Samsung time difference positioning method based on reverse rotation

Abstract

The invention relates to a three-satellite time difference positioning method based on reverse translucent rotation, which comprises the following steps: a first auxiliary satellite and a second auxiliary satellite respectively receive radiation source signals, obtain first and second reverse translucent forwarding signals based on the respectively received radiation source signals and self-positioning position information, and reversely forward the first and second reverse translucent forwarding signals to a main satellite; the primary satellite generates a primary satellite hidden forwarding signal based on a radiation source signal and self-positioning position information received by the primary satellite and the received first and second reverse transparent forwarding signals, and sends the primary satellite hidden forwarding signal to a ground receiving station; the ground receiving station carries out interference offset and demodulation translation on the hidden forwarding signal of the main satellite to obtain a radiation source signal received by the main satellite and self-positioning position information of the main satellite, and radiation source signals received by the first and second auxiliary satellites and self-positioning position information of the first and second auxiliary satellites; obtaining time difference information between the primary satellite and the first secondary satellite and between the primary satellite and the second secondary satellite; and constructing a time difference equation and an earth surface constraint equation to jointly solve and obtain a radiation source positioning position. Concealed transmission of forwarded signals and accurate positioning of the radiation source are realized.

Description

Technical Field

[0001] The invention relates to the technical field of radio positioning, and in particular to a three-star time difference positioning method based on reverse transmission. Background Art

[0002] Three-satellite time difference positioning technology is one of the means to obtain high-precision positioning of radiation sources. Generally speaking, this positioning system requires complex inter-satellite links and high-precision time references between satellites in order to obtain real-time positioning capabilities on the satellite. However, due to the weak processing capabilities on the satellite, the positioning efficiency of this method for radiation source signals drops sharply and cannot meet the needs of large-scale radiation source signal positioning.

[0003] If the positioning system includes low-orbit satellites, its transparent forwarding is affected by the geographical location of the ground receiving station, and large-scale real-time transparent forwarding cannot be achieved. The positioning area is greatly limited, and due to the Doppler frequency shift characteristics of low-orbit satellites, the signal-to-noise ratio loss of scrambled covert forwarding will be relatively large. If the positioning system uses all synchronous orbit satellites (usually referring to geosynchronous orbit satellites, which belong to the category of high-orbit satellites), real-time transparent forwarding can be achieved, and the signal-to-noise ratio loss of covert forwarding using scrambling is small, but the three stars are in synchronous orbits, and their positioning configuration is not ideal, resulting in positioning blind spots in low-latitude areas near the equator. Summary of the invention

[0004] In view of the above analysis, an embodiment of the present invention aims to provide a three-star time difference positioning method based on reverse transparent transmission, so as to solve the technical problems that the existing high-orbit three-star time difference positioning has positioning blind spots in low-latitude areas and low-orbit satellites cannot transparently forward in a large range in real time.

[0005] The present invention provides a three-star time difference positioning method based on reverse transmission, comprising the following steps:

[0006] Step S1, the first and second secondary satellites receive radiation source signals respectively, obtain first and second reverse transparent forwarding signals based on the respectively received radiation source signals and self-positioning position information, and forward them reversely to the primary satellite;

[0007] Step S2: the master satellite generates a master satellite concealed forwarding signal based on the radiation source signal received by itself, the self-positioning position information of the master satellite, and the first and second reverse transparent forwarding signals received, and sends the signal to the ground receiving station;

[0008] Step S3, the ground receiving station performs interference cancellation and demodulation and decompression processing on the hidden forwarding signal of the primary satellite to obtain the radiation source signal received by the primary satellite and the self-positioning position information of the primary satellite, as well as the radiation source signal received by the first and second secondary satellites and the self-positioning position information of the first and second secondary satellites; based on the radiation source signals received by the primary satellite, the first and second secondary satellites, the time difference information between the primary satellite and the first secondary satellite, and between the primary satellite and the second secondary satellite is obtained; based on the time difference information and the self-positioning position information of the primary satellite, the first and second secondary satellites, a time difference equation is constructed, and the time difference equation and the earth surface constraint equation are jointly solved to obtain the positioning position of the radiation source.

[0009] Furthermore, the primary satellite generates a primary satellite concealed forwarding signal based on the radiation source signal received by itself, the primary satellite self-positioning position information, and the first and second received reverse transparent forwarding signals, including:

[0010] The primary satellite receives the ground radiation source signal, amplifies and filters it, and obtains the primary satellite broadband receiving signal;

[0011] Up-converting the primary satellite broadband received signal to obtain an up-converted primary satellite broadband received signal;

[0012] The master satellite self-positioning information is modulated and converted into digital-to-analog form to obtain a master satellite modulation signal;

[0013] Up-converting the master satellite modulation signal to obtain an up-converted master satellite modulation signal;

[0014] Adjusting the relative amplitude of the up-converted primary satellite bandwidth received signal and the up-converted primary satellite modulated signal, and combining them to obtain a primary satellite combined signal;

[0015] The primary satellite combines the primary satellite combined signal with the first and second reverse transparent forwarding signals to obtain a three-star combined signal;

[0016] The main satellite generates an interference signal, and after adjusting the amplitude, combines it with the combined signal of the three satellites to obtain a total combined signal;

[0017] The amplitude of the total combined signal is adjusted and amplified to obtain a primary satellite concealed forwarding signal.

[0018] Furthermore, the step S1 comprises:

[0019] The first and second secondary satellites receive ground radiation source signals respectively, and perform amplification and filtering processing respectively to obtain first and second secondary satellite broadband receiving signals;

[0020] Up-converting the first and second secondary satellite broadband received signals respectively to obtain the first and second secondary satellite up-converted broadband received signals;

[0021] The self-positioning position information of the first and second secondary satellites is modulated and converted into the first and second secondary satellite modulation signals after digital-to-analog conversion;

[0022] After the first and second secondary satellite modulation signals are up-converted respectively, the first and second secondary satellite up-converted modulation signals are obtained respectively;

[0023] Adjusting the relative amplitudes of the broadband received signal after up-conversion and the modulated signal after up-conversion by the first secondary satellite and then combining them, adjusting the amplitude of the combined signal and amplifying it to obtain a first reverse transparent forwarding signal;

[0024] The broadband received signal after up-conversion by the second secondary satellite and the modulated signal after up-conversion are adjusted in relative amplitude and then combined, and the amplitude of the combined signal is adjusted and amplified to obtain a second reverse transparent forwarding signal.

