KR101351282B1 - Enhancement method of unobserved area for radar system based on clutter map, and radar system using the same - Google Patents

Abstract

The present invention relates to a method for improving unobserved area of a clutter map-based radar system, and the method for improving the unobserved area of the radar system includes the steps of: (a) forming a clutter map by a process of setting a lowest altitude capable of beam transmission and a process of setting a waveform in a transmittable beam grid and setting an unobserved area; (b) updating the clutter map during regular searching. Thus, the present invention can improve low altitude detection performance without increasing frame time by reducing the unobserved area due to a clutter signal of an antenna side lobe. [Reference numerals] (AA) Altitude; (BB) Distance; (CC) Unobserved area; (DD) LFM waveform setting area; (EE) PT waveform setting area; (FF) Beam transmission prohibition area; (GG) Azimuth

Description

Enhancement method of unobserved area for radar system based on clutter map, and radar system using the same}

The present invention relates to an unobserved area improvement method of a radar system and a radar system using the same, and more particularly, to an unobserved area improvement method of a cluttermap-based radar system and a radar system using the same for reducing false target detection.

Radar systems detect false targets by strong reflected signals from ground clutter around the radar. To reduce such false targets, the radar system uses the clutter map technique for matched received signals.

The clutter map technique manages clutter information according to azimuth and elevation, so that the cluttered area is set as an unobserved area to reduce the false target caused by clutter.

Fig. 1 shows a clutter map composed of three dimensions of azimuth-elevation-distance. The clutter map stores a beam transmission prohibition zone, a minimum transmission altitude, waveform information, and unobserved area information for each azimuth-angle beam grid.

The unobserved region setting method of the clutter map technique can be generally performed in two steps. The first step is to find the average value of the magnitude of the clutter signal received for each distance section as shown in FIG. That is, the average value of the signal size is calculated by combining sampling data (xx range samples) of the received clutter signal.

The second step is to apply the threshold to the calculated signal size as shown in Figure 3 to set the actual unobserved region. That is, if the average value of the signal size is larger than the threshold value, the corresponding distance is set as the unobserved area (Blank 1, Blank 2, Blank 3).

The clutter map technique applies this method to all search beams to store and manage unobserved area information according to the elevation-azimuth angle.

However, the radar system using the clutter technique has a problem that the probability of not detecting a target increases due to the large unobserved area due to the clutter signal of the antenna side lobe at low altitude when there are many mountainous terrains. It acts as a factor in degrading performance.

KR 10-2011-0019520 A, Feb. 28, 2011, Fig. 1

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for improving the unobserved region of a radar system capable of improving low altitude detection performance without increasing the frame time by reducing the unobserved region due to the clutter signal of the antenna side lobe, and providing a radar system using the same. will be.

One aspect of the present invention for achieving the above object relates to a method for improving the unobserved region of the clutter map-based radar system, the method for improving the unobserved region of the radar system is to (a) to set the minimum elevation angle for beam transmission Forming a clutter map by setting a waveform on the transmittable beam grid and setting an unobserved region; And (b) updating the cluttermap during regular search.

The setting of the lowest elevation angle at which the beam transmission is possible may include: transmitting and receiving a PT (Pulse Train) waveform to a beam grid for setting the lowest elevation angle at which the beam transmission is possible; If the maximum value of the first signal received after the transmission and reception of the PT waveform is greater than or equal to the first threshold value, the beam grid corresponding to the first signal is set as a transmission prohibition zone and an additional PT waveform is added to each azimuth beam grid. Transmitting and receiving; And setting a beam grid corresponding to the second signal as a transmission prohibition zone when the maximum value of the second signal received after performing the transmitting and receiving of the additional PT waveform is equal to or greater than a first threshold value, and setting the lowest transmittable angle for each azimuth angle. The method may include setting a PT waveform on the excited beam grid.

