CN119667676B

CN119667676B - A design method for high-resolution wide-swath SAR based on reflector system

Info

Publication number: CN119667676B
Application number: CN202411749085.3A
Authority: CN
Inventors: 郭磊; 孙嘉; 党红杏; 李诗润; 刘昕; 向天舜; 侯若涵; 雷苏力
Original assignee: Xian Institute of Space Radio Technology
Current assignee: Xian Institute of Space Radio Technology
Priority date: 2024-12-02
Filing date: 2024-12-02
Publication date: 2025-11-04
Anticipated expiration: 2044-12-02
Also published as: CN119667676A

Abstract

This application relates to a high-resolution wide-swath SAR design method based on a reflector system. By using range-direction multi-feed wide-beam coverage, simultaneous multi-beam transmission and reception high-gain imaging technology, and high-isolation feed distribution technology, the SAR can achieve sub-meter resolution and 50-kilometer swath width high-resolution wide-swath imaging, meeting the future requirements of high-resolution wide-swath SAR based on reflector systems.

Description

High-resolution wide SAR design method based on reflecting surface system

Technical Field

The application relates to the field of space microwave remote sensing, in particular to a high-resolution broad-width SAR design method based on a reflection surface system.

Background

Synthetic aperture radar (SYNTHETIC APERTURE RADAR, SAR) is a microwave remote sensing radar that uses range-to-pulse compression and azimuth doppler to image, and can transmit pulse signals by itself and then process received echoes to obtain images. Unlike passive remote sensing equipment such as optics, hyperspectrum, etc., SAR is not influenced by bad weather such as cloud, rain, fog, etc., and can realize all-day and all-weather imaging. Meanwhile, as the electromagnetic frequency band operated by the SAR has certain penetrating power, the target hidden under vegetation or subsurface can be found, and the SAR is widely applied to various aspects such as topographic mapping, geological exploration, marine application, agriculture and forestry monitoring, disaster assessment, military reconnaissance, scientific research and the like. The high-resolution wide-range SAR capable of simultaneously realizing high resolution and wide swath is an important direction of future SAR system development. However, due to the minimum antenna area limitations, SAR designs in the prior art are inconsistent in achieving both high resolution and wide swath.

Disclosure of Invention

In order to overcome at least one defect in the prior art, the application provides a high-resolution wide SAR design method based on a reflecting surface system.

In a first aspect, a method for designing a high-resolution broad-width SAR based on a reflective surface system is provided, including:

Calculating total beam width according to the observation breadth, and calculating the beam width of each beam according to the aperture of the distance-oriented antenna;

The method comprises the steps of designing a plurality of feeds, generating a plurality of beams by the plurality of feeds, and independently receiving and transmitting the plurality of beams, wherein the arrangement principle of the plurality of feeds is that the overlapping loss of the plurality of beams in the distance direction is less than 3dB, and the overlapping loss of the plurality of beams in the azimuth direction is more than 13dB.

In one embodiment, the total beamwidth is calculated from the observed breadth using the following formula:

wherein, the For the total beam width, θ _Inc is the beam incident angle, R _f is the distal slant range, and W _r is the observation width.

In one embodiment, the beam width of each beam is calculated from the distance to the antenna aperture using the following equation:

wherein, the For each beam, λ is the wavelength and D is the distance to the antenna aperture.

In one embodiment, the number of range beams is determined based on the total beam width and the beam width of each beam, using the following equation:

Wherein N is the number of distance beam, For the total beam width to be the same,For the beam width of each beam,Representing an upward rounding.

In one embodiment, where multiple beams are independently transceived, the required pulse repetition frequency satisfies the following equation:

Wherein, PRF is pulse repetition frequency, i is a positive integer greater than 1, R _n,j is proximal pitch of jth beam, R _f,j is distal pitch of jth beam, c is speed of light, τ _nadir is understar point echo width, Δτ is transmit-receive guard time, H is satellite height, τ _p is transmit pulse width.

