DE102012016475A1 - Method for directional bearing according to the monopulse principle - Google Patents

Abstract

The invention relates to a method for directional bearing according to the monopulse principle with a radar array antenna of a plurality of receiving elements whose phase position is individually adjustable, wherein the individual receiving elements of the array in several (N) horizontal lines (Z1, Z2, ... ZN) are arranged, with the following method steps: formation of sum and difference channels (SΔ, SΣ) from the signals of the individual receiving elements, formation of the monopulse ratio (r) from the sum and difference channels (SΔ, SΣ), determination of the angular deviation of Aiming of the antenna main beam direction in the horizontal direction by comparing the monopulse ratio (r) with the monopulse characteristic derived from the antenna characteristic of the array antenna, wherein - the phase angles of the individual antenna elements are set such that for each line alternately one to the left or to the antenna main beam direction r results in exactly the direction of the received signal, and that for each line the received signals are combined, and that - the sum channel (SΣ) of the monopulse processing is generated by combining the signals of all lines of the array antenna, wherein the signals of the left and right pivoted lines with the same sign are received, and that - the difference channel (SΔ) of the monopulse processing is generated by the combination of the signals of all lines of the array antenna, wherein the signals of the left and right pivoted lines with opposite signs.

Description

The invention relates to a method for directional bearing according to the monopulse principle according to the preamble of patent claim 1.

The monopulse principle is a principle used in radar technology for directional bearing. Bases for this principle are z. In Merill Skolnik: Radar Handbook, 2nd Edition; McGraw-Hill Book Company, Singapore 1980, Section 18.3 "Monopulse (Simultaneous Lobing)" and the EP 2 458 400 A1 described.

For the monopulse method, it is necessary to construct a sum and difference channel by a corresponding structure of an antenna configuration with these two channels and to equip each channel with a receiver. For an antenna consisting of N lines, 2 N receivers would be required if one wanted to apply the monopulse principle in the horizontal direction.

The invention has for its object to provide a directional bearing on the basis of the monopulse process and using a group antenna with line-wise arranged receiving elements, with which the number of required receivers can be reduced without limiting the monopulse capability of the antenna.

This object is achieved by the method according to the patent claim.

In the following the invention will be explained in more detail with reference to figures. Show it:

1 a representation of the phase assignment of the receiving elements of the individual antenna lines;

2 the representation of a group antenna with downstream beamforming,

3 the monopulse characteristic of the considered antenna configuration;

4 the antenna characteristic of the considered antenna (in antenna main beam direction).

According to the invention, a monopulse method for directional bearing is described for a radar antenna arranged line by line. The measurement of a horizontal target angle is made possible by suitable use of the sum channels of the antenna lines. In this case, a required according to the prior art for the monopulse capability differential channel in the antenna lines is not needed.

It is based on a radar array antenna with line by line arrangement (extending in the horizontal direction) of receiving elements whose phase angle is adjustable individually by means of phase shifter. The received signals are combined per antenna line in a summing network, wherein a directivity is formed in the horizontal plane. To summarize the output signals of the antenna lines is preferably a beamformer network available, which is preferably implemented as a digital beamforming.

The basic principle of the invention is the control of the receiving antenna, in which the receiving direction is alternately pivoted from line to line to the left and right relative to the main beam direction. For this purpose, the phase of the receiving elements in the individual antenna lines are set accordingly. Each receiving line forms a horizontally bundled diagram, with the diagrams pivoted to the left and to the right overlapping.

In 1 By way of example, the phase responses of the radiating elements of a group antenna (with N rows, Ifd No. 1, 2, 3,... N and M columns, Ifd. No. 1, 2,... M) are illustrated in the individual antenna rows. The odd-line phase lines (dashed lines) are set so that tilting from the antenna main beam direction is slightly left. In the case of the straight lines (solid lines), tilting slightly symmetrically to the right takes place. In the example shown, the phase change is linear along a line. This is not mandatory. Possible is z. As well as a curved course of the phases within a row without the desired effect of the invention is lost.

The extent of the tilting of the receiving direction set by the phase control can be comparatively small. It is typically chosen to be smaller than the beamwidth of the antenna.

