An inter-satellite link bidirectional measurement method based on simultaneous same-frequency full duplex system

Abstract

The application provides an inter-satellite link bidirectional measurement method based on a simultaneous same-frequency full duplex system, which overcomes the problem that the traditional time-division half duplex system cannot work simultaneously in the same frequency for receiving and transmitting, and can effectively improve the information transmission rate and the ranging accuracy; the inter-satellite transmission rate, the measurement frequency and the data update rate can be doubled; the inter-satellite simultaneous same-frequency measurement can greatly eliminate the ranging error caused by the relative motion between satellites, the clock deviation and the Doppler effect; the complex orbit model does not need to be established to improve the ranging accuracy, the time scale reduction error is greatly reduced, and the overall measurement performance is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of navigation inter-satellite link measurement and communication, and particularly relates to an inter-satellite link bidirectional measurement method based on a simultaneous and same frequency full duplex system. BACKGROUND

[0002] The Beidou-3 global satellite navigation system (BDS-3) was completed on July 31, 2020, and officially provides positioning, navigation and timing services to the world. The BDS-3 satellites are all equipped with Ka-band inter-satellite link payloads, which can realize the functions of precise orbit determination and time synchronization through inter-satellite precise measurement and data transmission. By establishing a measurement and communication link between navigation satellites, the inter-satellite link can continuously correct the long-term predicted ephemeris and clock parameters of the satellite without the support of the ground measurement and control system, autonomously generate navigation messages, and realize autonomous navigation function, thereby improving the orbit determination accuracy and enhancing the autonomous maintenance capability of the constellation configuration.

[0003] The current Beidou inter-satellite link measurement and communication adopts a time division half duplex mode, which uses a narrow beam antenna to establish a directional link and realize spatial multiplexing. For the entire constellation, there are multiple point-to-point inter-satellite links in any time slot, which shortens the measurement period and constructs a near real-time network. According to the time slot planning table pre-injected into the satellite by the ground, each satellite uses a polling method to establish a link with other satellites (or ground anchor stations). The Beidou inter-satellite link divides the time axis into "superframes" (one scheduling period, 1 minute) and further subdivides 1 superframe into multiple "time slots" (3 seconds), and activates the appropriate inter-satellite link in each time slot. A pair of linked satellites uses time division half duplex to send measurement signals to each other in the same time slot, where the forward measurement is completed in the first 1.5 seconds, and the backward measurement is completed in the second 1.5 seconds. The time division half duplex inter-satellite link time slot allocation is shown in FIG. Figure 1 In each 3-second time slot, multiple pairs of satellites will simultaneously establish a link, so that inter-satellite ranging can cover the entire constellation in a short period of time.

[0004] The inter-satellite bidirectional measurement method under the time division half duplex system can be described as follows:

[0005] Step 1, satellite i and satellite j establish an inter-satellite link according to the planning of the time slot table and with their own on-board frequency standards as the reference;

[0006] Step 2, in the first half of the time slot (1.5s), satellite i sends an information frame to satellite j, and the local baseband clock and carrier frequency are generated by the local frequency synthesizer;

[0007] Step 3, satellite j captures, tracks and demodulates the received signal, recovers the information frame, and extracts the frame transmission epoch time from it to calculate the local pseudo-range jointly with the local reception epoch time.

[0008] Fourthly, in the second half of the time slot (1.5s later), satellite j embeds the calculated local pseudo-range into the information frame and sends it to satellite i, and the information frame structure is the same as that sent by satellite i;

[0009] Fifthly, satellite i captures, tracks and demodulates the received signal, recovers the information frame, and extracts the pseudo-range embedded in the frame sending epoch from the information frame, and calculates the local pseudo-range by combining the sending epoch and the local receiving epoch;

[0010] Sixthly, the errors are corrected and the time scale is calculated by combining the local measured pseudo-range and the demodulated pseudo-range of the other party in the received information frame, and then the inter-satellite distance and clock difference are calculated.

