CN104914413A - Random sequence linear frequency modulation signal windowed pulse compression method - Google Patents

Abstract

The invention provides a random sequence linear frequency modulation signal windowed pulse compression method. By utilizing frequency-domain and time-domain distribution rules of a random sequence linear frequency modulation signal, sequence rearrangement is performed on the random sequence linear frequency modulation signal through a frequency-domain correction method, the waveform of the random sequence linear frequency modulation signal is reverted into a standard linear frequency modulation signal, and then processing is performed by through adoption of traditional windowing and pulse compressing methods, so good and stable pulse compression performance can be obtained, and the method is not sensitive to a random sequence change of the random sequence linear frequency modulation signal. The method can be suitable for pulse compression processing of various random sequence linear frequency modulation signals.

Description

A kind of random series linear FM signal windowing impulse compression method

Technical field

The invention belongs to Radar Signal Processing Technology field, be specially a kind of random series linear FM signal windowing impulse compression method.

Background technology

In order to solve in the range resolution of radar and average power contradiction between the two, obtain higher ranging and range rate precision and range-speed resolution, pulse compression technique is widely used in modern radar system.The high range resolution that pulse compression radar can keep short-pulse radar to have, can obtain again the strong detectability of broad pulse radar, and antijamming capability is strong.Different waveforms has different pulse compression performance, and at present in military radar field, modal radar waveform signal form is linear FM signal and phase-coded signal.Linear FM signal advantage to realize wider bandwidth, insensitive to Doppler frequency, and shortcoming is that pulse compression sidelobe is higher, and need windowing, waveform resources is less, and modulation rule is single, is easily identified and predicts; After phase-coded signal pulse compression, secondary lobe is lower, is conducive to realizing low intercepting and capturing performance, and waveform resources enriches, and lacks Doppler shift responsive, is difficult to realize large bandwidth signal.Existing linear FM signal and coded signal pulse compression simulation result are as depicted in figs. 1 and 2.

In order to address these problems, academia proposes multiple improvement Waveform Design, ites is desirable to can take into account both advantages, make up respective defect.The linear FM signal of random series is exactly wherein a kind of signal form.

Random series linear FM signal, this signal relatively with discrete frequency coded signal (DFCW).This signal mode of constructing is, first constructs normal linearity FM signal F (x), and signal is evenly divided into N number of segment f _nx (), every section is a code element, and it is numbered 1 ~ N, then to construct a codomain be the random series of 1 ~ N, according to the value of element each in sequence, corresponding code element is reconfigured successively, just realizes new waveform pattern.The architecture model of the linear FM signal of random series is as Fig. 3.

Random series linear FM signal possesses abundant code source resource, if the sequence segment number of signal is N, then known signal code source number be N! .For the random series linear FM signal that segments is 5, its yard of source number is 120.Random series linear FM signal can be expressed as:

$s\left(t\right)=\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{u}_n\left(t\right)v_n\left(t\right),t\∈(0,N{t}_p)$

v _n(t)＝exp(j2πf _c(t+(c _n-n)t _p)+jπk(t+(c _n-n)t _p) ²)

Wherein N is code element segmentation number; t _pfor code element section length; c _nfor random series; K is signal frequency modulation rate; f _cfor signal carrier frequency, j is imaginary symbols.

But random series linear FM signal inapplicable traditional impulse compression method, as shown in Figure 4 and Figure 5, adopt traditional impulse compression method, after its pulse compression, secondary lobe is far above the linear FM signal of standard, because which limit the practical application of the linear FM signal of random series.

Summary of the invention

For solving the problem of the inapplicable traditional impulse compression method of random series linear FM signal, the present invention devises a kind of process of pulse-compression scheme, utilize frequency domain and the time domain regularity of distribution of the linear FM signal of random series, by the method for frequency-domain correction, sequence reorganization is carried out to the linear FM signal of random series, it is a linear FM signal of standard by its wave recovery, traditional windowing and impulse compression method is adopted to process again, better and stable pulse compression performance can be obtained, insensitive to the random series change of the linear FM signal of random series.The present invention is applicable to the process of pulse-compression of the linear FM signal of various random series.

Technical scheme of the present invention is:

Described a kind of random series linear FM signal windowing impulse compression method, is characterized in that: adopt following steps:

Step 1: according to the coded sequence of the linear FM signal of random series, obtains the frequency-domain correction factor of each code element in the linear FM signal of random series, and wherein the frequency-domain correction factor of i-th code element is wherein j is imaginary symbols, represent the frequency range of i-th code element, a _iwhen expression transforms to normal linearity FM signal from the linear FM signal of random series, the displacement of i-th code element in time domain;

Step 2: carry out FFT process to the linear FM signal echo data of the random series received, by the FFT result of each code element with corresponding frequency-domain correction fac-tor, then carries out IFFT process, obtains the normal linearity FM signal after sequence reorganization;

Step 3: the normal linearity FM signal after sequence reorganization carries out conventional windowing and process of pulse-compression.

