A method for adaptive antenna gain control of satellite-borne GNSS-R

Abstract

A satellite-borne GNSS-R adaptive antenna gain control method, the satellite-borne GNSS-R adaptive antenna gain control method comprising: in response to the antenna of a GNSS-R satellite being set as a variable gain antenna, obtaining a reflection signal transmitted by the antenna of the GNSS-R satellite, the reflection signal being obtained after a signal from the GNSS satellite is reflected by a mirror reflection point, the mirror reflection point being located on the surface of the earth; the gain of the antenna comprising a first gain and a second gain, obtaining at least one delay-Doppler diagram of the mirror reflection point according to the reflection signal; determining a signal-to-noise ratio of the reflection signal according to the at least one delay-Doppler diagram; and sending an adjustment signal according to the signal-to-noise ratio of the reflection signal and a target signal-to-noise ratio, the adjustment signal being used to adjust the gain of the antenna.

Description

Technical Field

[0001] The present invention relates to the field of satellite detection, and in particular to a satellite-borne GNSS-R adaptive antenna gain control method. Background Art

[0002] As a passive remote sensing technology, Global Navigation Satellite System Reflectometry (GNSS-R) technology has the advantages of low cost and high temporal and spatial resolution. By analyzing the GNSS satellite signals reflected by the earth's surface, sea surface height, sea surface wind field, sea ice distribution, soil moisture and biomass can be detected. Spaceborne GNSS-R is to carry the receiver and antenna on the GNSS-R satellite, and achieve wide coverage and high-density observation by simultaneously receiving surface reflection signals from different GNSS satellites. Usually, due to factors such as processing power, hardware resources and instrument power consumption, spaceborne GNSS-R observation missions mostly use fixed-gain antennas. However, the earth's surface is a complex observation area, and fixed-gain antennas cannot meet the mission requirements of different types of detection areas. Summary of the invention

[0003] In view of this, the present invention provides a satellite-borne GNSS-R adaptive antenna gain control method, which is applied to a satellite-borne bistatic radar, and the satellite-borne bistatic radar includes a GNSS-R satellite and a GNSS satellite.

[0004] As a first aspect of the present invention, the spaceborne GNSS-R adaptive antenna gain control method comprises:

[0005] In response to the antenna of the GNSS-R satellite being set as a variable gain antenna, a reflection signal transmitted by the antenna of the GNSS-R satellite is obtained, where the reflection signal is obtained after the signal from the GNSS satellite is reflected by a mirror reflection point, and the mirror reflection point is located on the surface of the earth; the gain of the antenna includes a first gain and a second gain, and the first gain is greater than the second gain;

[0006] Obtain at least one delay Doppler map of the mirror reflection point according to the reflection signal;

[0007] determining a signal-to-noise ratio of the reflected signal based on at least one delay-Doppler map;

[0008] An adjustment signal is sent out according to the signal-to-noise ratio of the reflected signal and the target signal-to-noise ratio, and the adjustment signal is used to adjust the gain of the antenna, wherein the gain of the antenna after adjustment is a minimum gain that meets a preset condition, and the preset condition is that the signal-to-noise ratio of the reflected signal is greater than the target signal-to-noise ratio, and the target signal-to-noise ratio is the minimum signal-to-noise ratio of the reflected signal when determining the target parameters of the location of the mirror reflection point, and the target parameters are surface parameters with target accuracy.

[0009] According to an embodiment of the present invention, a method for determining a target signal-to-noise ratio includes:

[0010] Obtaining the location of the mirror reflection point according to at least one delay Doppler map;

[0011] Determine the ground surface state at the location of the mirror reflection point according to the location of the mirror reflection point;

[0012] The target signal-to-noise ratio is determined according to the surface state of the location of the mirror reflection point and at least one delay Doppler map.

[0013] According to an embodiment of the present invention, when the surface state of the location of the mirror reflection point is the ocean, the surface parameter is the wind speed;

[0014] Determining the target signal-to-noise ratio according to the surface state of the location of the mirror reflection point and at least one delay Doppler map includes:

[0015] The expected wind speed inversion standard deviation is obtained according to the surface state at the location of the mirror reflection point;

[0016] determining a normalized bistatic radar cross section relative standard deviation based on an expected wind speed inversion standard deviation and at least one delay-Doppler map;

[0017] The target signal-to-noise ratio is determined based on the relative standard deviation of the normalized bistatic radar cross section.