[0011] The current inter-satellite link adopts time division half duplex system for measurement and communication, and the receiving and transmitting cannot work at the same frequency at the same time, the one-way transmission rate is only 50% of the total channel rate, the link building process is complex, the time scale correction and error correction are large, and there are problems of low communication efficiency, large time delay and limited inter-satellite measurement accuracy. SUMMARY

[0012] Therefore, the current simultaneous full duplex technology is relatively mature, which can be introduced into the inter-satellite link measurement and communication process. The inter-satellite link adopts the simultaneous full duplex system, which can effectively break the time and frequency constraints, overcome the problem that the current time division half duplex system cannot realize the simultaneous receiving and transmitting of signals in the same frequency band, simplify the link building process, and realize continuous transmission and precise measurement between satellites. In terms of transmission, the inter-satellite transmission rate, measurement frequency and data update rate can be doubled. In terms of measurement, simultaneous frequency operation can effectively eliminate the ranging errors caused by inter-satellite relative motion, clock bias and Doppler effect, without the need to establish a complex model to improve the ranging accuracy and improve the performance of inter-satellite relative measurement.

[0013] An inter-satellite link bidirectional measurement method based on the simultaneous full duplex system, comprising:

[0014] Firstly, satellite i and satellite j establish an inter-satellite link based on their respective on-board time scales according to the time slot table;

[0015] Secondly, satellite i and satellite j agree on the same transmission time and simultaneously send information frames with the same structure to each other;

[0016] Thirdly, the two satellites capture, track and demodulate the received useful signal, recover the information frame, and extract the information frame sending epoch from the information frame, and calculate the local pseudo-range by combining the local epoch;

[0017] The fourth step involves embedding the calculated local pseudorange into the information frame and sending it to the other party. Both parties then use their locally calculated pseudoranges and the pseudoranges demodulated from the information frame to construct the inter-satellite two-way observation equations.

[0018]

[0019] Where c represents the speed of light, ρ ij ρ represents the pseudorange value measured by satellite i transmitting and satellite j receiving. ji This represents the pseudorange value measured by satellite j transmitting from satellite i. t s1 t represents the system time of the signal transmitted by satellite i. r1 t represents the system time at which satellite j receives the signal. s2 t represents the system time of the signal transmitted by satellite j. r2 The system time of the signal received by satellite i; r j (t s2 ) and r j (t r1 ) represents the spatial position of satellite j when transmitting and receiving signals, r i (t s1 ) and r i (t r2 ) represents the spatial position of satellite i when transmitting and receiving signals. |r j (t r1 )-r i (t s1 )| and |r i (t r2 )-r j (t s2 )| represent the propagation distance from satellite i to satellite j and the propagation distance from satellite j to satellite i, respectively. dt i dt represents the deviation between the satellite clock time and the navigation system time. j The deviation between the satellite clock time and the navigation system time is:

[0020]

[0021] in, and When the local clock face of satellite i represents the time it sends and receives signals, and Indicates the local clock time of satellite j for transmitting and receiving signals;

[0022] and These represent the transmission and reception channel delays of satellite i, respectively. and These represent the transmission and reception channel delays of satellite j, respectively. and Indicates the gravitational delay of a two-way link. and This indicates the time delay caused by the periodic relativistic effects of the two-way link. and ε represents the time delay caused by the phase center deviation of the bidirectional link. ij With ε ji Indicates bidirectional link measurement noise;

[0023] Fifth, the direct correction method is used to perform bidirectional time-scale reduction, and the reduction time t0 = t s1 The two-way observation equation is then corrected to:

[0024]

[0025] Where, ΔD ij and ΔD ji Let dT(t,t0) be the inter-satellite distance correction for the two-way measurements between satellite i and satellite j, and let dT(t,t0) be the clock error correction from time t to time t0. j (t r1 ,t0) indicates that satellite j starts from t r1 The clock error correction from time t0 to time t0, dT i (t s1 ,t0) represents satellite i from t s1 The clock error correction from time t0 to time t0, dT i (t r2 ,t0) represents satellite i from t r2 The clock error correction from time t0 to time t0, dT j (t s2 ,t0) indicates that satellite j starts from t s2 The clock error correction from time t0 to time t0;

[0026] Ignoring clock error correction, then:

[0027]

[0028] For the distance correction, we have:

[0029] ΔD ij =|r j (t r1 )-r i (t s1 )|-|r j (t0)-r i (t0)|

[0030] ΔD ji =|r i (t r2 )-r j(t s2 )|-|r j (t0)-r i (t0)|

[0031] wherein:

[0032]

[0033] v j (t) represents the running speed of satellite j, e ij (t) represents the unit direction vector of satellite i pointing to satellite j; for

[0034] First-order Taylor series expansion is carried out and high-order terms are ignored, and we have:

[0035]

[0036] Similarly, we have:

[0037]

[0038] v i (t) represents the running speed of satellite i, e ji (t) represents the unit direction vector of satellite j pointing to satellite i;

[0039] The distance correction amount is written as:

[0040]

[0041] Sixth step, the device time delay, gravity time delay, periodic relativistic effect, phase center deviation and other system errors are corrected, and the improved pseudo-range is obtained:

[0042]

[0043] wherein, and is the improved pseudo-range, and represents the sum of the residual errors and link measurement errors after time scale reduction and system error correction;

[0044] Seventh step, the sum of the two-way improved pseudo-range formula is obtained, and the inter-satellite distance is obtained:

[0045]

[0046] wherein, ε d is the inter-satellite ranging error;

[0047] Eighth step, the difference between the two-way improved pseudo-range formula is obtained, and the inter-satellite clock difference is obtained:

[0048]

[0049] Wherein, epsilon t is the inter-satellite time comparison error.

[0050] Further, in the second step, the satellite i and the satellite j baseband clock, carrier frequency are generated by each satellite locally, and are not related to the other satellite, and there is no frequency and phase relationship constraint between the two.

[0051] Further, after the second step is completed, it further includes: when the signal reaches the satellite receiving end, first, through active and passive isolation and cancellation in the antenna domain, a self-interference suppression effect of about 100dB is realized.

[0052] Further, after the self-interference suppression effect of about 100dB is realized, it further includes: the transceiver channel adopts a superheterodyne system, in order to ensure that the simultaneous self-interference does not saturate the channel, an interference reconstruction cancellation network is used to further suppress the self-interference in the radio frequency domain.

[0053] Further, after the interference reconstruction cancellation network in the radio frequency domain is used to further suppress the self-interference, it further includes: on the basis of the conventional digital baseband transmission and reception module, a digital domain self-interference suppression processing is added to suppress the self-interference entering the digital baseband after spatial and radio frequency cancellation.

[0054] The present application has the following beneficial effects:

[0055] The present application proposes an inter-satellite link bidirectional measurement method based on a simultaneous frequency full duplex system, which overcomes the problem that the traditional time division half duplex system cannot work simultaneously in the same frequency, and can effectively improve the information transmission rate and the ranging accuracy; the inter-satellite transmission rate, the measurement frequency and the data update rate can be doubled; the simultaneous frequency measurement between satellites can greatly eliminate the ranging error caused by the relative motion between satellites, the clock deviation and the Doppler effect; without establishing a complex orbit model to improve the ranging accuracy, the time scale calculation error is greatly reduced, and the overall measurement performance is improved. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 It is a time division half duplex inter-satellite link time slot allocation schematic diagram;

[0057] Figure 2 It is a simultaneous frequency full duplex self-interference suppression position schematic diagram;

[0058] Figure 3 It is a bidirectional measurement timing diagram under the simultaneous frequency full duplex system;

[0059] Figure 4 It is a bidirectional measurement principle schematic diagram under the simultaneous frequency full duplex system;

[0060] Figure 5A flow chart of a two-way measurement method for an inter-satellite link based on a simultaneous same frequency full duplex system. DETAILED DESCRIPTION

[0061] The application will be described in detail below with reference to the accompanying drawings and examples.

[0062] The application provides a two-way measurement method for an inter-satellite link based on a simultaneous same frequency full duplex system, which can effectively improve the information transmission rate and inter-satellite ranging accuracy.

[0063] First, the feasibility of the application of full duplex technology is analyzed. If the simultaneous same frequency full duplex technology is introduced into the Beidou inter-satellite link communication and measurement system, the satellite receiving end needs to receive a self-interference signal P SI , that is, the signal of the transmitting antenna directly entering the receiving end, which can be suppressed below the noise level of the receiver, thereby not affecting the normal inter-satellite communication and measurement. After the self-interference signal is transmitted by the antenna, it is received by the receiving antenna. Considering the influence of loss factors such as transmitting circuit loss and polarization loss, the required amount of self-interference suppression C of the system can be calculated as follows:

[0064] [C]=[EIRP]-[L P ]-[N](dB)

[0065] Wherein, EIRP is the equivalent isotropic radiated power, L P is the antenna polarization loss, and N is the receiver thermal noise power. The Beidou inter-satellite link budget table is given below, as shown in Table 1.

