CN108011653B - Self-adaptive rapid capture tracking system and method - Google Patents
Self-adaptive rapid capture tracking system and method Download PDFInfo
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- CN108011653B CN108011653B CN201711344263.4A CN201711344263A CN108011653B CN 108011653 B CN108011653 B CN 108011653B CN 201711344263 A CN201711344263 A CN 201711344263A CN 108011653 B CN108011653 B CN 108011653B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7073—Synchronisation aspects
- H04B1/7087—Carrier synchronisation aspects
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7073—Synchronisation aspects
- H04B1/7075—Synchronisation aspects with code phase acquisition
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
- H04L7/02—Speed or phase control by the received code signals, the signals containing no special synchronisation information
- H04L7/033—Speed or phase control by the received code signals, the signals containing no special synchronisation information using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
- H04L7/0016—Arrangements for synchronising receiver with transmitter correction of synchronization errors
- H04L7/002—Arrangements for synchronising receiver with transmitter correction of synchronization errors correction by interpolation
- H04L7/0025—Arrangements for synchronising receiver with transmitter correction of synchronization errors correction by interpolation interpolation of clock signal
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
- H04L7/02—Speed or phase control by the received code signals, the signals containing no special synchronisation information
- H04L7/027—Speed or phase control by the received code signals, the signals containing no special synchronisation information extracting the synchronising or clock signal from the received signal spectrum, e.g. by using a resonant or bandpass circuit
- H04L7/0274—Speed or phase control by the received code signals, the signals containing no special synchronisation information extracting the synchronising or clock signal from the received signal spectrum, e.g. by using a resonant or bandpass circuit with Costas loop
Abstract
The invention discloses a self-adaptive rapid capturing and tracking system and a method, wherein the system comprises: the high-dynamic direct-spread source module comprises a high-dynamic direct-spread baseband signal generating module and an up-conversion module, wherein the high-dynamic direct-spread baseband signal generated by the high-dynamic direct-spread baseband signal generating module is converted into a radio frequency band by the up-conversion module and is transmitted; the baseband rapid capturing and tracking module comprises a down-conversion module, an AD sampling module, an accumulation calculation module, an energy comparison module, a timing feedback module, a signal compensation module, an initialization frequency and pseudo code phase module, a pseudo code tracking module, a de-spreading module, a carrier tracking module, a demodulation module, a bit synchronization module, a data recovery module and a bit error rate statistics module. The method has the advantages of estimating the frequency and the pseudo code phase of the signal, quickly finishing the acquisition and tracking, occupying less space vehicle system resources, being simple and convenient to verify and being capable of quickly acquiring and tracking.
Description
Technical Field
the invention relates to a self-adaptive rapid acquisition tracking system and a method, belonging to the technical field of spacecraft receiving equipment.
background
The ground model measurement station and the measurement and control station have different equipment, different signal-to-noise ratio switching exists, the signal-to-noise ratio is changed along with the launching of the spacecraft, and in addition, the received signal contains large Doppler frequency shift and first and second derivatives thereof due to acceleration and jerk generated by relative motion. Under the conditions of self-adaptive signal-to-noise ratio and high dynamic, the rapid acquisition and tracking of the signals are key technologies to be solved by a spacecraft receiver, and have an important position in the national information security strategy.
At present, system performance verification of a spacecraft receiver can be divided into simulation verification and flight verification. The simulation verification is that in a laboratory environment, a high-dynamic direct sequence spread source module is used for carrying out baseband signal simulation on a transmitting signal, so that at the present that the resources of a measurement and control station are in shortage, the high-dynamic direct sequence spread source module occupies less resources, in addition, basic parameters of the high-dynamic direct sequence spread source module can be configured, wireless channel characteristics (such as various interference modes of single tone, narrow band, broadband, multi-tone, frequency sweep, frequency hopping and the like) can also be conveniently selected to be added in one or more modes, the simulation verification undoubtedly has great advantages, and the reliability of the simulation verification is favorably improved. The most important link in the simulation verification is to require that all system indexes of the receiver exceed the requirement of flight verification and reserve margin.