[0018] According to an embodiment of the present invention, determining a target signal-to-noise ratio according to a normalized bistatic radar cross section relative standard deviation includes:

[0019] Determine the normalized signal-to-noise ratio according to the relative standard deviation of the normalized bistatic radar cross section;

[0020] The target signal-to-noise ratio was determined based on the normalized signal-to-noise ratio.

[0021] According to an embodiment of the present invention, determining a target signal-to-noise ratio according to the normalized signal-to-noise ratio includes:

[0022] The target signal-to-noise ratio is obtained according to the normalized signal-to-noise ratio and the gain of the antenna when receiving the reflected signal.

[0023] According to an embodiment of the present invention, the normalized signal-to-noise ratio, the gain of the antenna when receiving the reflected signal, and the target signal-to-noise ratio satisfy the following relationship:

[0024] ;

[0025] Among them, SNR db represents the target signal-to-noise ratio, G R Represents the gain of the antenna when receiving the reflected signal, R T represents the distance between the GNSS satellite and the specular reflection point, R R represents the distance between the specular reflection point and the receiver of the GNSS-R satellite, and NSNR represents the normalized signal-to-noise ratio.

[0026] According to an embodiment of the present invention, the normalized signal-to-noise ratio and the normalized relative standard deviation of the bistatic radar cross section satisfy the following relationship:

[0027] ;

[0028] Where R is a parameter that characterizes the incoherent average effectiveness of the reflected signal. represents the number of delay-Doppler images, Represents the relative standard deviation of the normalized bistatic radar cross section.

[0029] According to an embodiment of the present invention, the delay-Doppler map of the mirror reflection point includes a pixel matrix, and the pixel matrix includes M×N pixel points;

[0030] The normalized signal-to-noise ratio and the relative standard deviation of the normalized bistatic radar cross section satisfy the following relationship:

[0031] ;

[0032] in, is the covariance matrix of the average delay-Doppler power image after normalizing (M×N)×(M×N) pixels, ( ) represents the index of the average delay Doppler image power image covariance matrix, 1< , 1<j , 1< , 1< , τ represents the time delay axis of the delay Doppler graph, f represents the frequency axis of the delay Doppler graph, It represents the average delay-Doppler power matrix of M delay pixels × N Doppler pixels after the thermal noise of the reflected signal is removed, The average delay-Doppler map power matrix is ​​represented by Line Column pixels, Indicates Line The values ​​of the pixels in the column, norm represents normalization, and S represents the signal part of the reflection signal with the noise removed.

[0033] According to an embodiment of the present invention, the relative standard deviation of the normalized bistatic radar cross section is determined by the following formula:

[0034] ;

[0035] in, represents the expected wind speed retrieval standard deviation, represents the sensitivity of wind speed to the reflected signal, represents the normalized bistatic radar cross section, Indicates the wind speed at 10 meters above the sea surface. It indicates the number of delay-Doppler images obtained within 1 second that are incoherently accumulated.

[0036] According to an embodiment of the present invention, the antenna is an array antenna.

[0037] According to an embodiment of the present invention, the embodiment of the present invention proposes to set the antenna of the GNSS-R satellite as a variable gain antenna, and adjust the gain of the antenna by comparing the signal-to-noise ratio of the reflected signal and the target signal-to-noise ratio. However, the gain of the antenna is related to the detection area. When the gain of the antenna is large, the detection area is small, and when the gain of the antenna is small, the detection area is large. By setting the target signal-to-noise ratio, the gain of the antenna is adjusted to the minimum gain when the preset conditions are met, which can take into account the signal-to-noise ratio and the detection area of ​​the signal, thereby improving the observation capability of the GNSS-R satellite for different surface conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0039] Figure 1 A flow chart of a satellite-borne GNSS-R adaptive antenna gain control method provided according to an embodiment of the present invention is shown.

