Ultrahigh frequency subsequent satellite uplink and downlink signal time difference extraction method and system

Abstract

The invention relates to an ultrahigh frequency subsequent satellite uplink and downlink signal time difference extraction method and system. The method comprises the following steps: step 1, accessing uplink and downlink signals; step 2, frequency spectrum scanning carrier detection; step 3, estimating modulation identification parameters; step 4, identifying channel codes; step 5, identifying a specific signal; step 6, extracting user data; step 7, performing uplink and downlink matched filtering; and step 8, time difference estimation. Through UFO satellite signal detection, specific signal identification, specific user data extraction and UFO satellite uplink and downlink signal time difference estimation based on specific user signal data, the problems of user data separation, uplink and downlink time delay estimation of different users and the like under a UFO satellite TDMA system are effectively solved; timing mechanism monitoring and processing of a UFO satellite TDMA system can be effectively supported.

Description

Technical Field

[0001] The invention belongs to the technical field of monitoring and processing of ultra-high frequency follow-up satellite signals, and in particular relates to a method and system for extracting time differences of uplink and downlink signals of ultra-high frequency follow-up satellites. Background Art

[0002] The specific satellite is the UHF follow-on satellite (UFO). Each UFO satellite provides 39 UHF channels, including 21 5kHz narrowband channels, 17 25kHz relay channels and 1 25kHz fleet broadcast channel. It adopts the TDMA system, and different users use pre-allocated or dynamically allocated time slots for communication. Since the UFO satellite uses the UHF frequency band and the satellite beam is wide, when monitoring and processing the uplink and downlink signals of the UFO satellite, it is first necessary to detect and identify the uplink and downlink signals of the UFO satellite in the UHF frequency band. The UFO satellite communication adopts the TDMA system. After detecting and identifying the uplink and downlink signals of the UFO satellite, it is also necessary to distinguish different users who use the same frequency for communication, that is, it is necessary to extract the time slot data of different users. On the basis of completing the above processing, the signal data and other data used by the user for ranging are extracted, the uplink and downlink signal matching of the same user is completed, and finally the time difference estimation of the uplink and downlink signals of the UFO satellite is completed. How to achieve user data separation under the TDMA system of the UFO satellite, the uplink and downlink delay estimation of different users, and meet the needs of UFO satellite signal monitoring and processing is a problem that needs to be solved. Summary of the invention

[0003] The purpose of the present invention is to provide a method and system for extracting the time difference of uplink and downlink signals of a UHF successor satellite. Through the technologies of UFO satellite uplink and downlink signal detection and identification, UFO satellite signal user data extraction, uplink and downlink signal matching, cross-correlation time difference extraction, etc., the time difference extraction of UFO satellite uplink and downlink signals is realized, and the network access process of specific users in the UFO satellite uplink and downlink signals and the timing synchronization of specific users during the network are monitored, so as to support the monitoring of the TDMA system timing mechanism of the UFO satellite and use the timing mechanism to realize further monitoring and processing of the system.

[0004] The present invention provides a method for extracting time difference of uplink and downlink signals of a UHF successor satellite, comprising the following steps:

[0005] Step 1: Access the UFO satellite uplink and downlink signals through two signal channels;

[0006] Step 2: Perform spectrum scanning and carrier detection on the signals of the two channels respectively, and perform burst signal detection on the detected UFO satellite uplink and downlink signals to confirm whether they are irregular burst signals;

[0007] Step 3, respectively perform nonlinear transformation on the signals detected by the two channels, perform spectrum analysis on the transformed signals, detect the peak of the spectrum data, complete the modulation recognition including BPSK, QPSK, CPM, FSK signals according to the distribution characteristics of the spectrum peak, and estimate the signal carrier frequency and modulation rate according to the spectrum peak;

[0008] Step 4, demodulate the signal according to the signal modulation identification result to obtain demodulated data, calculate the bit difference of the demodulated data, determine the data transmission structure, calculate and verify the check relationship of the demodulated data according to the data transmission structure and the template information of the specific protocol, and complete the channel coding identification of the demodulated data according to the identification matching template of the convolutional code and the RS code and the data structure characteristics and the data check relationship;