The performance verification of the spacecraft receiver system can be realized by utilizing the technology. However, under different signal-to-noise ratios and high dynamic environments (such as foreign GPS, Beidou system and measurement and control satellite in China), not only the capturing time but also the capturing success rate are ensured. This is a severe challenge for spacecraft receiver design.
disclosure of Invention
The invention aims to solve the problems that the existing capturing and tracking system occupies large equipment complexity, is difficult to verify and cannot realize capturing and tracking rapidly,
The technical means for solving the problem is to provide a system and a method for self-adapting high-low signal-to-noise ratio and high-dynamic direct sequence spread spectrum signals, thereby realizing rapid acquisition and tracking. The invention specifically adopts the following technical scheme to solve the technical problems:
an adaptive-based fast acquisition tracking system, comprising:
the high-dynamic direct-spread source module comprises a high-dynamic direct-spread baseband signal generating module and an up-conversion module, wherein the high-dynamic direct-spread baseband signal generated by the high-dynamic direct-spread baseband signal generating module is converted into a radio frequency band by the up-conversion module and is transmitted;
The baseband fast capturing and tracking module comprises a down-conversion module, an AD sampling module, an accumulation calculation module, an energy comparison module, a timing feedback module, a signal compensation module, an initialization frequency and pseudo code phase module, a pseudo code tracking module, a de-spreading module, a carrier tracking module, a demodulation module, a bit synchronization module, a data recovery module and an error rate statistics module, wherein after the down-conversion module receives signals through a wireless channel, radio frequency band signals are converted into baseband signals, and after the signals are sampled by the AD sampling module, the accumulation calculation module combines the data rate and the frequency offset to carry out segmentation according to the Doppler frequency of a carrier wave, and coherent and incoherent accumulation is carried out; the energy comparison module judges and selects the maximum value of the comparison according to the accumulated result of the accumulation calculation module, the timing feedback module generates a timing pulse according to the judged result of the energy comparison module, and the signal compensation module controls the accumulated frequency according to the timing pulse and searches the whole Doppler frequency range of the carrier wave to obtain a confirmation value; the initialization frequency and pseudo code phase module converts the confirmation value of the timing feedback module into frequency and pseudo code phase and inputs the frequency and pseudo code phase into the pseudo code tracking module and the carrier tracking module respectively; the pseudo code tracking module performs pseudo code tracking after adjacent chips on the left and right of the initialized pseudo code phase are confirmed again, and the baseband data and the pseudo code are stripped by the despreading module; the carrier tracking module is used for carrying out timing update on the carrier phase through a phase-locked loop after the frequency discrimination result assists the acceleration and speed components, and correcting and compensating the real-time residual error to the pseudo code tracking module; the demodulation module carries out coherent demodulation according to the phase after carrier tracking obtained by the carrier tracking module, and after a bit synchronization module generates timing interpolation and adjusts a bit timing clock, a data recovery module detects a synchronous word sequence in data by using bit timing and aligns the data according to a frame format to obtain recovered data; and the error rate statistic module compares the high-dynamic direct-sequence spread spectrum source data source with the obtained recovery data bit by bit to calculate the system error rate.
Further, as a preferred technical solution of the present invention: the high-dynamic direct-spread baseband signal generating module generates a high-dynamic direct-spread baseband signal which can configure speed, acceleration and jerk.
Further, as a preferred technical solution of the present invention: the accumulation calculation module is used for taking absolute values and adding the absolute values through an FIR filter after the data rate and the frequency deviation are combined and segmented according to the Doppler frequency of the carrier wave so as to achieve the required capture signal-to-noise ratio.
Further, as a preferred technical solution of the present invention: the AD sampling module adopts an AD9148 type digital-to-analog converter.
further, as a preferred technical solution of the present invention: the accumulation calculation module adopts a V5SX95T type FPGA chip.
the invention provides a self-adaptive rapid acquisition tracking system and a method thereof, wherein the method comprises the following steps:
The generated high dynamic direct sequence spread spectrum baseband signal is converted to a radio frequency band and is sent;
Changing the received radio frequency band signal into a baseband signal, segmenting the carrier Doppler frequency by combining the data rate and the frequency offset after sampling, and performing coherent and noncoherent accumulation; judging and selecting the maximum value of the comparison according to the accumulated result, and generating a timing pulse according to the judgment result; controlling the accumulated frequency according to the timing pulse, searching the whole dynamic range of the carrier to obtain a confirmation value, converting the confirmation value into frequency and a pseudo code phase, and respectively carrying out pseudo code tracking and carrier tracking;
The pseudo code tracking comprises the steps of confirming adjacent chips on the left and right sides of an initialized pseudo code phase again, tracking the pseudo code, stripping baseband data and the pseudo code, and sending the stripped baseband data and the pseudo code into carrier tracking; the carrier tracking comprises the steps of carrying out timing updating on the carrier phase through a phase-locked loop after the frequency discrimination result assists acceleration and speed components, and correcting and compensating real-time residual errors to a pseudo code tracking process; carrying out coherent demodulation according to the phase tracked by the obtained carrier, detecting a synchronous word sequence in data by using bit timing after generating timing interpolation and adjusting a bit timing clock, and aligning the data according to a frame format to obtain recovered data; and comparing the high-dynamic direct sequence spread spectrum source data source with the obtained recovery data bit by bit, and counting the error rate of the system.
further, as a preferred technical solution of the present invention: in the method, a high-dynamic direct spread baseband signal with configurable speed, acceleration and jerk is generated.
Further, as a preferred technical solution of the present invention: in the method, after the pseudo code frequency is segmented by combining the data rate and the frequency offset, absolute values are taken and added through an FIR filter to achieve the required capture signal-to-noise ratio.
further, as a preferred technical solution of the present invention: in the method, when the whole dynamic range of the carrier wave is searched to obtain the confirmation value, the maximum value is searched again only for the initial pseudo code adjacent phase for confirming again.
Effects of the invention
By adopting the technical scheme, the invention can produce the following technical effects:
The invention provides a self-adaptive rapid acquisition tracking system and a method thereof, which are a rapid acquisition tracking system with less equipment complexity and simple and convenient verification, and are used for adaptively judging the signal-to-noise ratio of a signal, confirming the initialization frequency and the pseudo code phase and compensating a direct-spread signal so as to realize rapid acquisition tracking. Compared with the prior art, the invention has the following advantages:
(1) The invention estimates the expected signal of the system without using inertial navigation data
The frequency and the pseudo code phase can quickly complete the acquisition and tracking, and occupy less space vehicle system resources;
(2) The invention has great flexibility in the stage of analog verification by the high dynamic direct spread source module, saves testing instruments and meters by the superposition of dynamic and channel characteristics on the baseband, has the function of analog flight verification, can provide direct connection of a baseband interface, and provides a radio frequency interface by only one up-converter.
(3) The invention depends on the data rate and the dynamic performance requirement, the accumulation calculation module and the signal compensation module can be divided, and different receiver performances can be realized according to the system requirement and the hardware resource condition.
(4) the energy comparison module and the timing feedback module realize the estimation of accurate frequency and pseudo code phase under different signal-to-noise ratio environments; the frequency and the pseudo code phase precision can be adjusted according to the system requirements and the hardware resource conditions.
Drawings
FIG. 1 is a schematic diagram of the system of the present invention.
Fig. 2 is a schematic diagram of the working principle of the high dynamic direct spread source module of the present invention.
Fig. 3 is a schematic diagram of the operating principle of the baseband fast acquisition tracking module of the present invention.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings.
The following describes embodiments of the present invention with reference to the drawings.
As shown in fig. 1, the present invention provides an adaptive fast acquisition tracking system, which mainly includes: the system comprises a high-dynamic direct spread source module and a baseband quick acquisition tracking module.
The high-dynamic direct-spread source module comprises a high-dynamic direct-spread baseband signal generating module and an up-conversion module, wherein the high-dynamic direct-spread baseband signal generated by the high-dynamic direct-spread baseband signal generating module is converted into a radio frequency band through the up-conversion module and is transmitted;
The baseband fast capturing and tracking module comprises a down-conversion module, an AD sampling module, an accumulation calculation module, an energy comparison module, a timing feedback module, a signal compensation module, an initialization frequency and pseudo code phase module, a pseudo code tracking module, a de-spreading module, a carrier tracking module, a demodulation module, a bit synchronization module, a data recovery module and a bit error rate statistics module, wherein the down-conversion module changes a radio frequency band signal into a baseband signal after being received by a wireless channel, the baseband signal is divided into a plurality of sections according to the dynamic range of a carrier wave by the accumulation calculation module after being sampled by the AD sampling module according to the data rate, and coherent and incoherent accumulation is carried out; the energy comparison module judges and selects the maximum value of the comparison according to the accumulated result of the accumulation calculation module, the timing feedback module generates a timing pulse according to the judged result of the energy comparison module, and the signal compensation module controls the accumulated frequency according to the timing pulse and searches the whole dynamic range of the carrier wave to obtain a confirmation value; the initialization frequency and pseudo code phase module converts the confirmation value of the timing feedback module into frequency and pseudo code phase and inputs the frequency and pseudo code phase into the pseudo code tracking module and the carrier tracking module respectively; the pseudo code tracking module performs pseudo code tracking after adjacent chips on the left and right of the initialized pseudo code phase are confirmed again, and the baseband data and the pseudo code are stripped by the despreading module; the carrier tracking module is used for carrying out timing update on the carrier phase through a phase-locked loop after the frequency discrimination result assists the acceleration and speed components, and correcting and compensating the real-time residual error to the pseudo code tracking module; the demodulation module carries out coherent demodulation according to the phase after carrier tracking obtained by the carrier tracking module, and after a bit synchronization module generates timing interpolation and adjusts a bit timing clock, a data recovery module detects a synchronous word sequence in data by using bit timing and aligns the data according to a frame format to obtain recovered data; and the error rate statistic module compares the high-dynamic direct-spread source data source obtained from the high-dynamic direct-spread baseband signal generation module with the obtained recovery data bit by bit to calculate the error rate of the system, wherein the high-dynamic direct-spread source data source is the content of a configurable data source, and comprises the length, the content, whether the data source is interrupted and a count value.
