RU2316022C1 - Method for measurement of object altitude at forming of object image on surface with the aid of on-board radar - Google Patents

Abstract

FIELD: radio detection and ranging.

SUBSTANCE: the method consists in forming of matrix Aα of the amplitudes of the reflected signal Aα(i,j)in i-x elements of range resolution and j-x elements of resolution of Doppler angle α at an anterolateral scanning, when the vector of the ground and the aerial sighting line are in the plane located at an acute angle to the surface, the transition to the anteroinferior scanning is accomplished by changing the direction of the carrier motion, when the vector of the ground speed and the aerial sighting line are in the plane located at a right angle to the surface, then the forming of matrix Bα of the amplitudes of reflected signal Bα(i,j)repeated in i-x elements of range resolution and j-x elements of Doppler angle α, than the obtained matrix Bα s converted to matrix B_H of the amplitudes of reflected signal B_H (I,k) in i-x elements of range resolution and k-x elements of conversion of altitude H representing the image of distribution of altitudes of the checked surface section in i-x elements of range resolution, which together with matrix Aα in the same range scale in brought out to the indicator screen with indication of the altitude value.

EFFECT: provided measurement of the object altitude on the surface.

Description

The invention relates to radar, and in particular to radar systems for monitoring the surface on the basis of an airborne radar station (RLS) operating in high resolution in azimuth — Doppler “narrowing” the radiation pattern (narrow beam) of an antenna (narrow-band Doppler filtering).

In this observation mode, the antenna line of sight (the axis of the beam) is at an acute angle to the vector of the ground speed of the radar carrier. In this case, the Doppler angle α _{j of the} deviation of the j-th reflection beam (within the BF) from the ground speed vector is measured in a plane located at an acute angle to the surface and corresponds to the j-th Doppler filter tuned to the frequency f _j . The orthogonal projections of these rays onto the surface plane form je columns of the matrix A _{α of the} radar image of the surface. RRL matrix rows correspond to the ith range resolution elements. The matrix elements are the amplitudes of the reflected signal A _α (i, j), fixed at the output jx of Doppler filters in ix range elements. Thus, the matrix A _{α of the} radar image of the surface is obtained in coordinates the range R _i is the Doppler angle α _j (range R _i is the Doppler frequency f _j ). For a more accurate image perception, the matrix A _α can be transformed into the matrix A _φ represented in the coordinate system, the range R _i is the azimuth φ _j (by converting α _j to φ _j ).

When A _α (i, j) is displayed on the indicator screen, a digital television image is obtained (with a gradation of the brightness of the points in amplitude), the spatial resolution of which allows you to observe the image of objects on the surface (Radar stations with digital synthesis of the antenna aperture. A.N. Antipov, V .T. Goryainov, A.N. Kulin et al. Edited by V.T. Goryainov, Moscow: Radio and Communications, 1988, 304 p.). However, with this method of obtaining radar images, the height of objects on the surface is not determined, which complicates the identification of images of objects when they are recognized. In this regard, it becomes necessary to measure the height of objects on the surface.

The closest in technical essence is the method of obtaining radar images of the surface in the mode of narrow-band Doppler filtering (Kondratenkov G.S., Frolov A.Yu. Radio visualization in the front viewing area of an onboard radar station with a synthesized antenna aperture. - Radio engineering, 2004, No. 1. P. 47-49). In accordance with this method, a matrix A _α RLI is formed, the elements of which A _α (i, j) represent the amplitudes of the reflection signals measured in the coordinate system ix of the range resolution elements and jx frequency resolution elements. The disadvantage of this method is that during the formation of radar images, the height of objects on the surface is not determined.

The technical result is aimed at measuring the height of objects on the surface by forming a matrix B _{H of the} image of the distribution of heights of the controlled surface area in the coordinates of the range R _i - height H _k together with the matrix A _{α of the} amplitude image in the coordinates of the range R _i - Doppler angle α _j .

The technical result of the proposed technical solution is achieved by the fact that the method of measuring the height of objects when forming an image of objects on the surface using the on-board radar, which consists in forming a matrix A _{α of the} amplitudes of the reflected signal A _α (i, j) in ix range resolution elements and jx Doppler resolution elements angle α (Doppler frequency f) in the anterolateral view, when the ground speed vector and the line of sight of the antenna are in a plane located at an acute angle to the surface, that by changing the direction of movement of the carrier, a transition is made to the front-low view when the ground speed vector and the line of sight of the antenna are in a plane located at right angles to the surface, then the formation of the matrix of _α amplitudes of the reflected signal B _α (i, j) in ix elements is repeated range resolution and jx elements of the Doppler angle α, then the resulting matrix B _{α is} converted into the matrix B _{H of the} amplitudes of the reflected signal B _H (i, k) in ix range resolution elements and kx height discretization elements H calculated by the formula

,

,

where R _i is the slant distance between the radar located at a height h and this i, jth element of range resolution and Doppler angle α _j , as a result, a matrix B _H with elements B _H (i, k) representing the image is formed the distribution of heights of the controlled surface area and objects on the surface in ix range resolution elements, which together with the matrix A _α in one range scale are displayed on the indicator screen with digital indication of the height values.

