A method for acquiring an average capture probability of a spiral scan

Abstract

A method for obtaining the average acquisition probability of a helical scan is presented, solving the problem that existing methods for obtaining acquisition probability cannot accurately measure the satellite's space acquisition capability, and belonging to the field of communications. This invention includes: uniformly generating N target points (x...) in an uncertain region of the helical scan. i y i Based on the spiral scan parameters and the coordinates of the dwell point, the spiral scan is used to calculate the helical scan for each target point (x). i y i The capture probability p(x) i y i , σ v ), for the capture probability p(x) i y i , σ v By fitting the data, the envelope function is obtained. Rotating the envelope function around the y-axis yields the probability distribution function P(x, y, σ). v );σ v Represents the vibration noise of the transmitting satellite; obtains the probability density function P(x, y, σ) of the receiving satellite appearing at (x, y). p ), σ p Standard deviation of satellite position change at the receiver; average acquisition probability

Description

TECHNICAL FIELD

[0001] The present application relates to acquisition technology of laser communication, and belongs to the field of communication. BACKGROUND

[0002] Satellite communication as an important means of communication, has an important role in the military and civilian fields of modern society. Compared with microwave communication, satellite optical communication has higher transmission rate and modulation bandwidth, compact system structure, small volume, light weight; most importantly, due to the small laser divergence angle, the light energy is concentrated, and a small transmission power can meet the demand of long-distance communication. However, due to the narrow beam and small divergence angle of the laser signal, it is very difficult to establish a system link under long-distance transmission. In order to establish a stable communication link, aiming, acquisition and tracking technology are needed. For space acquisition technology, acquisition probability is an important index to measure the acquisition performance of the system.

[0003] The prior art for the description of the capture probability is mainly divided into two categories. The first category is the regional capture probability represented by Xin, Li, Siyuan, et al. Analytical expression and optimization of spatial acquisition for intersatellite optical communications[J]. Optics express, 2011. This definition describes the influence of the position change of the target satellite in the uncertain area on the capture probability due to the relative motion of the satellite and the influence of the orbit error and other factors in the spatial capture process. It is worth pointing out that this definition usually defaults that the scanning beam width is large enough in the spatial capture process, and there is no missed scanning. As long as the satellite appears in the uncertain area, it will be captured. Therefore, this definition essentially only describes the probability of the satellite appearing in the uncertain area, and ignores the influence of the pointing error caused by the satellite platform vibration on the spatial capture. In fact, in the actual spatial capture process, there will be missed scanning even if the scanning beam width is large. Therefore, the influence of the pointing error caused by the satellite platform vibration on the capture probability is very important. Therefore, the regional capture probability cannot accurately describe the actual capture probability, and cannot describe the influence of the satellite platform vibration on the capture probability. In addition, foreign scholars proposed a capture probability method for any fixed position in the uncertain area in 2016 in Kaushal H, Kaddoum G. Optical Communication in Space: Challenges and Mitigation Techniques[J]. IEEE Communications Surveys & Tutorials, 2016, 19(1): 57-96. This definition analyzes the influence of the vibration caused by the satellite platform vibration on the capture probability. However, the biggest disadvantage of this definition is that the accurate position of the target satellite in the uncertain area must be given to calculate. However, in the actual spatial capture process, due to the relative motion of the satellite and the orbit error, it is impossible to accurately obtain the accurate position of the target satellite. The target satellite always has random motion relative to the center of the uncertain area, and the capture probability based on the fixed position cannot describe the influence of the random motion on the capture probability, which also limits the practical application of this definition. SUMMARY

[0004] In view of the problem that the existing capture probability acquisition method cannot accurately measure the spatial capture capability of the satellite, the application provides a spiral scanning average capture probability acquisition method.

[0005] A method for obtaining the average capture probability of helical scanning according to the present invention includes:

[0006] S1. Obtain the spiral scanning parameters;

[0007] S2. Calculate the coordinates of the dwell point of the spiral scan;

[0008] S3. Generate N target points (x) uniformly in the uncertain region of the spiral scan. i y i ), i = 1, ..., N, calculate the helical scan for each target point (x) based on the helical scan parameters and the coordinates of the dwell point. i y i The capture probability p(x) i y i , σ v ), for the capture probability p(x) i y i , σ v By fitting the data, the envelope function is obtained. Rotating the envelope function around the y-axis yields the probability distribution function P(x, y, σ). v (x, y) represents any point in the uncertain region of the helical scan, σ v This indicates the vibration noise of the satellite at the transmitting end;

[0009] S4. Obtain the probability density function P(x, y, σ) of the satellite appearing at (x, y). p ), σ p This represents the standard deviation of the satellite's position change at the receiving end;

[0010] S5, Average Capture Probability FOU represents the uncertain region of the helical scan.

