A fast acquisition and tracking method for large frequency deviation signals

Abstract

A method for fast capture and tracking of large frequency deviation signals belongs to the field of communication technology. The method is based on ephemeris and inertial navigation information, calculates relative velocity vector and relative acceleration vector, estimates Doppler frequency deviation and frequency deviation change rate, pre-compensates the receiver, reduces the receiver's capture frequency range, effectively reduces the complexity of reception and speeds up the capture speed; based on the PMF-FFT frequency deviation estimation algorithm, the frequency is precisely estimated and compensated to achieve periodic frequency tracking; based on the estimation of downlink frequency deviation, the uplink signal is frequency compensated to achieve closed-loop frequency synchronization of satellite and high-dynamic platform. The method can effectively reduce the signal capture complexity of high-dynamic platform receivers under large frequency deviation and speed up the capture and synchronization speed.

Description

Technical Field

[0001] The invention relates to the technical field of electronic communications, and in particular to a method for quickly capturing and tracking a large frequency deviation signal. Background Art

[0002] As a supplement to the ground communication system, the satellite communication system has the characteristics of "seamless" coverage of the ground, and can effectively support the communication needs of special ground areas such as the sky, air, sea and desert. At present, the measurement and control information transmission of high-dynamic platforms mainly adopts ground-based measurement and control methods, and there are few space-based measurement and control methods. Therefore, using the global Internet satellite communication system to ensure the measurement and control information transmission of high-dynamic platforms has become an inevitable choice. At the same time, since the flight time of high-dynamic and high-mobility platforms is relatively short, from a few to more than ten minutes, the use of satellites to provide measurement and control links for high-dynamic platforms can ensure the real-time control and telemetry of high-dynamic platforms, and at the same time, the frequency hopping anti-interference system is used to ensure the reliability of the system.

[0003] However, since the distance and relative speed of the high-dynamic platform relative to the satellite are changing in real time, the signal will produce a large Doppler frequency deviation, and rapid signal capture and synchronization become practical problems. Summary of the invention

[0004] In order to solve the problems of rapid capture of large Doppler frequency offset signals and rapid frequency synchronization between satellite communication systems and high dynamic platforms, the present invention provides a method for rapid capture and tracking of large frequency offset signals. The method utilizes the Doppler frequency offset, Doppler frequency offset change rate and periodic pilot signal PMF-FFT frequency offset estimation method calculated by satellite ephemeris and high dynamic maneuvering platform inertial navigation to achieve compensation for the large Doppler frequency offset.

[0005] The method for quickly capturing and tracking a large frequency deviation signal provided by the present disclosure mainly comprises the following steps:

[0006] S1, based on the satellite ephemeris and the high-dynamic platform inertial navigation, calculate the relative velocity vector and relative acceleration vector of the satellite and the high-dynamic platform, and estimate the Doppler frequency deviation and Doppler frequency deviation change rate caused by the relative motion between the two;

[0007] S2, based on Doppler frequency deviation and Doppler frequency deviation change rate, performs coarse frequency compensation of high dynamic platform receiver;

[0008] S3, capturing the downlink based on PMF-FFT, and performing fine compensation for the downlink signal frequency according to the frequency deviation estimated by PMF-FFT;

[0009] S4, compensating the uplink synchronization detection signal frequency based on the downlink frequency offset estimation value;

[0010] S5: The satellite estimates the frequency difference of the uplink synchronization detection signal and feeds back the estimated value to the high dynamic platform. The high dynamic platform further adjusts the transmission frequency according to the frequency difference estimate fed back by the satellite until the frequency difference meets the requirement, thus completing the satellite-side frequency synchronization.

[0011] Furthermore, the step S1 specifically includes:

[0012] Obtain satellite information through the preset satellite ephemeris: Assume that the satellite is a geostationary GEO satellite, and the velocity vector is , the acceleration vector is , the default ephemeris remains basically unchanged;

[0013] According to the inertial navigation information of the high dynamic platform, the velocity vector is obtained as , the acceleration vector is ;

[0014] Calculate the relative velocity vector between the satellite and the high dynamic platform: ;

[0015] The Doppler frequency shift is estimated as ;

[0016] Calculate the relative acceleration vector between the satellite and the high dynamic platform: ,

[0017] The Doppler frequency shift rate is estimated to be ;

[0018] Among them, c is the speed of light 3e8m / s.