[0009] Step 5, according to the specific protocol type, a specific signal identification feature library is constructed based on features including but not limited to signal preamble, modulation mode, modulation rate, channel coding mode, code rate, and burst time length, and the specific signal type is identified by using the signal identification feature library and a classic pattern recognition algorithm;

[0010] Step 6, determining the time slot and length occupied by the specific user data according to the data transmission division of the specific signal, and extracting the specific user data according to the time slot and length occupied by the specific user data;

[0011] Step 7: using the user data extracted from one of the two uplink and downlink signal channels as a template, performing matched filtering on the data of the other signal channel to complete the rough alignment of the data;

[0012] Step 8, use the phase spectrum delay estimation method to calculate the cross-power spectrum of the uplink and downlink signals, perform frequency domain weighted processing on the cross-power spectrum, use the weighted cross-power spectrum to estimate the phase corresponding to each frequency, and obtain the estimated value of the phase function, use the phase estimation value to complete a delay estimation, weight the single delay estimation, and then accumulate multiple weighted delay estimation values ​​to finally obtain the time difference of the UFO satellite uplink and downlink signals.

[0013] Furthermore, the two signal channels in step 1 satisfy two 30 MHz bandwidth signal accesses.

[0014] Furthermore, the step 2 comprises:

[0015] The maximum hold algorithm is used to process the scanned spectrum, the adaptive following noise extraction algorithm is used to estimate the noise floor in the scanned frequency band, and the multi-threshold method is used to detect the signal in the frequency domain;

[0016] The dynamic sliding double-window method is used to perform time domain energy detection to determine whether it is a burst signal and roughly locate the start and end points of the burst;

[0017] After confirming that it is a burst signal, the burst start and end points of the signal are accurately measured through wavelet transform, and the burst length and burst period of the burst signal are measured.

[0018] Furthermore, the identifiable signal types in step 5 include: CCOW, RCCOW, RANGE, LinkTest, and UserData.

[0019] Furthermore, the step 8 specifically includes:

[0020] 1) Calculate the user data power spectrum X1(f) of channel 1;

[0021] 2) Calculate the signal power spectrum X2(f) of the roughly aligned channel 2;

[0022] 3) Calculate the cross power spectrum

[0023] 4) Cross-power spectrum weighting processing;

[0024] 5) Calculate the phase function of the cross power spectral density function

[0025] 6) Calculate the estimated value of the delay

[0026] 7) Weight the single delay estimation value to obtain the final delay estimation value.

[0027] The present invention also provides a system for extracting time differences between uplink and downlink signals of a UHF successor satellite, comprising a time difference extraction module, wherein the time difference extraction module executes the method for extracting time differences between uplink and downlink signals of a UHF successor satellite.

[0028] The present invention also provides a non-transitory computer-readable storage medium, which stores computer instructions. When the computer instructions are executed by a processor, the method for extracting the time difference between uplink and downlink signals of a UHF successor satellite is implemented.

[0029] The present invention also provides an electronic device, comprising:

[0030] A memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the method for extracting time differences between uplink and downlink signals of a UHF successor satellite by executing the computer instructions.

[0031] By means of the above scheme, through the UHF follow-up satellite uplink and downlink signal time difference extraction method and system, through UFO satellite signal detection, specific signal identification, specific user data extraction, and UFO satellite uplink and downlink signal time difference estimation based on specific user signal data, the problems of user data separation under the UFO satellite TDMA system, uplink and downlink delay estimation of different users, etc. are effectively solved, which can effectively support the monitoring and processing of the timing mechanism of the UFO satellite TDMA system.

