Intersatellite ranging system, method, device and data processing terminal

Abstract

The present invention belongs to the field of quantum navigation and positioning technology, and discloses an inter-satellite ranging system, method, device and data processing terminal. The inter-satellite ranging system includes: a photon transceiver unit, which is used to generate entangled photon pairs, transmit signal photons to the satellite to be measured and the internal optical path, and receive signal photons reflected by the satellite to be measured and the internal optical path; a coincidence counting unit, which is used to associate the received signal photons with the idle photons to obtain their second-order correlation curves; a distance measurement unit, which is used to perform DFT phase difference weighted processing on two second-order correlation curves generated by the optical path difference inside and outside the system to obtain the actual optical path difference from the satellite to be measured to the system. The present invention uses a photon matching method to filter out the cosmic space stray light entering the photon detector to a large extent, thereby improving the signal-to-noise ratio. The present invention adopts an improved coincidence counting algorithm, and the calculation rate is greatly improved compared with the traditional coincidence counting algorithm.

Description

Technical Field

[0001] The present invention belongs to the technical field of quantum navigation and positioning, and in particular relates to an inter-satellite ranging system, method, device and data processing terminal. Background Art

[0002] At present, the quantum positioning system (QPS) based on quantum technology is a new positioning technology with high positioning accuracy and strong confidentiality. It uses the unique entanglement properties of entangled photon pairs to perform coincidence measurement and obtain the phase difference information of two photons. It can provide rich navigation information such as position, speed, and time for various spacecraft such as near-earth and deep space. The quantum ranging technology was first proposed by Dr. Vittorio Giovannetti and Dr. Lorenzo Maccone of the Massachusetts Institute of Technology and their mentor Professor Lloyd in 2001. In the same year, the relevant paper was published in "Nature", proposing an idealized experimental method and system for quantum ranging positioning. In 2005, Dr. Massimiliano F. Sacchi successfully distinguished two quantum states with the minimum error probability using entangled photon pairs. In 2007, Dr. Jerey H. Shapiro. In 2008, Professor Seth Lloyd proposed the concept of quantum illumination and proved that the use of entangled photon pairs can improve the sensitivity of photon counting. In 2009, Dr. James F. Smith III proposed the effect of atmospheric attenuation on the transmission performance of entangled photons and gave a correction method. In 2011, Dr. Marco Lanzagorta published the book "Quantum Radar" as a reference book on quantum ranging. In 2019, Dr. Lorenzo Maccone and Dr. Changliang Ren proposed a new quantum measurement protocol that can solve the three-dimensional spatial coordinates of non-cooperative targets, achieving the goal of quantum ranging positioning.

[0003] Compared with the application of quantum mechanics in computing, communication and other fields, there are relatively few studies on quantum mechanics in ranging and positioning in China. From the relevant domestic and foreign literature, there are very limited research reports on quantum ranging and positioning. Only theoretical research is carried out in some laboratories of a few universities, but it is limited to basic principles, potential advantages, major defects, etc. There is no substantial application progress, which is obviously lagging behind the research and application abroad. In 2004, Zhang Huanyang, Zhang Guanjie and others introduced the basic principles of quantum ranging and positioning and analyzed its potential advantages and application value compared with traditional ranging and positioning. In 2009, Yang Chunyan, Wu Dewei and others used interferometric quantum positioning to study the positioning system of the optimal constellation and proposed a high-precision positioning scheme combining traditional ranging and positioning technology with quantum measurement. In 2010, Li Yongfang, Wang Zhaohua and others analyzed the influence of the coherence of entangled photon pairs and laser width on positioning accuracy, and explored the method of generating entangled photon pairs using spontaneous parametric down-conversion. In 2013, Zeng Guihua's team at Shanghai Jiao Tong University conducted a distance measurement experiment based on quantum entanglement and achieved a distance measurement accuracy of 200μm at a distance of 1043.3m. In 2018, Cong Shuang's team at the National University of Defense Technology proposed a positioning method based on three satellites carrying a quantum entanglement system and gave the influencing factors of atmospheric attenuation.

[0004] Judging from the current development of quantum mechanics in China, the research foundation of some basic theories and key technologies for quantum ranging and positioning is available in China and is also in a leading position internationally, especially in the preparation technology of quantum entanglement sources and the research of quantum invisible transmission, which can provide a solid backing for the realization of QPS engineering in the future. However, the simulation of related experimental systems is in its infancy, and intersatellite positioning and ranging is still in a vacuum state, which has far-reaching and significant research on intersatellite high-precision ranging.

[0005] Through the above analysis, the problems and defects of the prior art are as follows:

[0006] (1) There is relatively little research in China on the application of quantum mechanics in ranging and positioning. The research reports on quantum ranging and positioning are very limited. The few studies that exist are limited to basic principles, potential advantages, major defects, etc. There is no substantial progress in application, and it lags significantly behind research and application abroad.