[0025] Furthermore, the concealed forwarding signal of the primary satellite is concealedly forwarded to the ground receiving station through a forwarding link between the primary satellite and the ground receiving station.

[0026] Furthermore, the ground receiving station uses a ground receiving and positioning system to perform interference cancellation and demodulation and translation processing on the hidden forwarding signal of the primary satellite to obtain the radiation source signal received by the primary satellite and the first and second secondary satellites, as well as the self-positioning position information of the primary satellite and the first and second secondary satellites.

[0027] Based on the self-positioning position information, the position vectors r1, r2, and r3 of the primary satellite, the first secondary satellite, and the second secondary satellite in the geocentric fixed coordinate system are obtained, and the position vector of the radiation source in the geocentric fixed coordinate system is set to r p

[0028] Based on r1, r2, r3, r p and the speed of light, and obtain the real time difference Δt between the radiation source signal reaching the primary star and the first secondary star 21 pt The expression of, and the real time difference Δt between the primary star and the second secondary star 31 pt Expression of

[0029] The ground receiving and positioning system extracts the radiation source signals received by the primary satellite, the first secondary satellite, and the second secondary satellite as s1(n), s2(n), and s3(n), respectively, and calculates the estimated time difference Δt between s1(n) and s2(n) 21 pa , the estimated time difference Δt between s1(n) and s3(n) 31 pa ;

[0030] Based on Δt21 pt , Δt 31 pt With Δt 21 pa , Δt 31 pa The relationship between them is converted to construct the time difference equation.

[0031] Furthermore, the time difference equation is solved jointly with the earth surface constraint equation, as shown in formulas (1)-(3):

[0032]

[0033] Among them, formulas (1)-(2) are time difference equations, and formula (3) is the earth surface constraint equation; x pe ,y pe 、z pe are the coordinates of the radiation source in the x-axis, y-axis, and z-axis directions of the geocentric fixed coordinate system, respectively. pe ,y pe ,z pe ] T =r p , a and e are the semi-major axis and flattening of the Earth respectively.

[0034] Further, the interference signal bandwidth is consistent with the three-star combined signal bandwidth, and the interference signal amplitude is higher than the three-star combined signal amplitude;

[0035] The interference signal spectrum overlaps with the three-star combined signal spectrum, and the three-star combined signal is buried under the interference signal spectrum;

[0036] The interference signal is a spread spectrum signal with a known spread spectrum code.

[0037] Furthermore, the first and second reverse transparent forwarding signals are reversely forwarded to the host satellite through the first and second inter-satellite links respectively.

[0038] Furthermore, the primary satellite, the first and second secondary satellites have the same ground reception working frequency band.

[0039] Furthermore, the primary satellite is a high-orbit satellite, and the first and second secondary satellites are low-orbit satellites.

[0040] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0041] 1. The present invention is based on the method of reverse transparent forwarding from the low-orbit secondary satellite to the primary satellite and unified concealed forwarding to the ground by the high-orbit primary satellite. At the same time, an interference signal is added to the forwarded signal of the primary satellite, and the interference is offset on the ground, thereby realizing flexible and concealed forwarding of the received signal on the ground; the primary satellite adopts a synchronous orbit satellite, and the secondary satellite adopts two low-orbit satellites. Three-star time difference positioning processing is performed on the ground to realize high-precision positioning of all radiation source signals in the working frequency band, thereby significantly improving the positioning efficiency of large-scale radiation source signals;

[0042] 2. The present invention overcomes the positioning blind spot problem of the high-orbit three-star time difference positioning system in low-latitude areas. By combining high-orbit satellites and low-orbit satellites, the present invention can achieve real-time transparent forwarding over a large range, effectively expand the positioning coverage, and reduce the positioning blind spots caused by geographical location restrictions;

[0043] 3. The radiation source positioning capability of the present invention is based on the positioning processing capability of the ground receiving station and is not limited by the onboard processing capability. It can achieve high-precision positioning of all radiation source signals within the three-star common view area, greatly improving the positioning efficiency of the radiation source;

[0044] 4. The low-orbit satellite of the present invention transparently forwards the high-orbit satellite in reverse. The high-orbit satellite adopts scrambling technology to perform confidential transmission, thereby realizing the covert forwarding of the signal received on the ground, and at the same time overcoming the limitation that the transparent forwarding of the low-orbit satellite is restricted by the location of the ground receiving station;

[0045] 5. The satellite self-positioning information of the present invention is modulated and transferred to the ground receiving station simultaneously with the forwarding signal, which is decoupled from the ground operation and control system, making positioning more flexible.

[0046] 6. The three-star time difference positioning method of the present invention can expand the processing capacity of the ground receiving station according to specific needs, and can adapt to different application scenarios and positioning needs.

[0047] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The drawings are only for the purpose of illustrating specific embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0049] Figure 1 This is a flow chart of a Samsung time difference positioning method based on reverse transmission in an embodiment of the present invention;

[0050] Figure 2 This is a schematic diagram of a framework for reverse transparent forwarding of a receiving payload by a secondary satellite in an embodiment of the present invention;

[0051] Figure 3 The relative frequency spectrum relationship between the modulation signal and the broadband receiving signal in the embodiment of the present invention;

[0052] Figure 4 This is a schematic diagram of a framework for concealed forwarding of receiving payloads from a primary satellite to the ground in an embodiment of the present invention;

[0053] Figure 5 The relative relationship between the primary and secondary satellite transparent forwarding spectrum and the interference signal spectrum in the embodiment of the present invention;

[0054] Figure 6 This is the process of positioning the radiation source signal by the ground receiving and positioning system in the embodiment of the present invention;

[0055] Figure 7 The position relationship between the primary satellite, the first secondary satellite, the second secondary satellite, and the ground radiation source in the geocentric fixed coordinate system in the embodiment of the present invention;