[0032] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a flow chart of the method for extracting the time difference of uplink and downlink signals of UHF successor satellite of the present invention;

[0034] Figure 2 This is a flow chart of spectrum scanning carrier detection of the present invention;

[0035] Figure 3 This is a specific signal identification flow chart of the present invention;

[0036] Figure 4 The figure is a schematic diagram of an electronic device according to the present invention. DETAILED DESCRIPTION

[0037] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0038] Ginseng Figure 1 As shown, this embodiment provides a method for extracting the time difference of uplink and downlink signals of a UHF successor satellite. First, the UHF frequency band signal is accessed, and then the specific user target data is extracted, the uplink and downlink data of the user are matched, the uplink and downlink time difference is estimated, and finally the time difference calculation of the uplink and downlink signals of the UFO satellite is realized. The specific process is as follows:

[0039] 1) Uplink and downlink signal access

[0040] UFO satellite uplink and downlink signal time difference extraction requires access to UFO satellite uplink and downlink signals. In order to meet the full probability signal detection and time difference extraction, uplink and downlink signal access meets 2 30MHz bandwidth signal access.

[0041] 2) Spectrum scanning carrier detection

[0042] The signals of the two channels are spectrally scanned respectively, and the maximum value holding algorithm is used to process the scanned spectrum. The processed spectrum data is used for signal detection in the frequency domain. The adaptive following noise extraction algorithm is used to estimate the noise floor in the scanning frequency band, and the multi-threshold method is used to detect the signal in the frequency domain. After the signal detection in the frequency domain is completed, the time domain energy detection is continued. The time domain energy detection uses a dynamic sliding double window method to detect whether it is a burst signal and roughly locate the start and end points of the burst. After confirming that it is a burst signal, the burst start and end points of the signal are accurately measured through wavelet transform, and the burst length, burst period and other values ​​of the burst signal are measured.

[0043] 3) Modulation identification parameter estimation

[0044] The signals detected by the two channels are respectively transformed nonlinearly, and the spectrum analysis is performed on the transformed signals to detect the peak values ​​of the spectrum data. According to the distribution characteristics of these spectrum peak values, the modulation recognition of BPSK, QPSK, CPM, FSK and other signals is completed, and the signal carrier frequency, modulation rate and other parameters are estimated according to the spectrum peak values.

[0045] 4) Channel coding identification

[0046] After completing the signal modulation identification of the two channels, the signal is demodulated according to the identification results to obtain demodulated data of a certain length. The bit difference of the demodulated data is calculated to determine the data transmission structure. According to the data transmission structure, combined with the template information of the specific protocol, the verification relationship of the demodulated data is calculated and verified. Finally, according to the identification and matching template of the convolutional code and RS code, combined with the data structure characteristics and data verification relationship, the channel coding identification of the demodulated data is completed.

[0047] 5) Specific signal recognition

[0048] According to the specific protocol type, a specific signal identification feature library is constructed based on the signal preamble, modulation mode, channel coding mode, burst time length, etc. The signal identification feature library is used to identify the specific signal type using the classic pattern recognition algorithm. The identifiable signal types include: CCOW, RCCOW, RANGE, Link Test, User Data, etc. The specific signal identification process is as follows: Figure 3 shown.

[0049] 6) User data extraction

[0050] According to the data transmission division of the specific signal, the time slot and length occupied by the specific user data are determined. The specific user data is extracted according to the time slot and length occupied by the specific user data. The user data that can be extracted supports 25kHz channels of format 1 and format 2, as well as specific user data of 5kHz channels.

[0051] 7) Uplink and downlink matched filtering

[0052] Using the user data extracted from a certain channel, such as the downlink signal channel, as a template, matched filtering is performed on the data of another channel to complete the rough alignment of the data.

[0053] 8) Time difference estimation

[0054] Based on uplink and downlink matched filtering, the phase spectrum delay estimation method is used to estimate the time difference between uplink and downlink signals.

[0055] The basic principle of phase spectrum delay estimation: According to the Wiener-Hinchin theorem, the correlation function of a signal and its power spectrum are Fourier transforms of each other. The delay D of the correlation function is expressed as the phase function of the power spectrum density function in the frequency domain through Fourier transform, that is, In this way, the estimated value of the delay is obtained by the phase estimate of the power spectral density function:

[0056] In order to improve the estimation performance of the algorithm under low signal-to-noise ratio, the power spectral density function can be pre-whitened, that is, weighted in the frequency domain, just like the generalized correlation delay estimation method.

