CN112684418A - Weak signal extraction method of pulse Doppler radar echo - Google Patents
Weak signal extraction method of pulse Doppler radar echo Download PDFInfo
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Abstract
The invention provides a weak signal extraction method of pulse Doppler radar echo, which comprises the following steps: over-sampling and quantizing the radar intermediate frequency echo; low-pass filtering; matching and filtering; range-pulse matrix coherent accumulation; and tracking and intercepting the dynamic range of the range-Doppler matrix data. The invention well solves the problem that the acceptance performance can not be improved by a pulse compression technology under the condition of extremely narrow pulse based on the noise suppression of the combination of high-power oversampling and a matched filter, and improves the signal-to-noise ratio of an echo signal by coherent accumulation of a distance-pulse matrix so as to further suppress the noise. The dynamic range tracking interception method for the range-Doppler matrix data solves the contradiction between the dynamic range and the precision of digital signal processing under the condition of a low-cost receiver. The invention preferably provides a complete technical solution for extracting the weak signal of the pulse Doppler radar echo, and has certain practical function in the aspect of detecting the weak signal of the pulse meteorological radar echo.
Description
Technical Field
The invention relates to the technical field of radar signal processing, in particular to a weak signal extraction method based on pulse Doppler radar echo.
Background
The problem that how to effectively extract weak signals in echoes of the pulse Doppler radar within the range of 20-300 meters of a near field is solved by the industry. The echo signal is characterized by a very weak strength and a short detection distance, which results in a high pulse repetition frequency, which results in a very short effective time of the narrow pulse for detection, and if radar detection means such as pulse compression is adopted, a digital-to-analog conversion device with a very high sampling frequency is required, which increases the cost of the application product.
On the other hand, in embedded applications, software and hardware resources for radar signal processing are limited, so that in the whole radar processing algorithm, the operation of floating point numbers is replaced by signed integer numbers, and the disadvantage of using fixed point numbers is the shortage of dynamic range.
Disclosure of Invention
The invention aims to solve the problem that the receiving performance can not be improved by a pulse compression technology under extremely narrow pulses, and adopts the technical scheme that: a weak signal extraction method of pulse Doppler radar echo comprises the following steps:
over-sampling and quantizing the radar intermediate frequency echo;
low-pass filtering;
matching and filtering;
range-pulse matrix coherent accumulation;
and tracking and intercepting the dynamic range of the range-Doppler matrix data.
In a further improvement, the radar intermediate frequency echo oversampling and quantization comprises the following steps:
using repetition period T in radar systemsppiThe frequency spectrum of an ideal echo signal comprises zero frequency, fundamental frequency and infinite harmonic component as a narrow rectangular pulse of 2 us;
wherein the zero frequency f00Hz, fundamental frequency f1500KHz, harmonic fn＝n×500KHz；
The harmonic wave can be known from Fourier series theoryNumber of times n>Engineering bandwidth B of ideal echo signal at 10 hoursr＝5MHz。
In a further improvement, the matched filtering includes the following steps:
after low-pass filtering, the image spectrum introduced by the digital sampling is removed;
and (3) matched filtering calculation:
wherein the design parameters
PτIs at a sampling frequency fsNumber of samples within the duration of the lower narrow pulse.
In a further refinement, the range-pulse matrix coherent accumulation comprises the following steps:
the distance-pulse matrix is denoted as d (l), and is a 2048 × 25 complex matrix, each row is a set of different sampling points, each column is a set of sampling points at the same distance in different pulse periods, and G d (l) matrices are accumulated to obtain a 2048 × 25 complex matrix:
in a further improvement, the dynamic range tracking interception of the range-doppler matrix data comprises the following steps:
convert the range-pulse matrix E (p) to a range-Doppler matrix F (p), where the x-column elements of F (p) are denoted as fp(x), the magnification factor S (x) in the x-th column is 2λ(x)Wherein λ (x) is fpThe number of extended sign bits of the element with the largest absolute value in (x).
Compared with the prior art, the invention has the following beneficial effects:
the invention well solves the problem that the acceptance performance can not be improved by a pulse compression technology under the condition of extremely narrow pulse based on the noise suppression of the combination of high-power oversampling and a matched filter, and improves the signal-to-noise ratio of an echo signal by coherent accumulation of a distance-pulse matrix so as to further suppress the noise. The dynamic range tracking interception method for the range-Doppler matrix data solves the contradiction between the dynamic range and the precision of digital signal processing under the condition of a low-cost receiver. The invention preferably provides a complete technical solution for extracting the weak signal of the pulse Doppler radar echo, and has certain practical function in the aspect of detecting the weak signal of the pulse meteorological radar echo.
Drawings
The invention is further illustrated with reference to the following figures and examples.
FIG. 1 is a flow chart of a weak signal extraction method of a pulse Doppler radar echo according to the present invention;
fig. 2 illustrates the problem of interference caused by overlapping of the self frequency spectrum of the echo signal and the sampling image frequency spectrum of the echo signal, which is introduced by the reduction of the sampling quantization frequency of the radar echo signal.
Detailed Description
In order to make the disclosure more complete and complete, reference may be made to the accompanying drawings, in which like references indicate the same or similar elements, and to the various embodiments of the disclosure described below. However, it should be understood by those skilled in the art that the examples provided below are not intended to limit the scope covered by the present application. In addition, the drawings are only for illustrative purposes and are not drawn to scale.