Beneficial effect

The present invention carries out frequency-domain correction by the linear FM signal of random series and resets process, the linear FM signal of standard is corrected in time domain, for windowing below and process of pulse-compression provide condition, improve the pulse compression performance of the linear FM signal of random series, thus obtain lower pulse pressure secondary lobe.This method has adapted to the linear FM signal application demand of random series, facilitates the process of signal.The present invention does not limit the linear FM signal encoding characteristics of random series, is applicable to the linear FM signal process of various types of random series.

Accompanying drawing explanation

Fig. 1: linear FM signal emulated data figure;

Fig. 2: 13 Barker code signal simulation data plots;

Fig. 3: random series linear FM signal schematic diagram;

Fig. 4: random sequence signal time-domain windowed pulse pressure Local map;

Fig. 5: linear FM signal time-domain windowed pulse pressure Local map;

Fig. 6: random series linear FM signal sequence reorganization treatment scheme;

Fig. 7: echoed signal non-power window pulse compression Local map;

Fig. 8: random sequence signal conventional windowing pulse pressure Local map;

Fig. 9: compression of signal pulse result Local map after sequence reorganization.

Embodiment

Below in conjunction with specific embodiment, the present invention is described:

This embodiment is one and adopts random series linear FM signal as transmitted waveform on half radar simulator in kind, line order of going forward side by side rearrangement process of pulse-compression.

The method that frequency domain is reset is based on the displacement property of Fourier Tranform, and its formula is as follows

If:

Then have: (a is real number),

According to this formula, only need to be multiplied by a factor at the frequency domain of signal pass through inverse Fourier Tranform again, just can obtain time-domain position move after signal f (t ± a).

The present embodiment sequence reorganization process of pulse-compression is exactly the coding characteristic according to the linear FM signal of random series, its random series code determines its signal frequency domain and the time domain regularity of distribution, according to its rule, each code element fragment position correction signal is generated at frequency domain, frequency domain position punching row process is carried out with the radar echo signal received, linear for former random series FM signal is changed into normal linearity FM signal in time domain, finally carry out general pulse compression windowing process, obtain pulse compression result, the concrete step adopted below:

Step 1: according to the coded sequence of the linear FM signal of random series, obtains the frequency-domain correction factor of each code element in the linear FM signal of random series, and wherein the frequency-domain correction factor of i-th code element is wherein j is imaginary symbols, represent the frequency range of i-th code element, a _iwhen expression transforms to normal linearity FM signal from the linear FM signal of random series, the displacement of i-th code element in time domain;

Step 2: carry out FFT process to the linear FM signal echo data of the random series received, by the FFT result of each code element with corresponding frequency-domain correction fac-tor, then carries out IFFT process, obtains the normal linearity FM signal after sequence reorganization;

Step 3: the normal linearity FM signal after sequence reorganization carries out conventional windowing and process of pulse-compression.

The signal parameter of this embodiment setting guinea pig is: signal carrier frequency 9GHz, signal pulsewidth 35us, chirp rate Kr=100010 ⁹hz/ second, signal subsection random series is (7,2,5,4,3,1,6).

When simulation run, radar simulator is according to time beat, simulation random series linear FM signal radio-frequency echo wave, after down coversion, carry out sampling processing, employing sequence reorganization windowing process method in process, in order to contrast, is also by non-windowing disposal route and conventional windowing process method.

Result is as shown in Fig. 7 ~ Fig. 9, signal after sequence reorganization is that sample carries out pulse compression with basis signal, due to signal distortion impact, main peak amplitude comparison with standard linear FM signal slightly declines (about 0.5dB), although the secondary lobe distribution of signal is not as good as normal linearity FM signal, but than directly carrying out the situation of pulse compression, near region and far field secondary lobe have obvious reduction, after windowing, main-side lobe ratio can reach about 23dB, improve 10dB than non-windowing pulse pressure, improve 5dB than conventional windowing pulse pressure.

Claims (1)

1. a random series linear FM signal windowing impulse compression method, is characterized in that: adopt following steps:

Step 1: according to the coded sequence of the linear FM signal of random series, obtains the frequency-domain correction factor of each code element in the linear FM signal of random series, and wherein the frequency-domain correction factor of i-th code element is wherein j is imaginary symbols, represent the frequency range of i-th code element, a _iwhen expression transforms to normal linearity FM signal from the linear FM signal of random series, the displacement of i-th code element in time domain;

Step 2: carry out FFT process to the linear FM signal echo data of the random series received, by the FFT result of each code element with corresponding frequency-domain correction fac-tor, then carries out IFFT process, obtains the normal linearity FM signal after sequence reorganization;

Step 3: the normal linearity FM signal after sequence reorganization carries out conventional windowing and process of pulse-compression.