CN-121996906-A - Correction method for spectral distortion of Chirp transformation spectrum analyzer

CN121996906ACN 121996906 ACN121996906 ACN 121996906ACN-121996906-A

Abstract

The invention provides a correction method of spectral distortion of a Chirp transformation spectrum analyzer, which comprises the steps of establishing a broadened line phase error model and a compressed line phase error model of the Chirp transformation spectrum analyzer, estimating the broadened line phase error and the compressed line phase error through a Chirp signal phase error estimation method based on the broadened line phase error model and the compressed line phase error model, establishing a system simulation model of the Chirp transformation spectrum analyzer according to the broadened line phase error and the compressed line phase error, predicting the spectral distortion generated by a detected signal in the Chirp transformation spectrum analyzer by using the system simulation model, constructing a correction curve and a wiener inverse filter based on the predicted spectral distortion, and correcting an actual spectrum output by the Chirp transformation spectrum analyzer by using the correction curve and the wiener inverse filter.

Inventors

LIU MENGWEI
HU BAIFAN
Xie Lurui
HU YUANYUAN
WANG WEN

Assignees

中国科学院声学研究所

Dates

Publication Date: 20260508
Application Date: 20251217

Claims (7)

1. A method for correcting spectral distortion of a Chirp-shift spectrum analyzer, comprising: establishing a broadened line phase error model and a compressed line phase error model of the Chirp transformation spectrum analyzer; estimating the phase error of the broadening line and the phase error of the compression line by a Chirp signal phase error estimation method based on the phase error model of the broadening line and the phase error model of the compression line; According to the phase error of the stretching line and the phase error of the compressing line, a system simulation model of the Chirp transformation spectrum analyzer is established, and the system simulation model is utilized to predict the spectrum distortion generated by the measured signal in the Chirp transformation spectrum analyzer; constructing a correction curve and a wiener inverse filter based on the predicted spectral distortion; And correcting the actual frequency spectrum output by the Chirp transformation frequency spectrum analyzer by using the correction curve and the wiener inverse filter.
2. The correction method of claim 1, wherein the stretched line phase error model is: Where k 1 is the frequency modulation slope of the broadened line, f 1 is the initial frequency of the broadened line, For the phase error of the stretched line, T represents the time domain and T 1 is the duration of the stretched line; the compressed line phase error model is as follows: where k 2 is the chirp rate of the compression line, f 2 is the initial frequency of the compression line, For the phase error of the compressed line, T represents the time domain and T 2 is the duration of the compressed line response.
3. The correction method according to claim 2, wherein estimating the broadened line phase error and the compressed line phase error by the Chirp signal phase error estimation method includes: extracting phase information and frequency range of the stretching wire and the compression wire, carrying out phase unwrapping on the phase information to obtain continuous frequency-phase characteristics, carrying out quadratic polynomial fitting on the continuous frequency-phase characteristics by utilizing a least square method to obtain fitted quadratic phase curves, determining actual frequency modulation slopes of the stretching wire and the compression wire according to the fitted quadratic phase curves, and subtracting the continuous frequency-phase characteristics from the fitted quadratic phase curves to obtain phase error curves in the frequency range of the stretching wire and the compression wire.
4. The correction method according to claim 3, wherein establishing a system simulation model of a Chirp-shift-spectrum analyzer based on the stretched-line phase error and the compressed-line phase error, and predicting spectral distortion generated in the Chirp-shift-spectrum analyzer by a measured signal using the system simulation model, comprises: An ideal stretching line model and an ideal compression line model are built, phase errors of the stretching lines are added into the ideal stretching line model to obtain a stretching line simulation model, and phase errors of the compression lines are added into the ideal compression line model to obtain a compression line simulation model; Selecting N test signals with different frequencies in the measurement bandwidth of a Chirp variation spectrum analyzer, and predicting to obtain a predicted frequency f p (k), a predicted amplitude A p (k) and a predicted distorted pulse compression output spectrum of each test signal by using the system simulation model Calculating the frequency offset of each test signal: Δf(k)=f p (k)-f i (k),k=1,2,3,......,N wherein Δf (k) represents the frequency offset, k is the index of the frequency bin, f p (k) represents the predicted frequency, f i (k) represents the signal true frequency, and calculating the amplitude attenuation coefficient of each test signal: α(k)=A p (k)/A i (k),k=1,2,3,......,N Where α (k) represents an amplitude attenuation coefficient, k is an index of a frequency point, a p (k) represents a predicted spectral amplitude, and a i (k) represents a spectral amplitude in an ideal state, and calculating a distortion channel response of each test signal: Where H (f) represents the distorted channel response, f is the frequency, Representing the predicted distorted pulse compressed output spectrum, and P (f) represents the ideal pulse compressed output spectrum.
5. The correction method of claim 4, wherein the N different frequency test signals are equally frequency spaced within the measurement bandwidth.
6. The correction method according to claim 4, wherein constructing a correction curve and a wiener inverse filter based on the predicted spectral distortion, comprises: resampling the frequency offset and amplitude attenuation coefficients of the N test signals to enable the sampling rate to be consistent with that of the Chirp transformation spectrum analyzer, and obtaining a resampled frequency offset curve delta f (omega) and an amplitude attenuation coefficient curve alpha (omega), wherein omega is the angular frequency of the test signals; The calculated frequency correction curve is: C f (ω)=-Δf(ω) wherein, C f (omega) is a frequency correction curve, omega is the angular frequency of the input signal, and Δf (omega) is a resampled frequency offset curve; the calculated amplitude correction curve is: G A (ω)=1/α(ω) Wherein G A (omega) is an amplitude correction curve, omega is the angular frequency of an input signal, and alpha (omega) is an amplitude attenuation coefficient curve after resampling; The wiener inverse filter is constructed as follows: Wherein, P ss (f) is the ideal signal to be recovered, P nn (f) is the power spectrum density of the system noise, H (f) is the distorted channel response, H * (f) is the complex conjugate of H (f), and G (f) is the wiener inverse filter formula.
7. The correction method of claim 6, wherein correcting the actual spectrum output by the Chirp-transformed spectrum analyzer using the correction curve and a wiener inverse filter comprises: Measuring an actual signal by a Chirp transformation spectrum analyzer to obtain a frequency spectrum, adding a frequency in the frequency spectrum to a corresponding correction value in the frequency correction curve, multiplying an amplitude in the frequency spectrum by the corresponding correction value in the amplitude correction curve, and correcting waveform distortion of a pulse compression result by a wiener inverse filter.

