KR102317246B1 - Method and apparatus for reducing number of radar target detection operations - Google Patents

Abstract

An object of the present invention is to reduce the number of fast Fourier transforms performed to obtain target information through a signal number discrimination technique. The configuration of the present invention is as follows. The distance is detected by calculating the distance frequency by performing the distance fast Fourier transform on the received signal. By determining the number of targets, it is determined whether there is one target at the same distance. When it is determined that there is only one target, the angle is detected by calculating the range frequency of the receiving channels (range FFT), and the speed is detected by performing a fast Fourier transform (Doppler FFT) on one channel. When there are multiple targets at the same distance through the determination of the number of targets, distance frequencies are obtained for all chirps of all channels in the same manner as in the existing method. Fast Fourier transform is performed once more with the distance frequency on the Doppler axis, a value greater than or equal to the threshold value is selected for the Doppler axis, the number of detections M is determined, and the angle and velocity for the value are detected on the Doppler axis.

Description

Method and apparatus for reducing number of radar target detection operations

The present invention relates to a technique for reducing unnecessary calculations used to obtain target information (distance, speed, and angle) in an FMCW radar system having a plurality of receiving antennas.

The radar transmits the signal generated according to the system requirements through the antenna and then detects the echo signal that is reflected from the target using the antenna and receiver, and then determines the distance, speed, angle, etc. of the target through signal processing. It performs the detection function. The waveform of the radar signal is largely divided into pulse radar, continuous waveform (CW) radar, and frequency modulated CW (FMCW) radar according to its shape.

The FMCW radar uses a signal whose frequency is modulated with time, and estimates the distance of the target according to the beat frequency component, which is the difference between the transmitted signal and the received signal, and the target's distance according to the Doppler frequency component. Deduce the movement speed. In the application field for detecting moving objects, the fast-chirp train modulation method is mainly used to reduce the effect of the Doppler frequency change on the beat frequency.

1 illustrates a general method of detecting a distance, speed, and angle using a 2D FFT (Two Dimensional Fast Fourier Transform) technique in a radar system.

When the transmitter of the FMCW radar transmits a signal through multiple channels, the receiver receives the signal reflected from the target. The transmission/reception control unit transmits a bit signal, which is a difference between the transmission signal and the reception signal, to the signal processing unit. The signal processing unit performs signal processing using a frequency difference (beat frequency, beat frequency) between transmission and reception. The beat frequency contains frequency change information about the target's distance and Doppler (velocity). The amplitude and phase values of the signal on the frequency axis are obtained by fast Fourier transform (FFT) on the range and Doppler, that is, the speed axis, of the bit signal obtained from several reception chirps for a specific time. .

)와 도플러 주파수(

)를 이용하여 도 2의 우측에 나타낸 계산식으로 얻어진다. N개의 표적에 대해서 처리가 완료되었는지 확인(14)하여 N개의 처리가 완료되면 검출 동작이 종료된다.That is, as in FIG. 1, the target range frequency is obtained by FFT on the bit signal (11), and the distance frequency obtained from several chirps is FFTed on the Doppler axis to obtain frequency information about the target speed ( 12). The angle information is calculated using the phase difference between multiple reception channels. In the distance-velocity frequency domain obtained through 2D-FFT, the frequency at which the signal magnitude exceeds the threshold is recognized as a target (13) and the frequency domain corresponding to each channel Calculate the phase of the target to detect the angle. Distance (R) and speed (V) information is the distance frequency (

) and the Doppler frequency (

) using the calculation formula shown on the right side of FIG. 2 . It is checked whether the processing of the N targets is completed (14), and when the N processing is completed, the detection operation is terminated.

은 주파수 스윕(sweep)의 대역폭을 의미하고,

는 주파수가 sweep되는 동안의 시간, 즉, 파형이 전송되는 시간을 의미한다.

는 전송되는 파형의 중심 주파수를 의미하고, c는 빛의 속도를 의미한다.The left side of FIG. 2 shows the case of using the Fast-Ramp waveform among the transmission waveforms of the FMCW radar, and the right side shows the calculation formulas for distance and speed when this waveform is used. in Figure 2

is the bandwidth of the frequency sweep,

is the time during which the frequency is swept, that is, the time the waveform is transmitted.

is the center frequency of the transmitted waveform, and c is the speed of light.

