High-dynamic spread spectrum signal rapid acquisition algorithmTechnical Field
The invention relates to the technical field of spread spectrum signal rapid acquisition algorithms, in particular to a high-dynamic spread spectrum signal rapid acquisition algorithm.
Background
The spread spectrum communication technology is an information transmission mode, the frequency bandwidth occupied by signals is far larger than the minimum bandwidth necessary for the transmitted information, the expansion of the frequency band is completed by an independent code sequence, and the spread spectrum communication technology is realized by a coding and modulating method and is independent of the transmitted information data; the same code is used for carrying out related synchronous receiving, despreading and recovering the transmitted information data at a receiving end, the application and service range of high-speed moving bodies such as airplanes, satellites and the like is larger and larger at present, but the spread spectrum signals of the high-speed moving bodies are still captured under high dynamic conditions, and a receiver receives carrier signals under the high dynamic conditions, so that the Doppler frequency offset is larger, the Doppler change rate is higher, the effective capturing speed of the signals is influenced, and therefore the invention provides a high-dynamic spread spectrum signal rapid capturing algorithm.
Disclosure of Invention
The invention aims to provide a high-dynamic spread spectrum signal rapid acquisition algorithm, which is used for calculating the Doppler frequency change rate, obtaining a signal with the frequency change rate eliminated through compensation, acquiring a pseudo code phase only by one-time pseudo code acquisition, and realizing rapid acquisition with short acquisition time.
In order to achieve the purpose, the invention provides the following technical scheme: a high dynamic spread spectrum signal fast acquisition algorithm comprises the following steps:
the method comprises the following steps: acquiring a signal R1, obtaining a signal Rt after delay time t, and performing autocorrelation operation on the signal R1 and the signal Rt of the delay time t based on the Doppler shift estimation technology of FFT;
step two: processing the autocorrelation operation result of the signal R1 and the signal Rt of the delay time t thereof by using FFT to perform frequency offset analysis, and obtaining the Doppler frequency change rate k;
step three: reconstructing a spread spectrum signal R2 by compensating the signal frequency offset according to the frequency change rate k of the obtained Doppler frequency offset;
step four: carrying out FFT (fast Fourier transform) processing on the spread spectrum signal R2, preprocessing a local carrier signal, and multiplying the local carrier signal and the local carrier signal to obtain a result X;
step five: the result X is subjected to IFFT processing to obtain correlation peaks at all phases of the spread signal R2 and the local carrier signal, and the correlation peaks are maximized.
As a still further scheme of the invention:
in the first step, the down-conversion processing needs to be performed on the signal R1 and the signal Rt before the autocorrelation processing is performed on the signal R1 and the signal Rt at the delay time t, so that the influence of white noise in the signal R1 and the signal Rt at the delay time t is reduced.
As a still further scheme of the invention:
the signal R2 reconstructed by compensation in the third step is a signal from which the frequency change rate is removed.
As a still further scheme of the invention:
in the fourth step, FFT transformation processing is performed on the spread spectrum signal R2, so as to perform FFT frequency estimation on the signal R2, so as to estimate the initial doppler frequency offset Fd.
As a still further scheme of the invention:
the step five of preprocessing the local carrier signal comprises the following steps:
s5.1: carrying out fast Fourier transform processing on the local carrier signal;
s5.2: and performing conjugation processing on the local carrier signal subjected to the fast Fourier transform processing.
As a still further scheme of the invention:
the method also comprises the steps of comparing and processing the capture threshold;
and analyzing and comparing the maximum value obtained in the step five with a capture threshold.
As a still further scheme of the invention:
and when the capturing threshold is compared and processed, the maximum value obtained in the step five is larger than the capturing threshold, and the capturing is finished.
As a still further scheme of the invention:
and during the comparison processing of the capture threshold, modifying the local carrier signal frequency and the pseudo code phase when the maximum value obtained in the step five is smaller than the capture threshold, and entering the next round of capture.