The setting of the waveform to the transmittable beam grid and the setting of the unobserved region may include: transmitting and receiving a linear frequency modulation (LFM) waveform to set the waveform to the beam grid above the lowest elevation and to set the unobserved region; Calculating a first average value of the signal size for each distance section for each beam grid and calculating a second average value of the signal size for each distance section for each beam grid for a reception signal of a sub-lobe channel received from a separate sub-lobe antenna; When the first average value is greater than or equal to the second threshold value and the first average value is greater than or equal to the third threshold value, a distance section of the corresponding beam grid is set as an unobserved region, and the first average value is smaller than or equal to the second threshold value. Setting a distance section of a corresponding beam grid as an LFM waveform when a first average value is smaller than the third threshold value; And setting the beam grid as a PT waveform when the ratio of the set unobserved region is greater than or equal to a fourth threshold, and setting the beam grid as an LFM waveform when the ratio of the set unobserved region is smaller than a fourth threshold. It may include.

Step (b) may include determining whether the search beam is an LFM waveform or a PT waveform; And (b2) performing a process of setting a waveform in the transmittable beam grid and setting an unobserved region when the search beam is an LFM waveform, and additional LFM waveforms every predetermined T frame when the search beam is a PT waveform. And transmitting and receiving a signal and setting a waveform in the transmittable beam grid and setting an unobserved region.

A cluttermap-based radar system according to another aspect of the present invention for achieving the above object includes a transceiver for transmitting and receiving a radar signal and a controller for performing signal processing and control operations for target detection in association with the transceiver. The control unit may include a minimum elevation setting module for setting a minimum elevation angle at which beam transmission is possible, an unobserved area setting module for setting waveforms and an unobserved area at a transmittable beam grid, and the minimum elevation setting module; And a clutter map updating module for updating the clutter map formed by the unobserved area setting module.

The lowest elevation setting module transmits and receives a PT (Pulse Train) waveform to a beam grid for setting the lowest elevation possible for the beam transmission, and the maximum value of the first signal received after the transmission and reception of the PT waveform is the first threshold. If the value is greater than or equal to the value, the beam grid corresponding to the first signal is set as a transmission prohibition zone, and an additional PT waveform is transmitted and received to the beam grid for each azimuth angle, and the maximum value of the second signal received after the transmission and reception of the additional PT waveform is If the first threshold value is greater than or equal to, the beam grid corresponding to the second signal may be set as a transmission prohibition zone, and the PT waveform may be set to the beam grid having the lowest high angle transmittable for each azimuth angle.

The unobserved region setting module transmits / receives a linear frequency modulation (LFM) waveform to set a waveform on a beam grid above the lowest elevation and sets an unobserved region, and transmits a first average value of a signal size for each distance section for each beam grid. The received signal of the sub-lobe channel received from the separate sub-lobe antenna is also calculated by calculating a second average value of the signal size for each distance section for each beam grid, wherein the first average value is greater than or equal to the second threshold value and the first average value is the third average value. If the threshold value is greater than or equal to the distance interval of the beam grid is set as an unobserved region, and if the first average value is smaller than the second threshold value or the first average value is smaller than the third threshold value, the distance interval of the beam grid is set. Is set to the LFM waveform, and if the ratio of the unobserved region is greater than or equal to a fourth threshold, the beam grid is set to the PT waveform and the ratio of the unobserved region is set to. If it is smaller than the fourth threshold, the beam grid may be set as an LFM waveform.

The cluttermap update module determines whether the search beam is an LFM waveform or a PT waveform, and performs the unobserved region setting module when the search beam is an LFM waveform, and every predetermined T frame when the search beam is a PT waveform. After transmitting and receiving additional LFM waveforms, the unobserved region setting module may be performed.

As a result, the present invention finds the lowest possible elevation of the beam transmission, sets the unobserved region in the beam grid above the lowest elevation, removes the unobserved region due to the clutter signal of the side lobe, and uses the sublobe channel, and the beam above the lowest elevation. By assigning waveforms to the grid and updating the cluttermap in real time during regular search, we can improve low-altitude detection without reducing frame time by reducing unobserved areas due to clutter signals on the antenna side lobes.