[0056] Figure 8 The positional relationship between the three-star nadir point and the typical radiation source in the embodiment of the present invention;

[0057] Fig. 9 It is a CEP (Circular Error Probable) distribution diagram (unit: km) of the three-star time difference positioning based on reverse transmission in an embodiment of the present invention;

[0058] Fig.10 This is the CEP distribution map (unit: km) of the high-orbit three-star time difference positioning in the embodiment of the present invention. DETAILED DESCRIPTION

[0059] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0060] In order to overcome the above-mentioned defects of the prior art and give full play to the advantages of the long baseline of the high-orbit and low-orbit combination and the advantages of the concealed forwarding of the high-orbit satellite, the present invention proposes a three-star time difference positioning method based on reverse transparent forwarding, which reversely and transparently forwards the radiation source signal and satellite self-positioning information in the working frequency band of the low-orbit satellite to the synchronous orbit satellite (i.e., the high-orbit satellite, the main satellite), and after combining with the radiation source signal and satellite self-positioning information in the working frequency band of the synchronous orbit satellite, the synchronous orbit satellite uniformly scrambles and conceals the forwarding to the ground receiving station, and then the ground performs interference cancellation and radiation source signal positioning processing, thereby realizing the three-star time difference positioning of all radiation source signals in the working frequency band. Exemplarily, it is suitable for the UHF (Ultra High Frequency, ultra-high frequency, frequency range between 300MHz-3GHz) frequency band and application environments with complex signal environments.

[0061] The three-star time difference positioning method based on reverse transparent transmission proposed in the present invention can overcome the positioning blind spot problem of the high-orbit three-star time difference positioning system in low-latitude areas; transparent forwarding is based on the high-orbit satellite (i.e., the main satellite), and covert transmission is performed through additional interference signals, thereby realizing the confidential and covert forwarding of the ground-received signal, and at the same time overcoming the limitation that the transparent forwarding of the low-orbit satellite is restricted by the position of the ground receiving station; the satellite self-positioning information is modulated to obtain a modulated signal, and the modulated signal is transmitted to the ground receiving station simultaneously with the forwarding signal, which is decoupled from the ground operation and control system, and the positioning application is more flexible; by improving the computing power of the ground receiving and positioning system of the ground receiving station, high-precision positioning of all radiation source signals in the working frequency band can be achieved, greatly improving the positioning efficiency.

[0062] The present invention has broad application prospects in multi-satellite high-precision positioning. The three-star time difference positioning method proposed in the present invention can achieve high-precision positioning of ground stationary or slow targets, but if it is expanded to a four-star time difference positioning system, it can also achieve high-precision positioning of aerial targets, and is also suitable for positioning high-speed dynamic targets, and even expanded to a multi-star time difference positioning system to obtain useful information of higher dimensions of radiation source signals.

[0063] The present invention is suitable for the high-and-low-orbit joint time difference positioning in which a low-orbit satellite transparently forwards the radiation source signal within the working frequency band to a synchronous orbit satellite, thereby realizing high-precision positioning of the radiation source signal, overcoming the limitation that the transparent forwarding of the low-orbit satellite is restricted by the position of the ground receiving station, and avoiding the technical problem of the high-orbit three-star time difference positioning system having a positioning blind spot in low-latitude areas.

[0064] In view of the problem that the current high-orbit three-star time difference positioning method has a positioning blind spot in the low-latitude area within 10 degrees north and south latitude, and the limitation that the transparent forwarding of low-orbit satellites is restricted by the position of ground receiving stations, the present invention adopts a synchronous orbit satellite combined with two low-orbit satellites to reversely transparently forward to the high-orbit satellite through the low-orbit satellite, rather than directly transparently forwarding to the ground, thus avoiding the transparent forwarding of the low-orbit satellite being restricted by the position of the ground receiving station, realizing flexible and concealed forwarding and high-precision positioning of the radiation source signal, and overcoming the technical problem of positioning blind spots in low-latitude areas of the high-orbit three-star time difference positioning system.

[0065] A specific embodiment of the present invention discloses a three-star time difference positioning method based on reverse transmission, such as Figure 1 As shown, the following steps are included:

[0066] Step S1, the first and second secondary satellites receive radiation source signals respectively, obtain first and second reverse transparent forwarding signals based on the respectively received radiation source signals and self-positioning position information, and forward them reversely to the primary satellite;

[0067] Step S2: the master satellite generates a master satellite concealed forwarding signal based on the radiation source signal received by itself, the self-positioning position information of the master satellite, and the first and second reverse transparent forwarding signals received, and sends the signal to the ground receiving station;

[0068] Step S3, the ground receiving station performs interference cancellation and demodulation and decompression processing on the hidden forwarding signal of the primary satellite to obtain the radiation source signal received by the primary satellite and the self-positioning position information of the primary satellite, as well as the radiation source signal received by the first and second secondary satellites and the self-positioning position information of the first and second secondary satellites; based on the radiation source signals received by the primary satellite, the first and second secondary satellites, the time difference information between the primary satellite and the first secondary satellite, and between the primary satellite and the second secondary satellite is obtained; based on the time difference information and the self-positioning position information of the primary satellite, the first and second secondary satellites, a time difference equation is constructed, and the time difference equation and the earth surface constraint equation are jointly solved to obtain the positioning position of the radiation source.

[0069] The primary satellite, the first secondary satellite and the second secondary satellite have the same ground receiving working frequency band.

[0070] Exemplarily, the working frequency band range of the three-star ground receiving working frequency band may be the UHF band; the three-star simultaneously receives the ground radiation source signal;

[0071] The primary satellite is a high-orbit satellite, and the first and second secondary satellites are low-orbit satellites.

