CN-122026943-A - Burst spread spectrum signal rapid capturing method

Abstract

The invention discloses a burst spread spectrum signal rapid capturing method. The method comprises the steps of firstly, carrying out ADC sampling on a received intermediate frequency signal, carrying out quadrature down-conversion and low-pass filtering to obtain a homodromous signal and a quadrature signal, combining the homodromous signal and the quadrature signal into a complex form to obtain a complex baseband signal, dividing the complex baseband signal into a plurality of sections, windowing each section of signal, carrying out partial matched filtering and fast Fourier transformation on the windowed signal to obtain a normalized amplitude-frequency response, carrying out correction on an original threshold value by using energy loss, carrying out capture judgment by using the corrected threshold value, carrying out interpolation by using an A-P-life algorithm, calculating a Doppler frequency fine estimation value, finally, calculating interpolation comprehensive confidence, and adopting the Doppler frequency fine estimation value if the interpolation comprehensive confidence is larger than or equal to a set threshold value, otherwise adopting the Doppler frequency coarse estimation value. The probability of large frequency offset caused by correction direction errors can be effectively reduced, and the anti-interference performance and stability of a follow-up tracking loop are improved.

Inventors

• Yi Bozhao
• GAO ZHENBIN

Assignees

• 河北工业大学

Dates

Publication Date

20260512

Application Date

20260226

Claims (3)

1. 1. A method for fast acquisition of burst spread spectrum signals, comprising the steps of: The method comprises the steps of firstly, carrying out ADC sampling on a received intermediate frequency signal to obtain an intermediate frequency digital signal, generating an orthogonal intermediate frequency carrier signal, multiplying the intermediate frequency digital signal with the orthogonal intermediate frequency carrier signal respectively, and then carrying out low-pass filtering to obtain a homodromous signal and an orthogonal signal; correcting the original threshold value by using energy loss, and performing capture judgment by using the corrected threshold value; Correction threshold value Expressed as: (8) Wherein, the As the original threshold value is set, Is energy loss; Thirdly, interpolation is carried out by utilizing an A-P-Rife algorithm to obtain a correction direction and a correction stepping value; correcting the step value Calculated from formula (11): (11) Wherein, the The amplitude-frequency response is represented and, Representing a normalized amplitude-frequency response peak index; For correcting the direction judgment sign, the value is 1 or-1; Representing the amplitude; calculating a Doppler frequency fine estimate value according to (12) : (12) Wherein, the For the sampling frequency to be the same, For a partial matching of the filter length, Counting FFT points; calculating interpolation comprehensive confidence coefficient, if the interpolation comprehensive confidence coefficient is larger than a set threshold value, adopting a Doppler frequency fine estimation value, and if the interpolation comprehensive confidence coefficient is smaller than the set threshold value, adopting a Doppler frequency rough estimation value; Calculating the confidence of the interpolation amplitude according to (13) : (13) Wherein, the Is a constant value, and is used for the treatment of the skin, Representing an absolute value; Calculating signal to noise ratio confidence according to (14) : (14) Wherein, the As a result of the threshold value being set, Representing the signal-to-noise ratio estimate; calculating an interpolation integrated confidence according to (15) : (15) Wherein, the 、 As the weight coefficient of the light-emitting diode, ; If the interpolation comprehensive confidence coefficient is larger than or equal to the set threshold value, adopting a Doppler frequency fine estimation value, otherwise adopting a Doppler frequency rough estimation value as follows ; (16)。
2. 2. The method of claim 1, wherein the raw threshold value is calculated by: (9) Wherein, the As the variance of the noise is the value of the variance of the noise, For the probability of a false alarm in the system, Is the number of search units.
3. 3. The burst spread spectrum signal fast acquisition method according to claim 1, wherein the energy loss is calculated by the following formula: (7) In the formula, As a window function.