Preferably, the high dynamic direct spread baseband signal generating module generates a high dynamic direct spread baseband signal with configurable speed, acceleration and jerk. The data rate, carrier update rate, and pseudo code rate are affected by doppler. Specifically, the relative moving speed affects the doppler frequency, i.e., the frequency offset value, the relative acceleration affects the doppler change rate, i.e., the frequency first-order change rate, and the relative jerk affects the doppler change rate, i.e., the frequency second-order change rate; the channel characteristics can be achieved by controlling the interference signal, noise signal, scaling factor of the high dynamic source to achieve the required signal-to-noise ratio and interference-to-signal ratio.
The accumulation calculation module segments the pseudo code frequency by combining the data rate and the frequency offset, and absolute values are taken and added through an FIR filter so as to achieve the required capture signal-to-noise ratio. The timing feedback module finishes the jumping condition of a single frequency, the energy comparison module performs comparison after the whole cycle is finished, the pseudo code phase and the frequency deviation value with the maximum value are determined, searching is performed again at the position close to the pseudo code phase, the optimal pseudo code phase can be selected after one comparison, and the pseudo code tracking and the carrier tracking can be rapidly completed by combining the frequency deviation value.
In this embodiment, the high dynamic direct spread source module unit in the present invention preferably uses an AD9148 model digital-to-analog converter of AD company, which samples the generated baseband signal to 140M, and converts the baseband signal to a radio frequency band by an up-converter; the data rate and the pseudo code rate of the baseband signal are added by a frequency division clock to be subjected to dynamic change after conversion, the carrier rate is subjected to dynamic change effect by adjusting a phase corresponding to a storage cosine ROM module in the FPGA, and the proportion of the dynamic change effect is simulated according to the frequency after the conversion.
The fast capturing and tracking module of the base band is converted to the base band by a down converter, an AD9239 type digital-to-analog converter of AD company is adopted to sample signals converted to 140M, 4 paths of sampling signal input are supported, a V5SX95T type FPGA chip is adopted, an accumulation calculation module is realized in the FPGA, then fast capturing and tracking of the base band are carried out, the Doppler frequency of a carrier wave of the sampling signals obtained by the AD9239 type digital-to-analog converter is divided into a plurality of sections according to the data rate, and coherent and incoherent accumulation is carried out; the energy comparison module judges the accumulated result and selects the maximum value of the comparison; the timing feedback module generates a timing pulse according to the comparison result; the signal compensation module is used for controlling the accumulation frequency according to the timing pulse and searching the whole dynamic range of the carrier wave; initializing a frequency and pseudo code phase module, converting a confirmation value fed back at regular time into a frequency and a pseudo code phase, and inputting the frequency and the pseudo code phase into a pseudo code tracking module and a carrier tracking module; the pseudo code tracking module is used for carrying out pseudo code tracking after adjacent chips on the left and right of the initialized pseudo code phase are confirmed again; the de-spreading module is used for stripping the baseband data from the pseudo code; the carrier tracking module is used for carrying out timing update on the carrier phase through the phase-locked loop after the frequency discrimination result assists the acceleration component and the speed component, and correcting and compensating the real-time residual error to the pseudo code tracking loop; the demodulation module is used for carrying out coherent demodulation by utilizing the phase information after carrier tracking; the bit synchronization module generates timing interpolation and adjusts a bit timing clock; the data recovery module detects a synchronous word sequence in the data by using bit timing and aligns the data according to a frame format; and the error rate statistic module is used for comparing the high-dynamic direct sequence spread spectrum source data source with the recovery data bit by bit and counting the error rate of the system.
