CN112910499B - Spread spectrum signal accurate acquisition system - Google Patents

Spread spectrum signal accurate acquisition system Download PDF

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CN112910499B
CN112910499B CN202110185085.5A CN202110185085A CN112910499B CN 112910499 B CN112910499 B CN 112910499B CN 202110185085 A CN202110185085 A CN 202110185085A CN 112910499 B CN112910499 B CN 112910499B
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pseudo code
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CN112910499A (en
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金磊
王娜
曾富华
王媛
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Southwest Electronic Technology Institute No 10 Institute of Cetc
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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
    • H04B1/70751—Synchronisation aspects with code phase acquisition using partial detection
    • H04B1/70753—Partial phase search

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Abstract

The spread spectrum signal accurate capturing system disclosed by the invention has the advantages of good processing real-time performance, small frequency measurement error, high estimation accuracy and low adaptive signal-to-noise ratio. The invention is realized by the following technical scheme: the sampling buffer module performs down-sampling processing on the received signal and controls ping-pong reading and writing of the sampled data; the compensation correction module divides the Doppler frequency shift range into a plurality of frequency subslots to perform frequency compensation of carrier Doppler frequency shift and phase correction of pseudo code Doppler frequency shift on the sampled data; the parallel search of the pseudo code phase is realized by adopting a double-block expansion technology and fast Fourier transform; the double measurement of full coherent integration, carrier Doppler frequency shift and change rate thereof is realized by adopting a change rate compensation technology and fast Fourier transform; and obtaining the correlation information of the integral peak value by adopting a comparison searching method for all the integral processing data, and solving out the accurate pseudo code initial phase, pseudo code Doppler frequency shift, carrier Doppler frequency shift and carrier Doppler change rate of the spread spectrum signal.

Description

Spread spectrum signal accurate acquisition system
Technical Field
The invention belongs to the field of wireless communication, and relates to a spread spectrum signal accurate capturing system based on double-block expansion.
Technical Field
Spread spectrum communication has become a consensus for its advantages of strong anti-interference and anti-multipath capability, high spectrum utilization, multiple access communication, etc. The spread spectrum technology, as a modern communication system based on the information theory, has many unique advantages because it uses pseudo-random codes to spread spectrum modulate data information: when the method is used in communication, the method has the characteristics of strong anti-interference capability, low transmitting power, high interception resistance and good confidentiality, and has the characteristics of code division multiple access and random site selection; in the ranging process, pseudo-random code ranging is adopted, so that the ranging precision can be greatly improved. Due to the above advantages, with the rapid development of microelectronics, very large scale integrated circuit technology, and digital signal processing technology, the spread spectrum technology is widely applied in the fields of wireless local area network, mobile communication, satellite navigation, aerospace, deep space exploration, etc., and the status of spread spectrum communication is becoming more and more important under the strong demands of military and civil communication.
The acquisition of the spread spectrum signal is used as a key link of the synchronization of the spread spectrum communication system, and the system can track the pseudo code and the carrier only after the acquisition of the pseudo code and the frequency is completed, so that the data demodulation is completed, and the information which is transmitted by the communication system can be known. The purpose of signal acquisition is to synchronize the locally generated replica C/a code with the C/a code modulated on the carrier to achieve correlated despreading and accurate tracking of the code phase. The capture of the spread spectrum signal is to utilize sharp autocorrelation of pseudo-random code, the received signal and pseudo-random code produced in the local are made into correlation operation, the result of the correlation operation is compared with detection threshold, if it is greater than threshold value, it is indicated that the capture is successful, otherwise, the capture process is continued, actually, it is to make two-dimensional search process to carrier frequency and pseudo-code phase of the received signal, the carrier frequency and pseudo-code phase which are captured and estimated are directly initialized to tracking loop, so as to help processing channel to make tracking synchronization to the received signal, the pseudo-code phase capture is aimed at making the difference between pseudo-code phase of the local signal and pseudo-code phase of the received signal smaller, so that the code loop can make fast and reliable pseudo-code synchronization, the carrier frequency capture is aimed at making the difference between carrier frequency of the local signal and carrier frequency of the received signal smaller, so that the carrier loop can make fast and reliable frequency synchronization, if the error between the local signal and the received signal exceeds the traction range of the tracking loop, the tracking loop usually cannot enter the lock normally, so how to accurately, quickly and effectively capture the carrier frequency and the pseudo code phase of the spread spectrum signal becomes a key core technology of the spread spectrum communication system.