[0019] Furthermore, the high dynamic platform receiver frequency coarse compensation method in step S2 includes:

[0020] Assume the working frequency of the high dynamic platform receiver is , the frequency after compensation is :

[0021]

[0022] in, is the operating frequency, and the Doppler frequency deviation is , the Doppler frequency deviation change rate is , the high dynamic platform receiving working frequency is set to , to achieve rapid capture of downlink signals; t is time, with a typical value of 10ms, that is, the typical platform inertial navigation provides speed and acceleration frequency of 100 times / second.

[0023] Furthermore, the specific method of step S3 includes:

[0024] Assume that the frequency offset residual after the coarse compensation in step S2 is , then the PMF-FFT frequency capture window is , ;

[0025] The frequency deviation estimated by PMF-FFT is , then the frequency after compensation is :

[0026] .

[0027] Furthermore, in step S4, the frequency compensation method for the uplink synchronization detection signal includes:

[0028] Assume the downlink signal frequency is , the uplink signal frequency is , the downlink frequency offset estimation value is ;

[0029] Uplink and downlink frequency ratio: ;

[0030] The uplink signal frequency compensation is: .

[0031] Furthermore, the step S5 specifically includes:

[0032] The satellite estimates the frequency difference of the uplink synchronous detection signal;

[0033] Feeding the frequency difference estimation result back to the high dynamic platform;

[0034] The high dynamic platform makes judgments based on the frequency difference estimate fed back by the satellite:

[0035] If the frequency difference is ≤5KHz, the satellite link frequency synchronization is considered complete;

[0036] Otherwise, adjust the sending frequency and send the detection signal until the frequency difference is ≤5KHz.

[0037] Compared with the prior art, the present invention has the following beneficial effects: (1) Doppler frequency offset estimation based on ephemeris and inertial navigation information is used to pre-compensate the receiver, thereby avoiding signal capture of a high-dynamic platform receiver under large frequency offset, reducing the complexity of reception and speeding up the capture speed; (2) Based on the PMF-FFT frequency offset estimation algorithm, the receiving frequency offset is precisely estimated and compensated to ensure system performance and reduce the number of satellite-side frequency synchronization times; (3) Based on the satellite's frequency difference estimation of the uplink signal, the sending frequency is adjusted, and through the closed-loop feedback, the frequency synchronization and tracking are accelerated. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The above and other objects, features and advantages of the present disclosure will become more apparent through a more detailed description of exemplary embodiments of the present disclosure in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present disclosure.

[0039] Figure 1 The present invention is a flowchart of a method for quickly capturing and tracking a large frequency deviation signal according to the present invention. DETAILED DESCRIPTION

[0040] The preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0041] The present disclosure provides a method for quickly capturing and tracking a large frequency deviation signal. The processing flow of the exemplary embodiment is shown in the attached figure. Figure 1 As shown in the figure, the method includes the following steps:

[0042] (1) Relative velocity vector calculation based on satellite ephemeris and high dynamic platform inertial navigation

[0043] The satellite velocity vector of the ephemeris position information High dynamic platform velocity vector with inertial navigation position information .

[0044] Calculate the relative velocity vector between the satellite and the high dynamic platform: , that is, the relative speed between the satellite and the high dynamic platform is =± .

[0045] (2) Doppler frequency deviation estimation based on the relative speed between the satellite and the high dynamic platform

[0046] The Doppler frequency deviation caused by the relative speed between the satellite and the high dynamic platform is: ,Right now

[0047]

[0048] in is the operating frequency, c is the speed of light 3e8m / s.

[0049] (3) Relative acceleration vector calculation based on satellite ephemeris and high dynamic platform inertial navigation

[0050] The satellite acceleration vector of the ephemeris position information High dynamic platform acceleration vector and inertial navigation position information .

[0051] Calculate the relative acceleration vector between the satellite and the high dynamic platform: , that is, the relative acceleration of the high-orbit satellite and the high-dynamic platform is =± .

[0052] (4) Estimation of Doppler frequency deviation change rate caused by the relative speed between the satellite and the high dynamic platform

[0053] The Doppler frequency deviation change rate caused by the relative speed of the satellite and the high dynamic platform is ,Right now

[0054]

[0055] in is the operating frequency, and the Doppler frequency deviation is , the Doppler frequency deviation change rate is , c is the speed of light 3e8m / s.