[0040] Figure 2 A schematic diagram of an array antenna provided according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0041] In the process of implementing the present invention, it was found that the gain level of the antenna determines the quality of the satellite-borne GNSS-R earth observation. In different earth observation tasks, different requirements are put forward for the collection of reflected signals, among which the gain of the antenna is an important factor of the reflected signal. Higher gain has good directivity and energy concentration, while lower gain can provide a wider observation range. At present, the antennas used by satellites performing satellite-borne GNSS-R missions are all fixed-gain antennas. In order to improve the observation capability of GNSS-R at different locations on the surface of the earth and better meet the needs of satellite-borne GNSS-R earth observation missions, this paper proposes a method for changing the antenna gain.

[0042] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0043] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0044] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0045] When using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, and C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc. When using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, or C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.

[0046] It should also be noted that the directional terms mentioned in the embodiments, such as "upper", "lower", "front", "back", "left", "right", etc., are only for reference to the drawings and are not intended to limit the scope of protection of the present invention. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or configurations will be omitted when they may cause confusion in the understanding of the present invention.

[0047] The data involved in the present invention (for example, including but not limited to user personal information) are collected, updated, analyzed, processed, used, transmitted, provided, disclosed, stored, etc., in accordance with the provisions of relevant laws and regulations, are used for legitimate purposes, and do not violate public order and good morals. In particular, necessary measures are taken for user personal information to prevent illegal access to user personal information data and maintain user personal information security and network security. The control method is applied to bistatic radar.

[0048] Figure 1 A flow chart of a satellite-borne GNSS-R adaptive antenna gain control method provided according to an embodiment of the present invention is shown. The control method is applied to a bistatic radar, wherein the bistatic radar includes a GNSS-R satellite and a GNSS satellite.

[0049] like Figure 1 As shown, the control method includes: operation S1 to operation S4.

[0050] In operation S1, in response to the antenna of the GNSS-R satellite being set as a variable gain antenna, a reflected signal transmitted by the antenna of the GNSS-R satellite is obtained, where the reflected signal is obtained by reflecting the signal from the GNSS satellite by a mirror reflection point, and the mirror reflection point is located on the surface of the earth; the gain of the antenna includes a first gain and a second gain, and the first gain is greater than the second gain.

[0051] In operation S2, at least one delay-Doppler map of the specular reflection point is obtained according to the reflection signal.

[0052] In operation S3, a signal-to-noise ratio of the reflected signal is determined according to at least one delay-Doppler map.

[0053] In operation S4, an adjustment signal is issued according to the signal-to-noise ratio of the reflected signal and the target signal-to-noise ratio, and the adjustment signal is used to adjust the gain of the antenna, wherein the gain of the antenna after adjustment is a minimum gain that meets a preset condition, and the preset condition is that the signal-to-noise ratio of the reflected signal is greater than the target signal-to-noise ratio, and the target signal-to-noise ratio is the minimum signal-to-noise ratio of the reflected signal when determining the target parameters of the location of the mirror reflection point, and the target parameters are surface parameters with target accuracy.

[0054] According to an embodiment of the present invention, the embodiment of the present invention proposes to set the GNSS-R satellite as a variable gain antenna, and adjust the gain of the antenna using the comparison result of the signal-to-noise ratio of the reflected signal and the target signal-to-noise ratio. However, the gain of the antenna is related to the detection area. When the gain of the antenna is large, the detection area is small, and when the gain of the antenna is small, the detection area is large. By setting the target signal-to-noise ratio, the gain of the antenna is adjusted to the minimum gain when the preset conditions are met, which can take into account the signal-to-noise ratio and the detection area of ​​the signal, thereby improving the observation capability of the GNSS-R satellite at different locations.

[0055] According to an embodiment of the present invention, the antenna can be adjusted in the following two ways: when the antenna is in the second gain and the signal-to-noise ratio of the reflected signal is less than the target signal-to-noise ratio, the adjustment signal is used to adjust the gain of the antenna to the first gain. When the antenna is in the first gain and the signal-to-noise ratio of the reflected signal is greater than the target signal-to-noise ratio, the adjustment signal is used to adjust the gain of the antenna to the second gain. According to an embodiment of the present invention, when the antenna is in the first gain and the signal-to-noise ratio of the reflected signal is greater than the target signal-to-noise ratio, it indicates that the detection area is small, and the gain of the antenna can be reduced to achieve detection in a larger range. Both of the above adjustment methods require that the signal-to-noise ratio of the reflected signal after adjustment is greater than the target signal-to-noise ratio.