[0072] The step S1 comprises:

[0073] The first and second secondary satellites receive ground radiation source signals respectively, and perform amplification and filtering processing respectively to obtain first and second secondary satellite broadband receiving signals;

[0074] Up-converting the first and second secondary satellite broadband received signals respectively to obtain the first and second secondary satellite up-converted broadband received signals;

[0075] The self-positioning position information of the first and second secondary satellites is modulated and converted into the first and second secondary satellite modulation signals after digital-to-analog conversion;

[0076] After the first and second secondary satellite modulation signals are up-converted respectively, the first and second secondary satellite up-converted modulation signals are obtained respectively;

[0077] Adjusting the relative amplitudes of the broadband received signal after up-conversion and the modulated signal after up-conversion by the first secondary satellite and then combining them, adjusting the amplitude of the combined signal and amplifying it to obtain a first reverse transparent forwarding signal;

[0078] The broadband received signal after up-conversion by the second secondary satellite and the modulated signal after up-conversion are combined after adjusting the relative amplitude, and the combined signal is amplitude adjusted and amplified to obtain a second reverse transparent forwarding signal.

[0079] The first and second secondary satellites respectively combine the working frequency band containing the radiation source signal (i.e., broadband receiving signal) with the modulated self-positioning information of the first and second secondary satellites, and then transparently forward them to the primary satellite through the first intersatellite link and the second intersatellite link respectively, and then combine them with the working frequency band containing the radiation source signal of the primary satellite (i.e., broadband receiving signal of the primary satellite) and the modulated self-positioning information of the primary satellite, and covertly forward them to the ground receiving station. After sampling and processing by the ground receiving and positioning system of the ground receiving station, high-precision positioning of the radiation source target signal is achieved.

[0080] The first and second secondary stars have the same structure. Figure 2 As shown, the secondary satellite reverse transparent forwarding receiving payload framework. The receiving payload framework of the first and second secondary satellites includes: a receiving antenna, a radio frequency front end, a modulation and digital-to-analog conversion module, a first up-converter, a second up-converter, a first adjustable attenuator, a second adjustable attenuator, a third adjustable attenuator, a combiner, a power amplifier and a reverse transparent forwarding antenna;

[0081] The first and second secondary satellites perform the same actions. The steps for the first and second secondary satellites to obtain the first and second reverse transparent forwarding signals are as follows:

[0082] (1) The first and second secondary satellites receive ground radiation source signals through receiving antennas respectively, and input the signals into the first and second secondary satellite radio frequency front ends respectively. After the ground radiation source signals are amplified and filtered by the radio frequency front ends, broadband receiving signals of the first and second secondary satellites containing the radiation source signals are obtained;

[0083] At the same time, the secondary satellite self-positioning information is input to the modulation and digital-to-analog conversion module for modulation, and the digital-to-analog conversion is performed to obtain the first and second secondary satellite modulation signals. Exemplarily, the modulation method is QPSK, Quadrature Phase Shift Keying, quadrature phase shift keying;

[0084] (2) The broadband receiving signals of the first and second secondary satellites are respectively input into the first up-converters of the first and second secondary satellites, and the first and second broadband receiving signals after up-conversion are output;

[0085] At the same time, the modulation signals of the first and second secondary satellites are respectively input into the second up-converters of the first and second secondary satellites for up-conversion, and the modulation signals of the first and second secondary satellites after up-conversion are respectively obtained; the broadband receiving signal is changed from the original UHF band signal to the Ku / Ka band signal, but the spectrum characteristics are not changed and are still the same;

[0086] (3) the first and second bandwidth received signals after up-conversion are input to the first adjustable attenuators of the first and second secondary satellites respectively;

[0087] The up-converted modulation signals of the first and second secondary satellites are respectively input into the second adjustable attenuators of the first and second secondary satellites;

[0088] By controlling the attenuation of the first and second adjustable attenuators (where the attenuation is a control value), the relative amplitude of the bandwidth receiving signal and the modulation signal is adjusted, and the first and second secondary satellite bandwidth receiving signals with adjusted relative amplitudes and the first and second secondary satellite modulation signals with adjusted relative amplitudes are output; the relative amplitude of the modulation signal and the broadband receiving signal is adjusted to ensure that the modulation signal has sufficient transmission power so that the ground can correctly obtain the satellite self-positioning information;

[0089] (4) combining the first secondary satellite broadband receiving signal with the adjusted relative amplitude and the first secondary satellite modulated signal to obtain the first secondary satellite combined signal, inputting the combined signal into the third adjustable attenuator of the first secondary satellite, adjusting the combined signal amplitude through the third adjustable attenuator of the first secondary satellite, and obtaining the first reverse transparent forwarding signal with the adjusted amplitude; flexibly controlling the transmission power of the reverse transparent forwarding signal to ensure the primary satellite receiving signal-to-noise ratio;

[0090] The broadband receiving signal of the second secondary satellite with adjusted relative amplitude and the modulated signal of the second secondary satellite are combined to obtain a combined signal of the second secondary satellite, and the combined signal is input into the third adjustable attenuator of the second secondary satellite. The amplitude of the combined signal is adjusted by the third adjustable attenuator of the second secondary satellite, and the signal after the amplitude adjustment is amplified by a power amplifier to obtain a second reverse transparent forwarding signal;

[0091] The first and second reverse transparent forwarding signals are reversely forwarded to the host satellite through the first and second inter-satellite links respectively.

[0092] like Figure 3 As shown, the relative frequency spectrum relationship between the modulated signal and the broadband received signal, the horizontal axis f represents the signal frequency, and the vertical axis x(t) represents the signal amplitude;

[0093] The modulation signal is set at the edge of the reverse transparent forwarding frequency band, or in an area where there is no broadband receiving signal, to avoid the modulation signal overlapping the radiation source signal in the broadband receiving signal, thereby reducing the interference that the modulation signal may cause to the radiation source signal (since the modulation rate required for satellite self-positioning information is very low, only a few kbps is needed, which means that the bandwidth required for the modulation signal is relatively small, so the modulation signal will occupy a few kHz of the bandwidth of the forwarding frequency band, and the broadband receiving signal band contains narrowband radiation source signals. As long as the modulation signal and the radiation source signal do not overlap, it will not affect the radiation source signal in the broadband forwarding signal band). At the same time, the modulation signal needs to be higher than the broadband receiving signal noise floor to ensure that the signal-to-noise ratio requirement for demodulation is met.

[0094] For the modulation signal being higher than the noise floor of the broadband receiving signal, exemplarily, for each receiving system, the power spectral density of its noise floor is known, assumed to be N0, and the bandwidth of the modulation signal is also known, assumed to be B. Therefore, assuming that the modulation signal is required to be 12dB higher than the noise floor, the modulation signal power is expressed as (N0+12)×B.

