JPH0682548A - Generation of clutter map data - Google Patents

Abstract

PURPOSE:To obtain a clutter mapping method requiring no radiation of radio wave by calculating the intensity of clutter signal received by a radar based on a topographic data and a clutter data. CONSTITUTION:Clutter map data is generated by calculating the intensity of clutter signal being received by a radar based on a topographic data, radio wave features of radar, and effective clutter reflection area density. Coverage and incident angle of radar beam are also determined based on topographic data and developing position. Intensity of receiving clutter signal is then calculated based on features of radar and effective clutter reflecting area density delta0 which depends on the type of topography irradiated with radar beam. The processing is executed entirely by means of a steering beam thus acquiring clutter map data required for searching/tracking radar in low space area signal processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for acquiring clutter map data required for low-air-range signal processing of a search and tracking radar on a computer without radiating radio waves.

[0002]

2. Description of the Related Art When a search and tracking radar is radiated at a low elevation angle,
Clutter (cl) that is unnecessary reflected waves from the ground surface, sea surface, etc.
utter) may be mixed in the received wave. Conventional clutter mapping measures the clutter signal strength by sequentially radiating radar waves of low elevation angle and measuring the received clutter signal strength.
(t Indicator: detection of moving target) and clutter map data in which areas for performing various signal processing such as blanking are set. MTI is a method of identifying a moving target signal using the Doppler effect.

[0003]

However, since the conventional method requires the emission of an actual radio wave, it takes a considerable amount of time to reach operation after the radar is deployed, and the clutter is required until the deployment. The map data cannot be obtained, which hinders the operation planning, such as determining the optimal deployment of the system. The present invention has been made in view of the above prior art, and an object of the present invention is to provide a clutter mapping method that does not require radio wave radiation.

[0004]

The structure of the present invention which achieves the above object is based on the terrain data including the radar deployment position, the radar radio wave specifications and the clutter data about the clutter effective reflection area density. The clutter map data is created by calculating the clutter signal strength received by the. That is, the clutter map data is created by the following process. As shown in FIGS. 3 to 7, the area irradiated by the radar beam and the radar beam incident angle are obtained from the ground floor data and the radar deployment position. The type of terrain irradiated by the radar beam, that is, the effective reflection area density σ ₀ and pulse width, beam width, transmission output of clutter depending on the type of forest, arable land, sea, road, etc.
The received clutter signal strength is calculated using radar specifications such as antenna gain. Carry out all the above processing with the steering beam,
Clutter map data necessary for signal processing such as an MTI processing execution area and a blanking area where target detection must be executed is acquired based on the radar capability.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the drawings. In the present embodiment, as shown in FIG. 1, a clutter signal strength calculation program, a clutter map processing program, and a result output program are executed based on a data file consisting of a topographic data file and a clutter data file.

(1) Data File (a) Terrain Data File The terrain data file contains the radar deployment position and the search range, and stores the altitude and terrain type at an arbitrary point as terrain data. An arbitrary point is, for example, a UTM (Universal Tr
ansverse Mercator) Represented by coordinates.

(B) Clutter Data File The clutter data file stores the clutter effective reflection area density σ ₀ for each terrain type and radar frequency band as data indicating the radar beam incident angle φ based on the actual measurement data. . TYPE in the figure: A, B,
C and D indicate types of topography. For example, A is an urban area, B is an arable land, C is a forest, and D is a road. The clutter data file can be incorporated in the calculation loop by the σ ₀ calculation model. Further, in the σ ₀ calculation routine, the state of the terrain in the area irradiated by the beam can be recognized from the terrain data file, and σ ₀ can be generated by the clutter data file using the type of terrain and the beam incident angle as arguments.

(2) Data processing calculation unit (a) Clutter signal strength calculation program This is a calculation loop for calculating the clutter signal strength for each radar transmission beam using the above data file, and is performed as follows. Setting of radar beam As shown in FIG. 3, beam center vector _Be (χ, θ)
To set. χ is an azimuth angle, and θ is an elevation angle (elevation angle). The elevation angle θ can have a negative value. Read topographic data Read topographic data in the beam direction from the topographic data file.

Calculation of the intersection of the beam center and the terrain As shown in FIG. 4, the intersection of the beam center and the terrain (x _P ,
Calculate y _P , z _P ). Calculation of Average Inclination Angle As shown in FIG. 5, the average inclination angle α _G of the terrain near the intersection is calculated. Calculation of beam incident angle The radar beam incident angle φ is calculated according to the following formula. φ = θ + α _G

Calculation of distance between radar and clutter The distance between radar and clutter is calculated according to the following equation. Here, R represents the distance between the beam center, the R _U distance between the beam upper and R _L is the distance between the beam lower. _{R = {(x P -x R} ) 2 + (y P -y R) 2 + (z P -
z _R ) ² } ^1/2 _RU = (R _i + k) · (1 + tan ² α) ^1/2 where k = {R _i (R _{i + 1} · cos β−R _i ) tan α} ÷ {R _{i + 1} · sin β− (R _{i + 1} · cos β−R _i ) tan α} α = θ _U −θ _i β = θ _i−1 −θ _{i RL} = (R _i + k) · (1 + tan ² α) ^1/2 However, k = {R _i (R _{i + 1} · cosβ−R _i ) tanα} ÷ {R _{i + 1} · sin β− (R _{i + 1} · cosβ−R _i ) tanα} α = θ _L −θ _i β = Θ _i-1 −θ _i

Calculation of Beam Irradiation Area The beam irradiation area A _e is calculated as shown in FIG. 7 according to the following equation. A _e = π · a · b where, a = 1/2 (R U -R L) tan (θ B / 2), b = {R U 2 + R L 2 -2R U R L cos (θ U -θ _L )} ^1/2 , θ _B is the beam width. Calculation of Clutter Effective Reflection Area Density Based on the radar beam incident angle φ, the clutter effective reflection area density σ ₀ is calculated from the clutter data file. In the clutter data file, the clutter effective reflection area density σ ₀ is actually measured and stored as basic data for each type of terrain (forest, arable land, sea, road, etc.), so that the accuracy of clutter mapping is improved.

Calculation of Clutter Signal Strength The clutter signal strength P _rc is calculated according to the following equation. P _rc = P _t · G _t · L _t · Loss · A _e · σ ₀ / (4π) ² R ⁴ (dB / m ² ), where P _t is the radar transmission power, G _t is the radar transmission antenna gain, and L _t is the radar transmission system gain, Loss is the atmospheric attenuation, A _e is the radar beam irradiation area, σ ₀ is the clutter effective reflection area density, and R is the reflection distance.

(B) Clutter Map Processing Program Using the calculated clutter signal intensity P _rc , the target signal (TGT signal) to clutter signal ratio S / C for various targets (effective reflection areas) is calculated, Mapping is executed by setting the anti-clutter signal processing method (MTI, blanking, etc.) corresponding to the search and tracking position of the radar. TGT signal strength P _rT = P _t · G _t · L _t · Loss · A _e · σ _T / (4π) ² _RT ⁴ (dB / m ² ) where σ _T is the target effective reflection area and R _T is the radar ~ Target distance.

Clutter signal ratio S / C S / C = P _rT -P _rc vs. clutter processing method The processing method of the signal received by the radar is set according to the magnitude of S / C and the specifications of the irradiation beam. Since this depends on the function and performance of the radar, an example of this routine is shown in FIG. Map data processing In order to use the set anti-clutter processing method for output processing for each irradiation beam, create a data file.

(3) Result Output Processing Program The result output processing program executes the clutter mapping result display processing as shown in FIG. (A) Map data display: This is a display example of an area in which anti-clutter signal processing such as MTI processing is performed. (B) Line-of-sight radar beam elevation angle: This is a display example of the beam elevation angle that can be seen without being affected by clutter. (C) Blanking range: This is an example in which an area where the target is not detected is displayed for each transmission beam. S1 to SN, M1 and the like indicate numbers of irradiation beams. For example, S1 is the short range beam No. 1, S2 is the short range beam No. 2, ..., SN is the short range beam N, and M1 is the medium range beam No. 1.

[0016]

As described above in detail with reference to the embodiments, the present invention provides the clutter map data necessary for the low sky region signal processing of the search and tracking radar, the terrain data including the radar deployment position, It is possible to obtain it on a computer based on the radar radio wave specifications and the clutter data about the clutter effective reflection area density. Therefore, the present invention does not require the emission of radar radio waves when performing clutter mapping. Therefore, it is possible to obtain clutter map data before radar deployment, and in consideration of the radar signal processing load and line-of-sight range, it is possible to detect targets, set the optimal radar deployment position for tracking, and optimize beam management.
In addition, the efficiency of preparation plans can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a clutter map creating method according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a display example according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing setting of an irradiation beam.

FIG. 4 is an explanatory diagram showing an intersection of a beam center and terrain.

FIG. 5 is an explanatory diagram showing calculation of an average inclination angle of the terrain near the intersection.

FIG. 6 is an explanatory diagram showing calculation of a distance between the radar and the clutter.

FIG. 7 is an explanatory diagram of a beam irradiation area.

FIG. 8 is an explanatory diagram showing a clutter processing method.

[Explanation of symbols]

sigma ₀ clutter radar cross density B _e-beam center vector χ azimuth angle theta elevation angle (elevation angle) alpha _G average inclination angle φ radar beam incidence angle A _e-beam irradiation area theta _B beamwidth

Claims (1)

[Claims] 1. A clutter data which is a clutter effective reflection area density corresponding to the radar beam incident angle for each terrain type and frequency band, by calculating the radar beam incident angle based on the terrain data including the radar deployment position and the search range. The calculated clutter effective reflection area density is calculated based on the calculated radar beam incident angle, and the clutter signal strength and target signal strength are calculated from the calculated clutter effective reflection area density and radar specifications. A method for creating clutter map data, which comprises creating a clutter map by calculating a target signal to clutter signal ratio from the signal strength and the target signal strength and setting a corresponding clutter signal processing method.