KR101163074B1 - Apparatus and method of measuring distance and velocity of moving object using pulse Doppler radar - Google Patents

Abstract

 An apparatus and method are provided for measuring the distance and velocity of a moving object using a pulsed Doppler radar. The apparatus according to the present invention includes a radar transceiver for transmitting a distance extraction pulse and a speed extraction pulse toward an object and receiving a distance extraction pulse and a speed extraction pulse reflected from the object, and activating when a distance extraction pulse is received. A distance detector for detecting a signal reflected from a clutter and a signal reflected from the moving object and detecting a distance of the moving object from a distance cell corresponding to the moving object; A speed detector which detects the speed of the moving object by frequency converting the result of storing the distance cell corresponding to the object at each pulse repetition interval (PRI) in the row direction, and a distance detector according to the type of the received pulse; And a switch for selectively activating the speed detector. The present invention extracts the velocity of the target using only the cells related to the moving object. The detection performance of the present invention is 93.5%, and the present invention can reduce hardware complexity by 66.2% compared to the prior art.

Description

Apparatus and method of measuring distance and velocity of moving object using pulse Doppler radar}

TECHNICAL FIELD The present invention relates to a technique for measuring the distance and velocity of a moving object using pulsed Doppler radars, and more particularly to a radar architecture having hardware that efficiently utilizes memory using only distance cells associated with moving objects.

Automotive radars are receiving more and more attention as near-field detectors for Intelligent Transport Systems (ITS). Vehicle detectors using loops have been used in the past. Compared to the loop detector, the vehicle radar has the advantage that it can detect distance and speed without having to contact the loop. In fact, pulsed Doppler radars are used in surveillance cameras and vehicle detection systems. Pulsed Doppler radar extracts the distance and velocity of an object by spectral analysis of each distance cell. In the pulse radar, a range gate method is used to extract a time delay in which a pulse is reflected back to an object, and a distance is determined by a value corresponding to the distance gate. In addition, when the speed is extracted from the pulse radar, the speed of the object may be estimated by measuring a phase change that is changed by the object for each pulse repetition interval (PRI). At this time, in order to measure the phase change in the pulse radar, the speed is estimated by frequency converting the accumulated distance gates for each pulse repetition interval. That is, the radar detects distance and velocity through a data matrix having dimensions where the dimensions are distance cells and Doppler frequencies. At this time, when extracting the distance and the speed, there is a problem in that the required memory size increases according to the number of distance gates and the number of pulse repetition intervals.

As such, according to the prior art, the memory size required for the operation is very large. The reason is the number of distance cells and the PRI. That is, according to a conventional pulsed Doppler radar, consecutive distance cells present in each PRI are stored in memory as a row vector of a matrix array. 1 is a diagram illustrating a memory structure used to extract distance and velocity in a pulsed Doppler radar of the prior art. Since successive PRI data are stored in successive rows in the matrix, each column of the matrix represents samples obtained at the corresponding distance during successive PRIs. For example, R _ij is defined as the i th distance cell within the j th pulse repetition interval of the pulse radar receiver. The velocity of the object in the pulse radar is extracted by fast Fourier transform (FFT) in the column direction of all pulse data stored in the memory. The distance of the object is determined by the distance cell after the velocity is extracted. Assuming that all data sizes are fixed in bytes, and that all samples of distance cells in the PRI are L and the number of PRIs during the updated time is M, the memory required for signal processing during the updated time is LxM bytes. do. The number of FFT operations requires that the sample size of the distance cell and L for the updated time be the same. Therefore, as the sample size of the distance cell increases, the memory size of the radar must also increase. Thus, not only hardware is expensive to implement the memory, but also the time required to detect distance and speed is long.

Therefore, for pulsed Doppler radars, there is an urgent need for memory efficient utilization techniques that improve the complexity required to detect distances and velocities relative to objects.

It is an object of the present invention to provide a method for measuring the distance and velocity of a moving object that can improve the memory efficiency of a pulsed Doppler radar.

In addition, another object of the present invention is to provide a technique that can reduce the time required to measure the distance and speed of the moving object using a pulsed Doppler radar.