Compared with the prior art, the high-resolution wide SAR design method based on the reflection surface system has the advantages that the SAR can realize sub-meter resolution and 50 km-level breadth high-resolution wide SAR requirements in the future by means of distance-to-multi-feed wide beam coverage, multi-beam receiving and transmitting high-gain imaging technology and high-isolation feed source distribution technology.

Drawings

The application may be better understood by reference to the following description taken in conjunction with the accompanying drawings, which are incorporated in and form a part of this specification, together with the following detailed description. In the drawings:

FIG. 1 shows a block flow diagram of a high resolution broad SAR design method for a reflector system;

FIG. 2 shows a graph of geometrical relationships of the simultaneous operation of multiple beams on a reflecting surface;

FIG. 3 shows a timing design result diagram;

fig. 4 shows a beam coverage map after design of a multi-beam feed arrangement;

FIG. 5 illustrates a beam high spatial isolation feed layout;

fig. 6 shows a system distance ambiguity (RASR) curve for different PRFs.

Detailed Description

Exemplary embodiments of the present application will be described hereinafter with reference to the accompanying drawings. In the interest of clarity and conciseness, not all features of an actual embodiment are described in the specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions may be made to achieve the developers' specific goals, and that these decisions may vary from one implementation to another.

It should be noted here that, in order to avoid obscuring the present application due to unnecessary details, only the device structures closely related to the solution according to the present application are shown in the drawings, and other details not greatly related to the present application are omitted.

It is to be understood that the application is not limited to the described embodiments, as a result of the following description with reference to the drawings. In this context, embodiments may be combined with each other, features replaced or borrowed between different embodiments, one or more features omitted in one embodiment, where possible.

The embodiment of the application provides a high-resolution wide SAR design method of a reflecting surface system, and fig. 1 shows a flow block diagram of the high-resolution wide SAR design method of the reflecting surface system, and referring to fig. 1, the method comprises the following steps:

Step S1, calculating total beam width according to the observed breadth, calculating the beam width of each beam according to the distance direction antenna caliber, and determining the number of the distance direction beams according to the total beam width and the beam width of each beam.

Figure 2 shows a graph of the geometrical relationship of the simultaneous operation of multiple beams on a reflecting surface. The total beam width is calculated according to the observed breadth, and the following formula is adopted:

The beam width of each beam is calculated according to the distance to the antenna aperture, and the following formula is adopted:

According to the total beam width and the beam width of each beam, determining the number of the distance beam, and adopting the following formula:

Table 1 shows the reflective surface on-board SAR system parameters.

TABLE 1

According to the system parameters of table 1, the required distance can be calculated to 5 beams to achieve coverage of 50km breadth.

And S2, designing a plurality of feeds, wherein the feeds generate a plurality of beams, the beams are independently transmitted and received, and the arrangement principle of the feeds is that the overlapping loss of the beams in the distance direction is less than 3dB, and the overlapping loss of the beams in the azimuth direction is greater than 13dB.

To achieve sub-meter high resolution, the system requires high antenna gain to meet the image signal to noise ratio requirements. In order to realize high antenna gain, the distance is to a plurality of wave beams by adopting a simultaneous independent receiving and transmitting technology, N independent wave beams are emitted simultaneously on a transmitting time sequence to irradiate the whole large breadth, each wave beam is connected with an independent transmitting device, and because each sub-wave beam is a narrow wave beam, the whole caliber gain of the antenna can be utilized to the maximum extent, the system receiving and transmitting gain is improved by N2 times, and the high-resolution wide imaging requirement is effectively met. When multi-beam is used for transmitting and receiving, different beam echoes need to be ensured to be sequentially received in turn through reasonable time sequence design, and a time sequence design result diagram is shown in fig. 3. N independent beams are designed to transmit simultaneously, the transmission pulse width is tau _p, a plurality of beams are independently transmitted and received, and the required pulse repetition frequency meets the following formula:

Wherein PRF is pulse repetition frequency, i is a positive integer greater than 1, R _n,j is proximal slant distance of jth wave beam, j is greater than or equal to 1 and less than or equal to N, R _f,j is distal slant distance of jth wave beam, c is light speed, τ _nadir is width of point echo under the satellite, deltaτ is transmitting and receiving protection time, H is satellite height, and τ _p is transmitting pulse width.