[0007] (2) Traditional intersatellite ranging methods cannot overcome the shot noise limit and have low ranging accuracy.

[0008] (3) The simulation of relevant experimental systems is in its infancy, and inter-satellite positioning and ranging is still in a vacuum state.

[0009] The difficulty of solving the above problems and defects is:

[0010] (1) It is difficult to build a high-brightness entangled source system; due to the low efficiency of nonlinear parameter down-conversion and the transmission loss of various optical devices, it is difficult to build a system with high brightness and high entanglement degree.

[0011] (2) Quantum entanglement involves a large amount of disentanglement phenomena, and this phenomenon is exacerbated as the measurement and positioning distance increases, making the measurement distance based on quantum entanglement ranging shorter.

[0012] The significance of solving the above problems and defects is:

[0013] (1) Using quantum entanglement to measure distance and locate can break the traditional distance measurement limit and theoretically achieve higher distance measurement and location accuracy.

[0014] (2) Building an intersatellite ranging system based on quantum entanglement can provide high-precision intersatellite distance information for subsequent specific applications such as satellite formation, satellite orbit determination, and intersatellite navigation. Summary of the invention

[0015] In view of the problems existing in the prior art, the present invention provides an inter-satellite ranging system, method, device and data processing terminal, and more particularly relates to an inter-satellite ranging system, method, device and data processing terminal based on quantum ranging, aiming to solve the problem that traditional inter-satellite ranging methods cannot overcome the shot noise limit and have low ranging accuracy.

[0016] The present invention is implemented in this way: an inter-satellite ranging system, the inter-satellite ranging system comprising:

[0017] A photon transceiver unit is used to generate entangled photon pairs, transmit signal photons to the satellite to be measured and the internal optical path, and receive signal photons reflected back from the satellite to be measured and the internal optical path;

[0018] A coincidence counting unit is used to correlate the received signal photons with the idler photons to obtain their second-order correlation curve;

[0019] The distance measurement unit is used to perform DFT phase difference weighted processing on the two second-order correlation curves generated by the optical path difference inside and outside the system to obtain the actual optical path difference from the satellite to be measured to the system.

[0020] Furthermore, the photon transceiver unit comprises:

[0021] The high-brightness quantum entangled source module is used to perform spontaneous parametric down-conversion of the laser emitted by the laser through the PPKTP crystal to generate entangled photon pairs, and then split the entangled photon pairs into two optical paths, signal light and idler light, through a polarization beam splitter;

[0022] A photon emission module is used to emit the signal path photons generated by the high-brightness quantum entanglement source module to the ranging / self-test module through a collimator;

[0023] The ranging / self-test module is used to switch the polarization lens so that the signal path photons in the self-test mode can only enter the photon detector through the internal optical path of the system, and the signal path photons in the ranging mode can be emitted into space;

[0024] The photon detection module is used to detect the photons in the signal path and the idle path through the photon detector, and output the time tag stream of the detected photons arriving at the detector;

[0025] The signal photon reflection device of the satellite to be measured comprises a conic reflector, which is used for reflecting the emitted signal photons back to the inter-satellite ranging system along the original path.

[0026] Among them, the ranging / self-test module includes a polarizer switching module and a polarization beam splitter; when in the self-test mode, a vertical polarizer is inserted into the signal light path in the system to filter out photons in other polarization states except the vertical polarization, and the vertically polarized photons are reflected at an angle of 45 degrees at the polarization beam splitter of the transmitting window to the polarization beam splitter at the receiving window, and then reflected at an angle of 45 degrees again to enter the photon detector; when in the ranging mode, a horizontal polarizer is inserted into the signal light path in the system to filter out photons in other polarization states except the horizontal polarization, and the horizontally polarized photons are transmitted at the polarization beam splitter of the transmitting window, reflected by the conical reflector of the satellite to be measured, and then transmitted at the polarization beam splitter of the receiving window to enter the photon detector.

[0027] Furthermore, the coincidence counting unit comprises:

[0028] A photon pair matching module is used to pair the signal path photons and the idle path photons detected by the photon detection module according to the estimated optical path difference to generate coarse matching photon pair data;

[0029] A second-order correlation function generation module is used to perform a coincidence operation on the coarse matching photon pair data generated by the photon pair matching module through an improved coincidence counting algorithm to generate a coincidence counting curve, i.e., a second-order correlation function;

[0030] The least squares fitting module is used to fit the second-order correlation curve by using the least squares method and the fitting function, generate fitting parameters and fitting curves, and analyze information such as the signal-to-noise ratio based on the fitting parameters and the fitting curves.

[0031] Furthermore, the distance measuring unit comprises:

[0032] The maximum likelihood estimation module is used to obtain the center offset position of the self-check coincidence count curve and the ranging coincidence count curve by the maximum likelihood estimation method, and to obtain the rough distance information from the inter-satellite ranging system to the satellite to be measured by difference;

[0033] The DFT phase difference weighting module is used to perform DFT phase difference weighting on the self-check coincidence count curve and the ranging coincidence count curve, and with the assistance of the maximum likelihood estimation method module, obtain the precise distance information from the inter-satellite ranging system to the satellite to be measured.

[0034] Another object of the present invention is to provide an inter-satellite ranging method using the inter-satellite ranging system, the inter-satellite ranging method comprising the following steps:

[0035] Step 1: generate entangled photon pairs through the photon transceiver unit, transmit signal photons to the satellite to be measured and the internal optical path, and receive signal photons reflected back by the satellite to be measured and the internal optical path;

[0036] Step 2, correlating the received signal photons with the idler photons through a coincidence counting unit to obtain their second-order correlation curve;

[0037] Step 3: The distance measurement unit performs DFT phase difference weighting processing on the two second-order correlation curves generated by the optical path difference inside and outside the system to obtain the actual optical path difference from the satellite to be measured to the system.

[0038] Furthermore, in step 2, the improved coincidence counting algorithm adopted by the second-order correlation function generation module of the coincidence counting unit includes:

[0039] For each pair of photons in the rough matching photon pair, calculate the detection time t of the idler photon i The time t at which the signal photon is detected s The time difference is compared with the window time t w Add half of the result to get T interval =(t s -t i )+t w / 2, divided by the sliding step length T slide Get the integer quotient a and remainder b; calculate t w -b divided by T slide The integer quotient d, in ((ad):a)*T slide The coincidence number at the corresponding time axis position is increased by 1, and the coincidence count curve, i.e., the second-order correlation function, is generated after the corresponding operation is performed on each pair of photons in the rough matching photon pair; the fitting formula adopted by the least squares fitting module is:

[0040]

[0041] Among them, a represents the maximum number of entangled photon pairs, b represents the center offset position of the second-order correlation function, and c determines the half-width of the second-order correlation function.

[0042] Further, in step 3, the maximum likelihood estimation method module of the distance measurement unit includes:

[0043] By considering the coincidence count curve as a normal distribution curve, repeating the number of coincidence photons corresponding to each time scale in the coincidence count curve for multiple times, performing maximum likelihood estimation based on the generated sequence, and obtaining the mean u of the normal distribution, u is regarded as the center offset position of the second-order correlation function;

[0044] The DFT phase difference weighting module of the distance measurement unit includes:

[0045] Perform N-point DFT on the self-test coincidence count curve and the ranging coincidence count curve to obtain the phase of each frequency point of the two curves and With the help of the rough distance information generated by the maximum likelihood estimation module, the effective upper frequency limit f is determined max ; For the two curves 0~f max The phase difference of the same frequency point in the frequency band is obtained by subtracting the phase The obtained 0~f max Phase difference of each frequency point in the frequency band Multiply it by the period T(k) to get the time difference information S(k), and determine the weight according to the frequency amplitude; wherein the weight coefficient formula is as follows:

[0046]

[0047] Where N is the total number of sampling points, k represents a frequency component in the frequency domain (k = 1, 2, ..., N), and n is determined by f max It is determined that k and n are both integer values, X1(k) and X2(k) are the amplitude sequences of the self-check coincidence count curve and the ranging coincidence count curve in the frequency domain after DFT transformation, and W(k) is the weight coefficient of S(k).

[0048] The DFT phase difference weighting formula is as follows:

[0049]

[0050] Among them, s0 is the precise distance information from the inter-satellite ranging system to the satellite to be measured.

[0051] Another object of the present invention is to provide a computer device, the computer device comprising a memory and a processor, the memory storing a computer program, and when the computer program is executed by the processor, the processor performs the following steps:

[0052] Entangled photon pairs are generated through the photon transceiver unit, signal photons are transmitted to the satellite to be measured and the internal optical path, and signal photons reflected back from the satellite to be measured and the internal optical path are received; the received signal photons are correlated with the idle photons through the coincidence counting unit to obtain their second-order correlation curves; the two second-order correlation curves generated by the optical path difference inside and outside the system are subjected to DFT phase difference weighted processing through the distance measurement unit to obtain the actual optical path difference from the satellite to be measured to this system.

[0053] Another object of the present invention is to provide a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the following steps:

[0054] Entangled photon pairs are generated through the photon transceiver unit, signal photons are transmitted to the satellite to be measured and the internal optical path, and signal photons reflected back from the satellite to be measured and the internal optical path are received; the received signal photons are correlated with the idle photons through the coincidence counting unit to obtain their second-order correlation curves; the two second-order correlation curves generated by the optical path difference inside and outside the system are subjected to DFT phase difference weighted processing through the distance measurement unit to obtain the actual optical path difference from the satellite to be measured to this system.

[0055] Another object of the present invention is to provide an information data processing terminal, wherein the information data processing terminal is used to implement the inter-satellite ranging system.