[0057] To further improve the estimation performance, multiple estimation values ​​may be weighted to obtain the final time difference estimation value.

[0058] The steps of estimating the time difference of UFO satellite uplink and downlink signals by phase spectrum delay are as follows:

[0059] ① Calculate the user data power spectrum X1(f) of channel 1

[0060] ② Calculate the signal power spectrum X2(f) of channel 2 after rough alignment

[0061] ③ Calculate the cross power spectrum

[0062] ④ Cross-power spectrum weighting processing

[0063] ⑤ Calculate the phase function of the cross power spectral density function

[0064] ⑥Calculate the estimated value of the delay

[0065] ⑦ Weight the single delay estimate to obtain the final delay estimate.

[0066] The present invention detects the UFO satellite uplink and downlink signals by performing spectrum scanning signal detection on the accessed UHF frequency band signal, and adopts dynamic adaptive technology to detect and discover the UFO satellite uplink and downlink signals, especially to accurately detect and discover the irregular burst signals using the TDMA system, and realizes the matching of the uplink and downlink signals through the matched filtering of the uplink and downlink channels, and performs rough alignment in time. The detection of UFO uplink and downlink signals lays the foundation for the monitoring of UFO satellite uplink and downlink signals.

[0067] The present invention establishes a specific signal feature library based on the preamble, burst time length, modulation mode, modulation rate, coding mode, code rate and other data of the UFO satellite uplink and downlink signals, combined with specific protocol information. The signal feature library is used to adopt a classic pattern recognition algorithm to achieve specific signal recognition.

[0068] The present invention is based on a generalized phase spectrum delay estimation algorithm. When the uplink and downlink signals are roughly aligned by matched filtering, the mutual power spectrum of the uplink and downlink signals is calculated and pre-whitened, that is, frequency domain weighting is performed. The weighted mutual power spectrum is used to estimate the phase corresponding to each frequency to obtain an estimated value of the phase function. The phase estimate is used to calculate the delay and complete a delay estimation. In order to improve the estimation accuracy and to improve the estimation performance under the condition of deterioration of the signal-to-noise ratio, the present invention weights a single delay estimation, accumulates multiple delay estimates, and finally obtains the time difference of the uplink and downlink signals of the UFO satellite, supporting the monitoring and further processing of the UFO satellite timing mechanism.

[0069] The present invention effectively solves the problems of user data separation under the UFO satellite TDMA system, uplink and downlink delay estimation of different users, etc. through UFO satellite signal detection, specific signal recognition, specific user data extraction, and UFO satellite uplink and downlink signal time difference estimation based on specific user signal data, and can effectively support the monitoring and processing of the timing mechanism of the UFO satellite TDMA system.

[0070] The present embodiment also provides a system for extracting the time difference of uplink and downlink signals of a UHF successor satellite, comprising a time difference extraction module, wherein the time difference extraction module executes the method for extracting the time difference of uplink and downlink signals of a UHF successor satellite.

[0071] This embodiment also provides a non-transitory computer-readable storage medium, which stores computer instructions. When the computer instructions are executed by a processor, the method for extracting the time difference between uplink and downlink signals of a UHF successor satellite is implemented.

[0072] Ginseng Figure 4 As shown, this embodiment also provides an electronic device, including:

[0073] A memory 201 and a processor 202, wherein the memory 201 and the processor 202 are communicatively connected to each other, the memory 201 stores computer instructions, and the processor 202 executes the computer instructions to execute the method for extracting the time difference of uplink and downlink signals of a UHF successor satellite.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the technical principles of the present invention, and these improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for extracting time difference of uplink and downlink signals of UHF successor satellite, characterized in that: The steps include: Step 1: Access the UFO satellite uplink and downlink signals through two signal channels; Step 2: Perform spectrum scanning and carrier detection on the signals of the two channels respectively, and perform burst signal detection on the detected UFO satellite uplink and downlink signals to confirm whether they are irregular burst signals; Step 3, respectively perform nonlinear transformation on the signals detected by the two channels, perform spectrum analysis on the transformed signals, detect the peak of the spectrum data, complete the modulation recognition including BPSK, QPSK, CPM, FSK signals according to the distribution characteristics of the spectrum peak, and estimate the signal carrier frequency and modulation rate according to the spectrum peak; Step 4, demodulate the signal according to the signal modulation identification result to obtain demodulated data, calculate the bit difference of the demodulated data, determine the data transmission structure, calculate and verify the check relationship of the demodulated data according to the data transmission structure and the template information of the specific protocol, and complete the channel coding identification of the demodulated data according to the identification matching template of the convolutional code and the RS code and the data structure characteristics and the data check relationship; Step 5, according to the specific protocol type, a specific signal identification feature library is constructed based on features including but not limited to signal preamble, modulation mode, modulation rate, channel coding mode, code rate, and burst time length, and the specific signal type is identified by using the signal identification feature library and a classic pattern recognition algorithm; Step 6, determining the time slot and length occupied by the specific user data according to the data transmission division of the specific signal, and extracting the specific user data according to the time slot and length occupied by the specific user data; Step 7: using the user data extracted from one of the two uplink and downlink signal channels as a template, performing matched filtering on the data of the other signal channel to complete the rough alignment of the data; Step 8, use the phase spectrum delay estimation method to calculate the cross-power spectrum of the uplink and downlink signals, perform frequency domain weighted processing on the cross-power spectrum, use the weighted cross-power spectrum to estimate the phase corresponding to each frequency, and obtain the estimated value of the phase function, use the phase estimation value to complete a delay estimation, weight the single delay estimation, and then accumulate multiple weighted delay estimation values ​​to finally obtain the time difference of the UFO satellite uplink and downlink signals.

2. The method for extracting time difference of uplink and downlink signals of UHF successor satellite according to claim 1, characterized in that: In step 1, the two signal channels meet the requirements for two 30 MHz bandwidth signal accesses.

3. The method for extracting time difference of uplink and downlink signals of UHF successor satellite according to claim 1, characterized in that: The step 2 comprises: The maximum hold algorithm is used to process the scanned spectrum, the adaptive following noise extraction algorithm is used to estimate the noise floor in the scanned frequency band, and the multi-threshold method is used to detect the signal in the frequency domain; The dynamic sliding double-window method is used to perform time domain energy detection to determine whether it is a burst signal and roughly locate the start and end points of the burst; After confirming that it is a burst signal, the burst start and end points of the signal are accurately measured through wavelet transform, and the burst length and burst period of the burst signal are measured.

4. The method for extracting time difference of uplink and downlink signals of UHF successor satellite according to claim 3, characterized in that: The identifiable signal types in step 5 include: CCOW, RCCOW, RANGE, Link Test, and User Data.

5. The method for extracting time difference of uplink and downlink signals of UHF successor satellite according to claim 4, characterized in that: The step 8 specifically includes: 1) Calculate the user data power spectrum X1(f) of channel 1; 2) Calculate the signal power spectrum X2(f) of the roughly aligned channel 2; 3) Calculate the cross power spectrum 4) Cross-power spectrum weighting processing; 5) Calculate the phase function of the cross power spectral density function 6) Calculate the estimated value of the delay 7) Weight the single delay estimation value to obtain the final delay estimation value.

6. A system for extracting time difference between uplink and downlink signals of UHF successor satellites, characterized in that: It comprises a time difference extraction module, and the time difference extraction module executes the method for extracting the time difference of uplink and downlink signals of a UHF successor satellite as described in any one of claims 1-5.

7. A non-transitory computer-readable storage medium, characterized in that: The non-transitory computer-readable storage medium stores computer instructions, and when the computer instructions are executed by the processor, a method for extracting time differences between uplink and downlink signals of a UHF successor satellite is implemented as described in any one of claims 1 to 5.

8. An electronic device, characterized in that: include: A memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the method for extracting time difference of uplink and downlink signals of a UHF successor satellite as described in any one of claims 1 to 5 by executing the computer instructions.

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