KR101035267B1 - Doppler radar based target displacement detection method and apparatus to prevent false alarm due to the background motions - Google Patents

Abstract

PURPOSE: Doppler radar based target displacement detection method and apparatus are provided to classify the movement of background and the movement of a real target. CONSTITUTION: A Doppler signal of a real target is received(S110). The phase of the Doppler signal is measured(S120). The real movement amount of the real target is measured based on the phase(S130). If the real movement amount of the real target is more than a pre-set critical value, the real target is verified as a detection target. If the real movement amount of the real target is lower than the pre-set critical value, the real target is eliminated(S140 to S160).

Description

Doppler RADAR based target displacement detection method and apparatus to prevent false alarm due to the background motions}

The present invention relates to surveillance and reconnaissance sensing technology, and more particularly, to a method and apparatus for preventing false alarms caused by background motion based on a Doppler radar.

Until now, surveillance and reconnaissance sensor networks aimed at detecting and identifying intruders have mainly used passive sensors such as acoustic, magnetic, vibration, and infrared sensors as target sensors.

In recent years, however, active sensors are being applied that can detect targets farther away than these passive sensors, and at the same time obtain more information such as the target's distance and the type of target. Radar is a representative example. .

Basically, in pulsed Doppler radar, the transmitter emits a pulse toward the detection area and receives the signal reflected from the target at the receiver to interpret the target information. Specifically, the distance between the target and the radar may be measured using the time difference between the transmitted signal and the reflected received signal, and the moving speed of the target may be measured using the Doppler signal included in the reflected signal.

In the case of using such a Doppler radar, it is possible to determine whether the Doppler signal is present and to easily separate the moving dynamic object from the static static object. Therefore, Doppler radar is mainly used to detect moving targets from a static type of clutter which has no movement other than the target.

For example, it is the most common concept used to detect a flying object moving in the air of a static environment or a ship moving in the sea of a static environment.

A clutter is an object that generates unwanted reflections, such as ground, bushes, trees, and obstacles, except for the target.If the clutter moves like a target to detect and generates a Doppler signal, it detects the target. There is a risk of false alarms.

If the Doppler signal generated by the clutter is significantly smaller than the Doppler signal generated by the target, the target can be distinguished from the clutter by simply comparing the size of the Doppler signal between the clutter and the target. However, if the Doppler signal from the clutter is similar in magnitude to the Doppler signal from the target, or if the Doppler signal from the clutter is larger, simply compare the magnitudes of the Doppler signals from the clutter and the target. Can't distinguish clutter from target.

Figure 1 illustrates a problem that occurs when detecting a target moving through the prior art Doppler radar.

According to FIG. 1, fixed walls, moving people, small bushes or trees swaying in the wind, large bushes or trees swaying in the wind generate Doppler signals of different sizes. Doppler signals are not generated because the fixed wall has no motion, but the Doppler signal is detected by the movement of moving people and large and small bushes or trees swaying in the wind, and the size is proportional to the size of the object and the size of the movement. .

In such a situation, if the target of interest of the radar is a human, and therefore attempts to distinguish the target from the non-target by setting the magnitude of the Doppler signal generated by human movement as a threshold, the small bush or tree may be ignored. However, the problem is that the motion of the bush or tree larger than the person exceeds the threshold, and thus cannot be distinguished from the motion of the person.

This situation occurs mainly when it is necessary to detect moving targets with humans in the bushes and wooded outdoor environments shaken by the wind. The size of the Doppler signal generated by a moving object is mainly proportional to the size of the object, because if a similar size or larger bush or tree is swayed by the wind, a Doppler signal of a similar size to a person's moving will be generated. There is a problem in that the size of the Doppler signal alone cannot distinguish between a person and a bush. In such a case, if a target moving based only on the magnitude of the Doppler signal is detected as in the conventional method, false alarms due to background movement of trees and trees swaying in the wind may occur frequently.

As described above, the conventional detection method using the Doppler radar is suitable for detecting the motion of an object in an indoor environment without background motion, but is not suitable for an outdoor environment with a lot of background motion. Therefore, in order to detect a moving target in an outdoor environment, a method of distinguishing the actual target from the background movement is required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to use a synchronous pulsed Doppler radar to breakthrough false alarms caused by background motion in an outdoor environment in which it is difficult to apply a conventional target detection method of a conventional Doppler radar. It is to provide a method and apparatus that can be reduced.

Another object of the present invention is to provide a detection method and apparatus having a low calculation amount so that detection can be performed even at a sensor node having low hardware performance using a synchronous pulsed Doppler radar.

In order to achieve the above object, the present invention provides a method and apparatus for acquiring a net movement amount by accumulating the phase change amount of the Doppler signal for a predetermined period with respect to the Doppler signal of the detected object, and distinguishing the background motion from the actual target. .

The method includes detecting a moving target, receiving a Doppler signal of the target, measuring a phase with respect to the Doppler signal, measuring a net moving amount of the target using the phase, and Determining the target to be tracked if the net movement amount exceeds a certain threshold value, and excluding the target from the target to be tracked if the net movement amount does not reach the threshold value.