The SAR system sensitivity (NESZ) is calculated as follows:

Wherein v _s is the platform flight speed, k is the Boltzmann constant, T is the system temperature, F _n is the noise figure, P is the transmit average power, G is the antenna gain, and ρ is the resolution. According to the calculation of the system parameters in the table 1, the sensitivity of the system is 21.24dB, the system design requirement is met, and the correctness of the system design is proved.

Because a plurality of wave beams transmit and receive signals at the same time, although different wave beam signals can be distinguished in echo space and time by irradiating different areas, other wave beam signals can enter a certain wave beam signal through side lobes due to the side lobes of an antenna, so that an aliasing signal is formed, and the image distance is blurred. Therefore, the receiving and transmitting isolation degree of a plurality of beams is required to be improved, the receiving and transmitting isolation degree is less than or equal to-26 dB through spatial isolation of feed source arrangement, and the image ambiguity is ensured to be better than-20 dB. The arrangement principle of the multiple feeds is that the overlapping loss of the multiple beams in the direction is less than 3dB, so that the beams can form a large width, and the overlapping loss of the multiple beams in the direction is more than 13dB. The beam receiving and transmitting isolation is ensured to be better than-26 dB. Fig. 4 shows a beam coverage map after design of a multi-beam feed arrangement.

FIG. 5 shows a beam high spatial isolation feed layout, the X _f axis represents azimuth direction, Y _f represents distance direction, the formed beam footprints are continuous in the distance direction, and the beams are not overlapped by spatial interleaving in the azimuth direction, so that the receiving and transmitting isolation is better than-26 dB, and the system distance ambiguity (RASR) can be effectively improved. The system distance ambiguity calculation formula is as follows:

Where θ _Inc,i represents the beam incident angle of the ith ambiguity region, G (θ _Inc,i) represents the antenna receiving gain of the ith ambiguity region beam incident angle θ _Inc,i, which is approximately equal to the antenna gain minus the transmit-receive isolation. R _f(θ_Inc,i) represents the distal tilt of the ith ambiguity zone beam incident angle θ _Inc,i, G is the antenna gain, R _f is the distal tilt, and θ _Inc is the beam incident angle.

According to the system parameters of Table 1, the distance ambiguity in the imaging range can be calculated to be better than-22 dB, and FIG. 6 shows the system distance ambiguity (RASR) curves under different PRFs, so that the requirements of less than or equal to-20 dB of the distance ambiguity are met, and the correctness of the system design is proved.

In summary, the application has the following technical effects:

According to the high-resolution wide SAR design method based on the reflecting surface system, through the distance-to-multi-feed wide beam coverage, the multi-beam receiving and transmitting high-gain imaging technology and the high-isolation feed source distribution technology, SAR can achieve sub-meter resolution and 50 km-level breadth high-resolution wide imaging, and the future reflecting surface system high-resolution wide SAR requirement is met.

The above description is merely illustrative of various embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily think about variations or substitutions within the scope of the present application, and the application is intended to be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. The high-resolution wide SAR design method based on the reflecting surface system is characterized by comprising the following steps of:

calculating total beam width according to the observed breadth, and calculating the beam width of each beam according to the aperture of the distance-oriented antenna;

The method comprises the steps of designing a plurality of feed sources, wherein the feed sources generate a plurality of wave beams, and the wave beams are independently transmitted and received, and the arrangement principle of the feed sources is that the overlapping loss of the wave beams in the distance direction is less than 3dB, and the overlapping loss of the wave beams in the azimuth direction is more than 13dB;

the multiple beams are independently transmitted and received, and the required pulse repetition frequency meets the following formula:

2. The method of claim 1, wherein the total beamwidth is calculated from the observed widths using the formula:

3. The method of claim 1 wherein the beam width of each beam is calculated from the distance to the antenna aperture using the formula:

4. The method of claim 1 wherein the number of range beams is determined based on the total beam width and the beam width of each beam using the formula: