Inter-satellite high-precision ranging system and method based on balanced timing detection technology
By using a high-precision inter-satellite ranging system based on balanced timing detection technology, and combining FPGA and balanced timing detection modules with optical frequency comb technology, the problems of phase-locked complexity, low signal-to-noise ratio and poor dynamic adaptability of inter-satellite ranging systems are solved, achieving femtosecond-level time synchronization and submicron-level ranging accuracy.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-04-03
AI Technical Summary
Existing high-precision inter-satellite ranging technologies suffer from problems such as complex phase-locked systems, heavy hardware burden, low signal-to-noise ratio, high background noise, and poor dynamic adaptability, making it difficult to meet the high-precision measurement requirements of long-distance, highly dynamic inter-satellite environments.
The high-precision inter-satellite ranging system based on balanced timing detection technology utilizes an FPGA time programming control module and a balanced timing detection module, combined with optical frequency comb technology for differential detection and time programming scanning, to achieve high sensitivity and dynamic tracking capability. It also uses a digital servo loop to lock the optical phase-locked loop, eliminating common-mode noise and adapting to high-speed relative motion.
It achieves femtosecond-level time synchronization and submicron-level ranging accuracy, possesses near-quantum-limit-level detection sensitivity and a very large dynamic adjustment range, and adapts to the Doppler shift caused by high-speed relative motion between satellites.
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Figure CN121784715A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of space precision measurement and time-frequency transfer technology, and in particular to an inter-satellite high-precision ranging system and method based on balanced timing detection technology. Background Technology
[0002] High-precision inter-satellite measurement and time synchronization are core technologies for space missions such as satellite navigation, deep space exploration, space gravitational wave detection, and distributed synthetic aperture radar. With the development of space technology, extremely high requirements have been placed on measurement distances (such as geostationary orbits above 30,000 km) and measurement accuracy (femtosecond / micrometer level).
[0003] Existing ranging technologies based on optical frequency combs (OFCs) mainly include schemes such as dual-comb asynchronous optical sampling (ASOPS) and linear optical sampling. However, traditional technologies face the following challenges in inter-satellite applications:
[0004] 1) The phase-locked loop system is complex and has a heavy hardware burden: Traditional dual-comb ranging usually requires strict phase coherence locking between the repetition frequency (frep) and carrier envelope offset frequency (fceo) between the two optical frequency combs. This usually requires complex analog electronic phase-locked loops, which increases the size and power consumption of the space-borne equipment and has a high failure rate in the harsh space radiation environment.
[0005] 2) High background noise and limited sensitivity: Although the linear detection scheme using photodiodes for direct detection is simple in structure, it has a low signal-to-noise ratio and is easily affected by background light noise. On the other hand, the method of using ordinary nonlinear crystals for intensity cross-correlation measurement often requires high incident light power and it is difficult to eliminate background base noise, making it difficult to meet the detection requirements of weak signals in inter-satellite links (loss is usually greater than 100 dB).
[0006] 3) Poor dynamic adaptability: Inter-satellite links suffer from large-scale Doppler frequency shifts due to high-speed relative motion (up to km / s). Traditional dual-comb systems with fixed repetition frequency differences struggle to achieve real-time, high-precision tracking and locking of high-speed dynamic targets.
[0007] Therefore, there is an urgent need for a measurement system that can adapt to long-distance, highly dynamic inter-satellite environments and has high sensitivity, low background noise, and integrated measurement and communication capabilities. Summary of the Invention
[0008] The technical problem to be solved by the present invention is how to provide an inter-satellite high-precision ranging system and method based on balanced timing detection technology that can significantly improve the system's sensitivity and anti-interference capability while ensuring high precision.
[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an inter-satellite high-precision ranging system based on balanced timing detection technology, comprising: a first satellite terminal and a second satellite terminal, wherein the first satellite terminal and the second satellite terminal are connected via a free-space optical link; the first satellite terminal includes a first FPGA time programming control module, wherein the output of a first onboard time-frequency reference source is divided into three paths, the first path being connected to the clock signal input of the first FPGA time programming control module, the second path being connected to the clock signal input of a first clock optical frequency comb, and the third path being connected to the clock signal input of a first tracking optical frequency comb; the first FPGA time programming control module... The output of the control module is divided into three paths: the first path is connected to the control terminal of the first tracking optical frequency comb, the second path is connected to the control terminal of the first clock optical frequency comb, and the third path is connected to the control terminal of the first laser communication module. The output terminal of the first clock optical frequency comb is connected to one input terminal of the first optical wavelength division multiplexing module. The first optical wavelength division multiplexing module is bidirectionally connected to the first laser transceiver module and the first laser communication module. One output terminal of the first optical wavelength division multiplexing module and one output terminal of the first tracking optical frequency comb are connected to one input terminal of the first balanced timing detection module. The output terminal of the first balanced timing detection module is connected to one input terminal of the first FPGA time programming control module.
[0010] The second satellite terminal includes a second FPGA time programming control module. The output of the second onboard time and frequency reference source is divided into three paths: the first path is connected to the clock signal input of the second FPGA time programming control module, the second path is connected to the clock signal input of the second clock optical frequency comb, and the third path is connected to the clock signal input of the second tracking optical frequency comb. The output of the second FPGA time programming control module is divided into three paths: the first path is connected to the control terminal of the second tracking optical frequency comb, the second path is connected to the control terminal of the second clock optical frequency comb, and the third path is connected to the control terminal of the second laser communication module. The output of the second clock optical frequency comb is connected to one input of the second optical wavelength division multiplexing module. The second optical wavelength division multiplexing module is bidirectionally connected to the second laser transceiver module and the second laser communication module. One output of the second optical wavelength division multiplexing module and one output of the second tracking optical frequency comb are connected to one input of the second balanced timing detection module. The output of the second balanced timing detection module is connected to one input of the second FPGA time programming control module.
[0011] This invention also discloses a high-precision inter-satellite ranging method based on balanced timing detection technology. The ranging method uses the ranging system and includes the following steps:
[0012] S1, Transmission and Preprocessing: Transmitting the optical pulse sequence emitted by the first clock optical frequency comb of the first satellite terminal. The optical pulse sequence transmitted to the second satellite terminal, via the second clock optical frequency comb of the second satellite terminal. Transmitted to the first satellite terminal A;
[0013] S2, Time Programming Scan: The FPGA time programming control module controls the numerically controlled oscillator (NCO) to generate a linearly varying frequency offset, causing a slight difference between the repetition frequency of the clock optical comb and the expected signal repetition frequency, so that the local clock optical comb pulses can be rapidly scanned in the time domain to search for and capture signal pulses transmitted from a remote location.
[0014] S3, Capture and Lock: When the clock optical comb pulse slides to a position overlapping with the incident signal pulse, the balanced timing detection module instantly responds and outputs an S-shaped error signal. After the threshold detection logic inside the FPGA time programming control module captures this signal, it immediately performs the following operations:
[0015] Stop scanning: The NCO (Numerical Controlled Oscillator) stops linearly changing its frequency;
[0016] Closed-loop locking: The error voltage output by the balanced optical cross-correlation module is used as feedback, and the phase of the clock optical frequency comb is adjusted in real time through the digital servo loop to lock at the zero crossing point of the S-curve; at this time, the clock optical frequency comb acts as a voltage-controlled oscillator in an optical phase-locked loop, and its output pulse sequence completely replicates the signal pulses that arrive remotely in the time domain.
[0017] S4, Parameter Calculation: The pseudorange time measured by the first satellite terminal from the second satellite terminal to the first satellite terminal. The second satellite terminal measured the pseudorange time from the first satellite terminal to the second satellite terminal. According to the principle of two-way time transfer:
[0018] ;
[0019] ;
[0020] in, For the time of flight of light in one direction, The deviation of the reference clock sources on the two satellites, This refers to the calibrated internal system latency;
[0021] Assuming the system delay has been calibrated and eliminated, after exchanging data via the communication link, the clock deviation between the two satellites is calculated as follows:
[0022] ;
[0023] And the absolute distance is:
[0024] ;
[0025] Considering the additional time drift introduced by the clock frequency difference between the two locations, a frequency difference correction term is introduced:
[0026] ;
[0027] By calculating the above parameters in real time, the FPGA time programming control module outputs control quantities to adjust the local atomic clock or directly outputs aligned time and frequency signals to achieve inter-satellite femtosecond-level time synchronization and submicron-level ranging.
[0028] The beneficial effects of adopting the above technical solution are as follows: 1) High detection sensitivity and signal-to-noise ratio: By adopting balanced timing detection technology and using differential detection, common mode intensity noise (such as background light and laser intensity noise) is effectively eliminated, achieving zero background detection and having a detection sensitivity close to the quantum limit.
[0029] 2) Strong dynamic tracking capability: It adopts TPFC technology and utilizes fully digital FPGA control, which has a large dynamic adjustment range and extremely high adjustment bandwidth, and can adapt to the Doppler frequency shift caused by high-speed relative motion between satellites.
[0030] 3) High ranging accuracy: Combining the scale function of the optical frequency comb with the femtosecond-level phase detection capability of balanced optical cross-correlation technology, it achieves sub-micron-level absolute distance measurement accuracy. Attached Figure Description
[0031] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.
[0032] Figure 1 This is an overall architecture diagram of the measurement system described in an embodiment of the present invention;
[0033] Figure 2 This is a schematic diagram showing the connection relationship of the balance timing detection module in the system described in this embodiment of the invention;
[0034] Figure 3 This is a schematic diagram (optical path details) of the balanced optical cross-correlation (BOC) principle in the system described in the embodiment of the present invention.
[0035] Figure 4 This is a detailed flowchart of the method described in the embodiments of the present invention. Detailed Implementation
[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0037] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below. Example 1
[0038] like Figure 1 As shown in the figure, this invention discloses an inter-satellite high-precision ranging system based on balanced timing detection technology, including: a first satellite terminal and a second satellite terminal, the first satellite terminal and the second satellite terminal being connected via a free-space optical link; the first satellite terminal includes a first FPGA time programming control module, the output of a first onboard time-frequency reference source is divided into three paths, the first path is connected to the clock signal input of the first FPGA time programming control module, the second path is connected to the clock signal input of a first clock optical frequency comb, and the third path is connected to the clock signal input of a first tracking optical frequency comb, the output of the first FPGA time programming control module... The terminal is divided into three paths: the first path is connected to the control terminal of the first tracking optical frequency comb, the second path is connected to the control terminal of the first clock optical frequency comb, and the third path is connected to the control terminal of the first laser communication module. The output terminal of the first clock optical frequency comb is connected to one input terminal of the first optical wavelength division multiplexing module. The first optical wavelength division multiplexing module is bidirectionally connected to the first laser transceiver module and the first laser communication module. One output terminal of the first optical wavelength division multiplexing module and one output terminal of the first tracking optical frequency comb are connected to one input terminal of the first balanced timing detection module. The output terminal of the first balanced timing detection module is connected to one input terminal of the first FPGA time programming control module.
[0039] The second satellite terminal includes a second FPGA time programming control module. The output of the second onboard time and frequency reference source is divided into three paths: the first path is connected to the clock signal input of the second FPGA time programming control module, the second path is connected to the clock signal input of the second clock optical frequency comb, and the third path is connected to the clock signal input of the second tracking optical frequency comb. The output of the second FPGA time programming control module is divided into three paths: the first path is connected to the control terminal of the second tracking optical frequency comb, the second path is connected to the control terminal of the second clock optical frequency comb, and the third path is connected to the control terminal of the second laser communication module. The output of the second clock optical frequency comb is connected to one input of the second optical wavelength division multiplexing module. The second optical wavelength division multiplexing module is bidirectionally connected to the second laser transceiver module and the second laser communication module. One output of the second optical wavelength division multiplexing module and one output of the second tracking optical frequency comb are connected to one input of the second balanced timing detection module. The output of the second balanced timing detection module is connected to one input of the second FPGA time programming control module.
[0040] The hardware configurations of the first satellite terminal and the second satellite terminal are completely identical. For the sake of simplicity, the following description focuses on each module of the first satellite terminal, but it also applies to the corresponding modules of the second satellite terminal.
[0041] The first or second tracking optical frequency comb is a time-programmable optical frequency comb (TPFC). It is used to generate optical pulse sequences with dynamically adjustable pulse intervals and phases. A reference phase signal is generated by a numerically controlled oscillator (NCO) inside the FPGA, which is digitally mixed and phase-detected with the electrical signal output from the optical frequency comb. The error signal is then fed back to the piezoelectric ceramic (PZT) or electro-optic modulator (EOM) inside the laser cavity via a feedback control loop, thereby achieving rapid scanning and real-time locking tracking of the incident signal pulse.
[0042] The first or second balanced timing detection module employs balanced optical cross-correlation (BOC) technology. This module utilizes a type II phase-matching nonlinear crystal (such as PPKTP or PPLN) to perform non-collinear sum-frequency analysis between the pulse (LO) of the local tracking optical frequency comb and the received link signal optical pulse (Signal). The sum-frequency light is then polarized and split before entering a balanced photodetector for differential detection, obtaining a zero-crossing phase detection curve (S-curve) used to extract ultra-high precision time synchronization error signals.
[0043] Furthermore, the first clock frequency comb is used as the emission source, employing a mode-locked fiber laser. Its repetition frequency (f...) rep ) and carrier envelope offset frequency (f ceo The signal is transmitted to the first satellite-borne time and frequency reference source to provide a stable optical time reference signal for the system. After modulation and amplification, the signal is transmitted to the other satellite via a link.
[0044] The first tracking optical frequency comb (TPFC) serves as the local oscillator (LO) at the receiver, employing time-programmable optical frequency comb technology. Instead of transmitting into space, it generates pulse sequences locally. Through precise control of the FPGA, its pulse timing and phase can be dynamically adjusted, enabling the local "copying" and tracking of received, weak, remote signals.
[0045] The first onboard time and frequency reference source provides a unified, high-precision frequency reference (such as a 10 MHz or 100 MHz standard signal) for all time and frequency devices within the first satellite terminal. The locking references for the first clock optical frequency comb and the first tracking optical frequency comb are derived from this (such as an onboard rubidium clock, cesium clock, or hydrogen clock), ensuring the stability of the local time reference.
[0046] The first FPGA time-programmable control module is the core of the TPFC, responsible for fully digital repetition rate and phase control. It utilizes an internal numerically controlled oscillator (NCO) to generate a dynamically adjustable reference phase signal. The signal is digitally mixed and phase-detected with the electrical signal output from the first tracking optical frequency comb. The generated error signal is then fed back to control the intracavity devices of the laser (piezoelectric ceramic PZT or electro-optic modulator EOM), thereby achieving rapid scanning, acquisition, and real-time locking of the incident signal pulse with sub-attosecond precision.
[0047] The first balancing timing detection module, as follows: Figure 2 (Module connection) and Figure 3 As shown in the (optical path principle) diagram, this module is the core component for achieving femtosecond-level high-precision time synchronization detection. This module receives two inputs: one is a long-distance transmitted signal light (separated by the first optical wavelength division multiplexing module), and the other is the local oscillator light output from the first tracking optical frequency comb. Internally, the module utilizes a type II phase-matching nonlinear crystal (such as PPKTP) for non-collinear sum-frequency detection and, through balanced differential detection technology, outputs an "S"-shaped phase detection curve to extract the femtosecond-level time synchronization error signal, which is then fed back to the first FPGA module for closed-loop control.
[0048] The first laser communication module is used to transmit telemetry data, coarse time stamps, and system status information during the initial establishment and maintenance of the inter-satellite link. This module typically uses a narrow-linewidth continuous-wave (CW) laser as an independent carrier source and employs an electro-optic modulator (EOM) for high-speed external modulation. To achieve rapid signal acquisition and coarse synchronization, the transmitter can load a pseudo-random binary sequence (PRBS) for spread spectrum modulation, and the receiver obtains coarse time-of-flight information through correlation demodulation to assist the TPFC in subsequent fine scanning.
[0049] The first optical wavelength division multiplexing (WDM) module is used to multiplex and demultiplex the ranging / time synchronization signal (optical frequency comb pulse) and the communication signal (CW laser) in the same physical optical path. Through a high-isolation WDM multiplexer, the system can perform spectral synthesis of the optical frequency comb signal link (precision ranging), the laser communication link (communication and coarse synchronization), and the shared RF modulation link signals at the transmitting end, and then combine them into a shared laser transceiver antenna. At the receiving end, the received mixed optical signals are precisely separated and sent to the balanced timing detection module and the laser communication receiving module respectively, achieving integrated measurement and communication.
[0050] The laser transceiver module includes a large-aperture telescope and an acquisition, tracking, and aiming (ATP) system for establishing and maintaining a highly stable free-space laser link.
[0051] Example 2
[0052] This invention also discloses a high-precision inter-satellite ranging method based on balanced timing detection technology. The method employs a two-way time comparison method to eliminate the uncertainty of link delay. The specific process is as follows: Figure 4 As shown, it includes the following steps:
[0053] Step S1: Transmission and Preprocessing. The clock optical frequency comb of the main satellite (i.e., the aforementioned first satellite terminal, also known as Satellite A) transmits a sequence of optical pulses. To the secondary satellite (i.e., the aforementioned second satellite terminal, also known as Satellite B); Satellite B's clock optical frequency comb emits a sequence of optical pulses. To satellite A. In order to distinguish signals and transmit coarse time information, optical pulses can be loaded with pseudo-random codes (PRBS) through electro-optic modulators.
[0054] Step S2: Time-Programmed Scan. In the initial stage, due to the unknown inter-satellite distance, the receiver's TPFC cannot predict the signal arrival time. At this time, the FPGA controls the TPFC to enter "scan mode". The FPGA instruction NCO generates a linearly varying frequency offset, causing a slight difference between the TPFC repetition frequency and the expected signal repetition frequency. This causes the local TPFC pulse to scan rapidly in the time domain to search for and capture remotely transmitted signal pulses.
[0055] Step S3: Capture and Lock. When the TPFC pulse "slips" to a position overlapping with the incident signal pulse (the overlap time window is typically on the order of femtoseconds), the balanced timing detection module instantly responds, outputting an "S"-shaped error signal. After the threshold detection logic inside the FPGA captures this signal, it immediately performs the following operations:
[0056] (1) Stop scanning: NCO stops the frequency of linear change.
[0057] (2) Closed-loop locking: The error voltage output by the BOC module is used as feedback, and the phase of the TPFC is adjusted in real time through the digital servo loop to lock at the zero-crossing point of the "S" curve. At this time, the TPFC acts as a voltage-controlled oscillator in an "optical phase-locked loop", and its output pulse sequence completely replicates the remotely arriving signal pulse in the time domain.
[0058] Step S4: Parameter calculation. At this point, satellite A measures the pseudorange time from B to A. (Obtained by comparing the digital status of the TPFC with the local clock), satellite B measured the pseudorange time from A to B. According to the principle of two-way time transfer:
[0059]
[0060]
[0061] in, It is the one-way light flight time (path flight time). The deviation of the reference clock sources on the two satellites, This refers to the calibrated internal system delay.
[0062] Assuming the system delay has been calibrated and eliminated, after exchanging data via the communication link, the clock deviation between the two satellites can be calculated as follows: And the absolute distance is:
[0063] Considering the additional time drift introduced by the clock frequency difference between the two locations, a frequency difference correction term also needs to be introduced:
[0064]
[0065] By calculating the above parameters in real time, the FPGA outputs control signals to adjust the local atomic clock or directly outputs aligned time and frequency signals, achieving inter-satellite femtosecond-level time synchronization and submicron-level ranging.
Claims
1. A high-precision inter-satellite ranging system based on balanced timing detection technology, characterized in that... include: A first satellite terminal and a second satellite terminal are connected via a free-space optical link. The first satellite terminal includes a first FPGA time programming control module. The output of the first onboard time and frequency reference source is divided into three paths: the first path is connected to the clock signal input of the first FPGA time programming control module, the second path is connected to the clock signal input of the first clock optical frequency comb, and the third path is connected to the clock signal input of the first tracking optical frequency comb. The output of the first FPGA time programming control module is divided into three paths: the first path is connected to the control of the first tracking optical frequency comb, the second path is connected to the control of the first clock optical frequency comb, and the third path is connected to the control of the first laser communication module. The output of the first clock optical frequency comb is connected to one input of the first optical wavelength division multiplexing module. The first optical wavelength division multiplexing module is bidirectionally connected to the first laser transceiver module and the first laser communication module. One output of the first optical wavelength division multiplexing module and one output of the first tracking optical frequency comb are connected to one input of the first balanced timing detection module. The output of the first balanced timing detection module is connected to one input of the first FPGA time programming control module. The second satellite terminal includes a second FPGA time programming control module. The output of the second onboard time and frequency reference source is divided into three paths: the first path is connected to the clock signal input of the second FPGA time programming control module, the second path is connected to the clock signal input of the second clock optical frequency comb, and the third path is connected to the clock signal input of the second tracking optical frequency comb. The output of the second FPGA time programming control module is divided into three paths: the first path is connected to the control terminal of the second tracking optical frequency comb, the second path is connected to the control terminal of the second clock optical frequency comb, and the third path is connected to the control terminal of the second laser communication module. The output of the second clock optical frequency comb is connected to one input of the second optical wavelength division multiplexing module. The second optical wavelength division multiplexing module is bidirectionally connected to the second laser transceiver module and the second laser communication module. One output of the second optical wavelength division multiplexing module and one output of the second tracking optical frequency comb are connected to one input of the second balanced timing detection module. The output of the second balanced timing detection module is connected to one input of the second FPGA time programming control module.
2. The high-precision inter-satellite ranging system based on balanced timing detection technology as described in claim 1, characterized in that: The first clock optical frequency comb is used as a transmission source. It employs a mode-locked fiber laser, and its repetition frequency frep and carrier envelope offset frequency fceo are fed to the first satellite-borne time and frequency reference source to provide an optical time reference signal for the first satellite terminal.
3. The high-precision inter-satellite ranging system based on balanced timing detection technology as described in claim 1, characterized in that: The first tracking optical frequency comb is used as a local oscillator at the receiving end, employing a time-programmed optical frequency comb method to generate pulse sequences locally.
4. The high-precision inter-satellite ranging system based on balanced timing detection technology as described in claim 1, characterized in that: The first satellite-borne time and frequency reference source provides a unified, high-precision frequency reference signal for all time and frequency devices within the first satellite terminal.
5. The high-precision inter-satellite ranging system based on balanced timing detection technology as described in claim 1, characterized in that: The first FPGA timing programming control module is responsible for fully digital repetition rate and phase control, and uses an internal numerically controlled oscillator (NCO) to generate a dynamically adjustable reference phase signal. The signal is digitally mixed and phase-detected with the electrical signal output from the first tracking optical frequency comb, and the generated error signal is fed back to control the devices inside the laser cavity.
6. The high-precision inter-satellite ranging system based on balanced timing detection technology as described in claim 1, characterized in that: The first balanced timing detection module is used to achieve femtosecond-level high-precision time synchronization detection. This module receives two inputs: one is the long-distance signal light separated by the first optical wavelength division multiplexing module and transmitted over a long distance, and the other is the local oscillator light output by the first tracking optical frequency comb. The module uses a type II phase-matching nonlinear crystal to perform non-collinear sum-frequency detection and outputs an "S"-shaped phase detection curve through balanced differential detection to extract the femtosecond-level time synchronization error signal, which is fed back to the first FPGA time programming control module for closed-loop control.
