CN112684418B - 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; distance-pulse matrix coherent accumulation; range-doppler matrix data dynamic range tracking truncation. The invention is based on the combination of high-power oversampling and a matched filter to inhibit noise, well solves the problem that the acceptance performance can not be improved by a pulse compression technology under extremely narrow pulse, and further inhibits noise by improving the signal-to-noise ratio of echo signals by distance-pulse matrix coherent accumulation. The range-Doppler matrix data dynamic range tracking interception method solves the contradiction between dynamic range and precision of digital signal processing under a low-cost receiver. The invention provides a complete technical solution for extracting the pulse Doppler radar echo weak signal, and has a certain practical effect on the aspect of pulse weather radar echo weak signal detection.
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
How to effectively extract weak signals in echoes of pulse Doppler radar in the range of 20-300 meters in the near field is a problem which is solved by the industry. One of the characteristics of echo signals is that the intensity is very weak, and in addition, the detection distance is short, resulting 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 are adopted, a digital-to-analog conversion device with extremely high sampling frequency is required, which increases the cost of the application product.
On the other hand, in embedded applications, all the hardware and software resources of 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 pulse, and adopts the following technical scheme: 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;
distance-pulse matrix coherent accumulation;
range-doppler matrix data dynamic range tracking truncation.
The further improvement is that the radar intermediate frequency echo oversampling quantization comprises the following steps:
employing repetition period T in radar system ppi A narrow rectangular pulse of =2us, the ideal echo signal itself spectrum contains zero frequency, fundamental frequency, infinite harmonic components;
wherein zero frequency f 0 =0hz, fundamental frequency f 1 =500 KHz, harmonic f n ＝n×500KHz；
From the Fourier series theory, the harmonic order n>10 engineering bandwidth of ideal echo signal B r ＝5MHz。
In a further refinement, the matched filtering includes the following steps:
after low-pass filtering, the mirror image spectrum introduced by digital sampling is removed;
and (3) matched filtering calculation:wherein design parameters->P τ Is at the sampling frequency f s The number of samples in the duration of the down-narrow pulse.
Further improved is that the distance-pulse matrix coherent accumulation comprises the following steps:
the distance-pulse matrix is marked as D (l), is a 2048×25 complex matrix, each row is a sampling point set with different behaviors, each column is a sampling point set with the same distance in different pulse periods, and G D (l) matrices are accumulated to obtain a 2048×25 complex matrix:
further improved, the dynamic range tracking interception of the distance-Doppler matrix data comprises the following steps:
converting the distance-pulse matrix E (p) into a distance-Doppler matrix F (p), the x column elements of F (p) being denoted as F p (: x), the magnification factor of the x-th column S (x) =2 λ(x) Wherein λ (x) is f p The number of extension symbol 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 is based on the combination of high-power oversampling and a matched filter to inhibit noise, well solves the problem that the acceptance performance can not be improved by a pulse compression technology under extremely narrow pulse, and further inhibits noise by improving the signal-to-noise ratio of echo signals by distance-pulse matrix coherent accumulation. The range-Doppler matrix data dynamic range tracking interception method solves the contradiction between dynamic range and precision of digital signal processing under a low-cost receiver. The invention provides a complete technical solution for extracting the pulse Doppler radar echo weak signal, and has a certain practical effect on the aspect of pulse weather radar echo weak signal detection.
Drawings
The invention will be further described with reference to the drawings and examples.
FIG. 1 is a flow chart of a weak signal extraction method of pulse Doppler radar echo of the present invention;
fig. 2 illustrates the problem of interference caused by overlapping of the self frequency spectrum of an echo signal and the sampling mirror image frequency spectrum of the echo signal due to the reduction of the sampling quantization frequency of the radar echo signal.
Detailed Description
For a more complete and thorough description of the present application, reference is made to the drawings, and to the following detailed description of various embodiments of the application, wherein like reference numerals represent the same or similar elements. However, it will be appreciated by those of ordinary skill in the art that the examples provided below are not intended to limit the scope of what is covered by the present application. Furthermore, the drawings are for illustrative purposes only and are not drawn to their original dimensions.
In one typical configuration of the present application, the terminal, the device of the service network, and the trusted party each include one or more processors (CPUs), input/output interfaces, network interfaces, and memory. The memory may include volatile memory in a computer-readable medium, random Access Memory (RAM) and/or nonvolatile memory, such as Read Only Memory (ROM) or flash memory (flash RAM). Memory is an example of computer-readable media. Computer readable media, including both non-transitory and non-transitory, removable and non-removable media, may implement information storage by any method or technology. The information may be computer readable instructions, data structures, subunits of a program, or other data. Examples of storage media for a computer 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, which can be used to store information that can be accessed by a computing device. Computer readable media, as defined herein, does not include non-transitory computer readable media (transmission media), such as modulated data signals and carrier waves.
As shown in fig. 1, the invention provides a weak signal extraction method of pulse doppler radar echo, which comprises the following steps:
s01, the intermediate frequency echo of the radar is subjected to oversampling quantization;
s02, low-pass filtering;
s03, matched filtering;
s04, performing coherent accumulation on a distance-pulse matrix;
s05, tracking and intercepting the dynamic range of the range-Doppler matrix data.
The further improvement is that the radar intermediate frequency echo oversampling quantization comprises the following steps:
in the radar system of the invention, the repetition period T is adopted ppi A narrow rectangular pulse of =2us whose ideal echo signal self-spectrum contains zero frequency, fundamental frequency, and infinite harmonic component, wherein zero frequency f 0 =0hz, fundamental frequency f 1 =500 KHz, harmonic f n =n×500KHz; from the Fourier series theory, the harmonic order n>At 10, harmonic f n The energy of (2) can be neglected in engineering, so that the engineering bandwidth B of the ideal echo signal can be considered r =5 MHz. Echo signal sampling frequency f in the system s > 5MHz, oversampling multiple M s Largely, according to the digital signal sampling theory, M s The larger the echo signal self frequency spectrum is, the less the overlapping interference part of the echo signal self frequency spectrum and the sampling mirror image frequency spectrum is, on the other hand, the over-sampling increases the number of sampling points in the duration of the narrow rectangular pulse by multiple times, and the noise suppression performance of the subsequent matched filtering is improved.
In a further refinement, the matched filtering includes the following steps:
after low pass filtering, mirroring by digital samplingThe spectrum is cleared. On the basis, the effective signal of noise improvement is further eliminated, and the matching filtering calculation is carried out:wherein design parameters->P τ Is at the sampling frequency f s The number of samples in the duration of the down-narrow pulse.
Further improved is that the distance-pulse matrix coherent accumulation comprises the following steps:
the distance-pulse matrix is marked as D (l), is a 2048×25 complex matrix, each row of sampling points is a set of sampling points with different behaviors, namely fast time dimension sampling, each column of sampling points with the same distance in different pulse periods is a set of sampling points with slow time dimension sampling, and G D (l) matrices are accumulated to obtain a 2048×25 complex matrix:
further improved, the dynamic range tracking interception of the distance-Doppler matrix data comprises the following steps:
the dynamic range tracking interception of the distance-Doppler matrix data is realized, FFT is a Fourier transform module, the distance-pulse matrix E (p) is converted into a distance-Doppler matrix F (p), and the x column elements of F (p) are marked as F p (: x), the magnification factor of the x-th column S (x) =2 λ(x) Wherein λ (x) is f p The number of extension symbol bits of the element with the largest absolute value in x.
FIG. 2 illustrates the problem of interference of the self-spectrum of the echo signal and the spectrum of the sampling mirror image caused by the reduction of the sampling quantization frequency of the echo signal of the radar, and the higher sampling frequency can solve the problem
With the above-described preferred embodiments according to the present invention as an illustration, the above-described descriptions can be used by persons skilled in the relevant art to make various changes and modifications without departing from the scope of the technical idea of the present invention. The technical scope of the present invention is not limited to the description, but must be determined according to the scope of claims.
Claims (1)
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;
distance-pulse matrix coherent accumulation;
distance-Doppler matrix data dynamic range tracking interception;
the radar intermediate frequency echo oversampling quantization comprises the following steps:
employing repetition period T in radar system ppi A narrow rectangular pulse of =2us, the ideal echo signal itself spectrum contains zero frequency, fundamental frequency, infinite harmonic components;
wherein zero frequency f 0 =0hz, fundamental frequency f 1 =500 KHz, harmonic f n ＝n×500KHz；
From the Fourier series theory, it can be known that the engineering bandwidth B of ideal echo signal when the harmonic frequency n is more than 10 r ＝5MHz；
The matched filtering comprises the following steps:
after low-pass filtering, the mirror image spectrum introduced by digital sampling is removed;
and (3) matched filtering calculation:wherein design parameters->P τ Is at the sampling frequency f s The number of samples within the duration of the lower narrow pulse;
the distance-pulse matrix coherent accumulation includes the steps of:
the distance-pulse matrix is denoted as D (l), and is a 2048×25 complex matrix, each behavior of which is a different set of sampling points, eachOne column is a set of sampling points at the same distance in different pulse periods, and G D (l) matrixes are accumulated to obtain 2048×25 complex matrixes:
the dynamic range tracking interception of the distance-Doppler matrix data comprises the following steps:
converting the distance-pulse matrix E (p) into a distance-Doppler matrix F (p), the x column elements of F (p) being denoted as F p (: x), the magnification factor of the x-th column S (x) =2 λ(x) Wherein λ (x) is f p The number of extension symbol bits of the element with the largest absolute value in x.
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