There are many specific methods of conventional spread spectrum signal acquisition systems. The sliding correlation method is simple, easy to realize engineering, wide in application, long in consumed time and low in capturing speed; the parallel frequency method adopts Fast Fourier Transform (FFT) of long points to complete search for carrier frequency at one time, but the capture time is in direct proportion to the length of the pseudo code, the signal sensitivity is easy to be deteriorated, and the consumption of hardware resources is large; the parallel code phase method adopts FFT to complete the long pseudo code phase search once, the capture speed is fast, but the carrier frequency search range is small, and the carrier frequency measurement error is large; based on a partial matched filter and an FFT (fast Fourier transform) capturing method, the method is used as a time-frequency two-dimensional parallel searching method, can overcome the defect of low searching speed and the defect of serious attenuation of a related peak value, but does not measure the Doppler change rate of a carrier wave and is difficult to adapt to a high-dynamic scene. Therefore, the method strategy of the traditional spread spectrum signal capturing system has respective advantages and disadvantages, can adapt to a certain specific application scene, but can not achieve optimal performance in the contradiction of mutual influence and restriction of signal-to-noise ratio threshold, high dynamic condition, capturing time, hardware resources and the like.
Disclosure of Invention
Aiming at the technical defects of the traditional spread spectrum signal capturing system, the invention provides the spread spectrum signal accurate capturing system which has the advantages of good processing real-time property, small frequency measurement error and high estimation accuracy, and can rapidly, effectively and accurately capture the spread spectrum signal in the scenes of high dynamic and low signal-to-noise ratio.
The above object of the present invention can be achieved by the following introduction, a spread spectrum signal accurate acquisition system comprising: sampling buffer module, compensation correction module, double block grouping module, local pseudo code module, double block zero filling module, 2N point FFT module, conjugation module, 2N point IFFT module, truncation processing module, change rate compensation module, carrier recovery module, M point FFT module and detection resolving module, its characterized in that: the sampling buffer module performs down-sampling processing on the received signal and controls ping-pong reading and writing of the sampled data; the compensation correction module divides the Doppler frequency shift range into a plurality of frequency subslots, carries out frequency compensation on the sampling data output by the sampling cache module according to the carrier Doppler frequency shift in the subslots, and carries out phase correction on the sampling data after frequency compensation according to the pseudo code Doppler frequency shift in the subslots; the double-block grouping module carries out double-block grouping processing on the sampling data output by the compensation correction module and then sends the sampling data to the first 2N-point FFT module, and fast Fourier transform is carried out on the sampling data double-block grouping data to obtain sampling data transform data; meanwhile, the double-block zero padding module sends a result of zero padding processing of the local pseudo code output by the local pseudo code module to a second 2N-point FFT module, fast Fourier transform is carried out on the local pseudo code double-block zero padding data, and local pseudo code transform data are obtained after conjugation; the 2N-point IFFT module performs complex multiplication operation according to sampling data transformation data output by the first 2N-point FFT module and local pseudo code transformation data output by the second 2N-point FFT module to obtain complex multiplication operation data; performing fast Fourier inverse transformation on the complex multiplication operation data, sending the inverse transformation data to a truncation processing module, performing truncation processing on the inverse transformation data, and writing the truncation data into a cache in a first-row and last-row mode; the change rate compensation module reads the truncated data from the cache in a first-row and second-row mode, the carrier Doppler change rate range is divided into a plurality of change rate subslots, the change rate compensation module performs change rate compensation on the read truncated data according to the carrier Doppler change rate in the change rate subslots, the carrier recovery module performs nonlinear transformation on the change rate compensated truncated data, the M-point FFT module performs fast Fourier transformation on the carrier recovered data, the absolute value is obtained, the obtained integral processing data is sent to the detection resolving module, the integral peak value related information is obtained by adopting a comparison searching method for all the integral processing data, and the accurate pseudo code initial phase, pseudo code frequency shift, carrier Doppler frequency shift and carrier Doppler change rate of the spread spectrum signal are resolved.