The main reason for performing the Doppler fast Fourier transform and estimating the angle in the FMCW radar is to separate targets with the same distance. Distance and velocity can be calculated only with the distance frequency and Doppler frequency results of one channel, but in the case of angles, the fast Fourier results of four channels are needed to see the phase difference between channels. That is, in order to estimate the angle, the distance fast Fourier transform and Doppler fast Fourier transform for all channels are required.

Accordingly, it is an object of the present invention to reduce the number of fast Fourier transforms performed to obtain target information through a signal number discrimination technique.

In order to solve the above problem, in most cases where there are multiple targets, since there is a high probability that the targets are not at the same distance, it is determined whether there is a target at the same distance in advance, and the distance frequency between channels when there is a single target at the same distance is high. If the angle is detected using only the phase result, the number of operations of the Doppler fast Fourier transform can be reduced.

The above solution will be described in more detail as follows.

The distance is detected by calculating the distance frequency by performing the distance fast Fourier transform on the received signal.

By determining the number of targets, it is determined whether there is one target at the same distance. When it is determined that there is only one target, the angle is detected by calculating the range frequency of the receiving channels (range FFT), and the speed is detected by performing a fast Fourier transform (Doppler FFT) on one channel.

When there are multiple targets at the same distance through the determination of the number of targets, distance frequencies are obtained for all chirps of all channels in the same manner as in the existing method.

Fast Fourier transform is performed once more with the distance frequency on the Doppler axis, a value greater than or equal to the threshold value is selected for the Doppler axis, the number of detections M is determined, and the angle and velocity for the value are detected on the Doppler axis.

The problem solving means of the present invention introduced above will become clearer by the drawings and the description of the embodiments to be described later.

Doppler FFT to obtain speed information by identifying whether the target is at a different distance in advance calculates only one channel and detects the angle with the phase difference obtained from the distance frequency. can

Figure 1: Flowchart of a typical radar signal processing
Figure 2: An example of a radar signal of a Fast-Ramp waveform used in the signal processing of Figure 1
Figure 3: A flowchart of radar signal processing according to the present invention
Figure 4: Cube representing the amount of fast Fourier transform calculation in the present invention
Figure 5: Cube showing the amount of fast Fourier transform calculation in a general method

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the detailed description in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, only this embodiment allows the disclosure of the present invention to be complete, and those of ordinary skill in the art to which the present invention pertains. It is provided to fully inform the person of the scope of the invention, and the present invention is defined by the description of the claims.

On the other hand, the terms used herein are for the purpose of describing the embodiment, not intended to limit the present invention. As used herein, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, "comprises" or "comprising" refers to the presence or addition is not excluded.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. First of all, in adding reference numerals to the components of each drawing, the same components are given the same reference numerals as much as possible even if they are shown in different drawings, and in describing the present invention, detailed information about related known components or functions is given. If the description may obscure the gist of the present invention, the detailed description thereof will be omitted.

In addition, the present invention will be described below with the terms '...step' or '...operation', which are component names of the method aspect, but even with the description of the method aspect, the description of the device aspect of the present invention is not covered. It is obvious that it can be

3 is a flowchart of signal processing for detecting a radar target (target) according to the present invention.

21: The digital signal for the received analog signal of channel 1 is applied to a fast Fourier transform (FFT) process.

22, 23: The number (N) detected in the distance frequency is determined by applying the threshold calculation technique of the distance FFT, and the distance is detected.

24: In conjunction with the last step 31, it is checked whether the processing is completed for the N pieces, and when the N processings are completed, the signal processing operation is terminated.