One aspect of the present invention for achieving the above object is directed to an apparatus for measuring the distance and speed of a moving object using a pulsed Doppler radar. The apparatus according to the present invention includes a radar transceiver for transmitting a distance extraction pulse and a speed extraction pulse toward an object and receiving a distance extraction pulse and a speed extraction pulse reflected from the object, and activating when a distance extraction pulse is received. A distance detector for detecting a signal reflected from a clutter and a signal reflected from the moving object and detecting a distance of the moving object from a distance cell corresponding to the moving object; A speed detector which detects the speed of the moving object by frequency converting the result of storing the distance cell corresponding to the object at each pulse repetition interval (PRI) in the row direction, and a distance detector according to the type of the received pulse; And a switch for selectively activating the speed detector. Particularly, the distance detector is a clutter based on a result of comparing the received distance extracting pulse with the number of distance extracting pulses for each PRI, and a result of comparing a predetermined threshold level with the result of the coherent integrator block. Clutter index extraction block for extracting the time index of the signal received from the clutter index, non-coherent integrator block for accumulating the square of the received distance extraction pulse by the number of distance extraction pulse, non-coherent A total index extraction block for extracting a time index of a signal received from all objects from the output of the runt integrator block as a total index, a clutter index removing block for removing a clutter index from the total index to obtain a moving object index, and a moving object And a distance calculating block for detecting the distance of the object from the distance cell corresponding to the. Furthermore, the speed detector includes a moving object selection block for storing a distance cell corresponding to a moving object index in a memory block, a fast fourier transform (FFT) block for frequency transforming distance cells stored in the memory block in a column direction, and a frequency transformed signal. It includes a speed calculation block for calculating the speed of the moving object based on the result.

Another aspect of the present invention for achieving the above objects relates to a method for measuring the distance and speed of a moving object using a pulsed Doppler radar. The method according to the present invention transmits a distance extraction pulse and a speed extraction pulse toward an object and receive the distance extraction pulse and the speed extraction pulse reflected from the object, when the distance extraction pulse is received, from the clutter A distance detecting step of detecting the reflected signal and the signal reflected from the moving object to detect the distance of the moving object from the distance cell corresponding to the moving object, and when the pulse for speed extraction is received, each distance cell corresponding to the moving object is determined. And a speed detection step of detecting the speed of the moving object by frequency converting the result stored for each pulse repetition interval PRI in the row direction. In particular, the distance detection step includes accumulating the received distance extraction pulses for each PRI by the number of distance extraction pulses, and comparing the predetermined threshold level with the result of the coherent integrator block. Extracting the time index of the signal as a clutter index, accumulating the squares of the received distance extraction pulses by the number of distance extraction pulses, and extracting the signals received from all objects from the output of the non-coherent integrator block. Extracting the time index as a total index, removing the clutter index from the total index to obtain a moving object index, and detecting a distance of the object from a distance cell corresponding to the moving object. Further, the speed detecting step includes storing the distance cells corresponding to the moving object index in the memory block, frequency converting the distance cells stored in the memory block in the column direction, and speed of the moving object based on the frequency converted result. Calculating a.

According to the present invention, since the pulse Doppler radar first specifies the distance cell related to the moving object among all the objects, and performs the frequency conversion ignoring other distance cells, the size of the memory required for measuring the distance and speed of the moving object. Decreases significantly.

1 is a diagram illustrating a memory structure used to extract distance and velocity in a pulsed Doppler radar of the prior art.
2 is a block diagram conceptually illustrating an apparatus 200 for measuring distance and speed of a moving object according to an exemplary embodiment of the present invention.
3 is a diagram illustrating a signal transmitted from a pulsed Doppler radar according to the present invention.
4 is a block diagram illustrating the distance detector 230 and the speed detector 250 shown in FIG. 1 in more detail.
5 is a graph showing the clutter detection probability with respect to the signal-to-noise ratio (SNR).
6 is a flowchart conceptually illustrating a method for measuring a distance and a speed of a moving object according to another aspect of the present invention.
7 is a graph comparing the present invention with the prior art.