Compared with the traditional spread spectrum signal capturing system, the invention has the following beneficial effects:
the processing is real-time. The invention carries out ping-pong read-write control on the sampled data in the sampling cache module, adopts fast Fourier transform to realize pseudo code phase parallel search based on the double-block expansion technology, and adopts multi-channel subslot parallel processing.
The frequency measurement precision is high. The invention adopts nonlinear transformation to complete carrier recovery on data, adopts change rate compensation technology and fast Fourier transformation to realize double measurement of carrier Doppler frequency shift and change rate thereof, further reduces measurement error of carrier frequency and effectively improves capture precision of received signals compared with the traditional spread spectrum signal capture system.
The adaptive signal-to-noise ratio is low. The invention adopts two-stage fast Fourier transform to realize full coherent integration on the sampling data, eliminates gain loss caused by incoherent integration, adopts carrier frequency compensation and pseudo code phase correction to carry out two-dimensional compensation correction on the sampling data, avoids the problem that signal energy cannot be effectively accumulated, and has higher integral processing gain compared with the traditional spread spectrum signal capturing system, thereby being applicable to application scenes with lower signal-to-noise ratio.
Drawings
Fig. 1 is a schematic diagram of the structure of the spread spectrum signal accurate acquisition system of the present invention.
Fig. 2 is a schematic structural diagram of the sample buffer module in fig. 1.
Fig. 3 is a schematic structural diagram of the compensation correction module in fig. 1.
Fig. 4 is a schematic structural diagram of the double-block zero padding module in fig. 1.
Fig. 5 is a schematic diagram of the structural principle of the dual block grouping module in fig. 1.
Fig. 6 is a schematic diagram of the structure of the rate of change compensation module of fig. 1.
The invention is further described with reference to the following figures and examples.
Detailed Description
See fig. 1. In a preferred embodiment described below, a spread spectrum signal accurate acquisition system comprises: sampling buffer module, compensation correction module, double block grouping module, local pseudo code module, double block zero filling module, 2N point FFT module, conjugation module, 2N point IFFT module, truncation processing module, change rate compensation module, carrier recovery module, M point FFT module and detection resolving module, wherein: the sampling buffer module performs down-sampling processing on the received signal and controls ping-pong reading and writing of the sampled data; the compensation correction module divides the Doppler frequency shift range into a plurality of frequency subslots, carries out frequency compensation on the sampling data output by the sampling cache module according to the carrier Doppler frequency shift in the subslots, and carries out phase correction on the sampling data after frequency compensation according to the pseudo code Doppler frequency shift in the subslots; the double-block grouping module carries out double-block grouping processing on the sampling data output by the compensation correction module and then sends the sampling data to the first 2N-point FFT module, and fast Fourier transform is carried out on the sampling data double-block grouping data to obtain sampling data transform data; meanwhile, the double-block zero padding module sends a result of zero padding processing of the local pseudo code output by the local pseudo code module to a second 2N-point FFT module, fast Fourier transform is carried out on the local pseudo code double-block zero padding data, and local pseudo code transform data are obtained after conjugation; the 2N-point IFFT module performs complex multiplication operation according to sampling data transformation data output by the first 2N-point FFT module and local pseudo code transformation data output by the second 2N-point FFT module to obtain complex multiplication operation data; performing fast Fourier inverse transformation on the complex multiplication operation data, sending the inverse transformation data to a truncation processing module, performing truncation processing on the inverse transformation data, and writing the truncation data into a cache in a first-row and last-row mode; the change rate compensation module reads the truncated data from the cache in a first-row and second-row mode, the carrier Doppler change rate range is divided into a plurality of change rate subslots, the change rate compensation module performs change rate compensation on the read truncated data according to the carrier Doppler change rate in the change rate subslots, the carrier recovery module performs nonlinear transformation on the change rate compensated truncated data, the M-point FFT module performs fast Fourier transformation on the carrier recovered data, the absolute value is obtained, the obtained integral processing data is sent to the detection resolving module, the integral peak value related information is obtained by adopting a comparison searching method for all the integral processing data, and the accurate pseudo code initial phase, pseudo code frequency shift, carrier Doppler frequency shift and carrier Doppler change rate of the spread spectrum signal are resolved.
See fig. 2. The sampling buffer module is according to the system working clock fsysSum signal sampling frequency fsampUsing the formula CWsamp＝fsamp×(232/fsys) Data conversion is carried out to obtain a signal sampling frequency control word CWsampGenerating a zero clearing pulse through a direct digital frequency synthesizer (DDS), continuously accumulating a received signal by an accumulator, outputting a data accumulated value when the zero clearing pulse is effective, performing integral zero clearing operation on the accumulator, circulating the process, performing down-sampling processing on the received signal, and when the total number of the sampled data exceeds (M +1) multiplied by N, switching a sampled data cache space by a ping-pong read-write control method by a ping-pong control unit, starting a data processing state, and realizing the quasi-real-time processing of the received signal, wherein N is 1/2 of the fast Fourier transform points in a 2N-point FFT module, and M is the fast Fourier transform points in an M-point FFT module.
See fig. 3. The compensation correction module divides the Doppler frequency shift range into totalNumber L +1 frequency subslots, Doppler shifted from minimum carrier
Figure GDA0003394540910000041
Searching in sequence to maximum carrier Doppler shift
Figure GDA0003394540910000042
Carrier doppler shift search stepping
Figure GDA0003394540910000043
Is composed of
Figure GDA0003394540910000044
The carrier Doppler shift search round L is in an element (0,1, L-1) and the carrier Doppler shift f in a frequency subslotdoplIs composed of
Figure GDA0003394540910000045
Using the calculation formula CWfreq＝fdopl×(232/fsamp) Data conversion is carried out to obtain carrier Doppler frequency shift control word CWfreqFor CWfreqAccumulating to obtain a query address, generating a local carrier of the carrier Doppler frequency shift through address mapping and table lookup, and performing complex multiplication operation by using the generated local carrier and sampling data output by the sampling cache module to complete frequency compensation of the carrier Doppler frequency shift; using the calculation formula CWcode＝fdopl×Rc/fRF×(232/fsamp) Performing data conversion, wherein RcFor pseudo code rate, fRFFor radio frequency, obtaining a pseudo code Doppler frequency shift control word CWcodeThe phase shift pulse is generated by a direct digital frequency synthesizer (DDS), and the sampling data after frequency compensation is subjected to phase correction by adopting an interpolation or external extraction method when the phase shift pulse is effective.
See fig. 4. The double-block zero padding module adopts a parallel pseudo code module 1, a pseudo code module 2 … pseudo code module M-1 and a pseudo code module M to perform zero padding operation on M multiplied by N local pseudo code sampling points output by a local pseudo code module, and converts the M multiplied by N local pseudo code sampling points into M multiplied by 2N local pseudo code double-block zero padding data.
See fig. 5. The double-block grouping module adopts a parallel data block 1, a data block 2 …, a data block M-1, a data block M and a data block M +1 to carry out double-block grouping operation on the (M +1) multiplied by N sample data after compensation and correction, and converts the (M +1) multiplied by N sample data into M multiplied by 2N double-block grouping data.
The 2N-point FFT module carries out M times of 2N-point fast Fourier transform on the M multiplied by 2N local pseudo code double-block zero padding data, and M multiplied by 2N local pseudo code transform data are obtained after conjugation; the 2N-point FFT module carries out M times of 2N-point fast Fourier transform on the M multiplied by 2N sampling data double-block grouped data to obtain M multiplied by 2N sampling data transform data; carrying out complex multiplication operation on the M × 2N local pseudo code conversion data and the M × 2N sampling data conversion data to obtain M × 2N complex multiplication operation data; the 2N-point IFFT module performs 2N-point fast Fourier inverse transformation on the M × 2N complex multiplication operation data M times to obtain M × 2N inverse transformation data.
The truncation processing module truncates the M × 2N inverse transform data output by the 2N-point IFFT module, that is, truncates the preceding N inverse transform data from the consecutive 2N inverse transform data to obtain M × N truncation data, and writes the M × N truncation data into the buffer in a first-and-last-column manner.
See fig. 6. The change rate compensation module divides the carrier Doppler change rate range into K +1 change rate subslots from the minimum carrier Doppler change rate
Figure GDA0003394540910000051
Searching in sequence to maximum carrier Doppler rate of change
Figure GDA0003394540910000052
Carrier doppler rate of change search stepping
Figure GDA0003394540910000053
Is composed of
Figure GDA0003394540910000054
The carrier Doppler change rate search round K belongs to (0, 1.,. K-1), and the carrier Doppler change rate f in the change rate subslotrateIs composed of
Figure GDA0003394540910000055
Using the calculation formula CWrate＝frate×[232/(fsamp/N)]2Data conversion is carried out to obtain carrier Doppler change rate control word CWrateFor CWrateAnd accumulating twice to obtain a query address, generating a local carrier wave of the carrier wave Doppler change rate by address mapping and table lookup, reading out N multiplied by M truncated data from a cache in a column-to-row mode, and performing complex multiplication operation by using the generated M-point local carrier wave and continuous M truncated data in the read N multiplied by M truncated data to complete the change rate compensation of the carrier wave Doppler change rate.
The carrier recovery module carries out nonlinear transformation on the N multiplied by M data output by the change rate compensation module to complete carrier recovery, the M-point FFT module carries out N times of M-point fast Fourier transformation on the N multiplied by M data output by the carrier recovery module, and the N multiplied by M integral processing data are obtained after an absolute value is taken.
The detection control module obtains the correlation information of the integral peak value by adopting a comparative search method for all integral processing data, and the method comprises the following steps: round of Doppler shift subslots lvppRound k of carrier doppler rate of change subslotsvpp2N point fast Fourier transform index NvppIndex M of M-point fast Fourier transformvppResolving to obtain the pseudo code initial phase of the received signal
Figure GDA0003394540910000056
Is nvpp×Rc/fsampObtaining the pseudo code Doppler frequency shift
Figure GDA0003394540910000057
Is composed of
Figure GDA0003394540910000058
Carrier doppler shift
Figure GDA0003394540910000059
Is composed of
Figure GDA0003394540910000061
Carrier doppler rate of change
Figure GDA0003394540910000062
Is composed of
Figure GDA0003394540910000063
The following is a concrete analysis by way of example:
the following is a concrete analysis by way of example:
taking the B1I signal emitted by a Beidou satellite as an example, the pseudo code rate Rc2.046Mcps, code length 2046 chips, radio frequency fRF1561.098MHz, system operating clock fsys60.0MHz, a carrier Doppler shift range of + -10.0kHz, and a carrier Doppler variation range of + -250.0 Hz/s.
Signal sampling frequency fsampThe frequency is 4.096MHz, the number of fast Fourier transform points 2N in the 2N-point FFT module is 8192, and the number of fast Fourier transform points M in the M-point FFT module is 256; the compensation correction module divides the Doppler frequency shift range into 51 frequency subslots, searches from the minimum carrier Doppler frequency shift of-10.0 kHz to the maximum carrier Doppler frequency shift of +10.0kHz in sequence, and searches for steps in the carrier Doppler frequency shift
Figure GDA0003394540910000064
The frequency compensation and the phase correction are completed on the sampling data by adopting the parallel processing of a plurality of paths of frequency subslots at 400 Hz; the double-block zero padding module performs zero padding processing on the local pseudo code output by the local pseudo code module; the double-block grouping module carries out double-block grouping processing on the compensated and corrected sampling data; the 2N-point FFT module carries out fast Fourier transform on the local pseudo code double-block zero padding data to obtain local pseudo code transform data by conjugation, the 2N-point FFT module carries out fast Fourier transform on the sampling data double-block grouping data to obtain sampling data transform data, and complex multiplication operation is carried out on the local pseudo code transform data and the sampling data transform data to obtain complex multiplication operation data; the 2N-point IFFT module carries out fast Fourier inverse transformation on the complex multiplication operation data to obtain inverse transformation data; the truncation processing module truncates the inverse transformation data output by the 2N point IFFT module to be listed in advanceWriting 256 × 4096 truncated data into the cache; the change rate compensation module divides the carrier Doppler change rate range into 51 change rate subslots, searches from the minimum carrier Doppler change rate of-250.0 Hz/s to the maximum carrier Doppler change rate of +250.0Hz/s in sequence, and searches for step by step the carrier Doppler change rate
Figure GDA0003394540910000065
The frequency conversion rate is 10Hz/s, multi-channel change rate subslots are adopted for parallel processing, 256 multiplied by 4096 truncated data are read out from a cache in a row-by-row mode, the generated 256-point local carrier and the continuous 256 truncated data in the 4096 multiplied by 256 truncated data are utilized for complex multiplication, a carrier recovery module carries out nonlinear transformation on the 4096 multiplied by 256 data output by a change rate compensation module to complete carrier recovery, an M-point FFT module carries out 4096 times of 256-point fast Fourier transformation on the 4096 multiplied by 256 data output by the carrier recovery module, and 4096 multiplied by 256 integral processing data are obtained after an absolute value is obtained; the detection control module obtains the correlation information of the integral peak value by adopting a comparative search method for all integral processing data, and calculates to obtain the accurate pseudo code initial phase, pseudo code Doppler frequency shift, carrier Doppler frequency shift and carrier Doppler change rate of the received signal.
Test analysis and verification: in the above application example, when the carrier-to-noise ratio C/N of the received signal is0When the Doppler frequency shift is more than or equal to 25dB & Hz, the detection probability is better than 95.0%, the measurement precision of the initial phase of the pseudo code is better than +/-0.25 code, the measurement precision of the Doppler frequency shift of the pseudo code is better than +/-0.5 Hz, the measurement precision of the Doppler frequency shift of the carrier is better than +/-2.0 Hz, and the measurement precision of the Doppler change rate of the carrier is better than +/-10.0 Hz/s.
The above detailed description of the embodiments of the present invention, and the detailed description of the embodiments of the present invention used herein, is merely intended to facilitate the understanding of the methods and apparatuses of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.

Claims (9)

1. A spread spectrum signal accurate acquisition system comprising: sampling buffer module, compensation correction module, double block grouping module, local pseudo code module, double block zero filling module, first 2N point FFT module, second 2N point FFT module, conjugation module, 2N point IFFT module, truncation processing module, change rate compensation module, carrier recovery module, M point FFT module and detection resolving module, its characterized in that: the sampling buffer module performs down-sampling processing on the received signal and controls ping-pong reading and writing of the sampled data; the compensation correction module divides the Doppler frequency shift range into a plurality of frequency subslots, carries out frequency compensation on the sampling data output by the sampling cache module according to the carrier Doppler frequency shift in the subslots, and carries out phase correction on the sampling data after frequency compensation according to the pseudo code Doppler frequency shift in the subslots; the double-block grouping module carries out double-block grouping processing on the sampling data output by the compensation correction module and then sends the sampling data to the first 2N-point FFT module, and fast Fourier transform is carried out on the sampling data double-block grouping data to obtain sampling data transform data; meanwhile, the double-block zero padding module sends a result of zero padding processing of the local pseudo code output by the local pseudo code module to a second 2N-point FFT module, fast Fourier transform is carried out on the local pseudo code double-block zero padding data, and local pseudo code transform data are obtained after conjugation; carrying out complex multiplication operation on the sampling data transformation data output by the first 2N-point FFT module and the local pseudo code transformation data output by the second 2N-point FFT module to obtain complex multiplication operation data; the 2N point I FFT module carries out fast Fourier inverse transformation on the complex multiplication operation data, the inverse transformation data is sent to a truncation processing module, truncation processing is carried out on the inverse transformation data, and the truncation data is written into a cache in a first-row and later-row mode; the change rate compensation module reads the truncated data from the cache in a first-row and second-row mode, the carrier Doppler change rate range is divided into a plurality of change rate subslots, the change rate compensation module performs change rate compensation on the read truncated data according to the carrier Doppler change rate in the change rate subslots, the carrier recovery module performs nonlinear transformation on the change rate compensated truncated data, the M-point FFT module performs fast Fourier transformation on the carrier recovered data, the absolute value is obtained, the obtained integral processing data is sent to the detection resolving module, the integral peak value related information is obtained by adopting a comparison searching method for all the integral processing data, and the accurate pseudo code initial phase, pseudo code frequency shift, carrier Doppler frequency shift and carrier Doppler change rate of the spread spectrum signal are resolved.
2. The spread spectrum signal accurate acquisition system of claim 1, wherein: the sampling buffer module is according to the system working clock fsysSum signal sampling frequency fsampUsing the formula CWsamp＝fsamp×(232/fsys) Data conversion is carried out to obtain a signal sampling frequency control word CWsampGenerating a zero clearing pulse through a direct digital frequency synthesizer (DDS), continuously accumulating a received signal by an accumulator, outputting a data accumulated value when the zero clearing pulse is effective, performing integral zero clearing operation on the accumulator, circulating the process, performing down-sampling processing on the received signal, and when the total number of the sampled data exceeds (M +1) multiplied by N, switching a sampled data cache space by a ping-pong read-write control method by a ping-pong control unit, starting a data processing state, and realizing the quasi-real-time processing of the received signal, wherein N is 1/2 of the fast Fourier transform points in a 2N-point FFT module, and M is the fast Fourier transform points in an M-point FFT module.
3. The spread spectrum signal accurate acquisition system of claim 1, wherein: the compensation correction module divides the Doppler frequency shift range into L +1 frequency subslots, and the Doppler frequency shift is carried out from the minimum carrier wave
Figure FDA0003394540900000011
Searching in sequence to maximum carrier Doppler shift
Figure FDA0003394540900000012
Carrier doppler shift search stepping
Figure FDA0003394540900000013
Is composed of
Figure FDA0003394540900000014
The carrier Doppler shift search round L is in an element (0,1, L-1) and the carrier Doppler shift f in a frequency subslotdoplIs composed of
Figure FDA0003394540900000021
Using the calculation formula CWfreq＝fdopl×(232/fsamp) Data conversion is carried out to obtain carrier Doppler frequency shift control word CWfreqFor CWfreqAccumulating to obtain a query address, generating a local carrier of the carrier Doppler frequency shift through address mapping and table lookup, and performing complex multiplication operation by using the generated local carrier and sampling data output by the sampling cache module to complete frequency compensation of the carrier Doppler frequency shift; using the calculation formula CWcode＝fdopl×Rc/fRF×(232/fsamp) Data conversion is carried out to obtain a pseudo code Doppler frequency shift control word CWcodeGenerating phase-shifted pulse by direct digital frequency synthesizer (DDS), and performing phase correction on the frequency-compensated sampling data by adopting an interpolation or extraction method when the phase-shifted pulse is effective, wherein fsampFor signal sampling frequency, RcFor pseudo code rate, fRFIs a radio frequency.
4. The spread spectrum signal accurate acquisition system of claim 1, wherein: the double-block zero padding module adopts a parallel pseudo code module 1, a pseudo code module 2 … pseudo code module M-1 and a pseudo code module M to perform zero padding operation on M multiplied by N local pseudo code sampling points output by a local pseudo code module, and converts the M multiplied by N local pseudo code sampling points into M multiplied by 2N local pseudo code double-block zero padding data; the double-block grouping module adopts a parallel data block 1, a data block 2 …, a data block M-1, a data block M and a data block M +1 to carry out double-block grouping operation on the (M +1) multiplied by N sample data after compensation and correction, and converts the (M +1) multiplied by N sample data into M multiplied by 2N double-block grouping data.