25: Since it is difficult to determine whether there are multiple targets (multi-targets) at the same distance with the distance frequencies detected by steps 21 to 23, the present invention performs a process of detecting the presence of multiple targets in the same range bin. . In the case of most multi-targets, since there is a high probability that the targets are not at the same distance, it is determined whether there are multiple targets at the same distance as in the procedure below. The basic starting point of the present invention is to reduce the number of operations of the Doppler fast Fourier transform by detecting the angle with the phase result of the distance frequency. In order to detect multiple targets at the same distance, a signal matrix X is generated using data equal to or greater than the number of receiving antennas around the index (Nth peak) of the corresponding frequency. In other words, in order to detect multiple targets at the same distance, from the range FFT (steps 21 to 23) results of the 1st chirp of each receiving channel, the range bin corresponding to the detected distance frequency (ie, the Nth range peak) A signal matrix X of size [1 × number of receiving antennas] is generated using the data in .

26: An eigenvalue is derived from the generated signal matrix using Equations 1 and 2.

Equation 1 refers to an expression, R is the covariance matrix of the process 25, the frequency signal obtained in the matrix of Figure 3 in the formula (1) for deriving a covariance matrix R, the same as the equation (2) derived eigenvalue equation.

는 수학식 1을 통해서 구하고자 하는 고유값이다.

이며 여기서 M은 수신 안테나 개수를 의미한다. I in Equation 2 is the identity matrix,

is an eigenvalue to be obtained through Equation (1).

where M means the number of receive antennas.

27: In the eigenvalue derived through Equation 2, as shown in the eigenvalue characteristic of Equation 3, the eigenvalue of noise, not the signal, is the dispersion value of noise, and the eigenvalue of the signal has a larger value than the eigenvalue of noise. Since it has a characteristic that appears, the number of targets can be determined using this characteristic. Therefore, the number of targets is determined using the eigenvalue characteristic of Equation (3).

In order to determine the number of targets, a minimum description length (MDL) (Equation 4) or a Gaussian MDL (GMDL) technique (Equation 5) may be used.

28: It is determined whether there is one target at the same distance through target number determination. If it is determined that there is one target, the procedure at the bottom left of FIG. 3 (same-distance single target detection) is performed, and when it is determined that there is not one target (ie, if the same-distance multi-target detection), the procedure at the bottom right of FIG. 3 (range bin multiple detection) is performed.

29, 30: In order to obtain the angle of the target, the angle is detected by calculating (range FFT) the distance frequencies of the receiving channels.

32, 33: Speed is detected by fast Fourier transform (Doppler FFT) of one channel to find the speed.

31: When the detection of the angle and speed is completed, processing is performed on the next signal in conjunction with step 24 above, and when the processing is completed for N pieces, the detection operation is terminated.

34: If there are multiple targets at the same distance through the determination of the number of targets in step 28, range FFT is performed on all chirps of all channels in the same manner as in the existing method to obtain the distance frequencies, and then all Doppler FFT is performed on the channel.

35, 37, 38: After fast Fourier transform of the distance frequency to the Doppler axis in step 34, a value greater than or equal to the threshold value is selected for the Doppler axis to determine the number of detections M, and the angle (38) and velocity ( 37) is detected on the Doppler axis. The process of obtaining frequency information on speed by FFT with the Doppler axis (37), and recognizing as a target the frequency at which the magnitude of the signal exceeds the threshold in the distance-velocity frequency domain obtained through 2D-FFT is recognized for each channel. The process 38 of detecting the angle of the target by calculating the phase of the corresponding frequency domain can be performed in the general manner described with reference to FIG. 1 .

36, 39: It is checked whether processing is completed for the M targets, and when the M processing is completed, the same-distance multi-target detection operation is terminated.

As described above, the present invention proposes a method of reducing the number of fast Fourier transform operations by determining whether there is a target at the same distance in advance, unlike the conventional method.

4 and 5 are cube diagrams showing the number of fast Fourier transform operations (computation amount) when there are two targets at different distances. It can be seen that the amount of fast Fourier transform calculation of the present invention of FIG. 4 is greatly reduced compared to the general method of FIG. 5 . In the case of FIG. 4 , it can be seen that the Number of Doppler FFT bins and the Number of range FFT bins are not performed for all the number of antennas.

If it is possible to determine whether the target is at a different distance in advance, it can be designed to calculate the Doppler FFT for only one channel and detect the angle with the phase difference obtained from the distance frequency to obtain velocity information.