[0056] (5) High dynamic platform receiver frequency coarse compensation based on Doppler frequency offset and Doppler frequency offset change rate:

[0057] The operating frequency of the high dynamic platform receiver is , the frequency after compensation is ,

[0058]

[0059] (6) Capture the downlink based on PMF-FFT, and perform fine frequency offset estimation and compensation:

[0060] Assume the frequency deviation estimated by PMF-FFT is , to achieve fine compensation for downlink signal frequency :

[0061]

[0062] (7) For uplink signals (frequency ) for frequency compensation, the frequency after compensation is :

[0063]

[0064]

[0065] (8) The satellite estimates the frequency difference of the uplink frequency compensated signal, and the estimated value is ;

[0066] The estimated value result is fed back to the high dynamic platform. The high dynamic platform determines whether the satellite-side frequency synchronization is completed according to the frequency difference estimated value fed back by the satellite. If it does not meet the requirements, the transmission frequency is further adjusted until When it is not greater than 5KHz, it is considered that the closed-loop frequency synchronization of the satellite and the high-dynamic platform is completed.

[0067] The above technical scheme is only an exemplary embodiment of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the application methods and principles disclosed in the present invention, and it is not limited to the method described in the above specific embodiment of the present invention. Therefore, the method described above is only preferred and does not have a restrictive meaning.

Claims

1. A method for quickly capturing and tracking a large frequency deviation signal, comprising the following steps: S1, based on the satellite ephemeris and the high-dynamic platform inertial navigation, calculate the relative velocity vector and relative acceleration vector of the satellite and the high-dynamic platform, and estimate the Doppler frequency deviation and Doppler frequency deviation change rate caused by the relative motion between the two; S2, based on Doppler frequency deviation and Doppler frequency deviation change rate, performs coarse frequency compensation of high dynamic platform receiver; S3, capturing the downlink based on PMF-FFT, and performing fine compensation for the downlink signal frequency according to the frequency deviation estimated by PMF-FFT; S4, compensating the uplink synchronization detection signal frequency based on the downlink frequency offset estimation value; S5: The satellite estimates the frequency difference of the uplink synchronization detection signal and feeds back the estimated value to the high dynamic platform. The high dynamic platform further adjusts the transmission frequency according to the frequency difference estimated value fed back by the satellite until the frequency difference meets the requirement, thus completing the satellite-side frequency synchronization. Wherein, the step S1 specifically includes: Obtain satellite information through the preset satellite ephemeris: Assume that the satellite velocity vector is , the acceleration vector is , the default ephemeris remains unchanged; According to the inertial navigation information of the high dynamic platform, the velocity vector is obtained as , the acceleration vector is ; Calculate the relative velocity vector between the satellite and the high dynamic platform: ; The Doppler frequency shift is estimated as ; Calculate the relative acceleration vector between the satellite and the high dynamic platform: , The Doppler frequency shift rate is estimated to be ; Where c is the speed of light 3e8m / s, is the downlink signal frequency; The high dynamic platform receiver frequency coarse compensation method in step S2 includes: Assume that the working frequency of the high dynamic platform receiver before compensation is , which is the downlink signal frequency, the frequency after compensation is : The Doppler frequency deviation change rate is , That is, after compensation, the operating frequency of the high dynamic platform receiver is set to , to achieve rapid capture of downlink signals; t is time, which is 10ms, that is, the platform inertial navigation provides speed and acceleration frequency 100 times / second.

2. The method according to claim 1, characterized in that The specific method of step S3 includes: Assume that the frequency offset residual after the coarse compensation in step S2 is , then the PMF-FFT frequency capture window is , ; The frequency deviation estimated by PMF-FFT is , then the frequency after compensation is : 。 3. The method according to claim 2, characterized in that In step S4, the frequency compensation method for the uplink synchronization detection signal includes: Assume the downlink signal frequency is , the uplink signal frequency is , the downlink frequency offset estimation value is ; Uplink and downlink frequency ratio: ; The uplink signal frequency compensation is: .

4. The method according to any one of claims 1 to 3, characterized in that: The step S5 specifically includes: The satellite estimates the frequency difference of the uplink synchronous detection signal; Feeding the frequency difference estimation result back to the high dynamic platform; The high dynamic platform makes judgments based on the frequency difference estimate fed back by the satellite: If the frequency difference is ≤5KHz, the satellite link frequency synchronization is considered complete; Otherwise, adjust the sending frequency and send the detection signal until the frequency difference is ≤5KHz.

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