the distance fuzzy ratio of each sub-band according to the distance fuzzy ratio formula of the broad SAR system, and then carrying out the width +_ of the sub-band under the condition of a given pulse repetition frequency>And (3) performing optimization selection to enable the distance ambiguity index of the wide SAR system to be met.
3. The method for designing a broad SAR scan mode system based on a multi-channel system according to claim 2, wherein said step 102 comprises:
to meet the breadth of the whole broad SAR systemNumber of scanning sub-bands +.>The following conditions are satisfied:
（1）
wherein,for the overlap ratio between sub-bands, +.>Representing an upward rounding function; scanning subband number +.>Is an integer;
in order to ensure the continuity of imaging of the wide SAR system along the azimuth direction in the scanning mode, the following conditions are satisfied:
（2）
in the above-mentioned method, the step of,to sum function, +.>For azimuth overlap rate, ++>For resolution improvement factor, +.>For azimuth antenna beam width, +.>Is->The slant distance of the sub-band; according to the above formula, resolution improvement factor +.>The method meets the following conditions:
（3）
in the above-mentioned method, the step of,representing a maximum function;
according to the resolution index requirementAnd resolution improvement factor->Obtain equivalent azimuth resolution->And its corresponding equivalent azimuth antenna length +.>Wherein->The spreading factor introduced for the treatment of windowing, +.>For satellite speed>The speed of the beam along the ground; in the case of satellite borne, ->At this time->。
4. The method for designing a broad SAR scan mode system according to claim 3, wherein said step 103 comprises:
according to the equivalent azimuth antenna lengthObtain equivalent azimuth antenna beam width +.>The method comprises the steps of carrying out a first treatment on the surface of the According to azimuth antenna length->And channel number->Determining gain of receiving sub-antenna over equivalent azimuth antenna beam widthWherein->Normalized antenna pattern at a certain azimuth angle for the receiving sub-antenna;
according to equivalent azimuth antenna beam widthAnd gain of the receiving sub-antenna in equivalent azimuth antenna beam width +.>Determining the transmit antenna length +.>The method comprises the steps of carrying out a first treatment on the surface of the Then according to the receiving sub-antenna length and the transmitting antenna length +.>Obtain equivalent azimuth antenna pattern->：
（4）
In the above-mentioned method, the step of,representing sinc function>Representing azimuth angle.
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