A method for automatic parameter design of variable pulse repetition frequency

Abstract

The invention discloses a parameter automatic design method of a variable pulse repetition frequency, and relates to the technical field of synthetic aperture radar system design. First, the ground observation area is determined according to the satellite / moon-based SAR system parameters and the observation requirements, and the slant range history parameters of the satellite and the ground observation area, the satellite / moon-based SAR system parameters and the preset parameters of PRF selection are read in. Then, the maximum and minimum slant ranges of the left / right side in the variable PRF design process are determined based on the slant range history parameters, and all PRF sets to be calculated are determined according to the preset parameters, and all PRFs that simultaneously meet the conditions of no obstruction of the transmitted pulse and no obstruction of the subsatellite point echo on the left / right side are selected, and the number of transmitted pulse cycles and subsatellite point echo cycles corresponding to each PRF are recorded, and one left PRF and one right PRF are selected in the same zebra diagram diamond frame, and the slant range center points of the selected left PRF and right PRF are connected, and the linear function corresponding to the straight line is calculated, and the PRF at each moment is calculated using the linear function.

Description

Technical Field

[0001] The invention relates to the technical field of synthetic aperture radar system design, and in particular to an automatic parameter design method for a variable pulse repetition frequency. Background Art

[0002] For synthetic aperture radar (SAR) based on artificial satellites or the lunar surface, the design of beam position parameters is a key step in the system design process. After determining the ground observation area based on system parameters and observation requirements (including antenna size, frequency band, incident angle range, imaging width, overlap, resolution, etc.), it is necessary to design appropriate pulse repetition frequency (PRF) values ​​for each beam position based on the slant range between the radar and the observation area to avoid obstruction of the transmitted pulse and the sub-satellite point echo.

[0003] The conventional PRF design method is to draw a zebra diagram based on the functional relationship between slant range or incident angle and PRF, and then select the PRF that avoids the obstruction of the transmitted pulse and the sub-satellite point echo based on the slant range of the wave position on the zebra diagram. When the duty cycle, protection window size and ground position of the wave position are determined, the range of variation of the slant range of the wave position from the radar during the illumination period determines the PRF design range of the wave position. The advantage of this conventional design method is that it is intuitive and visual, but the disadvantage is that for multiple wave positions to be designed, multiple manual attempts are required to select the PRF, and the overall slant range variation range of a certain wave position during the illumination period may be too large, making it impossible to select a single PRF that meets the non-obstruction condition. Summary of the invention

[0004] In order to cope with the possible situation that a certain wave position does not have a PRF that meets the conditions and reduce the azimuth ambiguity and range ambiguity of the radar, the present invention proposes a parameter automatic design method of variable pulse repetition frequency, adopts an observation strategy of variable PRF, takes the slant range parameters of the wave position at multiple moments as input parameters, and automatically designs the PRF corresponding to each moment.

[0005] A method for automatically designing parameters of a variable pulse repetition frequency for a spaceborne or moon-based SAR system comprises the following steps:

[0006] Step 1: Determine the ground observation area according to the satellite / moon-based SAR system parameters and observation requirements, and read in the slant range history parameters between the radar and the ground observation area, the satellite / moon-based SAR system parameters and the preset parameters for PRF selection;

[0007] The slant range history parameters are the maximum and minimum slant ranges between the radar and the ground observation area at each moment of the observation period centered on the moment of illumination of the radar beam center. The satellite / moon-based SAR system parameters include the protection window coefficient, duty cycle and sub-satellite point height. The preset parameters for PRF selection include the maximum and minimum PRF selection values, PRF selection step size and margin coefficient.

[0008] Step 2: Determine the maximum and minimum slant distances on the left and the maximum and minimum slant distances on the right in the variable PRF design process based on the slant distance history parameters, and determine all PRF sets to be calculated according to preset parameters.

[0009] The maximum slope distance on the left is the maximum slope distance among the maximum slope distances at all times, and the minimum slope distance on the left is the minimum slope distance corresponding to that moment; the minimum slope distance on the right is the minimum slope distance among the minimum slope distances at all times, and the maximum slope distance on the right is the maximum slope distance corresponding to that moment.

[0010] Step 3: Using the maximum and minimum slant ranges on the left side, select all PRFs on the left side that meet the conditions of no obstruction of the transmit pulse and no obstruction of the sub-satellite point echo from the PRF set to be calculated, and record them as the left PRF set. At the same time, record the number of transmit pulse cycles and sub-satellite point echo cycles corresponding to each PRF.