Description

Correction method for spectral distortion of Chirp transformation spectrum analyzer Technical Field The invention relates to the technical field of deep space spectrum detection, in particular to a correction method for spectrum distortion of a Chirp transformation spectrum analyzer. Background The Chirp transformation spectrum analyzer (Chirp Transform Spectrometer, CTS) is a spectrum detection system for realizing the spectrum analysis of the detected signal based on the Chirp transformation algorithm, and mainly comprises a Chirp signal (broadening line) for spreading and a matched filter (compression line) for matched filtering. The matched filter is usually a Chirp signal with the inverse frequency modulation slope of the broadening line, the measured signal is multiplied by the broadening line to realize signal broadening, and then convolved with the compression line to realize pulse compression, so that the frequency spectrum of the measured signal can be obtained. With the rapid development of the deep space exploration field, the variety of radiation substances to be detected is increasingly abundant. Deep space spectrum detection systems are also developed in the direction of large bandwidth, high frequency resolution and high frequency spectrum detection accuracy. The Chirp transformation spectrum analyzer has the advantages of high bandwidth, high frequency resolution, high sensitivity, low quality, low power consumption and the like, can be used for detecting ultra-fine spectral lines, weak spectral lines and high bandwidth spectral lines, and has certain advantages in the field of deep space detection. The chromatic dispersion characteristics of the high-bandwidth Chirp signal are difficult to be kept consistent in a band due to the phase error introduced in the generation process of the high-bandwidth Chirp signal, so that distortion phenomena such as pulse position deviation, pulse main lobe reduction, sidelobe lifting and the like occur in a pulse compression result, the output spectral line of the Chirp transformation spectrum analyzer is subjected to frequency deviation and amplitude attenuation, the accuracy and the reliability of a spectrum measurement result are seriously influenced, the phase error caused by a broadening line can be only compensated in the prior art, the phase error of the compression line is not effectively processed, and high-power consumption devices such as FPAG and DAC are required to be utilized, so that the high-bandwidth Chirp transformation spectrum analyzer is not suitable for application scenes with constraint on system power consumption such as deep space detection. For input frequencies with different frequencies, the frequency spectrum frequency band used by the stretching wire is inconsistent relative to the compression wire, so that the stretching wire cannot be compensated in a targeted manner according to the phase error of the compression wire. Therefore, a correction method for spectral distortion of a Chirp-shift-spectrum analyzer is required. Disclosure of Invention The invention aims to provide a correction method for spectrum distortion of a Chirp transformation spectrum analyzer, which is characterized in that a distortion prediction model is constructed by independently characterizing, jointly modeling and simulating a widening line and a compressing line, a frequency/amplitude correction curve and a wiener inverse filter are generated according to the distortion prediction model, and finally, the actually measured spectrum is comprehensively corrected at the rear end of signal processing, so that the frequency precision, the amplitude flatness and the pulse waveform quality of a CTS system are obviously improved. In order to achieve the above object, the present invention provides a method for correcting spectral distortion of a Chirp transformation spectrum analyzer, comprising: establishing a broadened line phase error model and a compressed line phase error model of the Chirp transformation spectrum analyzer; estimating the phase error of the broadening line and the phase error of the compression line by a Chirp signal phase error estimation method based on the phase error model of the broadening line and the phase error model of the compression line; According to the phase error of the stretching line and the phase error of the compressing line, a system simulation model of the Chirp transformation spectrum analyzer is established, and the system simulation model is utilized to predict the spectrum distortion generated by the measured signal in the Chirp transformation spectrum analyzer; constructing a correction curve and a wiener inverse filter based on the predicted spectral distortion; And correcting the actual frequency spectrum output by the Chirp transformation frequency spectrum analyzer by using the correction curve and the wiener inverse filter. Preferably, the broadened line phase error model is: Where k 1 is the frequency mod