KR101426226B1 - Signal processing method of radar - Google Patents

Abstract

A method for processing a radar signal according to an embodiment of the present invention comprises the steps of generating first data having speed channel data corresponding to multiple speed channels, respectively, by processing a received signal; generating second data having target speed channel data corresponding to a target speed channel among multiple speed channels by finite impulse response (FIR) filtering the received signal; combining the first data and the second data to generate third data; and calculating respective threshold values by distinguishing the target speed channel data constituting the third data and remaining speed channel data excluding the target speed channel data.

Description

[0001] SIGNAL PROCESSING METHOD OF RADAR [0002]

An embodiment according to the concept of the present invention relates to a radar signal processing method, and more particularly, to a radar signal processing method for detecting a low-speed starting target.

A radar is an all-weather sensor that uses electromagnetic waves to receive a signal reflected from a target and extract target information such as distance, altitude, bearing, and velocity of the target. In general, radar signals include unwanted clutter signals and artificial interfering signals around the target in addition to the desired target signal when the transmitted electromagnetic waves are received from the target in reflection. In particular, the distribution characteristics of clutter and interference noise signals change in various ways depending on the surrounding environment of radar operation in time, space, and spectral region. Also, in the radar platform movement, the center frequency of the Doppler shifts relatively and the fixed clutter on the ground also shifts and spreads the Doppler spectrum. This is a major factor that weakens the radar target detection performance. In order to efficiently perform radar performance analysis in a complex signal environment, real - time radar signal acquisition is essential, and it is very important to analyze signal characteristics such as target and clutter accurately.

1 and 2 show a general signal processing method of a pulse Doppler radar.

Referring to FIG. 1, signals are received according to a Pulse Repetition Interval (PRI). The received signals are processed by an MTI (Moving Target Indication) filter and Doppler filtering, and then subjected to a CFR (Constant False Alarm Rate) algorithm to extract target information. The general signal processing method of the radar shown in Fig. 1 is useful for detecting targets that are moving at high speed. This will be described in more detail with reference to FIG. 2 below.

Referring to FIG. 2, the processing of the received signals shown in FIG. 1 is shown. Specifically, referring to FIG. 2 (a), target returns for a target (e.g., an aircraft, a fighter) that is moving at high speed (e.g., 100 m / s to 2,000 m / s) The Power Spectral Density (PSD) of the clutter returns is shown. According to the signal processing method of FIG. 1, only a received signal for a desired target can be extracted and detected using a point where the frequency (speed) difference between the received signal and the clutter receiving signal for the target is clear.

That is, a method of applying MTI filtering (see FIG. 2 (b)) for removing only the low frequency part including the unwanted clutter, or excluding the cells corresponding to the clutter region from the signal processing So that only desired target information can be obtained. Referring to FIG. 2 (c), after the MTI filter is applied, the clutter signal is removed and the PSD in which only the target signal remains can be confirmed.

That is, according to the signal processing method of FIG. 1, the target in high-speed start-up is easy to extract the target signal because the difference in frequency (speed) between the speed of the target to be activated and the clutter receiving signal is large. However, if the target to be detected is not a high-speed maneuvering target but a target that is activated at a low speed (for example, 30 m / s or less) (for example, an RC UAV), the difference between the speed of the target and the frequency There is a problem that it is not easy to acquire target information.

Accordingly, an object of the present invention is to provide a radar signal processing method capable of detecting a low-speed starting target.

The problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

A method of processing a radar signal according to an exemplary embodiment of the present invention includes generating first data having velocity channel data corresponding to each of a plurality of velocity channels by processing a received signal and outputting the received signal as a finite impulse response (FIR) Generating second data having target velocity channel data corresponding to a target velocity channel among the plurality of velocity channels by filtering, generating third data by combining the first data and the second data, 3 data and the remaining speed channel data excluding the target speed channel data, and calculating a threshold value.

In one embodiment, the method may include generating a clutter map using the first data.

In one embodiment, the step of dividing the target velocity channel data constituting the third data and the remaining velocity channel data except for the target velocity channel data and calculating the threshold value respectively may be performed by using a Constant False Alarm Rate (CFAR) algorithm Calculating a temporary threshold value for the remaining rate channel data by comparing the threshold value for the remaining rate channel data calculated with reference to the clutter map and the temporary threshold value, , And calculating a threshold value for the target rate channel data using a CMFM (Cluster Map Constant False Alarm Rate) algorithm.

In one embodiment, the method further comprises processing the received signal to produce first data having velocity channel data corresponding to each of the plurality of velocity channels, and filtering the received signal by FIR (Finite Impulse Response) The step of generating second data having target velocity channel data corresponding to the target velocity channel may be performed in parallel.