[0011] As a preferred embodiment, in S3, the capture probability p(x) i y i , σ v To obtain the envelope function, the following methods are used:

[0012] according to Arrange p(x) from smallest to largest i y i , σ v The rearranged sequence is For q = 1, ..., N, perform least squares fitting to obtain the coefficient matrix C = [a0a1 ... a7] of the envelope function. T =A(A T A) -1 A T B;

[0013] in,

[0014] Envelope function y = a0 + a1x + ... + a7x 7 .

[0015] Preferably, in S4, the probability density function

[0016] As a preferred option, in S2, the dwell point S n coordinates (r) n cosθ n r n sinθ n ), Indicates the station S n The polar axis in polar coordinates Indicates the station S n The polar angle in the polar coordinate system, n = 1, 2, ..., K, where K represents the total number of dwelling points, d c I represents the pitch of the coarse aiming system. θ This indicates the scanning step size of the coarse aiming system.

[0017] As a preferred option θ u This represents the half-width of the uncertain region.

[0018] As a preferred option, the capture probability p(x) i y i , σ v ):

[0019]

[0020] in, Representative of the residence S n For (x) i y i The capture probability of ) This represents the probability density function corresponding to the random variable w, where the random variable w is determined by (x... i y i ) points to the center of the light spot, I0(·) represents the first-order modified Bessel function of the zeroth order, and a represents the dwell point S. n and (x) i y i The distance between them.

[0021] The beneficial effects of this invention are that it comprehensively considers the pointing error caused by factors such as satellite platform vibration and the impact of the random distribution of the target satellite in uncertain areas on the acquisition probability. Compared with existing technologies, the average acquisition probability is closer to the actual space acquisition process and can accurately measure the satellite's space acquisition capability. Attached Figure Description

[0022] Figure 1 is a schematic diagram of the principle of spiral scanning;

[0023] Figure 2 is the relationship between the average capture probability and the scanning beam width θ v under different noise σ s ;

[0024] Figure 3 is the relationship between the average capture probability and the noise σ v under different scanning beam width θ s . DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0026] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0027] The present application will be further described below with reference to the drawings and specific embodiments, but is not limited by the present application.

[0028] The average capture probability acquisition method of spiral scanning in the embodiment includes:

[0029] Step 1, acquiring spiral scanning parameters, including:

[0030] a scanning beam width θ s , a scanning step I θ , a pitch d c , an uncertain area half-width θ u , a standard deviation σ p of the satellite position change at the receiving end, and a vibration noise σ v of the satellite at the transmitting end;

[0031] Step 2, calculating the coordinates of the dwell point of spiral scanning:

[0032] the coordinates (r n cosθ n , r n sinθ n ) of the dwell point S n , representing the polar axis of the dwell point S n in the polar coordinate system, Indicates the station S n The polar angle in the polar coordinate system, n = 1, 2, ..., K, where K represents the total number of dwelling points, d c I represents the pitch of the coarse aiming system. θ This indicates the scanning step size of the coarse aiming system. θ u This represents the half-width of the uncertain region.

[0033] Step 3: Uniformly generate N target points (x) in the uncertain region of the spiral scan. i y i ), i = 1, ..., N, calculate the helical scan for each target point (x) based on the helical scan parameters and the coordinates of the dwell point. i y i The capture probability p(x) i y i , σ v ), for the capture probability p(x) i y i , σ v By fitting the data, the envelope function is obtained. Rotating the envelope function around the y-axis yields the probability distribution function P(x, y, σ). v (x, y) represents any point in the uncertain region of the helical scan, σ v This indicates the vibration noise of the satellite at the transmitting end;

[0034] Step 4: Obtain the probability density function of the satellite appearing at (x, y). σ p This represents the standard deviation of the satellite's position change at the receiving end;

[0035] Step 5, Average capture probability FOU represents the uncertain region of the helical scan.

[0036] This implementation obtains the acquisition probability of being captured at any point in the uncertain region of the helical scan and the probability density function of the satellite appearing at (x, y). Then, step 5 is used to obtain the average acquisition probability, comprehensively considering the pointing error caused by factors such as satellite platform vibration and the impact of the random distribution of the target satellite in the uncertain region on the acquisition probability. Compared with the prior art, the average acquisition probability is closer to the actual space acquisition process and can accurately measure the satellite's space acquisition capability.