[0011] The specific steps include:

[0012] A. Traverse the PRF set to be calculated, for each , calculate the corresponding pulse width according to the duty cycle .

[0013] B. Based on pulse width , determine the current Whether the condition of transmitting pulse not being blocked is met, if so, record the value and its corresponding number of transmitted pulse cycles; otherwise, the give up;

[0014] C. At the same time, judge the current Whether the condition of no obstruction of sub-satellite echo is met, if so, record the value and its corresponding sub-satellite point echo period number; otherwise, the give up;

[0015] D. Find the PRF set calculated in steps B and C that satisfies the conditions that the transmitted pulse and the sub-satellite point echo are not blocked, as well as the number of transmitted pulse cycles and sub-satellite point echo cycles corresponding to each PRF.

[0016] Step 4: Similarly, using the maximum and minimum slant ranges on the right side, calculate all PRFs on the right side that simultaneously meet the conditions of no obstruction of the transmit pulse and no obstruction of the sub-satellite point echo, record them as the right PRF set, and record the number of transmit pulse cycles and sub-satellite point echo cycles corresponding to each PRF.

[0017] Step 5: Using the number of transmit pulse cycles and the number of sub-satellite point echo cycles corresponding to each PRF in the left PRF set and the right PRF set, select one left PRF and one right PRF located in the same zebra diagram diamond frame.

[0018] The specific steps include:

[0019] A. Sort the PRFs in the left PRF set from small to large, and take the PRF; sort the PRFs in the right PRF set from large to small, and take the PRF on the left; The first PRF and the right PRFs form a group of PRFs.

[0020] B. Determine whether the extracted set of PRFs are located in the same diamond frame. If so, proceed to step C; if not, return to step A to select the next set of PRFs.

[0021] C. The two PRFs in the same diamond frame are adjusted according to the margin coefficient to obtain a set of new PRFs.

[0022] D. Determine whether the new PRF has the same number of transmit pulse cycles and the same number of sub-satellite point cycles. If so, output the group of PRFs and execute step 6; otherwise, return to step A to select the next group of PRFs;

[0023] Step 6: Connect the slant distance center points of the selected left PRF and right PRF on the zebra diagram, calculate the linear function corresponding to the straight line, and use the linear function to calculate the PRF at other times to obtain the design result of the variable pulse repetition frequency.

[0024] The first-order function is: ,in is the slope distance, a and b are the calculated coefficients.

[0025] The advantages of the present invention are:

[0026] ① When selecting PRF for a certain wave position, the overall slant range variation range of the wave position during the illumination period may be too large. If the conventional method is used, a single PRF that meets the conditions cannot be selected. The present invention decomposes the overall slant range variation range of the wave position when it is illuminated into the slant range at each moment in the illumination period, adopts a variable PRF observation strategy, selects a PRF at each moment, and thus obtains a PRF set that can be used for the wave position, reducing the ambiguity in the range and azimuth directions of the synthetic aperture radar.

[0027] ② For multiple wave positions to be designed, it is time-consuming and laborious to draw a zebra diagram and select PRF by manual attempts. The present invention adopts automated program design, draws a zebra diagram according to input parameters, and traverses and calculates whether the PRF within a given value range meets the conditions, thereby obtaining a PRF set suitable for the wave position to be designed, greatly improving calculation efficiency and saving labor costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The overall flow chart of the automatic parameter design method of the variable pulse repetition frequency of the present invention;

[0029] Figure 2 A schematic diagram of a diamond frame in a zebra diagram according to an embodiment of the present invention;

[0030] Figure 3 A schematic diagram of the results of the variable PRF designed by simulation calculation in an embodiment of the present invention on a zebra diagram. DETAILED DESCRIPTION

[0031] The technical scheme in the embodiment of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiment of the present application. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, some changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0032] Example: Taking a set of PRF design processes for spaceborne / moon-based SAR wave positions that adopt a variable PRF strategy as an example, the specific process is as follows: Figure 1 As shown, the following steps are included:

[0033] Step 1: Read in the slant range history parameters between the radar and the ground observation area, the relevant spaceborne / moon-based SAR system parameters, and the preset parameters of the PRF design, including:

[0034] A. Read in the slant range history parameters: Divide the observation period centered on the time of the radar beam center illumination into sampling points, recorded as the time sequence to be analyzed , read the slant distance corresponding to each moment, including the satellite and ground observation area in the first The maximum slope distance corresponding to the moment , minimum slope distance ,in .