The apparatus for detecting a moving target, comprising: an antenna for receiving a signal reflected from the target, a Doppler signal extractor for extracting a Doppler signal from the reflected signal, a phase meter for measuring a phase with respect to the Doppler signal, and A movement measuring device for measuring a net moving amount of the target by using a phase, and a controller for determining a target to be tracked when the net moving amount exceeds a specific threshold, and excluding a target to be detected if the net moving amount does not reach the threshold. do.

According to the present invention, a synchronous pulsed Doppler radar has an effect of dramatically reducing false alarms caused by background motion in an outdoor environment in which a conventional target detection method of a conventional Doppler radar is difficult to apply.

According to the present invention, a synchronous pulsed Doppler radar can be used to provide a detection algorithm that can be performed even at a sensor node having low hardware performance.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail. For the same procedures and components, in adding reference numerals to the respective procedures, adding reference numerals to the components in the drawings, or adding the reference numerals to the components in the drawings, the same procedures and components may be used in different drawings. Note that the same sign is used even if it is indicated in.

In addition, many specific details appear in the following description, which is provided to help a more general understanding of the present invention, and the present invention may be practiced without these specific matters to those skilled in the art. Will be self-explanatory. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

In the present invention, by distinguishing the movement caused by the background movement and the movement caused by the target, in order to overcome the limitation that a lot of false alarms caused by clutter movement when detecting the movement of the target in the outdoor environment, "net movement amount" "The concept of".

That is, when the background motion generates a Doppler signal having a larger motion than the target to distinguish the target from the background motion only by comparing the magnitude of the simple Doppler signal, the net amount of movement of the two objects is measured to determine whether the target is the background motion or not. By detecting, only a moving target can be detected to prevent false alarms of the Doppler radar.

The concept of "net movement amount" defined in the present invention is a value obtained by accumulating a movement amount of a target for a specific time, where the movement amount has a positive value when the target moves forward with respect to the direction in which the Doppler radar emits the beam. When moving backwards, it is negative.

On the other hand, background movements such as trees and bushes that are shaken by wind are mainly shaken back and forth, so the Doppler signal is generated, but there is little distance actually moved when measured for a certain time. Can be distinguished from.

Figure 2 illustrates the concept of net movement amount, in accordance with the present invention.

In Figure 2, the direction of the arrow means the direction of movement, the length of the arrow means the amount of movement. According to FIG. 2, the target 1 moves away from the radar from t1 to t2, moves closer to the radar from t2 to t3, and moves away from the radar again from t3 to t4. If we calculate the net amount of movement of target 1 by accumulating the amount of movement from t1 to t4, the amount of movement due to the movement back and forth cancels each other and finally has a small value. It has this characteristic.

On the other hand, target 2 moves away from the radar from t1 to t2, and also moves away from t2 to t3, and when we accumulate the movement amount from t1 to t3, we can see that it has a much larger value than target 1, Moving objects, such as moving people, have this feature.

The net shift amount can be obtained using the phase change of the Doppler signal, since the phase shift amount of the Doppler signal corresponds to the change amount of the target distance, that is, the net shift amount of the target.

In general, in a synchronous radar, a signal reflected and received by a target may be separated into two types of signals through an in-phase channel and a right-phase channel, and the target is detected by analog-to-digital conversion.

3 illustrates a structural diagram of a synchronous Doppler radar according to an embodiment of the present invention.

According to FIG. 3, a synchronous Doppler radar includes an antenna 110 for receiving a signal reflected from a target, a Doppler signal extractor 120 for extracting a Doppler signal from the reflected signal, and an in-phase from the Doppler signal; I) and quadrature phase (Q) values, the phase meter 120 for measuring and measuring the phase, the movement meter 130 for measuring the net amount of movement of the target and background motion generating the Doppler signal, and the net amount of movement And a controller 140 for detecting the target by classifying the target according to the calculation result of the measurement unit.

In one embodiment of the present invention, a synchronous Doppler radar was used to measure the net movement of the target. The in-phase (I) and quadrature phase (Q) values of the Doppler signal can be obtained from the Doppler signal of the object received from the synchronous Doppler radar. Using the value, the phase value of the Doppler signal can be obtained according to the following equation (1).

By calculating the phase value, the net amount of movement of the target can be obtained through the amount of change in the phase value over time.

Since the structure and operation principle of the synchronous Doppler radar can be easily understood by those skilled in the art, detailed description thereof will be omitted here.

As described above, in order to obtain the net moving amount of the target, it is necessary to obtain the distance that the object moves purely. This is called a net shift amount, and in order to obtain a net shift amount in accordance with the present invention, the phase shift amount of the Doppler signal is accumulated and calculated, which is referred to as "phase unwrapping".

In other words, the phase unfolding process is called a phase continuity process. It is a technique commonly used to convert a discontinuous phase function into a continuous phase function to perform an additional signal processing process such as differential.

That is, the phase value of the Doppler signal has a value between -180 degrees and 180 degrees, and when the phases are drawn according to each measurement, a discontinuity point of the phase function is generated. A continuous phase function can be obtained, and can be obtained by the method shown in Equation 2 below.