[0095] For the signal-to-noise ratio requirements of demodulation, the demodulation signal-to-noise ratio threshold generally has a theoretical value, such as the QPSK bit error rate of 10 -4 When the signal-to-noise ratio is required to be 11.8dB, a margin of more than 3dB is generally required. If the bit error rate requirement is increased, the signal-to-noise ratio requirement must also be increased.

[0096] Step S2 includes steps S21-S22.

[0097] Step S21, the master satellite generates a master satellite concealed forwarding signal based on the radiation source signal received by itself, the master satellite self-positioning position information, and the first and second received reverse transparent forwarding signals, including:

[0098] The primary satellite receives the ground radiation source signal, amplifies and filters it, and obtains the primary satellite broadband receiving signal;

[0099] Up-converting the primary satellite broadband received signal to obtain an up-converted primary satellite broadband received signal;

[0100] The master satellite self-positioning information is modulated and converted into digital-to-analog form to obtain a master satellite modulation signal;

[0101] Up-converting the master satellite modulation signal to obtain an up-converted master satellite modulation signal;

[0102] Adjusting the relative amplitude of the up-converted primary satellite bandwidth received signal and the up-converted primary satellite modulated signal, and combining them to obtain a primary satellite combined signal;

[0103] The primary satellite combines the primary satellite combined signal with the first and second reverse transparent forwarding signals to obtain a three-star combined signal;

[0104] The main satellite generates an interference signal, and after adjusting the amplitude, combines it with the combined signal of the three satellites to obtain a total combined signal;

[0105] The amplitude of the total combined signal is adjusted and amplified to obtain a primary satellite concealed forwarding signal.

[0106] like Figure 4 The main satellite is responsible for receiving the ground radiation source signal, which is consistent with the first and second secondary satellites in receiving the ground radiation source signal.

[0107] like Figure 4 As shown, the hidden forwarding signal of the main satellite is obtained, and the specific implementation is as follows:

[0108] (1) Receive the ground radiation source signal through the main satellite receiving antenna, input it to the first RF front end of the main satellite, amplify and filter it, and obtain the main satellite broadband receiving signal;

[0109] The main satellite self-positioning information is input into the modulation and digital-to-analog conversion module of the main satellite for digital-to-analog conversion modulation to obtain the main satellite modulation signal;

[0110] (2) The broadband receiving signal of the primary satellite is input into the third up-converter of the primary satellite for up-conversion to obtain the broadband receiving signal of the primary satellite after up-conversion;

[0111] The main satellite modulation signal is input into the fourth up-converter of the main satellite for up-conversion to obtain the main satellite modulation signal after up-conversion;

[0112] (3) Inputting the up-converted broadband signal of the primary satellite to the fourth adjustable attenuator of the primary satellite, inputting the up-converted modulated signal of the primary satellite to the fifth adjustable attenuator of the primary satellite, adjusting the relative amplitudes of the up-converted broadband received signal and the up-converted modulated signal, and then combining them. The combined signal is input to the sixth adjustable attenuator of the primary satellite to adjust the amplitude, thereby obtaining a combined signal of the primary satellite;

[0113] (4) The primary satellite receives the first and second reverse transparent forwarding signals of the first and second secondary satellites through the reverse transparent signal receiving antennas of the first and second secondary satellites;

[0114] The first reverse transparent forwarding signal is input to the second RF front end for up-conversion and then input to the seventh adjustable attenuator for amplitude adjustment to obtain the first reverse transparent forwarding signal after the amplitude is adjusted;

[0115] The second reverse transparent forwarding signal is input to the third RF front end for up-conversion and then input to the eighth adjustable attenuator for amplitude adjustment to obtain a second reverse transparent forwarding signal with an adjusted amplitude;

[0116] The first and second reverse transparent forwarding signals after amplitude adjustment and the main satellite combined signal after up-conversion are combined to obtain a three-star combined signal;

[0117] (5) The main satellite generates an interference signal through the interference signal generation module, which is input into the ninth adjustable attenuator of the main satellite to adjust the amplitude, and then combined with the three-star combined signal, and the spectrum overlaps to obtain a total combined signal, so that the interference signal covers the three-star combined signal to achieve a concealment effect; then it is input into the tenth adjustable attenuator of the main satellite to adjust the amplitude, control the transmission power of the transparent forwarding signal to the ground, ensure the ground receiving station to receive it reasonably, and avoid power leakage; it is amplified by the main satellite power amplifier to obtain the main satellite concealed forwarding signal.

[0118] The interference signal bandwidth is consistent with the three-star combined signal bandwidth, and the interference signal amplitude is higher than the three-star combined signal amplitude;

[0119] The interference signal spectrum overlaps with the three-star combined signal spectrum, and the three-star combined signal is buried under the interference signal spectrum;

[0120] The interference signal is a spread spectrum signal with a known spread spectrum code.

[0121] The main satellite transmits the main satellite's covert forwarding signal to the ground receiving and positioning system of the ground receiving station through the forwarding link.

[0122] Step S22: Covertly forward the master satellite forwarding signal to the ground receiving and positioning system of the ground receiving station through the forwarding link between the master satellite and the ground receiving station.

[0123] The relative relationship between the forwarding spectrum of the primary satellite, the first secondary satellite and the second secondary satellite and the spectrum of the interference signal, such as Figure 5 As shown, the center frequencies of the forwarding spectra of the main satellite, the first secondary satellite and the second secondary satellite are f1, f2 and f3 respectively. A protection gap is left between the forwarding spectra of the main satellite, the first secondary satellite and the second secondary satellite to prevent mutual crosstalk between the signals. The spectrum of the interference signal overlaps with the forwarding spectrum of the concealed forwarding signal of the main satellite after combining, and the concealed forwarding signal of the main satellite is just buried under the spectrum of the interference signal, achieving a concealed forwarding effect to the ground.

[0124] Step S3 is divided into steps S31-S32.

[0125] Step S31: The ground receiving station decodes the hidden forwarding signal of the primary satellite to obtain the self-positioning position information of the primary satellite and the self-positioning position information of the first and second secondary satellites.