[0037] In step 3 of this implementation method, the capture probability p(x) i y i , σ v ):

[0038]

[0039] wherein, representing the residence point S n the capture probability of (x i , y i ), representing the probability density function corresponding to the random variable w, the random variable w being directed by (x i , y i ) to the spot center, I0(·) representing the zero-order modified Bessel function of the first kind, a representing the distance between the residence point S n and (x i , y i ).

[0040] The fitting method in step 3 of the embodiment has multiple types, for example, least square method. In step 3 of the embodiment, the least square method is used to fit the capture probability p(x i , y i , σ v ) to obtain the envelope function, and the method comprises:

[0041] According to arranging p(x i , y i , σ v ) from small to large, the sequence after rearrangement is q = 1, …, N, the least square fitting is performed to obtain the coefficient matrix C = [a0a1 … a7] of the envelope function T = A(A T A) -1 A T B;

[0042] wherein,

[0043] The envelope function is y = a0+a1x+…+a7x 7 .

[0044] The probability distribution function P(x, y, σ p ) is obtained by rotating the envelope function around the y axis:

[0045] wherein (x, y) represents the coordinates of any point in the uncertain area, σ v is the vibration noise of the transmitting satellite, and P(x, y, σ v ) describes the capture probability of the spiral scanning on any point (x, y) in the uncertain area;

[0046] Given the scanning parameters, the scanning step I θ = 18 μrad, the pitch d c = 20 μrad, and the standard deviation σ p=100μrad, half-width θ of the uncertain region u = 300 μrad. For example... Figure 2 As shown, with a scanning beam width θ s Using σ as the independent variable, we obtain the results under different noise levels. v Average capture probability and scan beam width θ under certain conditions s The relationship between them. For example... Figure 2 As shown, for a given vibration noise standard deviation σ v The average capture probability increases with the scan beam width θ s It increases with the increase of θ. s When the value is increased to a certain level, the average capture probability approaches 98.89%. At this point, the probability distribution function P(x, y, σ) v The average acquisition probability approaches 1. This approximates the probability that the target satellite will appear in the uncertain region. Figure 3 In the given scanning beam width θ s The average capture probability increases with vibration noise σ v It decreases as σ increases. This downward trend can be divided into three stages: 1) When σ increases... v When the value is small, the average capture probability increases with σ. v 1) The increase of σ remains basically unchanged; 2) When σ v When the value exceeds a certain threshold, the average capture probability will increase with σ. v 3) When σ increases and then decreases sharply; v As the beamwidth continues to increase, the downward trend of the average capture probability will level off, and at this point, the main factor affecting it will be the scanning beamwidth θ. s From the above analysis, it can be seen that when the scanning beam width θ s When the value is small, the main factor affecting the average capture probability is vibration noise σ. v Furthermore, this effect becomes smaller and smaller as the scan beam width increases.

[0047] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A method for obtaining the average acquisition probability of helical scanning, characterized in that, The method comprises: S1, acquiring a spiral scanning parameter; S2, calculating a dwell point coordinate of the spiral scanning. S3. Uniformly generate N target points in the spiral scan uncertainty region , Calculate the capture probability of each target point according to the spiral scan parameters and the coordinates of the dwell point Fit the capture probability , obtain the envelope function, and rotate the envelope function around the axis to obtain the probability distribution function ; represents any point in the uncertainty region of the spiral scan, represents the vibration noise of the transmitting satellite;​ S4, acquiring the probability density function of the satellite appearing at the receiving end , denotes the standard deviation of the satellite position change at the receiving end S5, average capture probability where FOU denotes the uncertainty region of the spiral scan; S2, the coordinates of the residence point , , represents the polar axis of the residence point in the polar coordinate system, represents the polar angle of the residence point in the polar coordinate system, , represents the total number of residence points, represents the pitch of the coarse aiming system, represents the scanning step of the coarse aiming system; , represents the uncertainty region half-width; In S3, the capture probability To perform fitting and obtain the envelope function, the methods include: According to from small to large , the re-arranged sequence is , , a least square fitting is performed to obtain a coefficient matrix of the envelope function ; wherein , ; envelope function ; Capture probability : wherein representing a residence point to the capture probability of representing a random variable the probability density function corresponding to the random variable by pointing to the center of the light spot, representing the first kind of Bessel function of zero order, representing a residence point and the distance between 2. The method of claim 1, wherein, In S4, the probability density function .

3. A computer-readable storage device storing a computer program, the computer program comprising instructions that, when executed by a computer, cause the computer to perform the method of any one of claims 1 to 2. The computer program is executed to implement the method according to any one of claims 1 to 2.

4. An average capture probability acquisition apparatus for helical scanning, comprising a storage device, a processor, and a computer program stored in the storage device and executable on the processor, characterized in that, The processor executes the computer program to implement the method according to any one of claims 1 to 2.

Images