Compared with the prior art, the invention has the beneficial effects that:
the invention discloses a high dynamic spread spectrum signal fast capturing algorithm, which obtains Doppler frequency change rate through frequency offset analysis calculation, compensates signal frequency offset reconstruction signals according to the Doppler frequency change rate k to obtain signals with the frequency change rate eliminated, then can obtain a pseudo code phase only by one-time pseudo code capturing without performing limited serial stepping search on Doppler and pseudo codes, has short capturing time, simultaneously realizes comparison analysis on a capturing threshold, and modifies the local carrier signal frequency and the pseudo code phase according to a comparison result to realize fast capturing of the high dynamic spread spectrum signal.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A fast acquisition algorithm for a high dynamic spread spectrum signal, comprising the steps of:
the method comprises the following steps: acquiring a signal R1, obtaining a signal Rt after delay time t, and performing autocorrelation operation on the signal R1 and the signal Rt of the delay time t based on the Doppler shift estimation technology of FFT;
step two: processing the autocorrelation operation result of the signal R1 and the signal Rt of the delay time t thereof by using FFT to perform frequency offset analysis, and obtaining the Doppler frequency change rate k;
step three: reconstructing a spread spectrum signal R2 by compensating the signal frequency offset according to the frequency change rate k of the obtained Doppler frequency offset;
step four: carrying out FFT (fast Fourier transform) processing on the spread spectrum signal R2, preprocessing a local carrier signal, and multiplying the local carrier signal and the local carrier signal to obtain a result X;
step five: the result X is subjected to IFFT processing to obtain correlation peaks at all phases of the spread signal R2 and the local carrier signal, and the correlation peaks are maximized.
In the first step, the down-conversion processing needs to be performed on the signal R1 and the signal Rt before the autocorrelation processing is performed on the signal R1 and the signal Rt at the delay time t, so that the influence of white noise in the signal R1 and the signal Rt at the delay time t is reduced.
The white noise is noise with power spectral density being constant in the whole frequency domain, and the down-conversion processing is performed on the signal R1 and the signal Rt with the delay time t, so that the white noise interference in the signal R1 and the signal Rt with the delay time t is removed, and the subsequent calculation processing on the signal R1 and the signal Rt with the delay time t is facilitated.
The signal R2 reconstructed by compensation in step three is a signal from which the rate of change of frequency is removed.
In the fourth step, FFT transformation processing is performed on the spread spectrum signal R2, so as to perform FFT frequency estimation on the signal R2, so as to estimate the initial doppler frequency offset Fd.
The step five of preprocessing the local carrier signal comprises the following steps:
s5.1: carrying out fast Fourier transform processing on the local carrier signal;
s5.2: and performing conjugation processing on the local carrier signal subjected to the fast Fourier transform processing.
The Doppler frequency change rate is obtained through frequency offset analysis and calculation, the signal frequency offset reconstruction signal is compensated according to the Doppler frequency change rate k to obtain a signal with the frequency change rate eliminated, then the pseudo code phase can be obtained only by one-time pseudo code capturing, the Doppler and pseudo code limiting serial stepping search is not needed, and the capturing time is short.
The method also comprises the steps of comparing and processing the capture threshold;
and analyzing and comparing the maximum value obtained in the step five with a capture threshold.
And when the capture threshold is compared and processed, the maximum value obtained in the step five is larger than the capture threshold, and the capture is finished.
And D, when the capturing threshold is compared and processed, the maximum value obtained in the step five is smaller than the capturing threshold, the local carrier signal frequency and the pseudo code phase are modified, and the next round of capturing is carried out.
The maximum value of the correlation peak values of the spread spectrum signal R2 and all phases of the local carrier signal is compared with a capture threshold, and the frequency and the pseudo code phase of the local carrier signal are modified according to the comparison result, so that the high-dynamic spread spectrum signal can be rapidly captured.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.