Fig. 1 shows a clutter map composed of three dimensions of azimuth-elevation-distance.
2 is a view for explaining a method of calculating the average signal size for each distance section.
3 is a view for explaining the unobserved region setting method of the conventional cluttermap-based radar system.
4 is a flowchart illustrating a method for improving an unobserved area of a radar system according to an exemplary embodiment of the present invention.
FIG. 5 is a flowchart for explaining operation S10 of FIG. 4.
FIG. 6 is a diagram illustrating beam grids for respective azimuth angles for explaining operation S10 of FIG. 4.
FIG. 7 is a flowchart for describing operation S20 of FIG. 4.
FIG. 8 is a diagram for describing operation S20 of FIG. 4.
FIG. 9 is a flowchart for explaining operation S30 of FIG. 4.
10 is a block diagram of a cluttermap based radar system according to another embodiment of the present invention.
11 is a comparative example for showing the unobserved region improvement method of the radar system and the effect of the radar system using the same according to an embodiment of the present invention.

Hereinafter, a method for improving an unobserved area of a radar system and a radar system using the same will be described with reference to the accompanying drawings.

4 is a flowchart illustrating a method for improving an unobserved area of a radar system according to an exemplary embodiment of the present invention. Referring to FIG. 4, in the method for improving the unobserved region of the cluttermap-based radar system according to the present embodiment, setting a minimum elevation angle at which the radar beam can be transmitted (S10) and setting a waveform in the transmittable beam grid. It may include the step of setting the observation area (S20) and updating the clutter map during the normal search (S30).

In the clutter map formation algorithm, steps S10 and S20 are parts for forming an initial clutter map, and step S30 is a part for updating the clutter map formed by these steps during regular search.

Hereinafter, the step of setting the minimum elevation of step S10 will be described in detail with reference to FIGS. 5 and 6. FIG. 5 is a flowchart for describing operation S10 of FIG. 4, and FIG. 6 is a diagram illustrating beam grids for respective azimuth angles for explaining operation S10 of FIG. 4.

Referring to FIG. 5, the radar system transmits and receives a PT waveform to the beam grid in order to set the lowest elevation angle at which the beam can be transmitted (S110).

The radar system determines whether the maximum magnitude A _max of the first signal received as shown in Equation 1 after the transmission and reception of the PT waveform in step S110 is smaller than the first threshold value C ₁ .

As a result of the above determination, when it is determined that the maximum value A _max of the first signal is greater than or equal to the first threshold value C ₁ , the radar system sets the beam grid corresponding to the received first signal as the transmission prohibition area. (S120).

Next, the radar system transmits and receives additional PT waveforms to the beam grid for each azimuth as shown in FIG. 6 for more accurate minimum elevation setting (S140).

The beam grid for each azimuth of FIG. 6 may be expressed by Equation 2.

Here, e _i is the highest elevation of the transmission prohibition zone for each azimuth, and e _{i + 1} is the elevation of the beam grid directly above the beam grid corresponding to e _i .

If the maximum magnitude A _max of the second signal received after the operation S140 is greater than or equal to the first threshold C ₁ , the radar system sets the beam grid corresponding to the second signal to the transmission prohibition area. (S150). Next, the radar system sets a PT waveform on the beam grid having the lowest elevation that can be transmitted for each azimuth (S170).

Hereinafter, with reference to FIGS. 7 and 8, step S20 according to the present embodiment will be described in detail. 7 is a flowchart for explaining operation S20 of FIG. 4, and FIG. 8 is a view for explaining an unobserved region setting step of operation S20 of FIG. 4.

Referring to FIG. 7, the radar system first transmits and receives a Linear Frequency Modulation (LFM) waveform in order to set a waveform in a beam grid above a minimum elevation and set an unobserved region (S210). In other words, the radar system transmits and receives LFM waveforms to beam grids other than the lowest elevation.

The radar system calculates a first average value An of the signal size for each distance section for each beam grid, and the received signal of the sub-lobe channel received from a separate sub-lobe antenna also has a second average value of the signal size for each distance section for each beam grid. A _SLBn ) is calculated (S220).

이상인지 판단한다(S230). 제3 임계값은 임의의 상수값 C₃에 제2 평균값(A_SLBn)을 곱하는 것에 의해 결정된다.In order to determine whether the corresponding distance section is an unobserved region, the next radar system uses a first average value A _n equal to or greater than a second threshold value C ₂ and a first average value A _n equals a third threshold value as shown in _Equation 3 below.

It is determined whether or not (S230). The third threshold value is determined by multiplying the arbitrary constant value C ₃ by the second average value A _SLBn .

As a result of the determination in step S230, when the first average value An satisfies the condition of Equation 3, the radar system determines that there is a clutter, and as shown in FIG. 8, the distance sections R ₂ and R _i of the corresponding beam grid. ) Is set to the unobserved region (S240).

On the other hand, if the first average value An does not satisfy the condition of Equation 3 as a result of step S230, the radar system determines that there is no clutter, and as shown in FIG. 8, the distance section R ₃ , R _N-1 ) is not set to the unobserved region, and the beam grid is set to the LFM waveform by step S260 described later.

보다 작으면, 레이더 시스템은 해당 거리구간을 미관측 영역으로 설정하지 않음으로써 안테나 부엽으로 인한 미관측 영역의 과다 설정을 방지할 수 있다.That is, even if the first average value A _n is greater than or equal to the second threshold value C ₂ , the average value A _n is the third threshold value.

If smaller, the radar system does not set the distance section to the unobserved region, thereby preventing over-setting of the unobserved region due to the antenna side lobe.

보다 작으면 평균값(A_n)이 임계값(C₂) 이상이라 하더라도 안테나 부엽에 의한 클러터 신호이기 때문이다.As such, the first average value A _n is a threshold value when the distance section is not set as the unobserved region.

This is because, if smaller, the average value A _n is a clutter signal due to the antenna side lobe, even if the threshold value C ₂ or more.

When it is determined that the ratio of the unobserved region set by the step S240 is less than the fourth threshold value C ₄ (S250), the radar system sets the corresponding beam grid as the LFM waveform (S260).

On the other hand, if it is determined that the ratio of the unobserved region set in step S240 is greater than or equal to the fourth threshold value C ₄ (S250), the radar system sets the corresponding beam grid as a PT waveform (S270).

Hereinafter, the step S30 performed after the step S20 will be described in detail with reference to FIG. 9. 9 is a flowchart illustrating a step of updating a clutter map of a method for improving an unobserved area of a radar system according to an exemplary embodiment of the present invention.

First, the radar system determines whether the search beam is an LFM waveform or a PT waveform (S310). When the search beam is an LFM waveform, the radar system performs the transmission waveform setting and the unobserved region setting step of step S20 of FIG. The control procedure of the unobserved area improvement method of the radar system according to the example is terminated (S320).

On the other hand, if the determination beam of step S310 is the PT waveform, the radar system additionally transmits and receives an LFM waveform every T frames (S330), and performs the transmission waveform setting and the unobserved area setting step of step S20 of FIG. The control procedure of the unobserved area improvement method of the radar system according to the embodiment is terminated (S340).

Hereinafter, a radar system using the unobserved area improvement method of the radar system according to the above-described embodiment will be described with reference to FIG. 10. 10 is a block diagram of a clutter map based radar system according to another embodiment of the present invention, the clutter map based radar system may include a transceiver 10 and a controller 20.

The transceiver 10 performs a function of transmitting and receiving a signal of a laser beam by using the main antenna and the sublobe antenna.

The controller 20 performs the method for improving the unobserved region of the radar system according to the above-described embodiment, and includes a minimum elevation setting module 22, an unobserved region setting module 24, and a clutter map updating module 26. Can be. The lowest elevation setting module 22 and the unobserved area setting module 24 may be functional modules for forming an initial clutter map, and the clutter map updating module 26 may be divided into functional modules for updating the formed clutter map.

The lowest elevation setting module 22 is a module for performing the control procedure corresponding to the above-described step S10 of FIG. 4, and the operation thereof is as described above with reference to FIG. 5, whereby the PT is set to the lowest elevation that can be transmitted for each azimuth. You can set the waveform.

The unobserved area setting module 24 is a module for performing a control procedure corresponding to the aforementioned step S20 of FIG. 4, and the operation thereof is as described above with reference to FIG. 7, whereby the unobserved area due to the antenna side lobe. It is possible to set the unobserved area while preventing excessive setting.

The clutter map update module 26 performs a control procedure corresponding to the aforementioned step S30 of FIG. 4, and the operation thereof is the same as described above with reference to FIG. 9.

The clutter map update module 26 may update the clutter map by performing the unobserved region setting module 24 when the search beam is an LFM waveform, and additionally transmit and receive an LFM waveform every frame when the search beam is a PT waveform. After performing the unobserved area setting module 24, the clutter map can be updated.

11 is a comparative example for showing the unobserved region improvement method of the radar system and the effect of the radar system using the same according to an embodiment of the present invention.

The left figure is a distribution of an unobserved region of the conventional unobserved area improvement method of the radar system, and the right figure is a distribution of an unobserved region of the unobserved area improvement method of the radar system according to an embodiment of the present invention. The first drawing from the upper side shows clutter map information in azimuth and elevation, the second drawing shows a histogram of unobserved regions by elevation, and the third drawing shows a histogram of unobserved regions by azimuth. The figure shows the histogram of the unobserved region by distance section.

As shown in FIG. 11, in the conventional method of improving the unobserved area of the radar system, the total number of unobserved areas is 448, whereas the method of improving the unobserved area of the radar system according to the present embodiment is less than 5 in total. A 98.8% reduction in viewing area can improve the detection performance of the target at low altitudes.

As described above, the method for improving the unobserved region of the radar system according to the present embodiment and the radar system using the same find the lowest elevation that can transmit the beam, set the unobserved region in the beam grid above the minimum elevation, and use the sublobe channel to remove the side lobe. Frame time is reduced by eliminating unobserved areas due to the signal, assigning waveforms to beam grids above the lowest elevation, and updating the clutter map in real time during normal search to reduce unobserved areas caused by clutter signals on the antenna side lobe. It can improve low altitude detection performance without increasing.

The method of improving the unobserved area of the radar system according to an embodiment of the present invention and the radar system using the same are not limited to the configurations and the methods of the embodiments described above and all or some of the embodiments may be selectively combined Lt; / RTI >

10: transceiver
20:
22: minimum elevation setting module
24: unobserved area setting module
26: Cluttermap Update Module

Claims (8)