In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings which illustrate preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In addition, in order to clearly describe the present invention, parts irrelevant to the description are omitted, and the same reference numerals in the drawings indicate the same members.

Throughout the specification, when a part is said to "include" a certain component, it means that it may further include other components, without excluding the other components unless otherwise stated. In addition, the terms "... unit", "... unit", "module", "block", etc. described in the specification mean a unit for processing at least one function or operation, which means hardware, software, or hardware. And software.

2 is a block diagram conceptually illustrating an apparatus 200 for measuring distance and speed of a moving object according to an exemplary embodiment of the present invention.

2, the apparatus 200 for measuring distance and speed of a moving object according to the present invention may include a radar transceiver 210, a distance detector 230, a speed detector 250, a switch 270, and a memory block ( 290).

The radar transceiver 210 transmits a distance extraction pulse and a speed extraction pulse toward an object and receives a pulse reflected from the object. In this case, the distance to the object is measured using the distance gate as described above. The distance detector 230 is activated when the distance extraction pulse reflected from the object is received by the radar transceiver 210, and the speed detector 250 is the speed reflected from the object by the radar transceiver 210. Activated when an extraction pulse is received. This activation is done via switch 270.

Here, the distance detector 230 determines a signal reflected from the clutter and a signal reflected from the moving object, and distinguishes the stationary object from the moving object using the signal. In addition, the distance detector 230 detects the distance of the moving object from the distance cell corresponding to the moving object.

In addition, the speed detector 250 detects the speed of the moving object by frequency converting the result of storing the distance cell corresponding to the moving object for each pulse repetition interval PRI in the row direction.

The memory block 290 also stores an array of distance cells, in order to obtain the velocity of the moving object, the radar extracts the distance cells associated with the moving object in the column direction. The data extracted from the memory block 290 is computed by the FFT processor and converted to the Doppler frequency.

The apparatus for measuring the distance and the speed of the moving object according to the present invention reduces complexity because it uses only the distance cell related to the moving object among all the distance cells.

That is, the method proposed in the present invention is different from storing data of all distance cells and pulse repetition intervals in the memory block 290 in order to measure the distance and velocity of the detection object. Classifiers and moving objects. The frequency of the moving object can be obtained by frequency converting only the distance cells corresponding to the extracted moving object in the column direction.

Detailed configurations of the distance detector 230 and the speed detector 250 will be described later in detail with reference to FIG. 4.

3 is a diagram illustrating a signal transmitted from a pulsed Doppler radar according to the present invention.

As shown in Figure 3, the pulse used in the pulse radar receiver according to the present invention is composed of a distance extraction pulse and a speed extraction pulse. The number of distance detecting pulses and the number of speed detecting pulses are N _D and N _V, respectively.

4 is a block diagram illustrating the distance detector 230 and the speed detector 250 shown in FIG. 1 in more detail.

In FIG. 4, the signal received through the ADC is selectively transmitted to one of the distance detector 410 and the speed detector 450 by the switch 1 (SW1). The switch 1 SW1 connects the distance detector when the distance detection pulse is received, and connects the speed detector when the speed detection pulse is received. The distance detector 410 may include a coherent integrator block 415, a coherent threshold detection block 420, a non-coherent integrator block 425, a non-coherent threshold detection block 430, and a clutter. An index removal block 435 and a distance computation block 450.

Coherent integrator block 415 is transitioned by switch 2 (SW2) for every sample (ie, distance cell). This block accumulates N _D times for each PRI. Coherent threshold detection block 420 extracts clutter by comparing the threshold level with the result of the coherent integrator block. The characteristics of signals received from clutters, such as buildings and stationary vehicles, are the same in all phases and the signals reflected from moving objects vary in phase so that all signals reflected through the coherent threshold detection block 420 are summed. In this case, only the clutter signal is detected. Therefore, the coherent threshold detection block 420 can detect clutter by summing signals received from moving objects having different phases. In this specification, this signal is defined as a clutter index in a distance cell. When the coherent threshold detection block 420 performs a clutter detection operation, the clutter detection probability in the additive white Gaussian noise (AWGN) channel is expressed by Equation 1 below.

는 상보적 가우시안 누적 분산 함수이다.
here,

Is the complementary Gaussian cumulative variance function.

5 is a graph showing the clutter detection probability with respect to the signal-to-noise ratio (SNR). Here, the probability of false alarm to be generated (P _FA) when the N is 30 _D is 10 ^-3, and 10 ^-4 are the time 50 days. If the SNR is 2 dB or more, the mode clutter is detected because the clutter detection probability in the coherent integrator block is one.

In addition, non-coherent integrator block 425 also performs a shift by switch 3 (SW3) and accumulates the square of the received signal ND times. Non-coherent threshold detection block 430 detects all signals, including clutter and moving objects. In this specification, this signal is defined as a total index among the distance cells. That is, the total index includes the index of the entire object including the clutter and the moving object.

The time index of the clutter and the entire object is then sent to the clutter index removal block 435. The clutter index removal block 435 then removes the clutter index from the total index. As a result, only the time index of the moving object is transmitted to distance calculation block 440 and moving object selection block 460. Therefore, because coherent integrator block 415 detects all unwanted distance cells, such as those associated with clutters with SNR greater than 2 dB, distance detector 440 only detects moving objects.

The speed detector 450 includes a moving object selection block 460, an object storage memory block 470, an FFT block 480, and a speed calculation block 490.

The moving object selection block 460 provides the distance cell to the memory block 470 based on the moving object index. Switch 4 (SW4) determines the storage location of the data memory transferred by the moving object selection block 460. The memory according to the present invention has N rows and M columns. N represents the number of moving object indices in the distance cell. Therefore, the radar according to the present invention reduces the memory size by N / L than the conventional one.

Data stored in the memory block 470 is processed by a Doppler matched filter. The output from the M pulses is fed back to the FFT processor 480. The FFT results are converted to the velocity of the moving object in velocity computation block 490.

In summary, as shown in FIG. 4, the clutter and the moving object classification algorithm are performed in the distance extraction part and extract only the moving object from the received signal. The speed of the moving object can be obtained by frequency converting only the distance cells corresponding to the extracted moving object index in the column direction.

6 is a flowchart conceptually illustrating a method for measuring a distance and a speed of a moving object according to another aspect of the present invention.

First, the radar transceiver 210 transmits the distance extraction pulse and the speed extraction pulse toward the object and receives the distance extraction pulse and the speed extraction pulse reflected from the object (S610). The signal transmitted from the pulsed Doppler radar is as described above with reference to FIG. 3.

When the distance extraction pulse reflected from the object is received by the radar transceiver 210, the signal reflected from the clutter and the signal reflected from the moving object are determined to determine the distance of the moving object from the distance cell corresponding to the moving object. It is detected (S630). In order to compare the clutter with the moving object, the phase of the signal reflected by the clutter does not change.

In addition, when the speed extraction pulse reflected from the object is received by the radar transceiver 210, frequency conversion of the result of storing the distance cell corresponding to the moving object for each pulse repetition interval PRI is performed in the row direction. The speed of the moving object is detected (S650). At this time, since the clutter index for the clutter is removed from the total index, only information on the moving object is stored in the memory. Therefore, not only the size of the memory is saved, but also the time required for frequency conversion is greatly reduced.

7 is a graph comparing the present invention with the prior art.

Referring to FIG. 7, when the memory size required by the prior art device is 1, the memory size required by the present invention is slightly larger than 0.2 when the number of objects is 40, and almost 0.2 when the number of objects is 30. And if you have 20 objects, you can see that they are less than 0.2. As such, the memory size required is significantly reduced when using the present invention.

In addition, the simulation results of the present invention are as follows.

First, the present invention is compared with the conventional radar according to the number of objects. Simulation parameters are as follows. The maximum distance is 150m, the resolution is 1m, and the number of distance cells in PRI is 150. The method according to the invention reduces the memory size by more than 73% for 40 objects, whereas in the conventional method the memory size is constant regardless of the number of objects.

In addition, the number of hardware resources required by the present invention is as follows as compared with the prior art.