[0035] B. Read in the relevant satellite / moon-based SAR system parameters and the preset parameters of the PRF design. The system parameters include: the protection window coefficient after the transmission pulse , Protection window coefficient before transmitting pulse , protection window coefficient after sub-satellite point echo , protection window coefficient before sub-satellite echo , Duty Cycle , Subsatellite point height . Preset parameters include: Minimum selection , Maximum Selection , PRF step size , left margin coefficient , right margin coefficient .

[0036] Step 2: Determine the maximum and minimum slope distances on the left side and the maximum and minimum slope distances on the right side of the variable PRF design process, and determine all PRF sets to be calculated according to preset parameters.

[0037] It should be noted that in the same diamond box of the zebra diagram, the smaller the PRF is, the more to the left it is, and the larger the corresponding maximum slope distance value is. Therefore, the larger the input slope distance is, the more you should select the PRF on the left side of the diamond box. Similarly, the smaller the slope distance is, the more you should select the PRF on the right side of the diamond box. Figure 2 As shown in the red box.

[0038] Among them, the maximum slope distance on the left side of the variable parameter PRF selection process is determined according to the slope distance history parameter , Minimum slope distance on the left , Maximum slope distance on the right , right minimum slope distance The method is as follows:

[0039] Calculate the maximum slope distance among the maximum slope distances at all times and its corresponding time sequence number , then the maximum slope distance on the left The minimum slope distance on the left is the minimum slope distance corresponding to that moment: .

[0040] Similarly, calculate the minimum slope distance among the minimum slope distances at all times and its corresponding time sequence number , then the minimum slope distance on the right is The maximum slope distance on the right is the maximum slope distance corresponding to that moment: .

[0041] The PRF set to be calculated is expressed as:

[0042]

[0043] Here, k is an integer, indicating the sequence number of each PRF in the PRF set to be calculated.

[0044] Step 3: Using the maximum and minimum slant ranges on the left side, calculate all PRFs (referred to as the left PRF set) that satisfy both the conditions of no obstruction of the transmitted pulse and no obstruction of the sub-satellite point echo on the left side and their corresponding number of transmitted pulse cycles and number of sub-satellite point echo cycles.

[0045] The specific steps are:

[0046] A. Traverse the PRF set to be calculated, for each , calculate the corresponding pulse width according to the duty cycle :

[0047]

[0048] B. Determine the current Whether the condition that the transmitted pulse is not blocked is met, as shown in the following formula:

[0049] { floor [ p n e a r ] = floor [ p f a r ] ( p n e a r − floor [ p n e a r ] ) ⋅ 1 prf > PE 1 ⋅ Tao ( p far − floor [ p far ] ) ⋅ 1 prf < 1 prf − PE 2 ⋅ Tao

[0050] in, , , is the speed of light, floor [ ⋅ ] is the floor function.

[0051] If satisfied, record the Value and its corresponding number of transmitted pulse cycles , P i n t = floor [ p n e a r ] .

[0052] C. Determine the current Whether the condition that the sub-satellite point echo is not blocked is met, as shown in the following formula:

[0053] { floor [ n n e a r ] = floor [ n f a r ] ( n n e a r − floor [ n n e a r ] ) ⋅ 1 prf > NE 1 ⋅ Tao ( n far − floor [ n far ] ) ⋅ 1 prf < 1 prf − NE 2 ⋅ Tao

[0054] in, , .

[0055] If satisfied, record the Value and its corresponding sub-satellite point echo period number , N i n t = floor [ n n e a r ] .

[0056] D. Find the PRF set calculated in steps B and C that satisfies the conditions that the transmitted pulse and the sub-satellite point echo are not blocked, as well as the number of transmitted pulse cycles and sub-satellite point echo cycles corresponding to each PRF.

[0057] Step 4: Using the maximum and minimum slant ranges on the right side, calculate all PRFs (referred to as the right PRF set) that simultaneously meet the conditions of no obstruction of the transmit pulse and no obstruction of the sub-satellite point echo on the right side and their corresponding transmit pulse cycle numbers and sub-satellite point echo cycle numbers.

[0058] The specific method of this step is the same as step 3. and Assign values ​​to and That's it.

