KR20010003946A - Method for detemining existence and/or nonexistence of target in a radar system - Google Patents

Abstract

PURPOSE: A method for deciding presence of a target fast in a radar system is provided to decide presence of a target faster than a former OS CFAR(ordered statistic constant false alarm rate) and to minimize the number of hardware DSP(digital signal processing) chips by deciding presence of a target through comparison between a test cell and each range cell in size and counting of number having a larger test cell than the range cells. CONSTITUTION: To decide presence of a target fast in a radar system, a test cell data is compared with each range cell of a received signal reflected from a target. A number having a larger test cell than the range cells is counted. The test cell is outputted as target data if the number exceeds a predetermined count value. In the comparing process, the test cell is multiplied by a constant. The predetermined count value is obtained by multiplication of (3/4)x(reference window cell size) of the received signal.

Description

METHOD FOR DETEMINING EXISTENCE AND / OR NONEXISTENCE OF TARGET IN A RADAR SYSTEM}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant false alarm rate (CFAR) signal processing processor in a radar system. In particular, the present invention relates to determining the presence of a target at high speed in a process of processing a constant false alarm rate (CFAR) signal. It is about a method.

In the signal processing algorithm used in the radar system, in order to distinguish the received signal reflected from the actual target from the noise signal, the average value of the received signal multiplied by a constant, that is, a threshold value must be calculated in real time. The CA CFAR algorithm is a method of obtaining a threshold value as an average value of a received signal and using the target detection. If the sequential statistics are used based on the magnitude order of the received signals instead of the average value, this is called OS CFAR. Referring to this in more detail with reference to the accompanying drawings,

First, FIG. 1 is a block diagram illustrating a constant false alarm rate (CFAR) signal processing algorithm used in a radar system, and FIG. 2 is a diagram illustrating received signal and threshold values when an OS (Ordered Statistic) CFAR algorithm is used. FIG. 3 illustrates a received signal and a threshold characteristic diagram when the CA (Cell Average) CFAR algorithm is used. Referring to FIG. 1, a sliding window (also referred to as a Reference Window Cell Size) composed of nm cells output from the detector 10 is applied to the CFAR processor 20. The cell at the center of the window ( ) Is referred to as a test cell 60 and the cells on both sides are referred to as guard cells. If the CFAR processor 20 employs the CA CFAR signal processing algorithm, the CFAR processor 20 calculates an average value by calculating the magnitude of the received signals, and the average value thus obtained is multiplied by a constant k in the comparator 40. Compared with the test cell size, it is output as data indicating whether or not the target is detected (this is referred to as output data). If the CFAR processor 20 employs an OS CFAR signal processing algorithm, the processor 20 lists the received cells in the order of size to obtain the fourth largest (for example, the fourth largest in 16 cells). Cell with value) Data with large value (hereafter Is used for comparison with a test cell. For reference, in FIGS. 2 and 3, the horizontal axis and the vertical axis represent the cell number and the magnitude of the received signal, respectively, and ① and ② represent the received signal and the threshold value. That is, FIG. 2 shows that four targets have been detected, and FIG. 3 shows that the range cell 130th has been detected as a target.

However, in the general OS CFAR described above, In order to calculate the real-time calculation, since the reference cells are listed in size order and the (1/4) th largest cell is used as a comparison value with the test cell, that is, the CFAR threshold value, the order of the received signals in the order of magnitude is large. Computation loads.

It is therefore an object of the present invention to provide a method for determining the presence or absence of a target at high speed in a radar system.

It is still another object of the present invention to provide a method of determining whether a target is present at high speed by calculating a 1 / 4th largest received signal in a reference window with only a small amount of calculation without ordering the received signal.

The present invention for achieving the above object is a method for determining the presence of a target at high speed in the radar system,

A cell data size comparison process for comparing each range cell of the received signal reflected from the target with the size of the test cell data;

A counting process of counting the number of cases in which the test cell has a larger value than the range cell;

Characterized in that the target data output process for outputting a test cell as the target data when the number of the case exceeds a predetermined count value.