7. The high-precision inter-satellite ranging system based on balanced timing detection technology as described in claim 1, characterized in that: The first laser communication module is used to transmit telemetry data, coarse time stamps, and system status information during the initial establishment and maintenance of the inter-satellite link. It uses a narrow linewidth continuous wave laser as an independent carrier light source and employs an electro-optic modulator for high-speed external modulation.
8. The high-precision inter-satellite ranging system based on balanced timing detection technology as described in claim 1, characterized in that: The first optical wavelength division multiplexing module is used to realize the multiplexing and demultiplexing of ranging / time synchronization signals and communication signals in the same physical optical path. Through the wavelength division multiplexer, the optical frequency comb signal link, the laser communication link and the shared radio frequency modulation link signals are spectrally synthesized at the transmitting end and combined into a shared laser transceiver antenna. At the receiving end, the received mixed optical signals are accurately separated and sent to the balanced timing detection module and the laser communication receiving module respectively, realizing the integrated measurement and communication.
9. The high-precision inter-satellite ranging system based on balanced timing detection technology as described in claim 1, characterized in that: The first laser transceiver module includes a large-aperture telescope and a capture, tracking and aiming system for establishing and maintaining a highly stable free-space laser link.
10. A high-precision inter-satellite ranging method based on balanced timing detection technology, wherein the ranging method uses the ranging system described in any one of claims 1-9, characterized in that, The method includes the following steps: S1, Transmission and Preprocessing: Transmitting the optical pulse sequence emitted by the first clock optical frequency comb of the first satellite terminal. The optical pulse sequence transmitted to the second satellite terminal, via the second clock optical frequency comb of the second satellite terminal. Transmitted to the first satellite terminal A; S2, Time Programming Scan: The FPGA time programming control module controls the numerically controlled oscillator (NCO) to generate a linearly varying frequency offset, causing a slight difference between the repetition frequency of the clock optical comb and the expected signal repetition frequency, so that the local clock optical comb pulses can be rapidly scanned in the time domain to search for and capture signal pulses transmitted from a remote location. S3, Capture and Lock: When the clock optical comb pulse slides to a position overlapping with the incident signal pulse, the balanced timing detection module instantly responds and outputs an S-shaped error signal. After the threshold detection logic inside the FPGA time programming control module captures this signal, it immediately performs the following operations: Stop scanning: The NCO (Numerical Controlled Oscillator) stops linearly changing its frequency; Closed-loop locking: The error voltage output by the balanced optical cross-correlation module is used as feedback, and the phase of the clock optical frequency comb is adjusted in real time through the digital servo loop to lock at the zero crossing point of the S-curve; at this time, the clock optical frequency comb acts as a voltage-controlled oscillator in an optical phase-locked loop, and its output pulse sequence completely replicates the signal pulses that arrive remotely in the time domain. S4, Parameter Calculation: The pseudorange time measured by the first satellite terminal from the second satellite terminal to the first satellite terminal. The second satellite terminal measured the pseudorange time from the first satellite terminal to the second satellite terminal. According to the principle of two-way time transfer: ； ； in, For the time of flight of light in one direction, The deviation of the reference clock sources on the two satellites, This refers to the calibrated internal system latency; Assuming the system delay has been calibrated and eliminated, after exchanging data via the communication link, the clock deviation between the two satellites is calculated as follows: ； And the absolute distance is: ； Considering the additional time drift introduced by the clock frequency difference between the two locations, a frequency difference correction term is introduced: ； By calculating the above parameters in real time, the FPGA time programming control module outputs control quantities to adjust the local atomic clock or directly outputs aligned time and frequency signals to achieve inter-satellite femtosecond-level time synchronization and submicron-level ranging.