In one embodiment, the step of processing the received signal to generate first data having velocity channel data corresponding to each of the plurality of velocity channels comprises filtering the received signal using a window function, And filtering the signal using a Doppler filter.

In one embodiment, the window function may include a Hamming Window function, a Hanning Window function, and a Chebyshev Window function.

In one embodiment, the step of generating the third data by combining the first data and the second data may include comparing the velocity channel data corresponding to the target velocity channel among the velocity channel data of the first data to the target velocity channel data To generate the third data.

According to the radar signal processing method according to the embodiment of the present invention, it is possible to detect a target that is activated at a low speed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to more fully understand the drawings recited in the detailed description of the present invention, a detailed description of each drawing is provided.
1 and 2 show a general signal processing method of a pulse Doppler radar.
3 is a block diagram illustrating a radar according to an embodiment of the present invention.
4 is a flowchart illustrating a signal processing method of a radar according to an embodiment of the present invention.
5 shows a signal received in step S110 of FIG.
FIG. 6 shows first data generated in step S130 of FIG.
FIG. 7 shows third data generated in step S150 of FIG.
FIG. 8 is a diagram for explaining steps S170 and S180 in FIG.
FIG. 9 is a view for explaining step S190 of FIG. 4. FIG.
FIG. 10 is a conceptual view illustrating a signal processing method of a radar according to an embodiment of the present invention.

It is to be understood that the specific structural or functional descriptions of embodiments of the present invention disclosed herein are only for the purpose of illustrating embodiments of the inventive concept, But may be embodied in many different forms and is not limited to the embodiments set forth herein.

Embodiments in accordance with the concepts of the present invention are capable of various modifications and may take various forms, so that the embodiments are illustrated in the drawings and described in detail herein. It should be understood, however, that it is not intended to limit the embodiments according to the concepts of the present invention to the particular forms disclosed, but includes all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

The terms first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms are intended to distinguish one element from another, for example, without departing from the scope of the invention in accordance with the concepts of the present invention, the first element may be termed the second element, The second component may also be referred to as a first component.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between. Other expressions that describe the relationship between components, such as "between" and "between" or "neighboring to" and "directly adjacent to" should be interpreted as well.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises" or "having", etc. are intended to specify the presence of stated features, integers, steps, operations, elements, parts or combinations thereof, , Steps, operations, components, parts, or combinations thereof, as a matter of principle.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the meaning of the context in the relevant art and, unless explicitly defined herein, are to be interpreted as ideal or overly formal Do not.

The present invention relates to a radar signal processing method, and more particularly, to a radar signal processing method for detecting a target that operates at a low speed. Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily carry out the technical idea of the present invention. .

3 is a block diagram illustrating a radar according to an embodiment of the present invention. Hereinafter, it is assumed that the radar is a pulse Doppler radar.

Referring to FIG. 3, a radar 100 according to an embodiment of the present invention includes a transceiver 110, a processing unit 120, and a buffer memory 130.

The transceiver 110 transmits the radio wave to the outside through the antenna (not shown) of the radar 100 and receives the radio wave from the outside.

The processing unit 120 receives a signal (hereinafter referred to as a "received signal") received from the transceiver 110. The processing unit 120 applies a window function to a received signal to obtain velocity channel data from the received signal and generates first data through a filtering operation using a Doppler filter.

The processing unit 120 filters the received signal using a finite impulse response (FIR) filter to obtain velocity channel data for the target region (e.g., the slow channel region) from the received signal. The FIR filter may be designed to have two features such that positive (+) velocity and negative (-) velocity filters are symmetrical with respect to the zero velocity. The two FIR filters may be designed such that the response characteristics of the filters have a conjugate relationship with each other. The processing unit 120 generates second data through a filtering operation using the FIR filter.

The processing unit 120 combines the first data and the second data to generate third data. The processing unit 120 generates a clutter map using the first data.

The processing unit 120 first applies the CFAR algorithm to the speed channel data (e.g., the fast channel area data) excluding the speed channel data corresponding to the second data among the plurality of speed channels constituting the third data And compares the calculated threshold value with the corresponding value of the clutter map to generate a larger value as the first threshold value. The processing unit 120 may be configured to generate the rate channel data (e.g., low-speed channel area data) corresponding to the second data among the plurality of rate channel data constituting the third data by using a CMFAR (Clutter Map Constant False Alarm Rate ) Algorithm to generate a second threshold value.

The buffer memory 130 may store the first and second thresholds generated by the processing unit 120. [ The buffer memory 130 may include any one of random access memories such as DRAM, SRAM, PRAM, MRAM, RRAM, and FRAM.

Hereinafter, the specific operation of the processing unit 120 will be described in detail with reference to FIGS. 4 to 9. FIG.