[0056] When the antenna is at the first gain and the signal-to-noise ratio of the reflected signal is less than the target signal-to-noise ratio, no adjustment can meet the preset conditions. At this time, no adjustment is made and the current reflected signal can be used to detect the surface parameters, but a quality control label can be added to this reflected signal. When the antenna is at the second gain and the signal-to-noise ratio of the reflected signal is greater than the target signal-to-noise ratio, this is the most ideal situation. No adjustment is required and the reflection can be used directly to detect the surface parameters.

[0057] According to an embodiment of the present invention, the ground surface parameters may be, for example, soil moisture, vegetation coverage, wind speed, and the like.

[0058] According to an embodiment of the present invention, by inverting the surface parameters at the locations of multiple mirror reflection points, the surface conditions of the area including multiple mirror reflection points can be obtained, including soil moisture, sea surface wind speed, inland water and flood range.

[0059] According to an embodiment of the present invention, a method for determining a target signal-to-noise ratio includes operations S41 to S43.

[0060] In operation S41, a location of a specular reflection point is obtained according to at least one delay-Doppler map;

[0061] In operation S42, the ground surface state at the location of the mirror reflection point is determined according to the location of the mirror reflection point;

[0062] In operation S43, a target signal-to-noise ratio is determined according to the ground state at the location of the specular reflection point and at least one delay-Doppler map.

[0063] According to an embodiment of the present invention, the surface state is a type of earth surface preset according to the needs of scientific mission detection, including land, ocean, etc. The target signal-to-noise ratio is determined in different ways under different surface states.

[0064] According to an embodiment of the present invention, when the surface state at the location of the mirror reflection point is ocean, the surface parameter is wind speed.

[0065] In operation S43, determining the target signal-to-noise ratio according to the surface state of the location of the mirror reflection point and at least one delay-Doppler map includes operations S431 to S433.

[0066] In operation S431, the expected wind speed inversion standard deviation is obtained according to the surface state at the location of the mirror reflection point.

[0067] In operation S432, a normalized bistatic radar cross section relative standard deviation is determined according to the expected wind speed inversion standard deviation and at least one delay-Doppler map;.

[0068] In operation S433, a target signal-to-noise ratio is determined according to a relative standard deviation of the normalized bistatic radar cross section.

[0069] According to an embodiment of the present invention, the relative standard deviation of the normalized bistatic radar cross section satisfies the following relationship:

[0070] (1).

[0071] In formula (1), represents the expected wind speed retrieval standard deviation, It is a pre-set known quantity used to characterize the accuracy of wind speed inversion. Indicates the sensitivity of wind speed to reflected signal. Indicates the wind speed at a height of 10 meters above the sea. represents the normalized bistatic radar cross section, is the parameter of the double-click radar, which is also a known quantity. It indicates the number of delay-Doppler images obtained within 1 second that are incoherently accumulated. Represents the relative standard deviation of the normalized bistatic radar cross section.

[0072] According to formula (1), the relative standard deviation of the normalized bistatic radar cross section can be determined as .

[0073] According to an embodiment of the present invention, determining a target signal-to-noise ratio according to a relative standard deviation of a normalized bistatic radar cross section includes the following steps.

[0074] Firstly, the normalized signal-to-noise ratio is determined according to the relative standard deviation of the normalized bistatic radar cross section.

[0075] Secondly, the target signal-to-noise ratio is determined according to the normalized signal-to-noise ratio.

[0076] According to an embodiment of the present invention, determining the target signal-to-noise ratio according to the normalized signal-to-noise ratio includes: obtaining the target signal-to-noise ratio according to the normalized signal-to-noise ratio and the gain of the antenna when receiving the reflected signal.

[0077] According to an embodiment of the present invention, the normalized signal-to-noise ratio, the gain of the antenna when receiving the reflected signal, and the target signal-to-noise ratio satisfy the following relationship:

[0078] (2).

[0079] Among them, SNR db is the target signal-to-noise ratio, G R represents the antenna gain of the GNSS-R satellite when receiving the reflected signal, R T represents the distance between the GNSS satellite and the specular reflection point, R R represents the distance between the specular reflection point and the receiver of the GNSS-R satellite, and NSNR represents the normalized signal-to-noise ratio.