[0066] Table 1: Beidou inter-satellite link budget parameter table

[0067]

[0068] The definition of the equivalent isotropic radiated power EIRP is

[0069] [EIRP]=[P t ]+[G t ]-[L s ](dB)

[0070] By substituting the corresponding parameter values in the budget parameter table, EIRP≈49.53dBW can be calculated. According to the Friis formula, the total noise temperature T s of the receiving system can be calculated as

[0071] T s =T a +(L N -1)T0+(F-1)LT0

[0072] By substituting the corresponding parameter values in the link budget parameter table, T s≈ 964.51 K, the receiver thermal noise power N is

[0073] [N] = [k] + [T s ]+ [B n ]≈ -125.65 dBW

[0074] By substituting the results calculated above, the system self-interference suppression requirement C can be obtained as

[0075] [C] = 49.53 dBW - 2 dB - (-125.65 dBW)≈ 173.18 dB

[0076] In order to achieve normal measurement communication, the isolation degree that the receiving end of the system needs to achieve must be greater than or close to this value, which makes the design difficulty and complexity of the system larger. However, in recent years, the academic community has carried out extensive and in-depth research on the theoretical basis and technical implementation of simultaneous same-frequency full-duplex technology, and the self-interference suppression level has gradually improved, and some achievements have been accumulated in the field of aerospace. The simultaneous same-frequency full-duplex inter-satellite link communication and measurement system is no longer unachievable.

[0077] At present, the industry widely carries out research on full-duplex self-interference suppression technology, and according to the position of full-duplex self-interference suppression, it can be roughly divided into spatial domain (antenna domain) self-interference suppression, analog domain self-interference suppression and digital domain self-interference suppression. Among them, the analog domain self-interference suppression can be further subdivided into radio frequency and intermediate frequency self-interference suppression, of which the radio frequency domain self-interference suppression is the main one.

[0078] Spatial domain self-interference suppression mainly reduces the near-field coupling effect between antennas by improving the isolation of transmit-receive antennas in space, and can be divided into passive suppression technology and active suppression technology. Passive suppression includes antenna separation, orthogonal polarization, near-field cancellation, feedback network isolation, decoupling structure design, and active suppression mainly uses transmit-receive beamforming technology. Since the Beidou inter-satellite link adopts a Ka-band narrow-beam phased array system, the research progress of array antenna spatial domain self-interference suppression with a center frequency in the range of 20GHz-30GHz is focused on. Table 2 shows the research status of array antenna spatial domain self-interference suppression.

[0079] Table 2 Research status of array antenna spatial domain self-interference suppression

[0080]

[0081]

[0082] The spatial domain self-interference suppression capability is limited and cannot completely eliminate the self-interference signal, and the residual self-interference signal is still greater than the useful signal, so further self-interference suppression needs to be performed in the radio frequency domain. The radio frequency domain self-interference suppression refers to performing self-interference suppression processing in the radio frequency front end, and the idea is to estimate the residual self-interference signal and remove it from the received radio frequency signal, thereby avoiding the saturation of the nonlinear device in the radio frequency receiving channel. According to the current research, the radio frequency domain self-interference suppression technology can be roughly divided into three kinds of direct radio frequency coupling interference suppression, digital auxiliary radio frequency interference suppression and device design with high isolation, and Table 3 is the research status of radio frequency domain self-interference suppression with a center frequency in the range of 20GHz-30GHz.

[0083] Table 3 Research status of radio frequency domain self-interference suppression

[0084]

[0085] The digital domain self-interference suppression refers to further canceling or suppressing the residual self-interference signal after the radio frequency self-interference suppression in the digital domain, and realizing the identification and demodulation of the useful signal. In the full duplex system, the near-end transmitting signal is considered to be known, and the self-interference channel characteristics are unknown. Therefore, the digital domain self-interference suppression needs to use the known transmitting self-interference signal to complete the estimation and compensation of the self-interference channel, and achieve the purpose of self-interference suppression. The current research on digital domain self-interference suppression technology mainly includes three kinds of self-interference channel reconstruction suppression, adaptive filtering self-interference suppression and nonlinear self-interference suppression. Table 4 shows the research status of digital domain self-interference suppression in recent years.