4 is a flowchart illustrating a signal processing method of a radar according to an embodiment of the present invention. 5 shows a signal received in step S110 of FIG. FIG. 6 shows first data generated in step S130 of FIG. FIG. 7 shows third data generated in step S150 of FIG. FIG. 8 is a diagram for explaining steps S170 and S180 in FIG. FIG. 9 is a view for explaining step S190 of FIG. 4. FIG.

Referring to FIG. 4, a radar signal processing method according to an embodiment of the present invention includes a step S110 of receiving a signal, a step S120 of applying a window function to received signals, (S140) of generating first data by FFT (Fast Fourier Transform) of signals, performing a FIR filtering on the received signals to generate second data (S140), combining the first and second data Generating a clutter map by using the first data in step S160, generating a clutter map using a constant false alarm rate (CFAR) algorithm for a first target channel of the third data, (S180) of applying a CM CFAR algorithm to the second target channel of the third data (S190), selecting a threshold for the first target channel (S180) (S200).

Hereinafter, each step will be described in detail.

In step S110, the transceiver 110 receives signals reflected from the target. Specifically, referring to FIG. 5, signals are received according to a Pulse Repetition Interval (PRI). The received signals are pulse signals, and are assumed to be repeatedly received every pulse repetition period.

In step S120, the processing unit 120 filters the received signals using a window function, for example, a Hamming Window function, a Hanning Window function, or a Chebyshev Window function do. The window function is not limited thereto, and various types of window functions may be used.

In step S130, the processing unit 120 performs Fast Fourier Transform (FFT) on the received signals filtered by the window function, thereby generating first data. The step S 130 may perform fast Fourier transform of the filtered reception signals using, for example, a Doppler filter. By using a Doppler filter, it is possible to identify a target that is moving at a relative speed.

Referring to FIG. 6, the first data is shown. The first data may be defined, for example, as array data for distance and velocity. The first data may comprise a plurality of rate channels. For example, FFT (0), FFT (1), FFT (2), ... , And FFT (Nfft / 2-1) may denote the respective rate channels. The sign (+ or -) of each velocity channel can be the direction of the velocity.

In step S140, the processing unit 120 generates the second data by filtering the received signal through the FIR filter. The second data may be defined as array data for the distance and the velocity in the same manner as the first data. However, the second data is data for a specific rate channel, unlike the first data. For example, the second data may be data for a slow channel region. The slow channel region may be preset. That is, the second data may be data for a rate channel of a predetermined range among a plurality of rate channels of the first data. To this end, a passband may be set so that the FIR filter can filter data corresponding to the slow channel region from the received signal. Meanwhile, the step S140 may be performed in parallel with the steps S120 and S130.

In step S150, the processing unit 120 may combine the first data and the second data to generate third data. Specifically, data for a rate channel that overlaps with the second data among the first data for a plurality of velocity channels is replaced with the second data, thereby forming the third data.

Referring to FIG. 7, the third data is shown. In the present embodiment, it is assumed that FFT (-1), FFT (0), and FFT (1) speed channels among the plurality of rate channels of the first data overlap with the second data. Therefore, the third data will consist of the second data for the FFT (-1), FFT (0), and FFT (1) channels and the first data for the other velocity channels.

In step S160, the processing unit 120 generates a clutter map using the first data. The clutter map may be generated using a magnitude value calculated based on the I / Q value of the distance and speed array data of the first data. The magnitude value is calculated using the following equation (1).

Further, the processing unit 120 may update the clutter map information of the clutter map every time the pulse radar is scanned according to the following equation (2) based on the magnitude value.

Where _j is the clutter map information, x _j is the size of the distance and velocity array data, n is the number of scans, w is the weight, j is the two-dimensional array [k] [i] Is the distance gate number).

On the other hand, the weight w can be defined as Equation (3) below.

Here, scantime is the time required for the radar to scan the entire search area once, and Averagingtime can be the time required to measure the intensity of the clutter around the radar installation area.

In step S170, the processing unit 120 calculates a threshold value for the first target channel by applying a CFAR algorithm to the first target channel of the third data. The first target channel may be a rate channel excluding the rate channel of the second data among the plurality of rate channels of the first data. That is, the first target channel may denote a fast channel region. The threshold value is calculated for each velocity channel. The CFAR algorithm is well known in the art, so a detailed description is omitted. The CFAR algorithm can be applied in various forms, for example, CA (Cell Averaging) CFAR, OS (Order Statistics) CFAR, MCA (Modified CA) CFAR algorithm, and the like.

In step S180, the processing unit 120 selects a first threshold value for the first target channel. Specifically, the threshold value calculated in step S170 is compared with a value corresponding to the first target channel of the clutter map generated in step S160, and a larger value is selected as the first threshold value.