[0056] Combining all the above technical solutions, the advantages and positive effects of the present invention are as follows: the intersatellite ranging system provided by the present invention particularly relates to quantum coincidence measurement technology, which utilizes its high-precision characteristics to accurately measure the relative distance between orbiting spacecraft, and can be used for accurate distance measurement between adjacent satellites, providing high-precision intersatellite distance information for subsequent specific applications such as satellite formation, satellite orbit determination, and intersatellite navigation.

[0057] The present invention introduces quantum entanglement into the ranging system, so that the upper limit of ranging accuracy exceeds the traditional measurement limit, such as the shot noise limit, and approaches or even reaches the Heisenberg limit; the invention introduces quantum entanglement into the ranging system and adopts a correlation method for measurement, so that the ranging system has a strong anti-interference ability, and the white noise has little effect on the ranging result. Even if there is co-frequency interference from the external environment, it will not have a great impact on the measurement accuracy.

[0058] The present invention uses a photon matching method to filter out the cosmic space stray light entering the photon detector to a large extent, thereby improving the signal-to-noise ratio; the present invention uses an improved coincidence counting algorithm, and the calculation rate is greatly improved compared with the traditional coincidence counting algorithm.

[0059] The present invention realizes real-time detection of changes in the internal optical path of the system by introducing a self-checking module into the ranging system, thereby eliminating the influence of changes in the internal optical path caused by external forces during the on-orbit process of the system on the ranging accuracy; the present invention adopts a DFT phase difference weighted algorithm to assign different weights to different frequency components according to their intensity, thereby suppressing the influence of noise on the phase difference, and the ranging result obtained is superior in accuracy to the ranging result obtained by maximum likelihood estimation and least squares fitting. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0061] Figure 1 The present invention provides a flow chart of the inter-satellite ranging method.

[0062] Figure 2 The figure is a structural block diagram of an inter-satellite ranging system provided by an embodiment of the present invention.

[0063] Figure 3 It is a schematic diagram of the application of the inter-satellite ranging system provided by an embodiment of the present invention.

[0064] Figure 4 It is a schematic diagram of a photon transceiver module in an intersatellite ranging system provided by an embodiment of the present invention.

[0065] Figure 5 The present invention provides a functional block diagram of a coincidence counting module in an inter-satellite ranging system.

[0066] Figure 6 It is a functional block diagram of a distance measurement module in an inter-satellite ranging system provided by an embodiment of the present invention.

[0067] Figure 7 It is a principle diagram of a DFT phase difference weighted algorithm in an inter-satellite ranging system provided by an embodiment of the present invention.

[0068] Figure 8 It is a self-checking and ranging coincidence counting curve diagram provided by an embodiment of the present invention.

[0069] Fig. 9 The embodiment of the present invention provides a least squares method for fitting the self-test compliance curve.

[0070] Fig.10 The least squares method is used to fit the ranging curve provided by the embodiment of the present invention.

[0071] Fig.11 It is a frequency domain phase spectrum diagram of a coincidence counting curve provided by an embodiment of the present invention.

[0072] Fig.12 It is a frequency domain amplitude spectrum diagram of a coincidence counting curve provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0073] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0074] In view of the problems existing in the prior art, the present invention provides an inter-satellite ranging system, method, device and data processing terminal, which are described in detail below with reference to the accompanying drawings.

[0075] like Figure 1 As shown, the inter-satellite ranging method provided by the embodiment of the present invention includes the following steps:

[0076] S101, generating entangled photon pairs through a photon transceiver unit, transmitting signal photons to the satellite to be measured and the internal optical path, and receiving signal photons reflected back from the satellite to be measured and the internal optical path;

[0077] S102, correlating the received signal photons with the idler photons through a coincidence counting unit to obtain a second-order correlation curve thereof;

[0078] S103, performing DFT phase difference weighting processing on two second-order correlation curves generated by the optical path difference inside and outside the system through a distance measurement unit to obtain an actual optical path difference from the satellite to be measured to the system.

[0079] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0080] Example 1

[0081] The present invention aims to propose an intersatellite ranging system based on quantum ranging, aiming to solve the problem that traditional intersatellite ranging methods cannot overcome the shot noise limit and have low ranging accuracy.

[0082] To achieve the above object, the system of the present invention comprises:

[0083] A photon transceiver unit is used to generate entangled photon pairs, transmit signal photons to the satellite to be measured and the internal optical path, and receive signal photons reflected back from the satellite to be measured and the internal optical path;

[0084] A coincidence counting unit is used to correlate the received signal photons with the idler photons to obtain their second-order correlation curve;

[0085] The distance measurement unit is used to perform DFT phase difference weighting processing on the two second-order correlation curves generated by the optical path difference inside and outside the system to obtain the actual optical path difference from the satellite to be measured to the system;