[0126] The ground receiving station uses a ground receiving and positioning system to perform interference cancellation and restoration processing on the hidden forwarding signal of the primary satellite to obtain the radiation source signals received by the primary satellite and the first and second secondary satellites;

[0127] Based on the self-positioning position information, the position vectors r1, r2, and r3 of the primary satellite, the first secondary satellite, and the second secondary satellite in the geocentric fixed coordinate system are obtained, and the position vector of the radiation source in the geocentric fixed coordinate system is set to r p

[0128] Based on r1, r2, r3, r p and the speed of light, and obtain the real time difference Δt between the radiation source signal reaching the primary star and the first secondary star 21 pt The expression of, and the real time difference Δt between the primary star and the second secondary star 31 pt Expression of

[0129] The ground receiving and positioning system extracts the radiation source signals received by the primary satellite, the first secondary satellite, and the second secondary satellite as s1(n), s2(n), and s3(n), respectively, and calculates the estimated time difference Δt between s1(n) and s2(n) 21 pa , the estimated time difference Δt between s1(n) and s3(n) 31 pa ;

[0130] Based on Δt 21 pt , Δt 31 pt With Δt 21 pa and Δt 31 pa The relationship between them is converted to construct the time difference equation.

[0131] The ground receiving and positioning system of the ground receiving station receives the hidden forwarding signal from the main satellite, such as Figure 6 shown.

[0132] The ground receiving and positioning system receives the hidden forwarding signal of the main satellite through the ground receiving antenna and performs digital processing; and cancels the interference signal through the interference cancellation technology to restore the transparent forwarding signal after the three stars are combined;

[0133] The main satellite hidden forwarding signal after the interference signal is offset is separated and processed to obtain: a main satellite combined signal, a first reverse transparent forwarding signal and a second reverse transparent forwarding signal.

[0134] Figure 6 The transparent forwarding signal of the central main satellite represents the combined signal of the main satellite; the transparent forwarding signal of the secondary satellite represents the first reverse transparent forwarding signal and the second reverse transparent forwarding signal.

[0135] The main satellite combined signal includes the main satellite broadband receiving signal carrying the radiation source signal and the main satellite modulation signal;

[0136] The first reverse transparent forwarding signal includes a first secondary satellite broadband receiving signal carrying a radiation source signal and a first secondary satellite modulation signal;

[0137] The second reverse transparent forwarding signal includes a second secondary satellite broadband receiving signal carrying a radiation source signal and a second secondary satellite modulated signal;

[0138] Decode and translate the modulation signal of the main satellite to obtain the self-positioning position information of the main satellite;

[0139] Decode and translate the modulation signal of the first secondary satellite to obtain the self-positioning position information of the first secondary satellite;

[0140] Decode and translate the modulation signal of the second secondary satellite to obtain the self-positioning position information of the second secondary satellite;

[0141] By processing the corresponding radiation source signals of the primary satellite, the first secondary satellite and the second secondary satellite, the time difference information is obtained;

[0142] Get the time difference information as follows:

[0143] like Figure 7 As shown in the figure, the primary satellite, the first secondary satellite, the second secondary satellite, and the radiation source (P) are in the geocentric fixed coordinate system (abbreviated as S e )’s positional relationship.

[0144] The position vectors of the primary satellite, the first secondary satellite, the second secondary satellite, and the radiation source in the geocentric fixed coordinate system are r1, r2, r3, r p , and obtain the real time difference Δt between the radiation source signal reaching the primary star and the first secondary star21 pt , the real time difference between reaching the primary star and the second secondary star Δt 31 pt , as shown in formulas (1)-(2):

[0145]

[0146] Where c is the speed of light.

[0147] The ground receiving and positioning system of the ground receiving station extracts the radiation source signals transparently forwarded by the primary satellite, the first secondary satellite, and the second secondary satellite as s1(n), s2(n), and s3(n), respectively, and processes the radiation source signals received by the primary and secondary satellites to obtain the estimated time difference Δt between s1(n) and s2(n) 21 pa , the estimated time difference Δt between s1(n) and s3(n) 31 pa , then the actual time difference Δt between the radiation source signal reaching the primary star and the first secondary star is 21 pt , the real time difference between reaching the primary star and the second secondary star Δt 31 pt , as shown in formulas (3)-(4):

[0148]

[0149] Substituting formula (3) and (4) into formula (1) and (2), we can obtain formula (5)-(6).

[0150] The time difference equation is solved jointly with the earth surface constraint equation, as shown in formulas (5)-(7):

[0151]

[0152]

[0153] Among them, formulas (5)-(6) are time difference equations, and formula (7) is the earth surface constraint equation; x pe ,y pe 、z pe are the coordinates of the radiation source in the x-axis, y-axis, and z-axis directions of the geocentric fixed coordinate system, respectively. pe ,y pe ,z pe ] T =r p , a and e are the semi-major axis and flattening of the Earth respectively.

[0154] If the radiation source is a ground target, the position of the ground radiation source is subject to the earth surface constraint.

[0155] Step S32: jointly solve the time difference equation and the earth surface constraint equation to obtain the positioning position of the radiation source.

[0156] By solving the simultaneous equations (5), (6), and (7), we can achieve high-precision positioning of the radiation source point P. pe ,y pe 、z pe .

[0157] The following is a positioning accuracy analysis of a three-star time difference positioning method based on reverse transmission proposed in the present invention, so as to guide the application of the positioning method in engineering design and actual business scenarios.

[0158] Differentiate both sides of formulas (5)-(7) to obtain:

[0159] (u 1p -u 2p )·dr p -(u 1p -u 12 )·dr1+(u 2p -u 12 )·dr2=cd(Δt 21 pa )

[0160] (u 1p -u 3p )·dr p -(u 1p -u 13 )·dr1+(u 3p -u 13 )·dr3=cd(Δt 31 pa )

[0161] g p ·dr p =0

[0162] Formula (8)

[0163] Among them, g p Related to the position of the ground radiation source, it is expressed as shown in formula (9):

[0164]

[0165] u 1p 、u 2p 、u 3p 、u 12 、u 13 are all unit vectors, expressed as shown in formula (10):

[0166]

[0167] Among them, r ij =||r i -r j ||.