As mentioned above, although the configuration of the present invention has been described in detail through preferred embodiments of the present invention, those of ordinary skill in the art to which the present invention pertains will appreciate the content disclosed in the present specification without changing the technical spirit or essential features of the present invention It will be understood that the present invention may be implemented in a specific form other than the above. It should be understood that the embodiments described above are illustrative in all respects and not restrictive. The scope of protection of the present invention is defined by the following claims rather than the above detailed description, and all changes or modifications derived from the claims and their equivalent concepts should be construed as being included in the technical scope of the present invention. .

Claims (10)

(1) performing a range fast Fourier transform (range FFT) on channel 1 of a signal transmitted from the radar is reflected by a target and received by each reception channel of the radar to calculate the distance frequency to detect the distance;
(2) determining whether there is one target or more than one multi-target at the same distance through target number determination;
(3) If there is one target at the same distance through the determination of the number of targets in (2), a range FFT (range FFT) is performed on all channels for the first chirp to detect the angle of the target, and the target speed performing a Doppler FFT on reception channel No. 1 for detection;
(4) If there are multiple targets at the same distance through the determination of the number of targets in (2), a range FFT (range FFT) is performed on all chirps of all channels to obtain a distance frequency, and then the distance FFT result is used and performing Doppler FFT on all channels to detect the angle and velocity. The method of claim 1, wherein for the distance detection of (1),
The digital signal for the received analog signal of channel 1 is applied to a range FFT process, and the number (N) detected at the distance frequency is determined by applying the threshold calculation technique of the range FFT (range FFT). A method of reducing the amount of radar target detection computation, comprising: The method of claim 1, wherein the step (2) determining the number of targets
A method of reducing a radar target detection computational amount, comprising the step of detecting whether multiple targets are present in the same range bin to check whether there are multiple targets at the same distance. The method according to claim 1, wherein in the step (2) determining the number of targets, in order to detect whether there are multiple targets at the same distance,
From the range FFT result of the 1st chirp of each reception channel performed in step (1), a signal matrix having a size of [1 × the number of reception antennas] using data in the range bin corresponding to each detected distance frequency create X,
Equation from the generated signal matrix

( R means the covariance matrix of the frequency signal matrix) and

( I is the identity matrix,

is the eigenvalue to be obtained through Equation 1,

, and M is the number of receiving antennas) to derive an eigenvalue,
An eigenvalue of noise, not a signal, is a variance value of noise, and the eigenvalue of a signal is a method of reducing the amount of radar target detection computation, comprising determining the number of targets using the characteristic of an eigenvalue in which a large value is obtained compared to the eigenvalue of noise . The method according to claim 1, wherein in the step (2) determining the number of targets,
A method of reducing the amount of radar target detection computation, characterized in that the number of targets is determined using one of a minimum description length (MDL) technique and a Gaussian MDL (GMDL) technique. delete The method of claim 1, wherein (4) calculating the distance frequency comprises:
A method of reducing a radar target detection computational amount, comprising: selecting a value equal to or greater than a threshold value with respect to a Doppler axis by performing Doppler FFT on a distance frequency to determine the number of detections M, and detecting an angle and velocity for the value in the Doppler axis. The signal transmitted from the radar is reflected by the target and the distance is detected by calculating the distance frequency by performing a distance fast Fourier transform on the signal received through each reception channel of the radar;
determining whether there is one target or more than one multi-target at the same distance through target count determination;
When there is one target at the same distance through the determination of the number of targets, range FFT (range FFT) is performed on all channels for the first chirp to detect the angle of the target, and receive channel No. 1 for speed detection of the target perform a Doppler FFT on
When there are multiple targets at the same distance through the determination of the number of targets, a range FFT (range FFT) is performed on all chirps of all channels to obtain a distance frequency, and then Doppler FFT is performed on all channels using the distance FFT result. and a processor configured to detect the angle and velocity by performing delete The method of claim 8, wherein the processor
In order to calculate the distance frequency executed when there are multiple targets through the target number determination, the distance frequency is Doppler FFT to select a value greater than or equal to the threshold value with respect to the Doppler axis to determine the number of detections M, and the angle and velocity for the value The apparatus for reducing the amount of radar target detection computation, further configured to detect on the Doppler axis.

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