阅读说明：本技术 基于分数阶傅里叶域滤波的多分量线性调频信号参数估计方法 (Multi-component linear frequency modulation signal parameter estimation method based on fractional order Fourier domain filtering ) 是由 苏汉宁 鲍庆龙 潘嘉蒙 户盼鹤 祝茜 唐泽家 王森 孙玉朋 于 2019-11-08 设计创作，主要内容包括：本申请涉及一种基于分数阶傅里叶域滤波的多分量线性调频信号参数估计方法。所述方法包括：根据预先获取的外辐射源直达波,建立线性调频信号的参数模板库,然后当接收到回波信号时,根据各个线性调频信号分量的模板脉冲宽度,确定观测帧长度,在所述参数模板库中进行匹配,得到回波信号中各个线性调频信号分量的实时脉冲宽度和实时调频斜率,针对每个匹配的线性调频信号分量,根据上升沿时间确定线性调频信号分量的脉冲到达时间,以及确定线性调频信号分量的实时中心频率,输出多分量线性调频信号中各个线性调频信号分量的脉冲到达时间、实时脉冲宽度、实时调频斜率以及实时中心频率。采用本方法能够准确估计出每个线性调频信号分量参数。(The application relates to a multi-component linear frequency modulation signal parameter estimation method based on fractional order Fourier domain filtering. The method comprises the following steps: establishing a parameter template library of the linear frequency modulation signals according to the pre-acquired external radiation source direct waves, then determining the length of an observation frame according to the template pulse width of each linear frequency modulation signal component when an echo signal is received, matching in the parameter template library to obtain the real-time pulse width and the real-time frequency modulation slope of each linear frequency modulation signal component in the echo signal, determining the pulse arrival time of each linear frequency modulation signal component according to the rising edge time and the real-time central frequency of each linear frequency modulation signal component in the multi-component linear frequency modulation signals according to each matched linear frequency modulation signal component, and outputting the pulse arrival time, the real-time pulse width, the real-time frequency modulation slope and the real-time central frequency of each linear frequency modulation signal component in the multi-component linear frequency modulation signals. By adopting the method, the component parameter of each linear frequency modulation signal can be accurately estimated.)

1. A method of fractional fourier domain filtering based multi-component chirp signal parameter estimation, the method comprising:

establishing a parameter template library of linear frequency modulation signals according to the external radiation source direct waves acquired in advance; the parameter template library comprises: the linear frequency modulation signal corresponds to the template parameter of each linear frequency modulation signal component; the template parameters include: template frequency modulation slope, template pulse width and template center frequency;

when an echo signal is received, determining the length of an observation frame according to the template pulse width of each linear frequency modulation signal component;

setting the order of fractional Fourier transform according to the template frequency modulation slope, and performing the fractional Fourier transform of the order on the observation frame to obtain the length of the real-time continuous observation frame of the characteristic parameter corresponding to the component of the linear frequency modulation signal;

matching in the parameter template library according to the length of the real-time continuous observation frame to obtain the real-time pulse width and the real-time frequency modulation slope of each linear frequency modulation signal component in the echo signal;

aiming at each matched linear frequency modulation signal component, performing inverse fractional Fourier transform on a starting frame of the length of a real-time continuous observation frame, and determining the pulse arrival time of the linear frequency modulation signal component according to the rising edge time;

acquiring the starting time and the straight line center frequency of any one frame in the length of the real-time continuous observation frame;

determining the real-time central frequency of a linear frequency modulation signal component according to the length of the observation frame, the pulse arrival time, the real-time frequency modulation slope, the real-time pulse width, the starting time of any one frame and the linear central frequency;

and outputting the pulse arrival time, the real-time pulse width, the real-time chirp rate and the real-time center frequency of each chirp signal component in the multi-component chirp signal.

2. The method according to claim 1, wherein the establishing a parameter template library of the chirp signals according to the pre-acquired direct wave of the external radiation source comprises:

determining the length of a template observation frame according to the pulse width of the external radiation source direct wave acquired in advance;

acquiring a template frequency modulation slope and a straight line center frequency of each linear frequency modulation signal component aiming at each observation frame, and recording the length of the continuous observation frame of the template with the same template characteristic parameters;

separating each linear frequency modulation signal component from an observation frame in an inverse fractional Fourier transform mode;

for each separated linear frequency modulation signal component, determining the pulse width of the linear frequency modulation signal component in the linear frequency modulation signal in the template continuous observation frame length, and determining the arrival time of the template pulse according to the rising edge time in the initial frame in the template continuous observation frame length;

determining the center frequency of the template according to the template frequency modulation slope and the straight line center frequency;

a parameter template library is created for each chirp signal component containing a template chirp rate, a template pulse width, and a template center frequency.

3. The method of claim 2, wherein obtaining a template chirp rate and a straight line center frequency for each respective chirp signal component for each observation frame, and recording template continuous observation frame lengths for which template feature parameters are the same, comprises:

searching in a preset first numerical range by a first step to obtain an initial order corresponding to each linear frequency modulation signal component;

according to the initial order, constructing a second numerical range corresponding to each linear frequency modulation signal component, and searching in the second numerical range in a second stepping mode to obtain an accurate order corresponding to each linear frequency modulation signal component;

and calculating the template frequency modulation slope and the straight line center frequency corresponding to each linear frequency modulation signal component according to the accurate order.

4. The method of claim 2, wherein separating each chirp signal component from an observation frame by means of an inverse fractional fourier transform comprises:

and separating the linear frequency modulation signal component on the frequency domain from the observation frame through a preset band-pass filter, and performing inverse fractional Fourier transform on the separated linear frequency modulation signal component to obtain a single-component linear frequency modulation signal on the time domain.

5. The method of claim 2, wherein for each of the separated chirp signal components, determining a template pulse width of the chirp signal component in its template continuous observation frame length, and determining a template pulse arrival time from a rising edge time in a starting frame in the template continuous observation frame length, comprises:

respectively detecting a first pulse width and a second pulse width corresponding to linear frequency modulation signal components in a start frame and an end frame in the length of the template continuous observation frame;

accumulating the first pulse width, the second pulse width and the lengths of the template continuous observation frames with the initial frames and the end frames removed to obtain the template pulse width;

and determining the arrival time of the template pulse according to the rising edge time in the initial frame in the length of the template continuous observation frame.

6. The method of claim 2, wherein determining the template center frequency from the template chirp rate and the straight line center frequency comprises:

selecting any one frame of the appointed linear frequency modulation signal component, and recording the starting time and the straight line center frequency of any one frame;

and determining the template central frequency according to the template observation frame length, the template pulse width, the starting time, the template pulse arrival time and the straight line central frequency.

7. The method of any one of claims 1 to 6, wherein setting an order of a fractional Fourier transform according to the template chirp rate, and performing the fractional Fourier transform of the order on the observation frame comprises:

setting orders of fractional Fourier transform according to the template frequency modulation slope, and setting a fractional Fourier transform channel for each order;

and when the observation frame is received, performing fractional order Fourier transform on the observation frame by adopting multiple channels.

8. An apparatus for fractional fourier domain filtering based multi-component chirp signal parameter estimation, the apparatus comprising:

the template library establishing module is used for establishing a parameter template library of the linear frequency modulation signal according to the external radiation source direct wave acquired in advance; the parameter template library comprises: the linear frequency modulation signal corresponds to the template parameter of each linear frequency modulation signal component; the template parameters include: template frequency modulation slope, template pulse width and template center frequency;

the matching module is used for determining the length of an observation frame according to the template pulse width of each linear frequency modulation signal component when an echo signal is received; setting the order of fractional Fourier transform according to the template frequency modulation slope, and performing the fractional Fourier transform of the order on the observation frame to obtain the length of the real-time continuous observation frame of the characteristic parameter corresponding to the component of the linear frequency modulation signal; matching in the parameter template library according to the length of the real-time continuous observation frame to obtain the real-time pulse width and the real-time frequency modulation slope of each linear frequency modulation signal component in the echo signal; aiming at each matched linear frequency modulation signal component, performing inverse fractional Fourier transform on a starting frame of the length of a real-time continuous observation frame, and determining the pulse arrival time of the linear frequency modulation signal component according to the rising edge time; acquiring the starting time and the straight line center frequency of any one frame in the length of the real-time continuous observation frame; determining the real-time central frequency of a linear frequency modulation signal component according to the length of the observation frame, the pulse arrival time, the real-time frequency modulation slope, the real-time pulse width, the starting time of any one frame and the linear central frequency;

and the output module is used for outputting the pulse arrival time, the real-time pulse width, the real-time frequency modulation slope and the real-time center frequency of each linear frequency modulation signal component in the multi-component linear frequency modulation signal.

9. A computer device comprising a memory and a processor, the memory storing a computer program, wherein the processor implements the steps of the method of any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the steps of the method of any one of claims 1 to 7.

Technical Field

The application relates to the technical field of radar signal processing, in particular to a multi-component linear frequency modulation signal parameter estimation method based on fractional order Fourier domain filtering.

Background

Under the drive of increasing emphasis on the concealed attack and hard killing functions of electronic systems, passive detection technology provides an important means for concealed detection and accurate orbit determination of space targets. The passive radar system based on the non-cooperative radar radiation source constructs a matched filter by estimating parameters of received direct wave signals transmitted by the non-cooperative radiation source, and detects and analyzes signal energy transmitted by a target reflection radiation source, so that the positioning and tracking of the target are realized. Therefore, accurate and rapid estimation of parameters of the direct wave of the non-cooperative radiation source is a precondition for the passive radar to complete detection and tracking tasks.

The LFM signal is a non-stationary external radiation source signal which is widely applied, and the low interception probability characteristic of the LFM signal is also an important reason for the wide application of the LFM signal in various radar systems. The non-cooperative external radiation source signal researched by the invention is an LFM signal, aiming at the problem of LFM signal parameter estimation, at present, many theoretically mature algorithms exist at home and abroad, but most algorithms cannot be directly applied to engineering practice, and most methods applied to the engineering at present mainly comprise a template matching method based on maximum likelihood estimation, namely, a parameter template is constructed to perform dechirp on an echo signal, but the method is not suitable for solving the problem of multi-component; another class of methods is time-frequency image based methods, however linear time-frequency transforms such as short-time fourier transforms are not suitable for use with low noise backgrounds (SNR <0dB), time-frequency resolution is low, and bilinear transforms such as wigner's distribution are affected by cross terms. Thus, there is a lack of an efficient and accurate estimation algorithm for multi-component LFM signals, especially time-frequency aliased and time-unsynchronised multi-component LFM signals, in engineering.

Disclosure of Invention

In view of the above, it is necessary to provide a multi-component chirp signal parameter estimation method based on fractional fourier domain filtering, which can solve the problem of inaccurate parameter estimation of multi-component chirp signals.

A method of fractional fourier domain filtering based multi-component chirp signal parameter estimation, the method comprising:

establishing a parameter template library of linear frequency modulation signals according to the external radiation source direct waves acquired in advance; the parameter template library comprises: the linear frequency modulation signal corresponds to the template parameter of each linear frequency modulation signal component; the template parameters include: template frequency modulation slope, template pulse width and template center frequency;

when an echo signal is received, determining the length of an observation frame according to the template pulse width of each linear frequency modulation signal component;

setting the order of fractional Fourier transform according to the template frequency modulation slope, and performing the fractional Fourier transform of the order on the observation frame to obtain the length of the real-time continuous observation frame of the characteristic parameter corresponding to the component of the linear frequency modulation signal;

matching in the parameter template library according to the length of the real-time continuous observation frame to obtain the real-time pulse width and the real-time frequency modulation slope of each linear frequency modulation signal component in the echo signal;

aiming at each matched linear frequency modulation signal component, performing inverse fractional Fourier transform on a starting frame of the length of a real-time continuous observation frame, and determining the pulse arrival time of the linear frequency modulation signal component according to the rising edge time;

acquiring the starting time and the straight line center frequency of any one frame in the length of the real-time continuous observation frame;

determining the real-time central frequency of a linear frequency modulation signal component according to the length of the observation frame, the pulse arrival time, the real-time frequency modulation slope, the real-time pulse width, the starting time of any one frame and the linear central frequency;

and outputting the pulse arrival time, the real-time pulse width, the real-time chirp rate and the real-time center frequency of each chirp signal component in the multi-component chirp signal.

In one embodiment, the method further comprises the following steps: determining the length of a template observation frame according to the pulse width of the external radiation source direct wave acquired in advance; acquiring a template frequency modulation slope and a straight line center frequency of each linear frequency modulation signal component aiming at each observation frame, and recording the length of the continuous observation frame of the template with the same template characteristic parameters; separating each linear frequency modulation signal component from an observation frame in an inverse fractional Fourier transform mode; for each separated linear frequency modulation signal component, determining the pulse width of the linear frequency modulation signal component in the linear frequency modulation signal in the template continuous observation frame length, and determining the arrival time of the template pulse according to the rising edge time in the initial frame in the template continuous observation frame length; determining the center frequency of the template according to the template frequency modulation slope and the straight line center frequency; a parameter template library is created for each chirp signal component containing a template chirp rate, a template pulse width, and a template center frequency.

In one embodiment, the method further comprises the following steps: searching in a preset first numerical range by a first step to obtain an initial order corresponding to each linear frequency modulation signal component; according to the initial order, constructing a second numerical range corresponding to each linear frequency modulation signal component, and searching in the second numerical range in a second stepping mode to obtain an accurate order corresponding to each linear frequency modulation signal component; and calculating the template frequency modulation slope and the straight line center frequency corresponding to each linear frequency modulation signal component according to the accurate order.

In one embodiment, the method further comprises the following steps: and separating the linear frequency modulation signal component on the frequency domain from the observation frame through a preset band-pass filter, and performing inverse fractional Fourier transform on the separated linear frequency modulation signal component to obtain a single-component linear frequency modulation signal on the time domain.

In one embodiment, the method further comprises the following steps: respectively detecting a first pulse width and a second pulse width corresponding to linear frequency modulation signal components in a start frame and an end frame in the length of the template continuous observation frame; accumulating the first pulse width, the second pulse width and the lengths of the template continuous observation frames with the initial frames and the end frames removed to obtain the template pulse width; and determining the arrival time of the template pulse according to the rising edge time in the initial frame in the length of the template continuous observation frame.

In one embodiment, the method further comprises the following steps: selecting any one frame of the appointed linear frequency modulation signal component, and recording the starting time and the straight line center frequency of any one frame; and determining the template central frequency according to the template observation frame length, the template pulse width, the starting time, the template pulse arrival time and the straight line central frequency.

In one embodiment, the method further comprises the following steps: setting orders of fractional Fourier transform according to the template frequency modulation slope, and setting a fractional Fourier transform channel for each order; and when the observation frame is received, performing fractional order Fourier transform on the observation frame by adopting multiple channels.

An apparatus for fractional fourier domain filtering based multi-component chirp signal parameter estimation, the apparatus comprising:

the template library establishing module is used for establishing a parameter template library of the linear frequency modulation signal according to the external radiation source direct wave acquired in advance; the parameter template library comprises: the linear frequency modulation signal corresponds to the template parameter of each linear frequency modulation signal component; the template parameters include: template frequency modulation slope, template pulse width and template center frequency;

the matching module is used for determining the length of an observation frame according to the template pulse width of each linear frequency modulation signal component when an echo signal is received; setting the order of fractional Fourier transform according to the template frequency modulation slope, and performing the fractional Fourier transform of the order on the observation frame to obtain the length of the real-time continuous observation frame of the characteristic parameter corresponding to the component of the linear frequency modulation signal; matching in the parameter template library according to the length of the real-time continuous observation frame to obtain the real-time pulse width and the real-time frequency modulation slope of each linear frequency modulation signal component in the echo signal; aiming at each matched linear frequency modulation signal component, performing inverse fractional Fourier transform on a starting frame of the length of a real-time continuous observation frame, and determining the pulse arrival time of the linear frequency modulation signal component according to the rising edge time; acquiring the starting time and the straight line center frequency of any one frame in the length of the real-time continuous observation frame; determining the real-time central frequency of a linear frequency modulation signal component according to the length of the observation frame, the pulse arrival time, the real-time frequency modulation slope, the real-time pulse width, the starting time of any one frame and the linear central frequency;

and the output module is used for outputting the pulse arrival time, the real-time pulse width, the real-time frequency modulation slope and the real-time center frequency of each linear frequency modulation signal component in the multi-component linear frequency modulation signal.

A computer device comprising a memory and a processor, the memory storing a computer program, the processor implementing the following steps when executing the computer program:

establishing a parameter template library of linear frequency modulation signals according to the external radiation source direct waves acquired in advance; the parameter template library comprises: the linear frequency modulation signal corresponds to the template parameter of each linear frequency modulation signal component; the template parameters include: template frequency modulation slope, template pulse width and template center frequency;

when an echo signal is received, determining the length of an observation frame according to the template pulse width of each linear frequency modulation signal component;

setting the order of fractional Fourier transform according to the template frequency modulation slope, and performing the fractional Fourier transform of the order on the observation frame to obtain the length of the real-time continuous observation frame of the characteristic parameter corresponding to the component of the linear frequency modulation signal;

matching in the parameter template library according to the length of the real-time continuous observation frame to obtain the real-time pulse width and the real-time frequency modulation slope of each linear frequency modulation signal component in the echo signal;

aiming at each matched linear frequency modulation signal component, performing inverse fractional Fourier transform on a starting frame of the length of a real-time continuous observation frame, and determining the pulse arrival time of the linear frequency modulation signal component according to the rising edge time;

acquiring the starting time and the straight line center frequency of any one frame in the length of the real-time continuous observation frame;

determining the real-time central frequency of a linear frequency modulation signal component according to the length of the observation frame, the pulse arrival time, the real-time frequency modulation slope, the real-time pulse width, the starting time of any one frame and the linear central frequency;

and outputting the pulse arrival time, the real-time pulse width, the real-time chirp rate and the real-time center frequency of each chirp signal component in the multi-component chirp signal.

A computer-readable storage medium, on which a computer program is stored which, when executed by a processor, carries out the steps of:

establishing a parameter template library of linear frequency modulation signals according to the external radiation source direct waves acquired in advance; the parameter template library comprises: the linear frequency modulation signal corresponds to the template parameter of each linear frequency modulation signal component; the template parameters include: template frequency modulation slope, template pulse width and template center frequency;

when an echo signal is received, determining the length of an observation frame according to the template pulse width of each linear frequency modulation signal component;

setting the order of fractional Fourier transform according to the template frequency modulation slope, and performing the fractional Fourier transform of the order on the observation frame to obtain the length of the real-time continuous observation frame of the characteristic parameter corresponding to the component of the linear frequency modulation signal;

matching in the parameter template library according to the length of the real-time continuous observation frame to obtain the real-time pulse width and the real-time frequency modulation slope of each linear frequency modulation signal component in the echo signal;

aiming at each matched linear frequency modulation signal component, performing inverse fractional Fourier transform on a starting frame of the length of a real-time continuous observation frame, and determining the pulse arrival time of the linear frequency modulation signal component according to the rising edge time;

acquiring the starting time and the straight line center frequency of any one frame in the length of the real-time continuous observation frame;

determining the real-time central frequency of a linear frequency modulation signal component according to the length of the observation frame, the pulse arrival time, the real-time frequency modulation slope, the real-time pulse width, the starting time of any one frame and the linear central frequency;

and outputting the pulse arrival time, the real-time pulse width, the real-time chirp rate and the real-time center frequency of each chirp signal component in the multi-component chirp signal.

According to the multi-component linear frequency modulation signal parameter estimation method, device, computer equipment and storage medium based on fractional Fourier domain filtering, in the real-time parameter estimation process, due to the fact that no prior parameter knowledge background exists, parameters of the direct wave of the external radiation source are estimated in a preprocessing mode, so that a parameter template library is established, and after the number template library is manufactured, real-time matching is carried out on the parameters and the echo signals, and time-frequency synchronization is achieved. The embodiment of the invention inherits the advantage of high estimation precision of fractional Fourier transform; by a template matching method, fractional Fourier transform is only performed on a limited number of fractional orders when echo data are processed in real time, so that the operation efficiency is improved; in addition, by means of fractional Fourier transform and inverse fractional Fourier transform time-frequency filtering, the multi-component linear frequency modulation signal with time-frequency aliasing and asynchronous time is decomposed into a single-component linear frequency modulation signal, and then each component parameter is accurately estimated.

Drawings

FIG. 1 is a schematic flow chart illustrating a method for estimating parameters of a multi-component chirp signal based on fractional Fourier domain filtering according to an embodiment;

FIG. 2 is a flowchart illustrating steps of creating a parameter template library according to one embodiment;

FIG. 3 is a schematic flow diagram of 9-pass parameter estimation in one embodiment;

FIG. 4 shows p in one embodiment_iA flow framework of fractional order Fourier transform processing;

FIG. 5 is a diagram illustrating the sliding of an observation frame on an echo signal during a certain time period in one embodiment;

FIG. 6 is a block diagram of an embodiment of an apparatus for estimating parameters of a multi-component chirp signal based on fractional Fourier domain filtering;

FIG. 7 is a diagram illustrating an internal structure of a computer device according to an embodiment.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

In one embodiment, as shown in fig. 1, there is provided a method for estimating parameters of a multi-component chirp signal based on fractional fourier domain filtering, comprising the steps of:

and 102, establishing a parameter template library of the linear frequency modulation signal according to the pre-acquired external radiation source direct wave.

The parameter template library comprises: the chirp signal corresponds to template parameters for each chirp signal component, the template parameters including: template chirp rate, template pulse width, and template center frequency.

Each parameter in the parameter template exists in the form of data and can be directly called by the terminal

And 104, when the echo signal is received, determining the length of the observation frame according to the template pulse width of each linear frequency modulation signal component.

Analyzing the pulse widths of all chirp components (chirp signal components) in the parameter template library, and selecting a proper observation frame length for the purpose of enabling different pulse widths to occupy different numbers of observation frames.

Specifically, in an embodiment, the number of sampling points occupied by the three pulse widths is 6000, 60000, and 600000, respectively, and if the length of the observation frame is 8192/Fs and Fs is the sampling frequency, in this example, Fs is 60MHz, then the number of consecutive observation frames that may be occupied by the three pulse widths is shown in the following table:

pulse width	Occupied observation frame
		100us
		1,2
1ms			8,9
	10ms	73,74

It is worth noting that the selection of the length of the observation frame is not unique, and the selection can be carried out according to actual requirements.

And 106, setting the order of fractional Fourier transform according to the template frequency modulation slope, and performing fractional Fourier transform on the order of the observation frame to obtain the length of the real-time continuous observation frame of the characteristic parameter corresponding to the component of the linear frequency modulation signal.

The real-time continuous observation frame length refers to the length of a continuous observation frame obtained by observing a linear frequency modulation signal component at a current frame, then continuously observing the linear frequency modulation signal component until the linear frequency modulation signal component disappears.

And 108, matching in a parameter template library according to the length of the real-time continuous observation frame to obtain the real-time pulse width and the real-time frequency modulation slope of each linear frequency modulation signal component in the echo signal.

Because the length of the obtained real-time continuous observation frame is the same as that of the template continuous observation frame in the parameter template library under a certain template frequency modulation slope, the length of the real-time continuous observation frame and the length of the template continuous observation frame in the parameter template library can be determined to be the same, and therefore the real-time pulse width and the real-time frequency modulation slope of each linear frequency modulation signal component in the echo signal are determined.

And step 110, aiming at each matched linear frequency modulation signal component, performing inverse fractional Fourier transform on the initial frame of the length of the real-time continuous observation frame, and determining the pulse arrival time of the linear frequency modulation signal component according to the rising edge time.

And 112, acquiring the start time and the straight line center frequency of any frame in the lengths of the real-time continuous observation frames, and determining the real-time center frequency of the linear frequency modulation signal component according to the length of the observation frames, the pulse arrival time, the real-time frequency modulation slope, the real-time pulse width, the start time of any frame and the straight line center frequency.

Step 114, outputting the pulse arrival time, the real-time pulse width, the real-time chirp rate, and the real-time center frequency of each chirp component in the multi-component chirp signal.

In the multi-component linear frequency modulation signal parameter estimation method based on fractional order Fourier domain filtering, in the process of real-time parameter estimation, due to the fact that no prior parameter knowledge background exists, parameters of external radiation source direct waves are estimated in a preprocessing mode, so that a parameter template library is established, and after the number template library is manufactured, real-time matching is carried out on the parameters and echo signals, and time-frequency synchronization is achieved. The embodiment of the invention inherits the advantage of high estimation precision of fractional Fourier transform; by a template matching method, fractional Fourier transform is only performed on a limited number of fractional orders when echo data are processed in real time, so that the operation efficiency is improved; in addition, by means of fractional Fourier transform and inverse fractional Fourier transform time-frequency filtering, the multi-component linear frequency modulation signal with time-frequency aliasing and asynchronous time is decomposed into a single-component linear frequency modulation signal, and then each component parameter is accurately estimated.