[0168] Converting formula (8) into matrix form, we get formula (11):

[0169]

[0170] make:

[0171] C=[(u 1p -u 2p ) (u 1p -u 3p ) p ] T Formula (12)

[0172] dT=[d(Δt 21 pa ) d(Δt 31 pa ) 0] T Formula (13)

[0173] dU1=[(u 1p -u 12 ) T dr1(u 1p -u 13 ) T dr1 0] T Formula (14)

[0174] dU2=[(u 2p -u 12 ) T dr2 (u 3p -u 13 ) T dr3 0] T Formula (15)

[0175] And transforming formula (11), we get the radiation source position error dr p :

[0176] dr p =C -1 (cdT+dU1-dU2) Formula (16)

[0177] Then the radiation source position error dr p The covariance matrix of It is expressed as formula (17):

[0178]

[0179] Assume that the satellite position error and time difference estimation error are Gaussian white noise and are uncorrelated with each other.

[0180] Right now:

[0181] E[dT]=[0 0 0] T Formula (18)

[0182]

[0183] E[dr i ]=[0 0 0] T (i=1,2,3) Formula (20)

[0184]

[0185] Among them, σ t21 , σ t31 are the time difference estimation errors between the first secondary star and the primary star, and between the second secondary star and the primary star, σ xei , σ yei , σ zei are the position errors of different satellites in the x-axis, y-axis, and z-axis directions respectively, then:

[0186] E[dr p ]=C -1 (cE[dT]+E[dU1]-E[dU2])=[0 0 0] T Formula (23)

[0187] Then, formula (17) is simplified to:

[0188]

[0189] Therefore, the radiation source position error dr p Covariance matrix It consists of three terms, namely E[dTdT T ], E[dU1dU1] related to the satellite position error T ]、E[dU2dU2 T ], the specific expression is as follows:

[0190]

[0191] In summary, the covariance matrix P of the ground radiation source position error is obtained drpThe covariance matrix provides a complete description of the positioning error distribution, including the magnitude and direction of the error. From the covariance matrix, the standard deviation of the positioning error (i.e., the square root of the variance) can be calculated, and then the CEP (Circular Error Probable) distribution of the positioning accuracy can be estimated.

[0192] A smaller CEP value indicates that the positioning has a higher accuracy, which means that the positioning positions of most ground radiation sources are close to the true position. On the contrary, a larger CEP value indicates a lower positioning accuracy.

[0193] In order to make the technical effect of the present invention more obvious, a specific example is given below to illustrate that a three-star time difference positioning system based on reverse transmission is established based on the method in the present invention, and then the CEP distribution of the positioning system is given.

[0194] Let two low-orbit satellites be secondary satellites and be in a sun-synchronous orbit at an altitude of 800 km. The distance between the two secondary satellites is 600 km (Sat1 and Sat2), and the beam width of the ground receiving antenna is 120 degrees. Let a geosynchronous orbit satellite be the primary satellite (GEO1), and the beam width of the ground receiving antenna is 5 degrees. The typical ground radiation source (ship) is in the common view area of ​​the three satellites. Their relative position relationship is as follows: Figure 8 shown.

[0195] Assume that the position error of the low-orbit satellite in each direction is 5m (1σ, σ is the mean square error), the position error of the high-orbit satellite in each direction is 200m (1σ), and the time difference estimation error of the radiation source signal is 600ns (1σ). Substitute each error into formula (24) to obtain the covariance matrix Covariance matrix Representing the error distribution, the CEP distribution of the positioning system can be obtained.

[0196] like Fig. 9 As shown in the figure, it can be seen that the positioning accuracy near the sub-satellite point of the low-orbit satellite is better than 2km, achieving high-precision positioning of the radiation source, and there is no positioning blind spot in the low-latitude area, while the typical high-orbit three-star time difference positioning system has a positioning blind spot in the low-latitude area, such as Fig.10 shown.

[0197] In summary, the three-star time difference positioning system based on reverse transmission according to the embodiment of the present invention has the following beneficial effects:

[0198] 1. The present invention is based on the method of reverse transparent forwarding from the low-orbit secondary satellite to the primary satellite and unified concealed forwarding to the ground by the high-orbit primary satellite. At the same time, an interference signal is added to the forwarded signal of the primary satellite, and the interference is offset on the ground, thereby realizing flexible and concealed forwarding of the received signal on the ground; the primary satellite adopts a synchronous orbit satellite, and the secondary satellite adopts two low-orbit satellites. Three-star time difference positioning processing is performed on the ground to realize high-precision positioning of all radiation source signals in the working frequency band, thereby significantly improving the positioning efficiency of large-scale radiation source signals;

[0199] 2. The present invention overcomes the positioning blind spot problem of the high-orbit three-star time difference positioning system in low-latitude areas. By combining high-orbit satellites and low-orbit satellites, the present invention can achieve real-time transparent forwarding over a large range, effectively expand the positioning coverage, and reduce the positioning blind spots caused by geographical location restrictions;

[0200] 3. The radiation source positioning capability of the present invention is based on the positioning processing capability of the ground receiving station and is not limited by the onboard processing capability. It can achieve high-precision positioning of all radiation source signals within the three-star common view area, greatly improving the positioning efficiency of the radiation source;

[0201] 4. The low-orbit satellite of the present invention transparently forwards the high-orbit satellite in reverse. The high-orbit satellite adopts scrambling technology to perform confidential transmission, thereby realizing the covert forwarding of the signal received on the ground, and at the same time overcoming the limitation that the transparent forwarding of the low-orbit satellite is restricted by the location of the ground receiving station;

[0202] 5. The satellite self-positioning information of the present invention is modulated and transferred to the ground receiving station simultaneously with the forwarding signal, which is decoupled from the ground operation and control system, making positioning more flexible.

[0203] 6. The three-star time difference positioning method of the present invention can expand the processing capacity of the ground receiving station according to specific needs, and can adapt to different application scenarios and positioning needs.