[0086] The photon transceiver unit comprises: a high-brightness quantum entangled source module, a photon emission module, a ranging / self-test module, and a photon detection module; the high-brightness quantum entangled source module is used to perform spontaneous parametric down-conversion on the laser emitted by the laser through a PPKTP crystal to generate entangled photon pairs, and to separate the entangled photon pairs into two optical paths of signal light and idle light through a polarization beam splitter; the photon emission module is used to emit the signal path photons generated by the high-brightness quantum entangled source module to the ranging / self-test module through a collimator; the ranging / self-test module is used to switch polarization lenses so that the signal path photons in the self-test mode enter the photon detector only through the internal optical path of the system, so that the signal path photons in the ranging mode are emitted into space; the photon detection module is used to detect the signal path and idle path photons through the photon detector, and output the time tag stream of the detected photons arriving at the detector; the signal photon reflection device of the satellite to be ranged comprises a corner cone reflector, which is used to reflect the emitted signal photons back to the inter-satellite ranging system along the original path;

[0087] The ranging / self-test module includes a polarizer switching module and a polarization beam splitter. When in the self-test mode, a vertical polarizer is inserted into the signal optical path in the system to filter out photons in polarization states other than vertical polarization. The vertically polarized photons are reflected at an angle of 45 degrees at the polarization beam splitter of the transmitting window to the polarization beam splitter of the receiving window, and then reflected again at an angle of 45 degrees to enter the photon detector. When in the ranging mode, a horizontal polarizer is inserted into the signal optical path in the system to filter out photons in polarization states other than horizontal polarization. The horizontally polarized photons are transmitted at the polarization beam splitter of the transmitting window, reflected by the conical reflector of the satellite to be measured, and then transmitted at the polarization beam splitter of the receiving window to enter the photon detector.

[0088] The coincidence counting unit comprises: a photon pair matching module, a second-order correlation function generating module, and a least square method fitting module; the photon pair matching module is used to pair the signal path photons and the idle path photons detected by the photon detection module according to the estimated optical path difference to generate coarse matching photon pair data; the second-order correlation function generating module is used to perform a coincidence operation on the coarse matching photon pair data generated by the photon pair matching module through an improved coincidence counting algorithm to generate a coincidence counting curve, i.e., a second-order correlation function; the least square method fitting module is used to fit the second-order correlation curve through the least square method and the fitting function to generate fitting parameters and a fitting curve, and analyze information such as the signal-to-noise ratio according to the fitting parameters and the fitting curve;

[0089] The specific idea of ​​the improved coincidence counting algorithm used in the second-order correlation function generation module is:

[0090] For each pair of photons in the rough matching photon pair, calculate the detection time t of the idler photon i The time t at which the signal photon is detected s The time difference is compared with the window time t w Add half of the result to get T interval =(t s -t i )+t w / 2, divided by the sliding step length T slide Get the integer quotient a and remainder b, and calculate t w -b divided by T slide The integer quotient d, finally in ((ad): a)*T slide The coincidence number at the corresponding time axis position is increased by 1. After performing the above operation on each pair of photons in the rough matching photon pair, a coincidence counting curve, i.e., a second-order correlation function, can be generated.

[0091] The fitting formula used by the least squares fitting module is: Where a represents the maximum number of entangled photon pairs, b represents the offset position of the center of the second-order correlation function, and c determines the half-height width of the second-order correlation function;

[0092] The distance measurement unit comprises: a maximum likelihood estimation method module and a DFT phase difference weighting module; the maximum likelihood estimation method module is used to obtain the center offset position of the self-check coincidence count curve and the ranging coincidence count curve by the maximum likelihood estimation method, and to obtain the rough distance information from the inter-satellite ranging system to the satellite to be measured by difference; the DFT phase difference weighting module is used to perform DFT phase difference weighting on the self-check coincidence count curve and the ranging coincidence count curve, and to obtain the accurate distance information from the inter-satellite ranging system to the satellite to be measured with the assistance of the maximum likelihood estimation method module.

[0093] The specific idea of ​​the maximum likelihood estimation module is:

[0094] By considering the coincidence count curve as a normal distribution curve, repeating the number of coincidence photons corresponding to each time scale in the coincidence count curve for multiple times, performing maximum likelihood estimation based on the generated sequence, and obtaining the mean u of the normal distribution, u is regarded as the center offset position of the second-order correlation function;

[0095] The specific idea of ​​the DFT phase difference weighting module is:

[0096] First, perform N-point DFT on the self-test coincidence count curve and the ranging coincidence count curve to obtain the phase of each frequency point of the two curves. and With the help of the rough distance information generated by the maximum likelihood estimation module, the effective upper frequency limit f is determined max, for the two curves 0~f max The phase difference of the same frequency point in the frequency band is obtained by subtracting the phase The obtained 0~f max Phase difference of each frequency point in the frequency band Multiply it by the period T(k) to get the time difference information S(k), and determine the weight based on the frequency amplitude. The weighting coefficient formula is as follows:

[0097]

[0098] Where N is the total number of sampling points, k represents a frequency component in the frequency domain (k = 1, 2, ..., N), and n is determined by f max Determine that k and n are both integer values, X1(k) and X2(k) are the amplitude sequences of the self-check coincidence count curve and the ranging coincidence count curve in the frequency domain after DFT transformation, and W(k) is the weight coefficient of S(k);

[0099] The DFT phase difference weighting formula is as follows:

[0100]

[0101] Where s0 is the precise distance information from the intersatellite ranging system to the satellite to be measured.