8, the remaining velocity channels excluding the velocity channels of the FFT (-1), FFT (0) and FFT (1), for example, FFT (3) Algorithm is applied to calculate the threshold value, respectively. Then, a larger value compared with the value corresponding to each speed channel in the clutter map will finally be selected as the first threshold value of each speed channel.

In step S190, the processing unit 120 calculates a second threshold value for the second target channel by applying a CM CFAR algorithm to the second target channel of the third data. And the second target may denote a rate channel of the second data. The CM CFAR algorithm refers to detecting the threshold value by referring to the clutter map generated in step S160. Specifically, referring to FIG. 9, for the velocity channels of the FFT (-1), FFT (0), and FFT (1), the threshold value is calculated by referring to the clutter map information of the clutter map do. The step S190 may be performed in parallel with the steps S170 and S180.

In step S200, the presence or absence of a target to be activated in the first target area and the second target area is detected using the first threshold value calculated in steps S170 and S180 and the second threshold value calculated in step S190 .

That is, the received signal is converted into the third data including the first target area (eg, the fast channel area) and the second target area (eg, the slow channel area) through steps S110 to S190, The first threshold value of the one target area and the second threshold value of the second target area are calculated through different processing.

Therefore, the radar signal processing method according to an embodiment of the present invention can detect all the targets that are activated at high speed and low speed. In particular, according to the radar signal processing method according to an embodiment of the present invention, the velocity channel data for the second target region (low-speed channel region) is separately filtered through the FIR filter, . The speed channel data for the second target area (low-speed channel area) is calculated through a process different from the speed channel data for the first target area (high-speed channel area). Accordingly, the problem that the velocity channel data for the target area is removed together with the clutter signal can be solved, and further, a target that is activated at a low speed can be detected.

FIG. 10 is a conceptual view illustrating a signal processing method of a radar according to an embodiment of the present invention.

Referring to FIG. 10, the received signals are filtered through the window functions WF and S1 and the Doppler filter S2, thereby generating first data (first data). In addition, the received signals are filtered through two FIR filters S3 and S4, thereby generating second data (2nd data). The generated first data (1st data) and second data (2nd data) are combined to generate third data (step S5). A clutter map is generated using the first data (S6).

Speed channel data (for example, high-speed channel area data) corresponding to the second data (second data) among the plurality of speed channel data constituting the third data (third data) is transmitted through the clutter map The threshold value is calculated. Alternatively, among the plurality of rate channel data constituting the third data (third data), the rate channel data excluding the rate channel data corresponding to the second data (2nd data) may be the threshold value calculated through steps S7 and S8 The larger value is calculated as the final threshold value.

Meanwhile, the radar signal processing method according to an embodiment of the present invention may be implemented in the form of a program command that can be executed through various computer means and recorded in a computer-readable medium.

Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magneto-optical media such as floptical media; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be determined by the equivalents of the claims of the present invention as well as the claims of the following.

100: Radar
110: Transmitting /
120: Processing unit
130: buffer memory

Claims (7)

Processing the received signal to generate first data having velocity channel data corresponding to each of the plurality of velocity channels;
Generating second data having target speed channel data corresponding to a target speed channel among the plurality of speed channels by FIR (Finite Impulse Response) filtering the received signal;
Generating third data by combining the first data and the second data, and generating a clutter map using the first data; And
And dividing the target velocity channel data constituting the third data and the remaining velocity channel data excluding the target velocity channel data to calculate a threshold value. delete The method as claimed in claim 1, wherein the step of dividing the target velocity channel data constituting the third data and the remaining velocity channel data excluding the target velocity channel data to calculate a threshold value,
Calculating a temporary threshold value for the remaining rate channel data using a CFAR (Constant False Alarm Rate) algorithm;
Comparing a threshold value for the remaining rate channel data calculated by referring to the clutter map with the temporary threshold value and calculating a larger value as a final threshold value; And
And calculating a threshold value for the target velocity channel data using a CMFAR (Cluster Map Constant False Alarm Rate) algorithm. The method according to claim 1,
Processing the received signal to generate first data having rate channel data corresponding to each of the plurality of rate channels; and performing FIR (Finite Impulse Response) filtering on the received signal to correspond to a target rate channel among the plurality of rate channels Wherein the step of generating second data having the target velocity channel data is performed in parallel. 2. The method of claim 1, wherein the step of processing the received signal to generate first data having rate channel data corresponding to each of the plurality of rate channels comprises:
Filtering the received signal using a window function; And
And filtering the filtered received signal using a Doppler filter. 6. The method of claim 5,
Wherein the window function includes a Hamming Window function, a Hanning Window function, and a Chebyshev Window function. The method according to claim 1,
Wherein the step of generating the third data by combining the first data and the second data includes updating the velocity channel data corresponding to the target velocity channel among the velocity channel data of the first data to the target velocity channel data, 3 Signal processing method of radar generating data.

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