[0204] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A three-star time difference positioning method based on reverse transmission, characterized in that: The steps include: Step S1, the first and second secondary satellites receive radiation source signals respectively, obtain first and second reverse transparent forwarding signals based on the respectively received radiation source signals and self-positioning position information, and forward them reversely to the primary satellite; Step S2: the master satellite generates a master satellite concealed forwarding signal based on the radiation source signal received by itself, the self-positioning position information of the master satellite, and the first and second reverse transparent forwarding signals received, and sends the signal to the ground receiving station; Step S3, the ground receiving station performs interference cancellation and demodulation and decompression processing on the concealed forwarding signal of the primary satellite to obtain the radiation source signal received by the primary satellite and the self-positioning position information of the primary satellite, as well as the radiation source signal received by the first and second secondary satellites and the self-positioning position information of the first and second secondary satellites; Based on the radiation source signals received by the primary satellite, the first satellite and the second satellite, the time difference information between the primary satellite and the first satellite and between the primary satellite and the second satellite is obtained; A time difference equation is constructed based on the time difference information and the self-positioning position information of the primary satellite and the first and second secondary satellites, and the time difference equation is jointly solved with the earth surface constraint equation to obtain the positioning position of the radiation source.

2. The method according to claim 1, characterized in that: The primary satellite generates a primary satellite concealed forwarding signal based on the radiation source signal received by the primary satellite, the primary satellite self-positioning position information, and the first and second received reverse transparent forwarding signals, including: The primary satellite receives the ground radiation source signal, amplifies and filters it, and obtains the primary satellite broadband receiving signal; Up-converting the primary satellite broadband received signal to obtain an up-converted primary satellite broadband received signal; The master satellite self-positioning information is modulated and converted into digital-to-analog form to obtain a master satellite modulation signal; Up-converting the master satellite modulation signal to obtain an up-converted master satellite modulation signal; Adjusting the relative amplitude of the up-converted primary satellite bandwidth received signal and the up-converted primary satellite modulated signal, and combining them to obtain a primary satellite combined signal; The primary satellite combines the primary satellite combined signal with the first and second reverse transparent forwarding signals to obtain a three-star combined signal; The main satellite generates an interference signal, and after adjusting the amplitude, combines it with the combined signal of the three satellites to obtain a total combined signal; The amplitude of the total combined signal is adjusted and amplified to obtain a primary satellite concealed forwarding signal.

3. The method according to claim 1, characterized in that: The step S1 comprises: The first and second secondary satellites receive ground radiation source signals respectively, and perform amplification and filtering processing respectively to obtain first and second secondary satellite broadband receiving signals; Up-converting the first and second secondary satellite broadband received signals respectively to obtain the first and second secondary satellite up-converted broadband received signals; The self-positioning position information of the first and second secondary satellites is modulated and converted into the first and second secondary satellite modulation signals after digital-to-analog conversion; After the first and second secondary satellite modulation signals are up-converted respectively, the first and second secondary satellite up-converted modulation signals are obtained respectively; Adjusting the relative amplitudes of the broadband received signal after up-conversion and the modulated signal after up-conversion by the first secondary satellite and then combining them, adjusting the amplitude of the combined signal and amplifying it to obtain a first reverse transparent forwarding signal; The broadband received signal after up-conversion by the second secondary satellite and the modulated signal after up-conversion are combined after adjusting the relative amplitude, and the combined signal is amplitude adjusted and amplified to obtain a second reverse transparent forwarding signal.

4. The method according to claim 2, characterized in that: The concealed forwarding signal of the primary satellite is concealedly forwarded to the ground receiving station through a forwarding link between the primary satellite and the ground receiving station.

5. The method according to claim 4, characterized in that: The ground receiving station uses a ground receiving and positioning system to perform interference cancellation and demodulation and translation processing on the hidden forwarding signal of the primary satellite, and obtains the radiation source signal received by the primary satellite, the first and second secondary satellites, and the self-positioning position information of the primary satellite, the first and second secondary satellites. Based on the self-positioning position information, the position vectors r of the primary satellite, the first secondary satellite and the second secondary satellite in the geocentric fixed coordinate system are obtained. 1 , r2, r3, and let the position vector of the radiation source in the geocentric fixed coordinate system be r p ; Based on r1, r2, r3, r p and the speed of light, and obtain the real time difference Δt between the radiation source signal reaching the primary star and the first secondary star 21 pt The expression of, and the real time difference Δt between the primary star and the second secondary star 31 pt Expression of The ground receiving and positioning system extracts the radiation source signals received by the primary satellite, the first secondary satellite, and the second secondary satellite as s1(n), s2(n), and s3(n), respectively, and calculates the estimated time difference Δt between s1(n) and s2(n) 21 pa , the estimated time difference Δt between s1(n) and s3(n) 31 pa ; Based on Δt 21 pt , Δt 31 pt With Δt 21 pa , Δt 31 pa The relationship between them is converted to construct the time difference equation.

6. The method according to claim 5, characterized in that: The time difference equation is solved jointly with the earth surface constraint equation, as shown in formulas (1)-(3): Among them, formula (1)-(2) are the time difference equations, and formula (3) is the earth surface constraint equation; x pe ,y pe 、z pe are the coordinates of the radiation source in the x-axis, y-axis, and z-axis directions of the geocentric fixed coordinate system, respectively. pe ,y pe ,z pe ] T =r p , a and e are the semi-major axis and flattening of the Earth respectively.

7. The method according to claim 2, characterized in that: The interference signal bandwidth is consistent with the three-star combined signal bandwidth, and the interference signal amplitude is higher than the three-star combined signal amplitude; The interference signal spectrum overlaps with the three-star combined signal spectrum, and the three-star combined signal is buried under the interference signal spectrum; The interference signal is a spread spectrum signal with a known spread spectrum code.

8. The method according to claim 1, characterized in that: The first and second reverse transparent forwarding signals are reversely forwarded to the host satellite through the first and second inter-satellite links respectively.

9. The method according to any one of claims 1 to 8, characterized in that: The primary satellite, the first secondary satellite and the second secondary satellite have the same ground receiving working frequency band.

10. The method according to any one of claims 1 to 8, characterized in that: The primary satellite is a high-orbit satellite, and the first and second secondary satellites are low-orbit satellites.

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