In the unobserved area improvement method of the clutter map-based radar system,
(a) forming a clutter map by setting a minimum elevation angle at which beam transmission is possible, and setting a waveform and setting an unobserved region in the transmittable beam grid; And
(b) updating the cluttermap during a normal search. The method of claim 1,
The process of setting the minimum elevation angle at which the beam transmission is possible,
Transmitting and receiving a PT (Pulse Train) waveform to a beam grid to set the lowest elevation possible for the beam transmission;
If the maximum value of the first signal received after the transmission and reception of the PT waveform is greater than or equal to the first threshold value, the beam grid corresponding to the first signal is set as a transmission prohibition zone and an additional PT waveform is added to each azimuth beam grid. Transmitting and receiving; And
If the maximum value of the second signal received after the step of transmitting and receiving the additional PT waveform is greater than or equal to the first threshold value, the beam grid corresponding to the second signal is set as the transmission prohibition zone and has the lowest elevation angle that can be transmitted for each azimuth angle. And setting up a PT waveform in the beam grid. The method of claim 1,
The process of setting a waveform and setting an unobserved region in the transmittable beam grid,
Transmitting and receiving a Linear Frequency Modulation (LFM) waveform to set a waveform on the beam grid above the lowest elevation and to set an unobserved region;
Calculating a first average value of the signal size for each distance section for each beam grid and calculating a second average value of the signal size for each distance section for each beam grid for a reception signal of a sub-lobe channel received from a separate sub-lobe antenna;
When the first average value is greater than or equal to the second threshold value and the first average value is greater than or equal to the third threshold value, a distance section of the corresponding beam grid is set as an unobserved region, and the first average value is smaller than or equal to the second threshold value. Setting a distance section of a corresponding beam grid as an LFM waveform when a first average value is smaller than the third threshold value; And
Setting the beam grid to the PT waveform when the ratio of the set unobserved region is greater than or equal to a fourth threshold, and setting the beam grid to the LFM waveform when the ratio of the set unobserved region is smaller than a fourth threshold. Method for improving the unobserved area of the radar system comprising a. The method of claim 1,
The step (b)
(b1) determining whether the search beam is an LFM waveform or a PT waveform; And
(b2) if the search beam is an LFM waveform, a waveform is set in the transmittable beam grid and an unobserved region is set; if the search beam is a PT waveform, an additional LFM waveform is provided for each T frame in advance. And performing a process of setting a waveform and setting an unobserved region in the transmittable beam grid after transmitting and receiving. In a cluttermap based radar system,
And a transmission and reception unit for transmitting and receiving a radar signal and a control unit for performing a signal processing and control operation for target detection in conjunction with the transmission and reception unit,
The control unit may include a minimum elevation setting module for setting a minimum elevation angle at which beam transmission is possible, an unobserved area setting module for setting waveforms and an unobserved area at a transmittable beam grid, and the minimum elevation setting module and the unobserved observation field. A cluttermap based radar system comprising a cluttermap updating module for updating a cluttermap formed by an area setting module. The method of claim 5,
The lowest elevation setting module transmits and receives a PT (Pulse Train) waveform to a beam grid for setting the lowest elevation possible for the beam transmission, and the maximum value of the first signal received after the transmission and reception of the PT waveform is the first threshold. If the value is greater than or equal to the value, the beam grid corresponding to the first signal is set as a transmission prohibition zone, and an additional PT waveform is transmitted and received to the beam grid for each azimuth angle, and the maximum value of the second signal received after the transmission and reception of the additional PT waveform is A cluttermap-based radar system comprising setting a beam grid corresponding to the second signal as a transmission prohibition zone and setting a PT waveform to a beam grid having the lowest elevation that can be transmitted for each azimuth angle when the threshold value is greater than or equal to the first threshold value. . The method of claim 5,
The unobserved region setting module transmits / receives a linear frequency modulation (LFM) waveform to set a waveform on a beam grid above the lowest elevation and sets an unobserved region, and transmits a first average value of a signal size for each distance section for each beam grid. The received signal of the sub-lobe channel received from the separate sub-lobe antenna is also calculated by calculating a second average value of the signal size for each distance section for each beam grid, wherein the first average value is greater than or equal to the second threshold value and the first average value is the third average value. If the threshold value is greater than or equal to the distance interval of the beam grid is set as an unobserved region, and if the first average value is smaller than the second threshold value or the first average value is smaller than the third threshold value, the distance interval of the beam grid is set. Is set to the LFM waveform, and if the ratio of the unobserved region is greater than or equal to a fourth threshold, the beam grid is set to the PT waveform and the ratio of the unobserved region is set to. A cluttermap-based radar system, characterized in that the beam grid is set as an LFM waveform when it is smaller than the fourth threshold. The method of claim 5,
The cluttermap update module determines whether the search beam is an LFM waveform or a PT waveform, and performs the unobserved region setting module when the search beam is an LFM waveform, and every predetermined T frame when the search beam is a PT waveform. A cluttermap based radar system, characterized in that to perform the unobserved region setting module after transmitting and receiving additional LFM waveforms.

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