The method is as follows.

1. In the high-resolution mode at the Doppler frequency (Doppler "narrowing" of the beam pattern) during an anterolateral view, a surface radar matrix A _{α is formed} with elements A _α (i, j) representing the signal amplitudes at the output jx of the Doppler filters corresponding to the jth Doppler angles α _j deviations of the reflected beam l radar from the vector of the ground speed ν of the carrier in ix range resolution elements. In this case, the vectors l and ν are in a plane located at an acute angle to the surface.

2. Change the direction of movement of the radar carrier - rotate the vector ν so that its orthogonal projection is directed towards the controlled surface area.

3. The newly formed matrix of radar data B with elements _α B _α (i, j), representing the signal amplitude at the output of the Doppler filters respectively jx j-th Doppler deviation angles α _j of the reflected radar beam from the motion vector ν ix carrier in range resolution elements. In this case, the vectors l and ν are located in a plane located vertically to the surface.

4. Recalculate the matrix B _α with elements B _α (i, j) into the matrix B _H with elements B _H (i, k) representing the amplitudes in kx discretization elements of height H in ix range resolution elements.

4.1. Moreover, for i, jx elements of the matrix B _α whose amplitudes B _α (i, j) exceed the threshold of reflection from the surface or objects, calculate the height H associated with the Doppler angle α _j according to the formula

where R _i is the distance along the oblique range between the radar located at a height h and this i, jth element of resolution of the range and Doppler angle α _j .

4.2. The number k of the height sampling element is determined, which depends on the number j of the Doppler angle, and the corresponding amplitude value B _α (i, j) is written to the element B _H (i, k). Thus, the matrix B _{H is} filled. The blank elements of the matrix In _H assign a zero value.

5. The matrices A _α (i, j) and B _H (i, k) are combined along the coordinate of the range (parallel transfer B _H along the axis i) taking into account the change in distance R due to a change in the direction of movement of the radar carrier.

6. The matrices A _α (i, j) and B _H (i, k) presented in the same range scale show the indicator screen with digital indication of the height values.

The accuracy of measuring the height H by the formula (1) is determined by the dimensions of the range resolution elements and the Doppler angle, and also depends on the accuracy of measuring the height h of the radar carrier (relative to the zero surface level), which is determined by the accuracy of navigation devices. With low measurement accuracy h, it is advisable to measure the relative height of objects (relative to the underlying surface) according to the formula

The proposed method allows to obtain the distribution of the height of objects on the surface in the elements of range resolution. The accuracy of measuring the maximum value of the height of an object in the matrix B _H (i, k) is determined by the resolution of the Doppler angle and range and is comparable with the accuracy of imaging of objects in the matrix A _α (i, j). The presence of the altitude distribution matrix enables the pilot to detect altitude obstacles along the low-altitude flight line, which increases the safety of such flights, as well as correctly identifies images of objects on the surface during high-altitude flights, which increases the likelihood of correct detection and recognition of radar objects.

Claims (1)

A method of measuring the height of objects when forming an image of objects on the surface using an onboard radar, which consists in forming a matrix Aα of amplitudes of the reflected signal A _α (i, j) in ix resolution elements of range and jx resolution elements of Doppler angle α (Doppler frequency f) in the anterolateral view when the ground speed vector and the line of sight of the antenna are in a plane located at an acute angle to the surface, characterized in that by changing the direction of movement of the carrier, the transition to the front-low survey, when the ground speed vector and the antenna line of sight are in a plane located at right angles to the surface, then the formation of the matrix of the amplitudes of the reflected signal B _α (i, j) in ix range resolution elements and jx elements of the Doppler angle α is repeated the resulting matrix B _{α is} recalculated into the matrix B _{n of the} amplitudes of the reflected signal B _n (i, k) in ix range resolution elements and k-x discretization elements of height H calculated by the formula H = hR _i sinα _j , where R _i is the distance along the oblique range between the radar located at a height h and the given i, jth element of resolving range and Doppler angle α _j , as a result, a matrix B _n with elements B _n (i, k) representing the image is formed the distribution of heights of the monitored surface area in ix range resolution elements, which together with the matrix A _α in one range scale is displayed on the indicator screen with indication of the height values.