In one embodiment, as shown in fig. 2, the step of establishing the parameter template library includes:

step 202, determining the length of the template observation frame according to the pulse width of the external radiation source direct wave acquired in advance.

In engineering application, hardware equipment often needs to process radar signals of a high-frequency band in a frame mode, and under the condition that part of radar sinkha pulse width priori knowledge exists, for example, the magnitude of the pulse width can be set according to the length of 1-2 times of the minimum pulse width, and the length (unit: s) of an observation frame can be set.

And 204, acquiring the template frequency modulation slope and the straight line center frequency of each linear frequency modulation signal component aiming at each observation frame, and recording the length of the continuous observation frame of the template with the same template characteristic parameters.

Step 206, each chirp signal component is separated from the observation frame by means of inverse fractional fourier transform.

Step 208, for each separated chirp signal component, determining a template pulse width of the chirp signal component in the chirp signal in its template continuous observation frame length, and determining a template pulse arrival time according to a rising edge time in an initial frame in the template continuous observation frame length.

And step 210, determining the template center frequency according to the template frequency modulation slope and the straight line center frequency.

Step 212, a parameter template library is created for each chirp signal component containing the template chirp rate, the template pulse width, and the template center frequency.

For step 204, in one embodiment, the initial order corresponding to each chirp signal component may be obtained by further performing a search in a preset first numerical range; and according to the initial order, constructing a second numerical range corresponding to each linear frequency modulation signal component, searching in the second numerical range by second stepping to obtain an accurate order corresponding to each linear frequency modulation signal component, and calculating a template frequency modulation slope and a straight line center frequency corresponding to each linear frequency modulation signal component according to the accurate order. In this embodiment, the order refers to an order for performing fractional fourier transform, and the searching step is divided into a coarse searching step and a fine searching step, so that an accurate order corresponding to each chirp signal component is accurately obtained, and a template chirp rate and a straight line center frequency are further calculated.

Specifically, the form of the chirp signal is:

where n (t) is additive white Gaussian noise, τ is time delay, n_cRepresenting the number of chirp components, p_w,iRepresenting the pulse width, f, of the ith chirp component_0,iRepresenting the centre frequency, mu, of the ith chirp signal component_iRepresenting the chirp rate of the ith chirp signal component.

The fractional fourier transform is defined as:

wherein, K_p(t, v) denotes a transformation kernel.

For the order P of the linear frequency modulation signal component, firstly, coarse searching is carried out, and the specific steps are as follows:

with a first further traversal of the interval [0,2 ]]At each P e [0,2 ∈ [ ]]Fractional Fourier transform to generate a row vector K_p(v) All the row vectors form a two-dimensional matrix, and then the local maximum value and the coordinate are searched on the two-dimensional matrixI.e. the parameters to be roughly measured for the current frame,can be represented by local maximum coordinates (v)_i,p_i) To obtain the result of the above-mentioned method,

secondly, local range fine search is carried out:

in a second, smaller step, inInternal search is carried out to obtain the accurate value of the order corresponding to each linear frequency modulation signal componentWhere M represents the resolution of the order, from which the chirp rate of the chirp signal component in the current frame can be calculated as:

the straight line center frequency is:

typically, as the observation frame slips, for the same chirp signal component,

the temperature of the molten steel is kept unchanged,

linear, and therefore, the length T e [1,2,3 ] of successive observation frames in which the parameter features occur can be recorded.]To roughly measure the pulse width P_w,1。

For step 206, in one embodiment, the step of separating each chirp component from the observation frame may be: and separating the linear frequency modulation signal component on the frequency domain from the observation frame through a preset band-pass filter, and performing inverse fractional Fourier transform on the separated linear frequency modulation signal component to obtain a single-component linear frequency modulation signal on the time domain.

In an embodiment, it is preferred to accurately estimate the chirp in the start and end frames for the entire bandThe length of the signal component, each chirp signal component appearing as a shock function at the corresponding order

The coordinates are

If the straight lines of the chirp signal components do not coincide on the time-frequency diagram in the current observation frame, that is,

all different, then the impact function may be centered

The band-pass filter of (1) is further separated, because the fractional Fourier transform is a reversible lossless transform, so that the filtered one

The recovery can be carried out through inverse fractional Fourier transform to obtain a single-component linear frequency modulation signal on a time domain, and the specific expression is as follows:

with respect to step 208, in one embodiment, the step of determining the template pulse width and the template pulse arrival time comprises: respectively detecting a first pulse width and a second pulse width corresponding to the linear frequency modulation signal components in the initial frame and the end frame in the length of the template continuous observation frame, accumulating the first pulse width and the second pulse width as well as the length of the template continuous observation frame with the initial frame and the end frame removed to obtain the width of the template pulse, and determining the arrival time of the template pulse according to the rising edge time in the initial frame in the length of the template continuous observation frame.

In a specific embodiment, the first pulse width and the second pulse width in the starting frame and the ending frame can be detected by a threshold detection method, and if the length of the template continuous observation frame is T, the expression of the template pulse width is as follows:

where Wo denotes an observation frame length,which represents the width of the pulses in the starting frame,

indicating the width of the pulses in the termination frame,

representing the template pulse width.