[0102] Example 2

[0103] Reference Figure 2 The invention discloses an intersatellite distance measurement system based on quantum distance measurement, comprising a photon transceiver module, a coincidence counting module and a distance measurement module. The photon transceiver module transmits signal photons to the satellite to be measured and the internal optical path, and receives the signal photons reflected by the satellite to be measured and the internal optical path, and outputs the time tag stream of the detected photons arriving at the detector to the coincidence counting module. The coincidence counting module generates a coincidence counting curve, fitting parameters and a fitting curve according to the dual-channel photon time tag stream through an improved coincidence counting algorithm and least squares fitting. The distance measurement module receives the self-check coincidence counting curve and the ranging coincidence counting curve generated by the coincidence counting module, and obtains the accurate distance information between the system and the satellite to be measured by adopting the DFT phase difference weighted algorithm.

[0104] Reference Figure 3 In the intersatellite ranging system, a stable optical path needs to be formed and maintained between satellite A and satellite B when measuring the distance of satellite B. Since the position of satellite B relative to satellite A cannot remain constant, the photon transceiver module needs to be installed on the outside of satellite A. By adjusting the pitch and roll angles of the photon transceiver module, the signal light is kept directly directed to the conical reflector of the satellite to be measured for a period of time, and the signal light reflected back by the conical reflector is received.

[0105] Reference Figure 4, entangled photon pairs are generated through a high-brightness quantum entanglement source. The photons in the entangled photon pairs enter the signal path and the idle path respectively. The idle path photons directly enter the photon detector 1 after a fixed optical path. When in the self-test mode, the signal path photons are directed to the vertical polarizer through the collimator to filter out photons in other polarization states except the vertical polarization. The vertically polarized photons are reflected at an angle of 45 degrees at the polarization beam splitter at the transmitting window to the polarization beam splitter at the receiving window, and then reflected at an angle of 45 degrees again to enter the photon detector 2. At this time, the optical path difference between the signal path and the idle path reflects the internal optical path difference of the system; When in ranging mode, the signal path photons are directed toward the horizontal polarizer through the collimator, and photons in other polarization states except horizontal polarization are filtered out. The horizontally polarized photons are transmitted through the polarization beam splitter of the transmitting window, reflected by the conical reflector of the satellite to be measured, transmitted through the polarization beam splitter of the receiving window, and enter the photon detector 2. At this time, the optical path difference between the signal path and the idle path reflects the sum of the optical path differences inside the system and outside the system. Photon detector 1 and photon detector 2 convert the optical signal into an electrical signal, and the time digital converter generates a dual-channel photon time tag stream based on the input electrical signal.

[0106] Reference Figure 5 The photon pair matching module sets the upper limit of the time difference of the matching photon pairs according to the estimated optical path difference, matches the dual-channel photon time flow data, and inputs the generated coarse matching photon pair data into the second-order correlation function generation module. The improved coincidence counting algorithm can quickly generate a coincidence counting curve, that is, a second-order correlation function. The coincidence counting curve is fitted by the least squares method according to the fitting formula to obtain the fitting curve and fitting parameters, which can be used to analyze information such as the signal-to-noise ratio.

[0107] Reference Figure 6 The self-check coincidence count curve and the ranging coincidence count curve generated by the photon pair matching module are simultaneously input into the maximum likelihood estimation module and the DFT phase difference weighting module of the distance measurement module. The maximum likelihood estimation module uses the maximum likelihood estimation method to obtain the center offset position of the self-check coincidence count curve and the ranging coincidence count curve, and makes a difference between the two center offset positions to obtain the rough distance information from the inter-satellite ranging system to the satellite to be measured. The DFT phase difference weighting module performs DFT processing on the self-check coincidence count curve and the ranging coincidence count curve, and performs phase difference weighting with the aid of the rough distance information. The phase difference weighting result is the precise distance information from the inter-satellite ranging system to the satellite to be measured.

[0108] Reference Figure 7 First, N points of sampling are performed on the self-test coincidence count curve and the ranging coincidence count curve, and the sampled data are subjected to FFT to obtain the amplitude X1(k) and X2(k) and phase of each frequency point in the frequency domain of the two sets of sampled data. and With the help of the rough distance information generated by the maximum likelihood estimation module, the effective upper frequency limit f is determinedmax , for the two curves 0~f max The phase of the same frequency point (k=1, 2, ..., n) within the frequency band and Difference to get phase difference And according to 0~f max The sum of the squares of the amplitudes of the two sets of data at each frequency point in the frequency band determines the weight of the phase difference of each frequency point, and the precise distance difference from the intersatellite ranging system to the satellite to be measured is output through weighted accumulation of the phase difference.