Fig. 2 shows the structure of an embodiment of the high dynamic direct spread source module of the present invention. The data rate data _ clk, the carrier update rate dds, and the pseudo code rate pn _ clk are all controlled by the speed (frequency offset value), the acceleration (frequency first order rate of change), and the jerk (frequency second order rate of change), the divided clock is 110M, the control counter is 64 bits wide, and a high dynamic data source with continuously changing phases can be generated, wherein the data rate and the pseudo code rate can be set, and the carrier center is 25M. Meanwhile, a signal-to-noise ratio control signal (controlling noise power) and an interference-to-signal ratio control signal (controlling interference power) are superposed with a high-dynamic data source on 25M, the superposed signals are input to an AD9148 type digital-to-analog converter, the AD9148 type digital-to-analog converter is multiplied to 165M by an SPI (serial peripheral interface) configured internal phase-locked loop, and after sampling, a 140M intermediate frequency signal is output and is output to an upper frequency converter.
Fig. 3 shows the structure of an embodiment of the baseband fast acquisition and tracking module in the present invention. The DDS generates 30M cos theta and sin theta, which are multiplied by the signals sampled by the AD D/A converter, and the high frequency components are eliminated through a low pass filter. And dividing the signal after low-pass filtering into K sections by taking the number of the pseudo codes corresponding to 1 data rate Ts as a point number N, wherein the K sections are the minimum accumulated number of the captured signal-to-noise ratio. And storing the pseudo code result with the same length into a ROM, multiplying the pseudo code stored in the ROM by the signal after low-pass filtering each time, finishing accumulation operation through an FIR filter, storing the absolute value of the FIR output result of the K sections, changing the pseudo code rate delta f and calculating the next time.
And the energy comparison module adds corresponding positions of the FIR output results and then compares the corresponding positions to obtain a maximum energy point. And the timing feedback module searches the frequency in the dynamic range once, and confirms the position and the frequency offset of the maximum value of the pseudo code phase by combining the energy comparison module. Meanwhile, initializing a frequency carrier phase and a pseudo code phase pn phase, performing pseudo code tracking and carrier tracking by taking the frequency carrier phase and the pseudo code phase pn phase as initial values, searching around the pseudo code phase pn phase by considering the delay between an energy comparison module and an actual signal, and confirming the position of the occurrence of the code sheet again; the frequency deviation has less influence and does not need to be confirmed again.
And the despreading module generates a corresponding pseudo code according to the position and the frequency difference of the code chip, despreads the code, and simultaneously feeds back the carrier residual error delta theta to a pseudo code tracking loop for auxiliary processing, so that the pseudo code tracking precision is improved. The demodulation module adopts a traditional Costas loop to demodulate, the bit synchronization algorithm carries out interpolation control according to the Gardner algorithm to generate the optimal sampling position of the data, and the error rate of the system is obtained by searching the synchronization sequence and comparing with the data source.
the key point of the invention is that the energy comparison module and the timing feedback module are used for dividing and searching the maximum value according to the frequency, so that the high and low signal-to-noise ratios can not be distinguished, the problem of inaccurate frequency estimation caused by the fact that part of algorithms exceed the capture threshold under the high signal-to-noise ratio is avoided, and in addition, the maximum value is searched again only by confirming the initial pseudo code adjacent phase again.
Secondly, the division of the K value only needs to meet the minimum sensitivity of signal capture, and meanwhile, only one module is needed for realizing the code, other modules can be reused, and the structure is clear;
Again, the phase generation of the direct spread spectrum dynamic source signal may satisfy: 2^64/110M (frequency precision Hz), 2^64/110M/110M (frequency first order rate of change precision Hz/s);
Finally, the simulation generation of interference and noise is convenient for the construction of a test system, and the system performance can be rapidly verified.