1 is a block diagram illustrating a signal processing algorithm generally used in a radar system, and more specifically, a block diagram illustrating a constant false alarm rate signal processing algorithm.

2 is a diagram illustrating a received signal and a threshold value when using a CA (Cell Average) Constant False Alarm Rate (CFAR) algorithm.

3 is a diagram illustrating a received signal and a threshold value when using an OS (Ordered Statistic) Constant False Alarm Rate (CFAR) algorithm.

Figure 4 is a flow chart for determining the presence of a target at high speed in the radar system according to an embodiment of the present invention.

Hereinafter, an operation according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

First of all, the present invention for determining the presence or absence of a target at high speed in a radar system is expressed in the following C language, and the flow diagram is illustrated in FIG. 4.

for (i = m; i <n; i ++) {

If (TEST CELL * (1 / k)> Rande cell [i]

counter = counter + 1;

}

if (counter> (3/4) * (n-m)),

then test cell becomes potential target

Hereinafter, referring to FIG. 4, a method for determining a target presence at high speed will be described in detail according to an embodiment of the present invention. First, m is initialized to i in step 100. At this time, m indicates the lowest cell number among the range cells (referred to as RC) in the sliding window 50 shown in FIG. As described above, when i is initialized to the lowest cell number, the size of the range cell RC [i] and the test cell (test cell TC) are compared in the next step, that is, step 110. Prior to this comparison, the test cell TC must first be multiplied by a constant 1 / k. If the test cell TC / k multiplied by the constant 1 / k is larger than the size of the first range cell RC [i], the counter is incremented by 1 and the process proceeds to step 130. In step 130, the CFAR processor checks whether the value of the counter accumulated so far exceeds (3/4) * (nm). The reason is that in the conventional OS-CFAR from the sliding window 50 Since the range cells are arranged in size order in real time calculation and then the first largest cell is used as a comparison value with the test cell, in order to prevent the time delay that occurs, the embodiment of the present invention simply A simple comparison loop is used to count the number of test cells that exceed the size of the range cell RC.

If the value of the accumulated counter does not exceed (3/4) * (n-m), the process proceeds to step 160 or 170 according to the magnitude comparison between i and n in step 150. That is, if the target is not determined until i exceeds n, the fast CFAR signal processing algorithm according to the embodiment of the present invention is terminated. If i has a value less than n, the process proceeds to step 170 to increase the value of i. After returning to step 110. N denotes the largest range number in the sliding window 50.

On the other hand, if the number of counts of the test cell TC / k having a value larger than the size of the range cell RC [i] exceeds (3/4) * (nm), the CFAR processor proceeds to step 140 to finally determine the counter value. The CFAR signal processing algorithm according to the embodiment of the present invention is terminated after outputting data (which is output data) for the increased test cell to be a target.

As described above, the present invention simply compares the size of the test cell with each of the range cells, and counts the number of cases where the test cell is larger than the size of the range cells, thereby determining the presence or absence of the target.

As described above, the present invention simply compares the size of a test cell with each range cell without arranging the received signals in order of size, and determines the presence or absence of a target by counting the number of cases where the test cell is larger than the size of the range cells. Therefore, it is possible to determine the presence or absence of a target at a faster speed than the conventional OS CFAR algorithm, and has the advantage of minimizing the number of hardware DSP chips

Claims (3)

In a method for determining the presence of a target at high speed in a radar system, A cell data size comparison process for comparing each range cell of the received signal reflected from the target with the size of the test cell data; A counting process of counting the number of cases in which the test cell has a larger value than the range cell; And a target data output process of outputting a test cell as target data when the number of cases exceeds a predetermined count value. The method of claim 1, wherein the test cell is multiplied by a constant 1 / k in the comparison process. The method of claim 1, wherein the predetermined count value is determined as a value of (3/4) * (reference window cell size) in the received signal.