5. The spread spectrum signal accurate acquisition system of claim 1, wherein: the second 2N-point FFT module carries out 2N-point fast Fourier transform on the M × 2N local pseudo code double-block zero padding data for M times, and M × 2N local pseudo code transform data are obtained after conjugation; the first 2N-point FFT module carries out 2N-point fast Fourier transform on the M multiplied by 2N sampling data double-block grouped data for M times to obtain M multiplied by 2N sampling data transform data; carrying out complex multiplication operation on the M × 2N local pseudo code conversion data and the M × 2N sampling data conversion data to obtain M × 2N complex multiplication operation data; the 2N-point IFFT module performs 2N-point fast Fourier inverse transformation on the M × 2N complex multiplication operation data M times to obtain M × 2N inverse transformation data.
6. The spread spectrum signal accurate acquisition system of claim 1, wherein: the truncation processing module truncates the M × 2N inverse transform data output by the 2N-point IFFT module, that is, truncates the preceding N inverse transform data from the consecutive 2N inverse transform data to obtain M × N truncation data, and writes the M × N truncation data into the buffer in a first-and-last-column manner.
7. The spread spectrum signal accurate acquisition system of claim 1, wherein: the change rate compensation module divides the carrier Doppler change rate range into K +1 change rate subslots from the minimum carrier Doppler change rate
Figure FDA0003394540900000022
Searching in sequence to maximum carrier Doppler rate of change
Figure FDA0003394540900000023
Carrier doppler rate of change search stepping
Figure FDA0003394540900000024
Is composed of
Figure FDA0003394540900000025
The carrier Doppler change rate search round K belongs to (0, 1.,. K-1), and the carrier Doppler change rate f in the change rate subslotrateIs composed of
Figure FDA0003394540900000026
Using the calculation formula CWrate＝frate×[232/(fsamp/N)]2Data conversion is carried out to obtain carrier Doppler change rate control word CWrateFor CWrateAccumulating twice to obtain a query address, generating a local carrier wave of the carrier wave Doppler change rate by address mapping and table lookup, reading out N multiplied by M truncated data from a cache in a column-to-row mode, and performing complex multiplication operation by using the generated M local carrier waves and continuous M truncated data in the read N multiplied by M truncated data to complete the change rate compensation of the carrier wave Doppler change rate, wherein fsampIs the signal sampling frequency.
8. The spread spectrum signal accurate acquisition system of claim 1, wherein: the carrier recovery module carries out nonlinear transformation on the N multiplied by M data output by the change rate compensation module to complete carrier recovery, the M-point FFT module carries out N times of M-point fast Fourier transformation on the N multiplied by M data output by the carrier recovery module, and the N multiplied by M integral processing data are obtained after an absolute value is taken.
9. The spread spectrum signal accurate acquisition system of claim 1, wherein: the detection resolving module obtains the correlation information of the integral peak value by adopting a comparative search method for all integral processing data, and the method comprises the following steps: round of Doppler shift subslots lvppThe turn k of the carrier doppler rate of change subslotvpp2N point fast Fourier transform index NvppIndex M of M-point fast Fourier transformvppResolving to obtain the pseudo code initial phase of the received signal
Figure FDA0003394540900000031
Is nvpp×Rc/fsampObtaining the pseudo code Doppler frequency shift
Figure FDA0003394540900000032
Is composed of
Figure FDA0003394540900000033
Carrier doppler shift
Figure FDA0003394540900000034
Is composed of
Figure FDA0003394540900000035
Carrier doppler rate of change
Figure FDA0003394540900000036
Is composed of
Figure FDA0003394540900000037
Wherein R iscFor pseudo code rate, fRFAt radio frequency, fsampIn order to be able to sample the frequency of the signal,
Figure FDA0003394540900000038
for the minimum carrier doppler shift to be used,
Figure FDA0003394540900000039
a step is searched for the carrier doppler shift,
Figure FDA00033945409000000310
is the minimum carrier doppler rate of change,
Figure FDA00033945409000000311
a step is searched for the carrier doppler rate of change.
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