[0080] According to an embodiment of the present invention, when the gain of the antenna changes, the target signal-to-noise ratio will also change accordingly.

[0081] According to an embodiment of the present invention, the target signal-to-noise ratio is the minimum value of the signal-to-noise ratio of the reflected signal used to invert the surface parameters with target accuracy. When the signal-to-noise ratio of the reflected signal is lower than the target signal-to-noise ratio, the reflected signal cannot be accurately inverted to obtain the surface parameters.

[0082] According to the embodiment of the present invention, when determining the target signal-to-noise ratio, formula (2) eliminates the influence of the antenna gain on the target signal-to-noise ratio. At the same time, formula (2) also shows that when the signal-to-noise ratio of the monitored reflected signal is lower than the target signal-to-noise ratio, the antenna gain is increased, and the signal-to-noise ratio of the reflected signal is enhanced.

[0083] According to an embodiment of the present invention, the normalized signal-to-noise ratio and the normalized relative standard deviation of the bistatic radar cross section satisfy the following relationship:

[0084] (3).

[0085] Where R is a parameter that characterizes the incoherent average effectiveness of the reflected signal. represents the number of delay-Doppler images, Represents the relative standard deviation of the normalized bistatic radar cross section.

[0086] According to an embodiment of the present invention, the Doppler image of the mirror reflection point includes a pixel matrix, and the pixel matrix includes M×N pixel points. Formula (3) can be further improved to Formula (4).

[0087] (4).

[0088] in, is the covariance matrix of the average delay-Doppler power image after normalizing (M×N)×(M×N) pixels, ( ) represents the index of the average delay Doppler image power image covariance matrix, 1< , 1<j , 1< , 1< , τ represents the time delay axis of the delay Doppler graph, f represents the frequency axis of the delay Doppler graph, It represents the average delay-Doppler power matrix of M delay pixels × N Doppler pixels after the thermal noise of the reflected signal is removed, The average delay-Doppler map power matrix is ​​represented by Line Column pixels, Indicates Line The values ​​of the pixels in the column, norm represents normalization, and S represents the signal part of the reflection signal without noise.

[0089] According to the embodiment of the present invention, the image of the mirror reflection point is further divided into a plurality of pixel points, which is conducive to further improving the accuracy.

[0090] According to an embodiment of the present invention, the trajectory of the antenna is a straight line in continuous time, the area where the mirror reflection point is located is constantly changing, and the signal-to-noise ratio of the reflected signal also changes dynamically. By monitoring the change in the signal-to-noise ratio at the location of the mirror reflection point, the required antenna gain level can be adaptively and dynamically selected. The change in the target signal-to-noise ratio shows the need for different antenna gain levels.

[0091] The signal-to-noise ratio of the reflected signal is continuously obtained and compared with the corresponding target signal-to-noise ratio. When it is detected that the signal-to-noise ratio of the reflected signal is lower than the set target signal-to-noise ratio, an adjustment signal is sent out. The adjustment signal is used to adjust the gain of the amplifier in the antenna or change the antenna directivity parameters to achieve a change in the gain of the antenna.

[0092] According to an embodiment of the present invention, the control method can be implemented by using a control device, which includes an acquisition module, a delay-Doppler map determination module, a signal-to-noise ratio determination module and an adjustment module.

[0093] In response to the antenna of the GNSS-R satellite being set as a variable gain antenna, the acquisition module is used to acquire the reflected signal transmitted by the antenna of the GNSS-R satellite, the reflected signal being obtained after the mirror reflection point reflects the signal from the GNSS satellite, and the mirror reflection point is located on the surface of the earth. The gain of the antenna includes a first gain and a second gain. The delay Doppler map determination module is suitable for obtaining at least one delay Doppler map of the mirror reflection point according to the reflected signal. The signal-to-noise ratio determination module is suitable for determining the signal-to-noise ratio of the reflected signal according to at least one delay Doppler map. The adjustment module is suitable for sending an adjustment signal according to the signal-to-noise ratio of the reflected signal and the target signal-to-noise ratio, and the adjustment signal is used to adjust the gain of the antenna. Among them, the gain of the antenna after adjustment is the minimum gain that meets the preset condition, the preset condition is that the signal-to-noise ratio of the reflected signal is greater than the target signal-to-noise ratio, the target signal-to-noise ratio is the minimum signal-to-noise ratio of the reflected signal when the target parameter of the location of the mirror reflection point is used to determine, and the target parameter is a surface parameter with target accuracy.