Description

Burst spread spectrum signal rapid capturing method Technical Field The invention belongs to the technical field of communication signal processing, and particularly relates to a burst spread spectrum signal rapid capturing method. Background Direct Sequence Spread Spectrum (DSSS) signals are often transmitted in bursts with low transmit power, and received signals are noise-like in nature, difficult to identify in noise, and often used in long-range interference-free communication scenarios. With the rapid development of the fields of low-orbit satellite communication, GNSS positioning, wireless communication and the like, the received signal often has the characteristics of large signal frequency offset, rapid dynamic change, low signal-to-noise ratio (SNR) and the like. Especially for bursty short-time signals, how to reliably acquire (i.e., detect and acquire code phase and frequency offset) in a limited time is a technical challenge. The prior art generally uses a parallel capturing method of partial matched filtering and fast fourier transform (PMF-FFT), firstly, the input signal is subjected to piecewise correlation by using a partial matched filter (PARTIAL MATCH FILTER, PMF) to reduce complexity by parallel processing, and then, the segmented signal is subjected to FFT, and all doppler signals are searched in parallel at one time, so that the capturing time is effectively shortened, and the fast capturing of the high dynamic signal is realized under a certain condition. However, the PMF-FFT parallel acquisition method still has limitations in the scenarios of low signal-to-noise ratio and large frequency offset. The FFT frequency domain searching has a fence effect, when the actual frequency of a signal falls between two discrete frequency points, the output amplitude can be obviously attenuated, the scallop loss can reduce the detection peak amplitude, and the misjudgment or the missing detection probability is increased. Typical measures are to window the data prior to FFT to broaden the main lobe, slow down the attenuation of the correlation peak as the frequency offset increases, and reduce the amplitude loss of the frequency domain output in the middle of the two points. However, the window function applies weights to the signal, resulting in a reduction in the amplitude of the correlation peak, which leads to power loss and severely affects the detection of weak signals. In addition, after the rough frequency offset is successfully detected, the frequency offset estimation precision needs to be further improved, so that the follow-up tracking loop can be quickly converged, and stable tracking is maintained. The traditional interpolation algorithm has the problem of direction judgment errors, so that frequency deviation is larger, and subsequent tracking loops are unlocked, and the demodulation process of signals is affected. Disclosure of Invention Aiming at the defects of the prior art, the invention aims to provide a burst spread spectrum signal rapid capturing method. The invention solves the technical problems by adopting the following technical scheme: A method for fast acquisition of burst spread spectrum signals, comprising the steps of: The method comprises the steps of firstly, carrying out ADC sampling on a received intermediate frequency signal to obtain an intermediate frequency digital signal, generating an orthogonal intermediate frequency carrier signal, multiplying the intermediate frequency digital signal with the orthogonal intermediate frequency carrier signal respectively, and then carrying out low-pass filtering to obtain a homodromous signal and an orthogonal signal; correcting the original threshold value by using energy loss, and performing capture judgment by using the corrected threshold value; Correction threshold value Expressed as: (8) Wherein, the As the original threshold value is set,Is energy loss; Thirdly, interpolation is carried out by utilizing an A-P-Rife algorithm to obtain a correction direction and a correction stepping value; correcting the step value Calculated from formula (11): (11) Wherein, the The amplitude-frequency response is represented and,Representing a normalized amplitude-frequency response peak index; For correcting the direction judgment sign, the value is 1 or-1; Representing the amplitude; calculating a Doppler frequency fine estimate value according to (12) : (12) Wherein, the For the sampling frequency to be the same,For a partial matching of the filter length,Counting FFT points; calculating interpolation comprehensive confidence coefficient, if the interpolation comprehensive confidence coefficient is larger than a set threshold value, adopting a Doppler frequency fine estimation value, and if the interpolation comprehensive confidence coefficient is smaller than the set threshold value, adopting a Doppler frequency rough estimation value; Calculating the confidence of the interpolation amplitude according to (13) : (13) Wherei