on the basis of the system, the invention also provides a quick acquisition tracking method based on self-adaptation, which comprises the following steps:
the generated high dynamic direct sequence spread spectrum baseband signal is converted to a radio frequency band and is sent;
Changing the received radio frequency band signal into a baseband signal, dividing the dynamic range of the carrier into a plurality of sections according to the data rate after sampling, and performing coherent and incoherent accumulation; judging and selecting the maximum value of the comparison according to the accumulated result, and generating a timing pulse according to the judgment result; controlling the accumulated frequency according to the timing pulse, searching the whole dynamic range of the carrier to obtain a confirmation value, converting the confirmation value into frequency and a pseudo code phase, and respectively carrying out pseudo code tracking and carrier tracking;
The pseudo code tracking comprises the steps of confirming adjacent chips on the left and right sides of an initialized pseudo code phase again, tracking the pseudo code, stripping baseband data and the pseudo code, and sending the stripped baseband data and the pseudo code into carrier tracking; the carrier tracking comprises the steps of carrying out timing updating on the carrier phase through a phase-locked loop after the frequency discrimination result assists acceleration and speed components, and correcting and compensating real-time residual errors to a pseudo code tracking process; carrying out coherent demodulation according to the phase tracked by the obtained carrier, detecting a synchronous word sequence in data by using bit timing after generating timing interpolation and adjusting a bit timing clock, and aligning the data according to a frame format to obtain recovered data; and comparing the high-dynamic direct sequence spread spectrum source data source with the obtained recovery data bit by bit, and counting the error rate of the system.
wherein, the method generates a high dynamic direct spread baseband signal with configurable speed, acceleration and jerk. Preferably, the method segments the pseudo code frequency by combining the data rate and the frequency offset, and adds the absolute values by an FIR filter to achieve the required acquisition signal-to-noise ratio.
And in the method, when the whole dynamic range of the carrier wave is searched to obtain the confirmation value, the maximum value is searched again only by searching the initial pseudo code adjacent phase again.
In conclusion, the system and the method of the invention have the advantages of estimating the frequency and the pseudo code phase of the expected signal of the system without using inertial navigation data, rapidly completing acquisition and tracking and occupying less system resources of a spacecraft.
the method is simple and convenient to verify, can quickly acquire and track, is a quick acquisition and tracking algorithm and a system with self-adaptive high and low signal-to-noise ratios and high dynamic direct sequence spread spectrum signals, and realizes the estimation of accurate frequency and pseudo code phase under different signal-to-noise ratio environments; the frequency and the pseudo code phase precision can be adjusted according to the system requirements and the hardware resource conditions.
It should be noted that the above description is only a preferred embodiment of the present invention, and it should be understood that various changes and modifications can be made by those skilled in the art without departing from the technical idea of the present invention, and these changes and modifications are included in the protection scope of the present invention.
Claims (9)
1. an adaptive-based fast acquisition tracking system, comprising:
The high-dynamic direct-spread source module comprises a high-dynamic direct-spread baseband signal generating module and an up-conversion module, wherein the high-dynamic direct-spread baseband signal generated by the high-dynamic direct-spread baseband signal generating module is converted into a radio frequency band by the up-conversion module and is transmitted;
The baseband fast capturing and tracking module comprises a down-conversion module, an AD sampling module, an accumulation calculation module, an energy comparison module, a timing feedback module, a signal compensation module, an initialization frequency and pseudo code phase module, a pseudo code tracking module, a de-spreading module, a carrier tracking module, a demodulation module, a bit synchronization module, a data recovery module and an error rate statistics module, wherein after the down-conversion module receives signals through a wireless channel, radio frequency band signals are converted into baseband signals, and after the signals are sampled by the AD sampling module, the accumulation calculation module combines the data rate and the frequency offset to carry out segmentation according to the Doppler frequency of a carrier wave, and coherent and incoherent accumulation is carried out; the energy comparison module judges and selects the maximum value of the comparison according to the accumulated result of the accumulation calculation module, the timing feedback module generates a timing pulse according to the judged result of the energy comparison module, and the signal compensation module controls the accumulated frequency according to the timing pulse and searches the whole dynamic range of the carrier wave to obtain a confirmation value; the initialization frequency and pseudo code phase module converts the confirmation value of the timing feedback module into frequency and pseudo code phase and inputs the frequency and pseudo code phase into the pseudo code tracking module and the carrier tracking module respectively; the pseudo code tracking module performs pseudo code tracking after adjacent chips on the left and right of the initialized pseudo code phase are confirmed again, and the baseband data and the pseudo code are stripped by the despreading module; the carrier tracking module is used for carrying out timing update on the carrier phase through a phase-locked loop after the frequency discrimination result assists the acceleration and speed components, and correcting and compensating the real-time residual error to the pseudo code tracking module; the demodulation module carries out coherent demodulation according to the phase after carrier tracking obtained by the carrier tracking module, and after a bit synchronization module generates timing interpolation and adjusts a bit timing clock, a data recovery module detects a synchronous word sequence in data by using bit timing and aligns the data according to a frame format to obtain recovered data; and the error rate statistic module compares the high-dynamic direct-sequence spread spectrum source data source with the obtained recovery data bit by bit to calculate the system error rate.