As for the template pulse arrival time, it can be determined based on the pulse arrival time in the start frame.

For step 210, in one embodiment, the step of determining the template center frequency comprises: selecting any one frame of the appointed linear frequency modulation signal component, and recording the starting time and the straight line center frequency of any one frame; and determining the central frequency of the template according to the length of the template observation frame, the width of the template pulse, the starting time, the arrival time of the template pulse and the central frequency of the straight line.

Specifically, the expression of the template center frequency is as follows:

wherein the content of the first and second substances,

indicating the start time of any one frame.

In one embodiment, the observation frame is subjected to a fractional fourier transform of order: setting orders of fractional Fourier transform according to the template frequency modulation slope, setting a fractional Fourier transform channel for each order, and performing fractional Fourier transform on an observation frame by adopting multiple channels when the observation frame is received.

Specifically, taking the simulated LFM signal as an example, the sampling frequency F_s60MHz, wideband LFM signal bandwidth {5MHz, 10MHz, 15MHz }, pulse width P_w，mE {100us,1ms, 10ms }, the center frequency is chosen to satisfy the nyquist sampling theorem. Assuming that these parameters are known, that is, all the parameters are selectable parameters in the template library, 9 channels can be designed to perform parameter estimation on the received signal, and the 9 channels respectively correspond to different p, as shown in fig. 3, where p is_iThe flow diagram of the fractional order fourier transform process is shown in fig. 4.

In another embodiment, taking the simulation signal in fig. 5 as an example, fig. 5 shows the sliding condition of the observation frame on the echo signal in a certain time period, and the information is as follows:

two narrow-band chirp components appear in frame 1, denoted as S₁，S₂And both disappear at frame 8.

A wideband chirp component, denoted S, appears in frame 3₃And only exists in the 3 rd frame.

In this example, of the 9 channels that were previously designed, 3 channels exhibited impulse characteristics on this segment of the signal. The matching process is shown in fig. 4: each channel carries out local maximum value detection on the corresponding p-order fractional Fourier domain; if the maximum value meeting the threshold condition is detected, recording the abscissa of the maximum value

Recording the length T of an observation frame with continuous peak values, completing matching if the tracked peak values disappear and meet the requirement that the pulse width is matched with T ∈ template, otherwise, continuously searching the next linear frequency modulation signal component meeting the requirement; furthermore, for narrowband chirp components, which have a chirp rate close to 0, with a limited p difference between the components (which is determined by the nature of the cotangent function), one narrowband component may also exhibit a shock characteristic in the fractional fourier transform domain corresponding to the other narrowband component, resulting in a spurious peak, as shown by S in fig. 4₁，S₂Two peaks appear in channel 1 and channel 2. Therefore, another decision criterion is introduced into the matching criterion, i.e. bandwidth matching, if the peak disappears,

a complete match is made. In this example, both peaks in channel 1 satisfy T-8, meeting the 1ms pulse matching condition, but for both chirp components

Equal to 9.555MHz and 5.12MHz, respectively, it is clear that the former is a perfect match, a 10MHz/1ms pulse, while the latter is more likely a 5MHz/1ms pulse, which is screened out in channel 1 and, conversely, detected in channel 2. Like S₃The broadband pulse has no ambiguity problem of discrimination of the narrowband pulse, and the matching is easily completed in the channel 3.

It should be understood that although the various steps in the flowcharts of fig. 1 and 2 are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise. Moreover, at least some of the steps in fig. 1 and 2 may include multiple sub-steps or multiple stages that are not necessarily performed at the same time, but may be performed at different times, and the order of performing the sub-steps or stages is not necessarily sequential, but may be performed in turn or alternately with other steps or at least some of the sub-steps or stages of other steps.

In one embodiment, as shown in fig. 6, there is provided a multi-component chirp signal parameter estimation device based on fractional fourier domain filtering, including: a template library creation module 602, a matching module 604, and an output module 606, wherein:

a template library establishing module 602, configured to establish a parameter template library of a chirp signal according to a pre-obtained external radiation source direct wave; the parameter template library comprises: the linear frequency modulation signal corresponds to the template parameter of each linear frequency modulation signal component; the template parameters include: template frequency modulation slope, template pulse width and template center frequency;

a matching module 604, configured to determine, when an echo signal is received, an observation frame length according to the template pulse width of each chirp signal component; setting the order of fractional Fourier transform according to the template frequency modulation slope, and performing the fractional Fourier transform of the order on the observation frame to obtain the length of the real-time continuous observation frame of the characteristic parameter corresponding to the component of the linear frequency modulation signal; matching in the parameter template library according to the length of the real-time continuous observation frame to obtain the real-time pulse width and the real-time frequency modulation slope of each linear frequency modulation signal component in the echo signal; aiming at each matched linear frequency modulation signal component, performing inverse fractional Fourier transform on a starting frame of the length of a real-time continuous observation frame, and determining the pulse arrival time of the linear frequency modulation signal component according to the rising edge time; acquiring the starting time and the straight line center frequency of any one frame in the length of the real-time continuous observation frame; determining the real-time central frequency of a linear frequency modulation signal component according to the length of the observation frame, the pulse arrival time, the real-time frequency modulation slope, the real-time pulse width, the starting time of any one frame and the linear central frequency;

an output module 606 for outputting the pulse arrival time, the real-time pulse width, the real-time chirp rate, and the real-time center frequency of each chirp component in the multi-component chirp signal.