[0086] Table 4 Research status of digital domain self-interference suppression

[0087]

[0088]

[0089] Through comprehensive analysis of Tables 2-4, it can be seen that the research on full duplex self-interference suppression technology at home and abroad is relatively in-depth, and the self-interference suppression capability in each domain has reached a high level. For the array antenna of Ka band, about 100dB of self-interference suppression effect can be achieved by using spatial separation, orthogonal polarization and decoupling structure design and other means. For the radio frequency domain of Ka band, more than 35dB of self-interference suppression effect can be achieved by means of multi-tap channel reconstruction, high-isolation device development, etc. For the digital domain self-interference suppression, with the introduction of artificial intelligence, deep learning and other technologies, the best suppression effect can be greater than 45dB.

[0090] The document

[22] for 20 MHz bandwidth of spread spectrum TT&C system, using multi-tap radio frequency cancellation and digital nonlinear self-jamming suppression method, through simulation and experimental verification found in the radio frequency domain and digital domain respectively reached 41.5 dB and 38 dB of self-jamming suppression effect, double domain joint elimination of about 81 dB of self-jamming signal, for the study of Beidou inter-satellite link full duplex communication measurement system has strong reference value. Comprehensive current research status at home and abroad can be known, based on Ka band array antenna, bandwidth of 20 MHz full duplex spread spectrum measurement communication system, can realize about 180 dB of self-jamming suppression level, higher than the calculated system self-jamming suppression demand C about 7 dB, therefore, the simultaneous self-jamming full duplex technology is introduced into the Beidou inter-satellite link communication measurement system is feasible.

[0091] The method is introduced below, assuming that the superframe length is 1 min, each time slot is 3 s, and a superframe contains 20 time slots. Figures 3 to 5 The timing diagram, schematic diagram and method flow chart of the inter-satellite link bidirectional measurement based on the simultaneous self-jamming full duplex system are shown in FIGS. 1-3, respectively. The method can be specifically divided into the following 11 steps:

[0092] In the first step, satellite i and satellite j establish an inter-satellite link based on their respective on-board frequency markers according to the planning of the time slot table.

[0093] In the second step, satellite i and satellite j agree on the same transmission time and simultaneously send information frames with the same structure to each other. The baseband clock and carrier frequency are generated locally by each satellite and are not synchronized with the other satellite, so there is no frequency and phase relationship constraint between the two satellites.

[0094] In the third step, when the signal reaches the satellite receiving end, the main and passive isolation and cancellation are first performed in the antenna domain to achieve about 100 dB of self-jamming suppression effect.

[0095] In the fourth step, the superheterodyne system is used in the transceiver channel. To ensure that the simultaneous self-jamming does not saturate the channel, an interference reconstruction cancellation network is used to further suppress the self-jamming in the radio frequency domain.

[0096] In the fifth step, based on the conventional digital baseband transmission and reception module, a digital domain self-jamming suppression process is added to suppress the self-jamming signal entering the digital baseband after spatial and radio frequency cancellation to the noise floor level.

[0097] In the sixth step, the two satellites capture, track, and demodulate the received useful signals to restore the information frame and extract the information frame transmission epoch from it. The local pseudorange is calculated jointly with the local epoch.

[0098] In the seventh step, the calculated local pseudorange is embedded in the information frame and sent to the other party. The local pseudorange and the demodulated pseudorange of the other party from the information frame are used to construct the inter-satellite bidirectional observation equation:

[0099]

[0100] Where c represents the speed of light, ρ ij ρ represents the pseudorange value measured by satellite i transmitting and satellite j receiving. ji This represents the pseudorange value measured by satellite j transmitting from satellite i. t s1 t represents the system time of the signal transmitted by satellite i. r1 t represents the system time at which satellite j receives the signal. s2 t represents the system time of the signal transmitted by satellite j. r2 The system time of the signal received by satellite i; r j (t s2 ) and r j (t r1 ) represents the spatial position of satellite j when transmitting and receiving signals, r i (t s1 ) and r i (t r2 ) represents the spatial position of satellite i when transmitting and receiving signals. |r j (t r1 )-r i (t s1 )| and |r i (t r2 )-r j (t s2 )| represent the propagation distance from satellite i to satellite j and the propagation distance from satellite j to satellite i, respectively. dt i dt represents the deviation between the satellite clock time and the navigation system time. j The deviation between the satellite clock time and the navigation system time is:

[0101]

[0102] in, and When the local clock face of satellite i represents the time it sends and receives signals, and This indicates the local clock time on which satellite j transmits and receives signals.