[0059] Step 5: Using the number of transmit pulse cycles and the number of sub-satellite point echo cycles corresponding to each PRF, select one left PRF and one right PRF located in the same zebra diagram diamond frame.

[0060] The meanings of the left PRF and the right PRF are: the minimum PRF and the maximum PRF selected by the spaceborne / moon-based SAR using the variable parameter method of the present invention within the input observation period. The specific steps are as follows:

[0061] A. Sort the PRF set on the left from small to large according to the PRF value, and take the PRF, denoted as , sort the PRF set on the right from large to small, and take the PRF, denoted as .

[0062] B. For the current and , determine whether they are in the same diamond box, the judgment condition is as follows:

[0063]

[0064] in, and They are The corresponding number of transmission pulse cycles and sub-satellite point echo cycles, and They are The corresponding transmission pulse cycle number and sub-satellite point echo cycle number are calculated in step 3.

[0065] If the condition is met, it means that the two PRFs are located in the same diamond frame, and then go to step C; if the condition is not met, return to step A to select the next group of PRFs.

[0066] C. When two PRFs are located in the same diamond frame, in order to leave a certain distance between the slant range of the PRFs on both sides and the occlusion area, the PRF sets on both sides are skipped. and PRF, take The left PRF and right PRF, where is the left residual coefficient, is the right margin coefficient, is the total number of PRFs in the left PRF set, is the total number of PRFs in the right PRF set.

[0067] D. Judgment and Do they have the same transmit pulse period number and the same sub-satellite point period number? If not, return to step A to select the next set of PRFs; if they are the same, output and , respectively and .

[0068] Step 6: Connect the slant distance center points of the selected left PRF and right PRF on the zebra diagram, calculate the linear function corresponding to the straight line, and select the PRF at other times on the straight line.

[0069] The specific method is:

[0070] A. At a pulse repetition frequency is the horizontal axis, the slope distance On the zebra map with ordinate as the vertical coordinate, calculate the coordinate point and coordinate points The linear function corresponding to the straight line connecting .

[0071] B. Calculate the slant distance center value corresponding to other times, and the time sequence number Represents other moments except the left slant distance and right slant distance moments (the specific number is determined according to usage requirements). The slope distance center value at this moment is .

[0072] C. Substitution , calculate the PRF selected at each moment.

[0073] In order to illustrate the effectiveness of this method, a set of spaceborne SAR position parameters that adopt a variable PRF strategy is taken as an example, and the slant range history parameters and preset parameters required by this method are given to conduct method tests to achieve the automatic design of variable PRF. The input parameters are shown in Tables 1, 2, and 3. With a time interval of 1 second, the PRFs at each moment are selected as shown in Table 4, and the schematic diagram on the zebra map is shown in Figure 3 As shown in Table 4 and Figure 3 It can be seen that the overall slant range variation range of this wave position has exceeded the slant range that can be covered by the diamond frame, and a single PRF that meets the conditions cannot be selected. The present invention adopts an observation strategy of variable PRF to automatically select the PRF corresponding to each sampling moment, effectively realizing the PRF design of this wave position.

[0074] surface Slope range parameters

[0075] Time serial number Sampling time(s) Minimum slope distance (m) Maximum slope distance (m) 1 -13.5 644558.96 649266.44 2 -13.0 644028.67 648680.41 3 -12.5 643519.11 648114.87 4 -12.0 643030.35 647569.89 5 -11.5 642562.42 647045.51 6 -11.0 642115.38 646541.78 7 -10.5 641689.27 646058.76 8 -10.0 641284.13 645596.48 9 -9.5 640899.99 645154.99 10 -9.0 640536.91 644734.33 11 -8.5 640194.90 644334.55 12 -8.0 639874.02 643955.69 13 -7.5 639574.28 643597.77 14 -7.0 639295.72 643260.84 15 -6.5 639038.37 642944.93 16 -6.0 638802.24 642650.07 17 -5.5 638587.38 642376.29 18 -5.0 638393.78 642123.62 19 -4.5 638221.49 641892.07 20 -4.0 638070.51 641681.68 21 -3.5 637940.85 641492.46 22 -3.0 637832.54 641324.44 23 -2.5 637745.57 641177.62 24 -2.0 637679.97 641052.03 25 -1.5 637635.74 640947.68 26 -1.0 637612.87 640864.57 27 -0.5 637592.59 640802.71 28 0.0 637576.18 640819.68 29 0.5 637557.12 640860.36 30 1.0 637559.44 640922.30 31 1.5 637583.13 641005.49 32 2.0 637628.20 641109.92 33 2.5 637694.63 641235.59 34 3.0 637782.42 641382.48 35 3.5 637891.56 641550.57 36 4.0 638022.04 641739.85 37 4.5 638173.85 641950.30 38 5.0 638346.97 642181.90 39 5.5 638541.38 642434.63 40 6.0 638757.07 642708.45 41 6.5 638994.01 643003.35 42 7.0 639252.18 643319.29 43 7.5 639531.55 643656.25 44 8.0 639832.10 644014.19 45 8.5 640153.79 644393.07 46 9.0 640496.60 644792.85 47 9.5 640860.48 645213.51 48 10.0 641245.40 645654.99 49 10.5 641651.33 646117.26 50 11.0 642078.22 646600.27 51 11.5 642526.04 647103.97 52 12.0 642994.73 647628.31 53 12.5 643484.26 648173.24 54 13.0 643994.56 648738.72 55 13.5 644525.61 649324.69 56 14.0 645077.34 649931.08