Hardware resources, except memory, are FFT processors and coherent integrator blocks. Referring to the prior art, the number of hardware resources required in the prior art is 361.5 complex multipliers, 4200 complex adders, and 28500 registers. However, in the device according to the present invention, one complex multiplier, 300 complex registers and 300 adders are required for the coherent integrator block and the non-coherent integrator block. Therefore, the number of hardware resources according to the present invention is 97.4 complex multipliers, 1420 complex adders, and 7900 registers.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art.

Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

The pulse radar receiver proposed in the present invention is expected to greatly contribute to the implementation of low-cost pulse radar because it can reduce the amount of computation required to extract the distance and speed of the detection target and efficiently apply the memory. In addition, it is expected to be applied to various vehicle applications, shipbuilding applications, robot applications, and security applications based on pulse radar.

Claims (6)

An apparatus for measuring distance and speed of a moving object using a pulsed Doppler radar,
A radar transceiver for transmitting a distance extraction pulse and a speed extraction pulse toward an object and receiving a distance extraction pulse and a speed extraction pulse reflected from the object;
A distance detector configured to be activated when the distance extraction pulse is received and detect a distance of the moving object from a distance cell corresponding to the moving object by determining a signal reflected from a clutter and a signal reflected from the moving object;
When the pulse for speed extraction is received, the pulse detection method is activated to frequency-translate the result of storing the distance cell corresponding to the moving object for each pulse repetition interval (PRI) in a row direction to detect the speed of the moving object. A speed detector; And
And a switch for selectively activating the distance detector and the speed detector according to the type of pulse received.
The method of claim 1, wherein the distance detector,
A coherent integrator block that accumulates the received distance extraction pulses for each PRI by the number of distance extraction pulses;
A clutter index extraction block for extracting a time index of a signal received from the clutter as a clutter index based on a result of comparing a predetermined threshold level with a result of a coherent integrator block;
A non-coherent integrator block that accumulates a square of received distance extraction pulses by the number of distance extraction pulses;
A total index extraction block for extracting a time index of a signal received from all objects from the output of the non-coherent integrator block as a total index;
A clutter index removal block that removes the clutter index from the total index to obtain a moving object index; And
And a distance calculating block for detecting a distance of the object from a distance cell corresponding to the moving object.
The method of claim 2, wherein the speed detector,
A moving object selection block that stores a distance cell corresponding to the moving object index in a memory block;
A fast fourier transform (FFT) block for frequency transforming distance cells stored in the memory block in a column direction; And
And a speed calculating block for calculating a speed of the moving object based on the frequency converted result. A method for measuring the distance and speed of a moving object using a pulsed Doppler radar,
Transmitting the distance extraction pulse and the speed extraction pulse toward the object and receiving the distance extraction pulse and the speed extraction pulse reflected from the object;
A distance detecting step of detecting a distance of the moving object from a distance cell corresponding to the moving object by determining a signal reflected from a clutter and a signal reflected from a moving object when the distance extraction pulse is received; And
And a speed detecting step of detecting a speed of the moving object by frequency converting a result of storing the distance cell corresponding to the moving object for each pulse repetition interval PRI in a row direction when the speed extraction pulse is received. Method for measuring the speed of the moving object, characterized in that.
The method of claim 4, wherein the distance detection step,
Accumulating the received distance extraction pulses by the number of distance extraction pulses for each PRI;
Extracting a time index of a signal received from the clutter as a clutter index based on a result of comparing a predetermined threshold level with a result of a coherent integrator block;
Performing in a non-coherent integrator block, accumulating a square of received distance extraction pulses by the number of distance extraction pulses;
Extracting, as a total index, a time index of a signal received from all objects from the output of the non-coherent integrator block;
Removing the clutter index from the total index to obtain a moving object index; And
Detecting a distance of the object from a distance cell corresponding to the moving object.
The method of claim 5, wherein the speed detection step,
Storing the distance cell corresponding to the moving object index in a memory block;
Frequency converting the distance cells stored in the memory block in a column direction; And
And calculating the speed of the moving object based on the frequency-converted result.

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