[0094] Each step of the control method provided according to an embodiment of the present invention is completed on the receiver of the GNSS-R satellite. The antenna of the GNSS-R satellite is used to receive the reflected signal and transmit the reflected signal, and the receiver is used to process the reflected signal. Each module of the control device of the present invention is arranged on the receiver. According to an embodiment of the present invention, the division of the surface state is completed in advance and is pre-set in the receiver.

[0095] According to an embodiment of the present invention, the antenna may be, for example, an array antenna.

[0096] Figure 2 FIG. 1 is a schematic diagram of an array antenna provided according to an embodiment of the present invention. Figure 2 The gain adjustment of the array antenna is described.

[0097] like Figure 2 As shown, the array antenna includes a plurality of sub-antennas arranged in an array, and each circle represents a sub-antenna. Figure 2 The antenna includes 9×9 sub-antennas arranged in an array as an example for description. Figure 2 In the figure, part (a) indicates that the antenna gain is in a high gain state, that is, a first gain state, or is called a high gain mode, and part (b) indicates that the antenna gain is in a low gain state, that is, a second gain state, or is called a normal gain mode.

[0098] The array antenna includes two serial ports, and multiple sub-antennas can form multiple combinations, that is, different sub-antenna groups. The receiver of the GBSS-R satellite is connected to the two serial ports of the antenna. The two serial ports are used to apply voltage to different combinations, thereby realizing the control of the array antenna ( Figure 2 The sub-antennas to which voltage is applied are indicated by solid circles. The first serial port is used to apply voltage to the sub-antenna group consisting of all sub-antennas (9×9 sub-antennas). At this time, the gain of the antenna is 15dBi (that is, the antenna is in high gain mode). The second serial port is used to apply voltage to the sub-antenna group consisting of the middle 5×5 sub-antennas. At this time, the gain of the antenna is 10dBi (that is, the antenna is in normal gain mode).

[0099] The embodiments of the present invention can meet the signal collection requirements for different surface conditions by maintaining the size of the original receiving antenna carried by the GNSS-R satellite unchanged and using an array antenna, thereby improving the detection capability of the GNSS-R satellite.

[0100] The embodiments of the present invention are described above. However, these embodiments are only for the purpose of illustration, and are not intended to limit the scope of the present invention. Although each embodiment is described above, it does not mean that the measures in each embodiment cannot be used in combination. The scope of the present invention is defined by the attached claims and their equivalents. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present invention.

Claims

1. A method for controlling a gain of a satellite-borne GNSS-R adaptive antenna, wherein the method is applied to a satellite-borne bistatic radar, wherein the satellite-borne bistatic radar comprises a GNSS-R satellite and a GNSS satellite, and wherein: The onboard GNSS-R adaptive antenna gain control method comprises: In response to the antenna of the GNSS-R satellite being set as a variable gain antenna, a reflection signal transmitted by the antenna of the GNSS-R satellite is obtained, wherein the reflection signal is obtained after a signal from the GNSS satellite is reflected by a mirror reflection point, and the mirror reflection point is located on the surface of the earth; the gain of the antenna includes a first gain and a second gain, and the first gain is greater than the second gain; Obtain at least one delay Doppler map of the mirror reflection point according to the reflection signal; determining a signal-to-noise ratio of the reflected signal according to the at least one delay-Doppler map; An adjustment signal is sent according to the signal-to-noise ratio of the reflected signal and the target signal-to-noise ratio, the adjustment signal being used to adjust the gain of the antenna, wherein the gain of the antenna after adjustment is a minimum gain that satisfies a preset condition, the preset condition being that the signal-to-noise ratio of the reflected signal is greater than a target signal-to-noise ratio, the target signal-to-noise ratio being a minimum signal-to-noise ratio of the reflected signal when determining a target parameter at the location of the mirror reflection point, and the target parameter being a surface parameter with a target accuracy.