[0076] surface Related system parameters

[0077] System Parameters Selected parameter value Protection window coefficient after transmitting pulse 1.3 Protection window coefficient before transmitting pulse 0.5 Protection window coefficient after sub-satellite point echo 1.3 Sub-satellite point echo front protection window coefficient 0 Duty Cycle 0.2 Subsatellite point height (m) 498384.15

[0078] surface Preset Parameters

[0079] Preset Parameters Selected parameter value Minimum selected PRF(Hz) 9050 Maximum selected PRF(Hz) 10250 PRF step size (Hz) 0.05 Left margin coefficient 0.125 Right margin coefficient 0.1

[0080] surface Variable PRF Design Results

[0081] Time serial number Sampling time(s) Selected PRF (Hz) 1 -13.5 9842.5 3 -12.5 9867.8 5 -11.5 9891.2 7 -10.5 9912.6 9 -9.5 9932.2 11 -8.5 9949.8 13 -7.5 9965.4 15 -6.5 9979.2 17 -5.5 9990.9 19 -4.5 10000.7 21 -3.5 10008.6 23 -2.5 10014.5 25 -1.5 10018.4 27 -0.5 10020.0 29 0.5 10020.3 30 1.0 10019.6 32 2.0 10016.6 34 3.0 10011.7 36 4.0 10004.8 38 5.0 9995.9 40 6.0 9985.1 42 7.0 9972.4 44 8.0 9957.7 46 9.0 9941.0 48 10.0 9922.4 50 11.0 9901.9 52 12.0 9879.5 54 13.0 9855.1 56 14.0 9828.9