In one embodiment, the length of a template observation frame is determined according to the pulse width of the external radiation source direct wave acquired in advance; acquiring a template frequency modulation slope and a straight line center frequency of each linear frequency modulation signal component aiming at each observation frame, and recording the length of the continuous observation frame of the template with the same template characteristic parameters; separating each linear frequency modulation signal component from an observation frame in an inverse fractional Fourier transform mode; for each separated linear frequency modulation signal component, determining the pulse width of the linear frequency modulation signal component in the linear frequency modulation signal in the template continuous observation frame length, and determining the arrival time of the template pulse according to the rising edge time in the initial frame in the template continuous observation frame length; determining the center frequency of the template according to the template frequency modulation slope and the straight line center frequency; a parameter template library is created for each chirp signal component containing a template chirp rate, a template pulse width, and a template center frequency.

In one embodiment, the method comprises the steps of searching in a preset first numerical range in a first step to obtain an initial order corresponding to each linear frequency modulation signal component; according to the initial order, constructing a second numerical range corresponding to each linear frequency modulation signal component, and searching in the second numerical range in a second stepping mode to obtain an accurate order corresponding to each linear frequency modulation signal component; and calculating the template frequency modulation slope and the straight line center frequency corresponding to each linear frequency modulation signal component according to the accurate order.

In one embodiment, the chirp signal component in the frequency domain is separated from the observation frame by a preset band-pass filter, and the separated chirp signal component is subjected to inverse fractional order fourier transform to obtain a single-component chirp signal in the time domain.

In one embodiment, a first pulse width and a second pulse width corresponding to a linear frequency modulation signal component in a starting frame and a finishing frame in the length of the template continuous observation frame are respectively detected; accumulating the first pulse width, the second pulse width and the lengths of the template continuous observation frames with the initial frames and the end frames removed to obtain the template pulse width; and determining the arrival time of the template pulse according to the rising edge time in the initial frame in the length of the template continuous observation frame.

In one embodiment, any one frame of a specified linear frequency modulation signal component is selected, and the starting time and the straight line center frequency of any one frame are recorded; and determining the template central frequency according to the template observation frame length, the template pulse width, the starting time, the template pulse arrival time and the straight line central frequency.

In one embodiment, the order of fractional Fourier transform is set according to the template frequency modulation slope, and a fractional Fourier transform channel is set for each order; and when the observation frame is received, performing fractional order Fourier transform on the observation frame by adopting multiple channels.

For specific limitations of the multi-component chirp signal parameter estimation device based on fractional fourier domain filtering, reference may be made to the above limitations of the multi-component chirp signal parameter estimation method based on fractional fourier domain filtering, and details are not repeated here. The modules in the above-mentioned fractional fourier domain filtering-based multi-component chirp signal parameter estimation apparatus can be implemented in whole or in part by software, hardware, and a combination thereof. The modules can be embedded in a hardware form or independent from a processor in the computer device, and can also be stored in a memory in the computer device in a software form, so that the processor can call and execute operations corresponding to the modules.

In one embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as shown in fig. 7. The computer device includes a processor, a memory, a network interface, a display screen, and an input device connected by a system bus. Wherein the processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device comprises a nonvolatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of an operating system and computer programs in the non-volatile storage medium. The network interface of the computer device is used for communicating with an external terminal through a network connection. The computer program is executed by a processor to implement a method for multi-component chirp parameter estimation based on fractional fourier domain filtering. The display screen of the computer equipment can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer equipment can be a touch layer covered on the display screen, a key, a track ball or a touch pad arranged on the shell of the computer equipment, an external keyboard, a touch pad or a mouse and the like.

Those skilled in the art will appreciate that the architecture shown in fig. 7 is merely a block diagram of some of the structures associated with the disclosed aspects and is not intended to limit the computing devices to which the disclosed aspects apply, as particular computing devices may include more or less components than those shown, or may combine certain components, or have a different arrangement of components.

In an embodiment, a computer device is provided, comprising a memory storing a computer program and a processor implementing the steps of the method in the above embodiments when the processor executes the computer program.

In an embodiment, a computer-readable storage medium is provided, on which a computer program is stored, which computer program, when being executed by a processor, carries out the steps of the method in the above-mentioned embodiments.

It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by hardware instructions of a computer program, which can be stored in a non-volatile computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. Any reference to memory, storage, database, or other medium used in the embodiments provided herein may include non-volatile and/or volatile memory, among others. Non-volatile memory can include read-only memory (ROM), Programmable ROM (PROM), Electrically Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), or flash memory. Volatile memory can include Random Access Memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms such as Static RAM (SRAM), Dynamic RAM (DRAM), Synchronous DRAM (SDRAM), Double Data Rate SDRAM (DDRSDRAM), Enhanced SDRAM (ESDRAM), Synchronous Link DRAM (SLDRAM), Rambus Direct RAM (RDRAM), direct bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.