[0109] The intersatellite distance measurement system based on quantum ranging described in the present invention can be used for accurate distance measurement between adjacent satellites, and provide high-precision intersatellite distance information for subsequent specific applications such as satellite formation, satellite orbit determination, and intersatellite navigation.

[0110] The technical effects of the present invention are described in detail below in conjunction with experiments.

[0111] For the distance to be measured with a length of 500ps*c (c is the speed of light), the maximum likelihood estimation method, the least squares method and the system solution are used for measurement respectively. The window size is set to 200ps and the number of DFT points is 20000. The results are as follows: Figure 8-Figure 12 .

[0112] Table 1 Measurement results

[0113]

[0114] After analyzing the results, it can be seen that compared with the least squares fitting method and the maximum likelihood estimation method, this ranging system has a smaller variance and mean square error, and the mean absolute error is less than 50 microns (ie 0.1668*c), which proves that this ranging system has a higher ranging accuracy.

[0115] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When the use is implemented in whole or in part in the form of a computer program product, the computer program product includes one or more computer instructions. When the computer program instructions are loaded or executed on a computer, the process or function described in the embodiment of the present invention is generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from one website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL) or wireless (e.g., infrared, wireless, microwave, etc.) mode) to another website site, computer, server or data center. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more available media integrated. The available medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid-state hard disk Solid State Disk (SSD)), etc.

[0116] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. An inter-satellite ranging system, It is characterized in that The inter-satellite ranging system comprises: A photon transceiver unit is used to generate entangled photon pairs, transmit signal photons to the satellite to be measured and the internal optical path, and receive signal photons reflected back from the satellite to be measured and the internal optical path; A coincidence counting unit is used to correlate the received signal photons with the idler photons to obtain their second-order correlation curve; The distance measurement unit is used to perform DFT phase difference weighting processing on the two second-order correlation curves generated by the optical path difference inside and outside the system to obtain the actual optical path difference from the satellite to be measured to the system; The distance measuring unit comprises: The maximum likelihood estimation module is used to obtain the center offset position of the self-check coincidence count curve and the ranging coincidence count curve by the maximum likelihood estimation method, and to obtain the rough distance information from the inter-satellite ranging system to the satellite to be measured by difference; The DFT phase difference weighting module is used to perform DFT phase difference weighting on the self-check coincidence count curve and the ranging coincidence count curve, and obtain the precise distance information from the inter-satellite ranging system to the satellite to be measured with the assistance of the maximum likelihood estimation module; The DFT phase difference weighting module of the distance measurement unit includes: Perform N-point DFT on the self-test coincidence count curve and the ranging coincidence count curve to obtain the phase of each frequency point of the two curves and k=1,2,…,N; with the help of the rough distance information generated by the maximum likelihood estimation module, determine the effective frequency upper limit f max ; For the two curves 0~f max The phase difference of the same frequency point in the frequency band is obtained by subtracting the phase The obtained 0~f max Phase difference of each frequency point in the frequency band Multiply it by the period T(k) to get the time difference information S(k), and determine the weight according to the frequency amplitude; wherein the weight coefficient formula is as follows: Where N is the total number of sampling points, k represents a frequency component in the frequency domain, k = 1, 2, ..., N, and n is determined by f max OK, k and n are both integer values, X 1 (k) and X 2 (k) are the amplitude sequences of the self-check coincidence count curve and the ranging coincidence count curve in the frequency domain after DFT transformation, w(k) is the weight coefficient of S(k); The DFT phase difference weighting formula is as follows: Among them, s 0 It is the precise distance information from the intersatellite ranging system to the satellite to be measured.

2. The inter-satellite ranging system according to claim 1, It is characterized in that The photon transceiver unit comprises: The high-brightness quantum entangled source module is used to perform spontaneous parametric down-conversion of the laser emitted by the laser through the PPKTP crystal to generate entangled photon pairs, and then split the entangled photon pairs into two optical paths, signal light and idler light, through a polarization beam splitter; A photon emission module is used to emit the signal path photons generated by the high-brightness quantum entanglement source module to the ranging / self-test module through a collimator; The ranging / self-test module is used to switch the polarization lens so that the signal path photons in the self-test mode can only enter the photon detector through the internal optical path of the system, and the signal path photons in the ranging mode can be emitted into space; The photon detection module is used to detect the photons in the signal path and the idle path through the photon detector, and output the time tag stream of the detected photons arriving at the detector; The signal photon reflection device of the satellite to be measured includes a corner reflector, which is used to reflect the transmitted signal photons back to the inter-satellite ranging system along the original path; Among them, the ranging / self-test module includes a polarizer switching module and a polarization beam splitter; when in the self-test mode, a vertical polarizer is inserted into the signal light path in the system to filter out photons in other polarization states except the vertical polarization, and the vertically polarized photons are reflected at an angle of 45 degrees at the polarization beam splitter of the transmitting window to the polarization beam splitter at the receiving window, and then reflected at an angle of 45 degrees again to enter the photon detector; when in the ranging mode, a horizontal polarizer is inserted into the signal light path in the system to filter out photons in other polarization states except the horizontal polarization, and the horizontally polarized photons are transmitted at the polarization beam splitter of the transmitting window, reflected by the conical reflector of the satellite to be measured, and then transmitted at the polarization beam splitter of the receiving window to enter the photon detector.