Claims

1. A method for automatically designing parameters of a variable pulse repetition frequency, characterized in that: For use with spaceborne or moon-based SAR systems, the following steps are included: Step 1: Determine the ground observation area according to the satellite / moon-based SAR system parameters and observation requirements, and read in the slant range history parameters between the radar and the ground observation area, the satellite / moon-based SAR system parameters and the preset parameters for PRF selection; Step 2: determining the maximum and minimum slant distances on the left and the maximum and minimum slant distances on the right in the variable PRF design process based on the slant distance history parameters, and determining all PRF sets to be calculated according to preset parameters; The maximum slope distance on the left is the maximum slope distance among all the maximum slope distances at all times, and the minimum slope distance on the left is the minimum slope distance corresponding to that moment; the maximum slope distance on the right is the minimum slope distance among all the minimum slope distances at all times, and the minimum slope distance on the right is the maximum slope distance corresponding to that moment; Step 3: Using the maximum and minimum slant ranges on the left side, select all PRFs on the left side that meet the conditions of no obstruction of the transmit pulse and no obstruction of the sub-satellite point echo from the PRF set to be calculated, record them as the left PRF set, and record the number of transmit pulse cycles and sub-satellite point echo cycles corresponding to each PRF; The specific steps include: A. Traverse the PRF set to be calculated, for each , calculate the corresponding pulse width according to the duty cycle ; B. Based on pulse width , determine the current Whether the condition of transmitting pulse not being blocked is met, if so, record the value and its corresponding number of transmitted pulse cycles; otherwise, the give up; C. At the same time, judge the current Whether the condition of no obstruction of sub-satellite echo is met, if so, record the value and its corresponding sub-satellite point echo period number; otherwise, the give up; D. Find the PRF set calculated in steps B and C that satisfies the conditions that the transmitted pulse and the sub-satellite point echo are not blocked, as well as the number of transmitted pulse cycles and sub-satellite point echo cycles corresponding to each PRF; Step 4: Similarly, using the maximum and minimum slant ranges on the right side, calculate all PRFs on the right side that simultaneously meet the conditions of no obstruction of the transmit pulse and no obstruction of the sub-satellite point echo, record them as the right PRF set, and record the number of transmit pulse cycles and sub-satellite point echo cycles corresponding to each PRF; Step 5: Using the number of transmission pulse cycles and the number of sub-satellite point echo cycles corresponding to each PRF in the left PRF set and the right PRF set, select one left PRF and one right PRF located in the same zebra diagram diamond frame; The specific steps include: A. Sort the PRFs in the left PRF set from small to large, and take the PRF; sort the PRFs in the right PRF set from large to small, and take the PRF on the left; The PRF and the right PRFs form a group of PRFs; B. Determine whether the extracted set of PRFs are located in the same diamond frame, and proceed to step C; if not, return to step A to select the next set of PRFs; C. Adjust the two PRFs in the same diamond frame according to the residual coefficient to obtain a set of new PRFs; D. Determine whether the new PRF has the same number of transmit pulse cycles and the same number of sub-satellite point cycles. If so, output the group of PRFs; otherwise, return to step A to select the next group of PRFs; Step 6, connect the slant distance center points of the selected left PRF and right PRF on the zebra diagram, calculate the linear function corresponding to the straight line, and use the linear function to calculate the PRF at other times to obtain the design result of the variable pulse repetition frequency; The linear function is: ,in is the slope distance, a and b are the calculated coefficients.

2. The method for automatically designing parameters of a variable pulse repetition frequency according to claim 1, characterized in that: The slant range history parameter is the maximum slant range and the minimum slant range between the radar and the ground observation area at each moment of the observation period centered on the moment of illumination of the radar beam center.

3. The method for automatically designing parameters of a variable pulse repetition frequency according to claim 1, characterized in that: The satellite-borne / moon-based SAR system parameters include protection window coefficient, duty cycle and sub-satellite point height.

4. The method for automatically designing parameters of a variable pulse repetition frequency according to claim 1, characterized in that: The preset parameters for PRF selection include maximum and minimum PRF selection values, PRF selection step size and margin coefficient.

5. The method for automatically designing parameters of a variable pulse repetition frequency according to claim 1, characterized in that: The PRF set to be calculated is expressed as: ,in, Select a value for the preset minimum PRF, Select a value for the preset maximum PRF, is the PRF step size, and k is the integer number representing each PRF in the PRF set to be calculated.

6. The method for automatically designing parameters of a variable pulse repetition frequency according to claim 1, characterized in that: Pulse Width The calculation formula is: ,in is the duty cycle.

7. The method for automatically designing parameters of a variable pulse repetition frequency according to claim 1, characterized in that: judge The formula for whether the condition of transmitting pulse not being blocked is met is: ;judge The formula for determining whether the condition of no obstruction of sub-satellite echo is met is: ; calculate The corresponding number of transmit pulse cycles is , the corresponding sub-satellite point echo period number is ; in, , , , , is the speed of light, is the floor function, is the protection window coefficient after the transmission pulse, is the protection window coefficient before transmitting pulse, is the protection window coefficient after the sub-satellite point echo, is the protection window coefficient before the sub-satellite echo.

8. The method for automatically designing parameters of a variable pulse repetition frequency according to claim 1, characterized in that: The formula for determining whether the i-th PRF on the left and the j-th PRF on the right are located in the same diamond box is: in, and They are The corresponding number of transmission pulse cycles and sub-satellite point echo cycles, and They are The corresponding number of transmit pulse cycles and sub-satellite point echo cycles.

9. The method for automatically designing parameters of a variable pulse repetition frequency according to claim 1, characterized in that: The calculation process of the linear function corresponding to the straight line obtained by connecting the slant distance center points of the left PRF and the right PRF is: Set the pulse repetition frequency is the horizontal axis, the slope distance On the zebra diagram with ordinate as the coordinate, calculate the PRF coordinate point on the left and the right PRF coordinate point The linear function corresponding to the straight line connecting .

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