In a typical configuration of the present application, the terminal, the device serving the network, and the trusted party each include one or more processors (CPUs), input/output interfaces, network interfaces, and memory. The memory may include forms of volatile memory in a computer readable medium, Random Access Memory (RAM) and/or non-volatile memory, such as Read Only Memory (ROM) or flash memory (flash RAM). Memory is an example of a computer-readable medium. Computer-readable media, including both non-transitory and non-transitory, removable and non-removable media, may implement information storage by any method or technology. Information may be computer readable instructions, data structures, program sub-units, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), Read Only Memory (ROM), Electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), Digital Versatile Discs (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic hard disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include non-transitory computer readable media (transient media), such as modulated data signals and carrier waves.
As shown in fig. 1, the present invention provides a method for extracting a weak signal of a pulse doppler radar echo, including the following steps:
s01, oversampling and quantizing the radar intermediate frequency echo;
s02, low-pass filtering;
s03, matched filtering;
s04, distance-pulse matrix coherent accumulation;
and S05, carrying out dynamic range tracking interception on the range-Doppler matrix data.
In a further improvement, the radar intermediate frequency echo oversampling and quantization comprises the following steps:
in the radar system of the invention, a repetition period T is adoptedppi2us, the ideal echo signal itself contains zero frequency, fundamental frequency and infinite harmonic component, wherein the zero frequency f00Hz, fundamental frequency f1500KHz, harmonic fnN × 500 KHz; the harmonic order n can be known from Fourier series theory>Harmonic f at 10 hoursnHas been considered to be an ideal echo signal, the engineering bandwidth B, is already negligible in engineeringr5 MHz. Echo signal sampling frequency f in the systems> 5MHz, oversampling multiple MsVery much, according to the digital signal sampling theory, MsThe larger the echo signal is, the less the overlapping interference part of the self frequency spectrum of the echo signal and the sampling mirror frequency spectrum of the echo signal is, and on the other hand, the oversampling enables the number of sampling points in the duration time of the narrow rectangular pulse to be multiplied, so that the noise suppression performance of the subsequent matched filtering is improved.
In a further improvement, the matched filtering includes the following steps:
after low pass filtering, the image spectrum introduced by the digital samples is removed. On the basis of matching, further eliminating noise and improving effective signals, and calculating matched filtering:
wherein the design parameters
PτIs at a sampling frequency fsNumber of samples within the duration of the lower narrow pulse.
In a further refinement, the range-pulse matrix coherent accumulation comprises the following steps:
the distance-pulse matrix is denoted as d (l), and is a 2048 × 25 complex matrix, each row is a set of different sampling points, i.e., fast time dimension sampling, each column is a set of sampling points at the same distance in different pulse periods, and is slow time dimension sampling, and G (l) matrices are accumulated to obtain the 2048 × 25 complex matrix:
in a further improvement, the dynamic range tracking interception of the range-doppler matrix data comprises the following steps:
tracking and intercepting the dynamic range of range-Doppler matrix data, and converting a range-pulse matrix E (p) into a range-Doppler matrix F (p) by using FFT (fast Fourier transform) as a Fourier transform module, wherein x columns of elements of the range-Doppler matrix F (p) are recorded as fp(x), the magnification factor S (x) in the x-th column is 2λ(x)Wherein λ (x) is fpThe number of extended sign bits of the element with the largest absolute value in (x).
FIG. 2 illustrates the interference problem of the superposition of the self frequency spectrum of the echo signal and the sampling image frequency spectrum thereof, which is introduced by the reduction of the sampling quantization frequency of the radar echo signal, and it can be seen that the problem can be solved by the higher sampling frequency
In light of the foregoing description of the preferred embodiment of the present invention, many modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.
Claims (5)
1. A weak signal extraction method of pulse Doppler radar echo is characterized by comprising the following steps:
over-sampling and quantizing the radar intermediate frequency echo;
low-pass filtering;
matching and filtering;
range-pulse matrix coherent accumulation;
and tracking and intercepting the dynamic range of the range-Doppler matrix data.
2. The method for extracting weak signals of pulse doppler radar echo according to claim 1, wherein the radar intermediate frequency echo is quantized by oversampling, comprising the steps of:
using repetition period T in radar systemsppiThe frequency spectrum of an ideal echo signal comprises zero frequency, fundamental frequency and infinite harmonic component as a narrow rectangular pulse of 2 us;
wherein the zero frequency f00Hz, fundamental frequency f1500KHz, harmonic fn＝n×500KHz；
The engineering bandwidth B of an ideal echo signal can be known from Fourier series theory when the harmonic frequency n is more than 10r＝5MHz。
3. The method of claim 2, wherein the matched filtering comprises the steps of:
after low-pass filtering, the image spectrum introduced by the digital sampling is removed;
and (3) matched filtering calculation:
wherein the design parameters
PτIs at a sampling frequency fsNumber of samples within the duration of the lower narrow pulse.
4. The method of claim 3, wherein the range-pulse matrix coherent accumulation comprises the following steps:
the distance-pulse matrix is denoted as d (l), and is a 2048 × 25 complex matrix, each row is a set of different sampling points, each column is a set of sampling points at the same distance in different pulse periods, and G d (l) matrices are accumulated to obtain a 2048 × 25 complex matrix:
5. the method for extracting weak signal of echo of pulse doppler radar according to claim 4, wherein the dynamic range tracking interception of range-doppler matrix data comprises the following steps:
convert the range-pulse matrix E (p) to a range-Doppler matrix F (p), where the x-column elements of F (p) are denoted as fp(x), the magnification factor S (x) in the x-th column is 2λ(x)Wherein λ (x) is fpThe number of extended sign bits of the element with the largest absolute value in (x).
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