[0103] and These represent the transmission and reception channel delays of satellite i, respectively. and These represent the transmission and reception channel delays of satellite j, respectively. and Indicates the gravitational delay of a two-way link. and This indicates the time delay caused by the periodic relativistic effects of the two-way link. with denotes the time delay caused by the phase center offset of the bi-directional link, ε ij with ε ji denotes the measurement noise of the bi-directional link;

[0104] The eighth step is to use the direct correction method to calculate the bi-directional time scale, and select the calculation time t0=t s1 The bi-directional observation equation can be modified as follows:

[0105]

[0106] where ΔD ij and ΔD ji are the inter-satellite distance correction amounts corresponding to the bi-directional measurement of satellite i and satellite j, and dT(t, t0) is the clock difference correction amount from time t to time t0, that is: dT j (t r1 ,t0) represents the clock difference correction amount of satellite j from time t r1 to time t0, dT i (t s1 ,t0) represents the clock difference correction amount of satellite i from time t s1 to time t0, dT i (t r2 ,t0) represents the clock difference correction amount of satellite i from time t r2 to time t0, and dT j (t s2 ,t0) represents the clock difference correction amount of satellite j from time t s2 to time t0.

[0107] For the clock difference correction amount dT(t, t0), the frequency stability of the on-board atomic clock is generally better than 10 -12 s / s order of magnitude, the maximum inter-satellite communication distance is about 70000 km, and the maximum inter-satellite transmission time delay is about 0.23 s, so the maximum value of the clock difference correction amount is only 10 -13 s order of magnitude, corresponding to a distance of about 0.03 mm, which can be ignored.

[0108]

[0109] For the distance correction amount, we have:

[0110] ΔD ij = |r j (t r1 )-r i (t s1 )|-|r j (t0)-r i (t0)|

[0111] ΔDji = |r i (t r2 )-r j (t s2 )| |r j (t0)-r i (t0)|

[0112] where:

[0113]

[0114] v j (t) represents the running speed of satellite j, e ij (t) represents the unit direction vector of satellite i pointing to satellite j. For

[0115] First-order Taylor series expansion is performed and high-order terms are ignored, and we have

[0116]

[0117] Similarly, we have:

[0118]

[0119] v i (t) represents the running speed of satellite i, e ji represents the unit direction vector of satellite j pointing to satellite i.

[0120] Therefore, the distance correction amount AD can be written as:

[0121]

[0122] The third term on the right side of the equation is the "dynamic compensation" term caused by the high-speed movement of the satellite, and the first two terms on the right side of the equation are the "space reduction" terms caused by the difference between the time of transmission and the time of reduction. Since the speed calculation accuracy of Beidou broadcast ephemeris can reach the level of 1 mm / s

[23] , and the satellite transmits signals at the same time, the inter-satellite clock difference can generally be kept within 2 ms

[24] , that is, |t s2 -t s1 |<2 ms. Therefore, after ephemeris calculation, the correction accuracy of the "space reduction" term can reach the order of 10 -3 mm, which can be ignored. Therefore, under the simultaneous same frequency full duplex system, the error of time scale reduction only needs to consider the "dynamic compensation" term, effectively improving the ranging accuracy.

[0123] Ninth, the device time delay, gravitational time delay, periodic relativistic effects, phase center deviation and other system errors are corrected to obtain the improved pseudo-range:

[0124]

[0125] wherein, with is the modified pseudo-range, with represents the sum of the residual error after time scale reduction and system error correction and the link measurement error.

[0126] The tenth step is to sum the two-way modified pseudo-range formula, and the inter-satellite distance can be obtained:

[0127]

[0128] wherein, ε d is the inter-satellite ranging error.

[0129] The eleventh step is to subtract the two-way modified pseudo-range formula, and the inter-satellite clock difference can be obtained:

[0130]

[0131] wherein, ε t is the inter-satellite time comparison error.