2. The satellite-borne GNSS-R adaptive antenna gain control method according to claim 1, characterized in that: The method for determining the target signal-to-noise ratio includes: Obtaining the location of the mirror reflection point according to the at least one delay Doppler map; Determine the surface state of the location of the mirror reflection point according to the location of the mirror reflection point; The target signal-to-noise ratio is determined according to the surface state of the location of the mirror reflection point and the at least one delay-Doppler map.

3. The satellite-borne GNSS-R adaptive antenna gain control method according to claim 2, characterized in that: When the surface state of the location of the mirror reflection point is ocean, the surface parameter is wind speed; Determining the target signal-to-noise ratio according to the surface state of the location of the mirror reflection point and the at least one delay Doppler map includes: Obtaining an expected wind speed inversion standard deviation according to the surface state of the location of the mirror reflection point; Determining a normalized bistatic radar cross section relative standard deviation according to the expected wind speed inversion standard deviation and the at least one delay-Doppler map; The target signal-to-noise ratio is determined according to the relative standard deviation of the normalized bistatic radar cross section.

4. The satellite-borne GNSS-R adaptive antenna gain control method according to claim 3, characterized in that: Determining the target signal-to-noise ratio according to the relative standard deviation of the normalized bistatic radar cross section includes: Determining a normalized signal-to-noise ratio according to the relative standard deviation of the normalized bistatic radar cross section; The target signal-to-noise ratio is determined according to the normalized signal-to-noise ratio.

5. The satellite-borne GNSS-R adaptive antenna gain control method according to claim 4, characterized in that: Determining the target signal-to-noise ratio according to the normalized signal-to-noise ratio includes: The target signal-to-noise ratio is obtained according to the normalized signal-to-noise ratio and the gain of the antenna when receiving the reflected signal.

6. The satellite-borne GNSS-R adaptive antenna gain control method according to claim 5, characterized in that: The normalized signal-to-noise ratio, the gain of the antenna when receiving the reflected signal, and the target signal-to-noise ratio satisfy the following relationship: ； Among them, SNR db represents the target signal-to-noise ratio, G R represents the gain of the antenna when receiving the reflected signal, R T represents the distance between the GNSS satellite and the mirror reflection point, R R represents the distance between the specular reflection point and the receiver of the GNSS-R satellite, and NSNR represents the normalized signal-to-noise ratio.

7. The satellite-borne GNSS-R adaptive antenna gain control method according to claim 6, characterized in that: The normalized signal-to-noise ratio and the normalized bistatic radar cross section relative standard deviation satisfy the following relationship: ； Wherein, R is a parameter characterizing the incoherent average effectiveness of the reflected signal, represents the number of delay-Doppler images, represents the relative standard deviation of the normalized bistatic radar cross section.

8. The satellite-borne GNSS-R adaptive antenna gain control method according to claim 7, characterized in that: The delay Doppler map of the mirror reflection point includes a pixel matrix, and the pixel matrix includes M×N pixel points; The normalized signal-to-noise ratio and the normalized bistatic radar cross section relative standard deviation satisfy the following relationship: ； in, is the covariance matrix of the average delay-Doppler power image after normalizing (M×N)×(M×N) pixels, ( ) represents the index of the average delay Doppler image power image covariance matrix, 1< , 1<j , 1< , 1< , τ represents the time delay axis of the delay Doppler image, f represents the frequency axis of the delay Doppler image, represents the average delay-Doppler map power matrix of M delay pixels×N Doppler pixels after the thermal noise of the reflected signal is removed, The average delay-Doppler image power matrix is ​​represented by Line Column pixels, Indicates the Line The values ​​of the pixels in the column are as follows: norm represents normalization, and S represents the signal portion from which noise is removed in the reflection signal.

9. The satellite-borne GNSS-R adaptive antenna gain control method according to claim 7 or 8, characterized in that: The relative standard deviation of the normalized bistatic radar cross section is determined by the following formula: ； in, represents the expected wind speed retrieval standard deviation, represents the sensitivity of wind speed to the reflected signal, represents the normalized bistatic radar cross section, Indicates the wind speed at 10 meters above the sea surface. It represents the number of non-coherently accumulated delay-Doppler images obtained within 1 second.

10. The satellite-borne GNSS-R adaptive antenna gain control method according to claim 1, characterized in that: The antenna is an array antenna.

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