는

번째 시간에서 펼쳐진 위상값을 의미하고,

번째 시간에서 측정된 위상값을 의미한다. 또한, mod는 프로그래밍 언어에서 흔히 쓰이는 모듈러스(modulus) 연산자로서, mod(X, Y)는 X-n*Y의 연산을 하는 것으로서 n은 X/Y보다 작은 정수 중 가장 큰 수를 의미한다.In Equation 2

Is

Means the phase value unfolded at the first time,

The phase value measured at the first time. In addition, mod is a modulus operator commonly used in programming languages, where mod (X, Y) is an operation of Xn * Y, where n is the largest integer smaller than X / Y.

In this way, the phase shift is performed on the Doppler signal to accumulate the amount of phase change for a predetermined time to obtain the net movement of the target. If the net movement over the predetermined time exceeds the threshold, the object generating the Doppler signal Can be determined to be the moving target.

A specific method for implementing the above object according to the present invention can be obtained through the following process.

4 illustrates a target movement detection algorithm of a synchronous pulse radar according to the present invention.

Referring to FIG. 4, the antenna 110 receives a Doppler signal of a target or clutter.

Phase detector 120 first obtains the in-phase (I) and quadrature phase (Q) values of the Doppler signal from the synchronous pulse radar to detect moving targets from the received signal ( S110), and calculates a phase for the Doppler signal through Equation 1 from the in-phase (I) value and the quadrature phase (Q) value of the Doppler signal (S120).

The movement amount measuring unit 130 calculates the net movement amount in which the phase change amount is accumulated with respect to the Doppler signal for a predetermined time using the calculated phase (E130).

The accumulated phase change amount is compared with a preset threshold value (S140), and when the accumulated phase change amount is larger than a threshold value, the controller 140 determines that the object generating the Doppler signal is a moving target (S150). If the tracking is smaller than the threshold value, the target generating the Doppler signal is determined as the noise or the movement of the clutter and is not tracked.

The threshold value determined by the movement of the target may be variably adjusted according to the outdoor environment, the strength of the wind, and the movement characteristic of the target according to the time for performing the phase spreading and the accumulated value of the net movement amount.

In addition, a list of non-target objects is placed on the radar and a list of non-target objects is generated. For the objects that generate a Doppler signal and are determined to be non-target because the net movement amount does not reach the threshold value, the radar is stored in the list. Another way to think about it is not to track from the start.

In the above description of the preferred embodiments of the present invention by way of example, the scope of the present invention is not limited only to these specific embodiments, the present invention is in various forms within the scope of the spirit and claims of the present invention May be modified, changed, or improved.

Figure 1 illustrates a problem that occurs when detecting a target moving through the prior art Doppler radar.

Figure 2 illustrates the concept of net movement amount, in accordance with the present invention.

3 illustrates a structural diagram of a synchronous Doppler radar according to an embodiment of the present invention.

4 illustrates a target movement detection algorithm of a synchronous pulse radar according to the present invention.

Claims (8)

In the detection method of a moving target, Receiving a Doppler signal of the target; Measuring phase with respect to the Doppler signal; Measuring the net amount of movement of the target using the phase; And Determining the target to be detected when the net movement amount exceeds a certain threshold value, and excluding the target from the target to be detected when the net movement amount does not reach the threshold value. The method of claim 1, Measuring the phase with respect to the Doppler signal, Doppler radar-based moving target detection method characterized in that it is obtained using the in-phase (I) value and quadrature-phase (Q) value of the Doppler signal. The method of claim 1, Doppler radar-based moving target detection method characterized in that the net amount of movement of the target is obtained through a phase unfolding value accumulated the amount of phase change of the target for a predetermined time. The method of claim 3, wherein Phase spread value of the net shift amount,

Is

Foraging through

.

Are each,

Doppler radar-based moving target detection method characterized in that the mean time and the measured phase of the target at the second time. In the detection device of the moving target, An antenna for receiving a signal reflected from the target; A Doppler signal extractor for extracting a Doppler signal from the reflected signal; A phase meter for measuring a phase with respect to the target from the Doppler signal; A movement amount measuring device for measuring a net movement amount of the target using the phase; And Doppler radar-based moving target detection apparatus comprising a controller for determining that the target is to be detected when the net movement amount exceeds a certain threshold, and excludes from the target to be detected when the net movement amount does not reach the threshold. The method of claim 5, The phase meter for measuring the phase with respect to the Doppler signal, The Doppler radar-based moving target detection apparatus of claim 1, wherein the Doppler radar-based moving target detection device is obtained using an in-phase (I) value and a quadrature-phase (Q) value of the Doppler signal. The method of claim 5, Doppler radar-based moving target detection apparatus characterized in that the net amount of movement of the target is obtained through a phase unfold value accumulated by the amount of phase change of the target for a predetermined time. The method of claim 7, wherein Phase spread value of the net shift amount,

Is

Foraging through

.

Are each,

Doppler radar-based moving target detection device means the spread phase and the measured phase of the target at the second time.

Images