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[0158] In summary, the above is only the preferred embodiment of the present application, and is not intended to limit the scope of protection of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. An inter-satellite link bidirectional measurement method based on a simultaneous same frequency full duplex system, characterized in that, Comprise: First, the satellite With the satellite According to the time slot table, the inter-satellite link is established based on the respective satellite frequency standard. Second step, satellite With satellite Agree the same launch time, while sending the same structure of the information frame to the other party; Third step, both satellites received useful signal acquisition, tracking, demodulation, and restore information frame, and extract information frame from the transmission of the ephemeris time, the joint local ephemeris time to calculate the local pseudo-range; Fourth step, the calculated local pseudo-range embedded in the information frame to the other side, both sides by local pseudo-range calculated from the information frame demodulated pseudo-range, build out the inter-satellite two-way observation equation: wherein denotes the speed of light, denotes a satellite transmitting a signal receiving a measured pseudo-range value, denotes a satellite transmitting a signal receiving a measured pseudo-range value; denotes a satellite the system time of the system transmitting a signal, denotes a satellite the system time of the system receiving a signal, denotes a satellite the system time of the system transmitting a signal, denotes a satellite the system time of the system receiving a signal; and denotes a satellite the spatial position at the time of transmitting and receiving a signal, and denotes a satellite the spatial position at the time of transmitting and receiving a signal; and denotes a satellite the propagation distance of a signal transmitted by a satellite received by a satellite the propagation distance of a signal transmitted by a satellite received by a satellite the deviation of the satellite clock time from the navigation system time, the deviation of the satellite clock time from the navigation system time, is wherein, with denotes a satellite transmitting and receiving signals, the local clock face time, with denotes a satellite transmitting and receiving signals, the local clock face time; denote the transmit and receive channel delays of the satellite denote the transmit and receive channel delays of the satellite denote the transmit and receive channel delays of the satellite denote the transmit and receive channel delays of the satellite denote the transmit and receive channel delays of the satellite denote the transmit and receive channel delays of the satellite denote the transmit and receive channel delays of the satellite​​​​​​​ Step 5, the double time scale is reduced by the direct correction method, and the reduction time is selected as Then the double observation equation is corrected as wherein and is a satellite , a satellite a corresponding inter-satellite distance correction of the bi-directional measurement, is a clock correction from time to time denotes a clock correction from time to time denotes a clock correction from time to time denotes a clock correction from time to time denotes a clock correction from time to time denotes a clock correction from time to time denotes a clock correction from time to time denotes a clock correction from time to time denotes a clock correction from time to time Neglect clock difference correction, then: For distance correction, there is: Where: the running speed of the satellite , the running speed of the satellite , the unit directional vector of the satellite; and performing a first-order Taylor series expansion on and neglecting high-order terms, we have: Similarly, there is: representing the speed of the satellite in operation, representing the speed of the satellite pointing to the satellite unit direction vector of the satellite; The distance correction is written as: Sixth step, the system error including device delay, gravity delay, periodic relativistic effects, phase center offset correction, to get the improved pseudo-range: wherein, with to improve the pseudorange, with denotes the sum of the residual errors after time scale reduction and system error correction and the link measurement errors. The seventh step, the sum of the two-way improved pseudo-range formula, get the inter-satellite distance: wherein, is the inter-satellite ranging error; The eighth step, the difference between the two-way improved pseudo-range formula, get the inter-satellite clock difference: wherein, is the inter-satellite time comparison error.

2. The method according to claim 1, wherein, In the second step, the satellite With the satellite The baseband clock and carrier frequency are generated locally by each satellite, and there is no frequency and phase relationship constraint between the two satellites.

3. The method of claim 2, wherein the method is based on an inter-satellite link bi-directional measurement in a simultaneous transmit-receive (STAR) full duplex system. After the completion of the second step, also includes: when the signal reaches the satellite receiver, first in the antenna domain by active isolation and cancellation, to achieve about 100 dB self-interference suppression effect.

4. The method of claim 3, wherein the method is based on an inter-satellite link bi-directional measurement in a simultaneous transmit-receive (STAR) system. After the implementation of about 100 dB self-interference suppression effect, also includes: transceiver channel using superheterodyne system, to ensure that the same frequency self-interference does not make the channel saturation, using interference reconstruction cancellation network in the radio frequency domain to further suppress self-interference.

5. The method of claim 4, wherein the method is based on an inter-satellite link bi-directional measurement in a simultaneous transmit-receive (STAR) system. After the implementation of interference reconstruction cancellation network in the radio frequency domain to further suppress self-interference, also includes: on the basis of the conventional digital baseband transmission and reception module, increase the digital domain self-interference suppression processing, to suppress the space and radio cancellation into the digital baseband of self-interference.

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