3. The inter-satellite ranging system according to claim 1, It is characterized in that The coincidence counting unit comprises: A photon pair matching module is used to pair the signal path photons and the idle path photons detected by the photon detection module according to the estimated optical path difference to generate coarse matching photon pair data; A second-order correlation function generation module is used to perform a coincidence operation on the coarse matching photon pair data generated by the photon pair matching module through an improved coincidence counting algorithm to generate a coincidence counting curve, i.e., a second-order correlation function; The least squares fitting module is used to fit the second-order correlation curve by using the least squares method and the fitting function, generate fitting parameters and the fitting curve, and analyze the signal-to-noise ratio information according to the fitting parameters and the fitting curve.

4. An inter-satellite ranging method for operating the inter-satellite ranging system according to any one of claims 1 to 3, It is characterized in that The inter-satellite ranging method comprises the following steps: Step 1: generate entangled photon pairs through the photon transceiver unit, transmit signal photons to the satellite to be measured and the internal optical path, and receive signal photons reflected back by the satellite to be measured and the internal optical path; Step 2, correlating the received signal photons with the idler photons through a coincidence counting unit to obtain their second-order correlation curve; Step 3: The distance measurement unit performs DFT phase difference weighting processing on the two second-order correlation curves generated by the optical path difference inside and outside the system to obtain the actual optical path difference from the satellite to be measured to the system.

5. The inter-satellite ranging method as claimed in claim 4, It is characterized in that In step 2, the improved coincidence counting algorithm adopted by the second-order correlation function generation module of the coincidence counting unit includes: For each pair of photons in the rough matching photon pair, calculate the detection time t of the idler photon i The time t at which the signal photon is detected s The time difference is compared with the window time t w Add half of the result to get T interval =(t s -t i )+t w / 2, divided by the sliding step length T slide Get the integer quotient a and remainder b; calculate t w -b divided by T slide The integer quotient d of ((ad):a)*T slide The coincidence number at the corresponding time axis position is increased by 1, and the coincidence count curve, i.e., the second-order correlation function, is generated after the corresponding operation is performed on each pair of photons in the rough matching photon pair; the fitting formula used by the least squares fitting module is: Among them, a represents the maximum number of entangled photon pairs, b represents the center offset position of the second-order correlation function, and c determines the half-width of the second-order correlation function.

6. The inter-satellite ranging method as claimed in claim 4, It is characterized in that In step 3, the maximum likelihood estimation method module of the distance measurement unit includes: By considering the coincidence counting curve as a normal distribution curve, repeating each time scale in the coincidence counting curve for the number of coincidence photons corresponding to that scale, performing maximum likelihood estimation based on the generated sequence, and obtaining the mean u of the normal distribution, u is regarded as the central offset position of the second-order correlation function.

7. A computer device, It is characterized in that The computer device includes a memory and a processor, the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the inter-satellite ranging method of the inter-satellite ranging system according to any one of claims 1 to 3, comprising the following steps: Entangled photon pairs are generated through the photon transceiver unit, signal photons are transmitted to the satellite to be measured and the internal optical path, and signal photons reflected back from the satellite to be measured and the internal optical path are received; the received signal photons are correlated with the idle photons through the coincidence counting unit to obtain their second-order correlation curves; the two second-order correlation curves generated by the optical path difference inside and outside the system are subjected to DFT phase difference weighted processing through the distance measurement unit to obtain the actual optical path difference from the satellite to be measured to this system.

8. A computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the inter-satellite ranging method of the inter-satellite ranging system according to any one of claims 1 to 3, comprising the following steps: Entangled photon pairs are generated through the photon transceiver unit, signal photons are transmitted to the satellite to be measured and the internal optical path, and signal photons reflected back from the satellite to be measured and the internal optical path are received; the received signal photons are correlated with the idle photons through the coincidence counting unit to obtain their second-order correlation curves; the two second-order correlation curves generated by the optical path difference inside and outside the system are subjected to DFT phase difference weighted processing through the distance measurement unit to obtain the actual optical path difference from the satellite to be measured to this system.

9. An information data processing terminal, It is characterized in that The information data processing terminal is used to implement the inter-satellite ranging system as claimed in any one of claims 1 to 3.

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