2. The adaptive-based fast acquisition tracking system according to claim 1, characterized in that: the high-dynamic direct-spread baseband signal generating module generates a high-dynamic direct-spread baseband signal which can configure speed, acceleration and jerk.
3. the adaptive-based fast acquisition tracking system according to claim 1, characterized in that: the accumulation calculation module is used for taking absolute values and adding the absolute values through an FIR filter after the data rate and the frequency deviation are combined and segmented according to the Doppler frequency of the carrier wave so as to achieve the required capture signal-to-noise ratio.
4. the adaptive-based fast acquisition tracking system according to claim 1, characterized in that: the AD sampling module adopts an AD9148 type digital-to-analog converter.
5. The adaptive-based fast acquisition tracking system according to claim 1, characterized in that: the accumulation calculation module adopts a V5SX95T type FPGA chip.
6. The method for fast acquisition and tracking system based on adaptation according to any of claims 1-5, characterized by comprising the steps of:
The generated high dynamic direct sequence spread spectrum baseband signal is converted to a radio frequency band and is sent;
Changing the received radio frequency band signal into a baseband signal, segmenting the carrier Doppler frequency by combining the data rate and the frequency offset after sampling, and performing coherent and noncoherent accumulation; judging and selecting the maximum value of the comparison according to the accumulated result, and generating a timing pulse according to the judgment result; controlling the accumulated frequency according to the timing pulse, searching the whole dynamic range of the carrier to obtain a confirmation value, converting the confirmation value into frequency and a pseudo code phase, and respectively carrying out pseudo code tracking and carrier tracking;
The pseudo code tracking comprises the steps of confirming adjacent chips on the left and right sides of an initialized pseudo code phase again, tracking the pseudo code, stripping baseband data and the pseudo code, and sending the stripped baseband data and the pseudo code into carrier tracking; the carrier tracking comprises the steps of carrying out timing updating on the carrier phase through a phase-locked loop after the frequency discrimination result assists acceleration and speed components, and correcting and compensating real-time residual errors to a pseudo code tracking process; carrying out coherent demodulation according to the phase tracked by the obtained carrier, detecting a synchronous word sequence in data by using bit timing after generating timing interpolation and adjusting a bit timing clock, and aligning the data according to a frame format to obtain recovered data; and comparing the high-dynamic direct sequence spread spectrum source data source with the obtained recovery data bit by bit, and counting the error rate of the system.
7. The method of claim 6, wherein a high dynamic direct spread baseband signal with configurable speed, acceleration and jerk is generated.
8. the method of claim 6, wherein after the carrier Doppler frequency is segmented by combining the data rate and the frequency offset, the absolute values are added by FIR filter to achieve the required acquisition signal-to-noise ratio.
9. the method of claim 6, wherein when searching the whole Doppler frequency range of the carrier to obtain the confirmation value, the re-confirmation only needs to search the initial pseudo code adjacent phase for the maximum value again.
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| CN201711344263.4A CN108011653B (en) | 2017-12-15 | 2017-12-15 | Self-adaptive rapid capture tracking system and method |
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| CN111562568B (en) * | 2020-04-30 | 2022-05-24 | 北京卫星信息工程研究所 | Radar transmitting end, receiving end, frequency synchronization method and transceiving networking radar |
| CN113452404B (en) * | 2021-08-31 | 2021-11-26 | 北京理工大学 | Multi-carrier spread spectrum capturing method and device, electronic equipment and storage medium |
| CN114448455B (en) * | 2022-02-07 | 2023-11-14 | 北京融为科技有限公司 | Gardner algorithm-based high-speed zero intermediate frequency IQ delay compensation system |
| CN115499909B (en) * | 2022-11-14 | 2023-01-17 | 长沙驰芯半导体科技有限公司 | Multi-stage phase tracking method and device for ultra-wideband |
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