As with any electronically controlled array antenna can be controlled by appropriate phase control of the antenna elements, the sum and difference beams in any direction. The inventive tilting of the receive direction to the left or right is superimposed on the nominal control angle of the array antenna.

Mathematically, the beam control according to the invention within a row n including the nominal control angle (α _steer ) can be described as follows: φ _m = 2π / λd _x m · sin (α _steer + (-1) ⁿ · Δα / 2)

Here, φ _{m is} the phase of the m th receiving element within the line with m = - (M - 1) / 2,..., (M - 1) / 2, d _{x is} the distance between two adjacent receiving elements and Δα / 2 describes the tilt of the receive direction from the antenna main beam direction.

The combination of the received signals of the individual lines and the formation of the receiving characteristic takes place in a, preferably digital, beamformer network. If one adds the signals of all lines, one receives a sum beam in the sense of the Monopulsprinzips.

If one adds the received signals of the lines which are swiveled in a first direction (eg to the left) and subtracts the received signals of the lines swiveled in the other direction, a difference diagram i results. S. of the monopulse principle.

mit

S_Σ:

Summensignal

S_Δ:

Differenzsignal

S_n:

Summensignal der Zeile n

N:

Anzahl der Zeilen.

This beamforming for obtaining the sum signal and the difference signal is described by

With

S _Σ :

sum signal

S _Δ :

difference signal

S _n :

Sum signal of line n

N:

Number of lines.

The values w _n can be used for a window function for lowering side lobes in the vertical direction and with an additional phase path for a vertical beam control.

2 shows a schematic view of the rows 1 and N of the N rows of a group antenna, adapted to generate sum and difference signal S _Σ , S _Δ . The antenna comprises in each line an analog distribution network with associated receivers E1, EN. After digitization in an A / D converter (not shown), the received signals of the individual lines are processed further by means of digital beamforming. According to the formulas given above, the signals are combined in the signal adders A1, AN, wherein the multipliers h _{Σ, 1} , h _{Σ, N} , h _{Δ, 1} , h _{Δ, N provide} the signals with the required signs. The quantities h _{Σ, 1} , h _{Σ, N} , h _{Δ, 1} , h _{Δ, N} are defined as follows:

With the sum and difference signals thus determined after beamforming, the so-called monopulse ratio r can be determined in accordance with the general monopulse principle.

Comparing this ratio with a monopulse characteristic precalculated from the antenna characteristics ( 3 ), a horizontal target angle can be determined as a deviation from the main beam direction of the antenna according to the general monopulse principle.

4 shows the antenna characteristics of the sum diagram S _Σ and the difference diagram S _Δ after beamforming. The illustration applies to a reception in the direction perpendicular to the antenna surface (boresight). For comparison, the conventional pencil beam PB is shown, resulting in the same phase control of all receiving elements. The sum diagram has a slightly lower antenna gain over the normal pencil beam characteristic, since the diagram is slightly defocused by the tilted directions of the invention.

As described, with the method according to the invention with a line-wise arranged antenna, a monopulse measurement in the horizontal plane can be realized. The antenna has only one sum channel per line. The monopulse capability is made possible without the individual antenna line having to be equipped with a differential channel.

On the basis of the signals of the individual, superimposed lines of the antenna, it is also possible to carry out the determination of target angles in the vertical direction. For this purpose, the methods known per se of digital array processing are available to the person skilled in the art for estimation in the vertical direction. For example, by appropriately controlling the beamforming coefficients, reception lobes can be simultaneously formed in a plurality of vertical viewing directions. By evaluating the received signals of adjacent reception lobes, a measurement of the target angle in the vertical direction can take place.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2458400 A1 [0002]

Claims (1)

Method for directional bearing according to the monopulse principle with a radar array antenna of a plurality of receiving elements whose phase position is individually adjustable, wherein the individual receiving elements of the array are arranged in a plurality of (N) horizontal lines (Z1, Z2, .... ZN) with the following method steps: - formation of sum and difference channels (S _Δ , S _Σ ) from the signals of the individual receiving elements, - formation of the monopulse ratio (r) from the sum and difference channels (S _Δ , S _Σ ), - determination of the angular deviation of the target from the antenna main beam direction in the horizontal direction by comparing the monopulse ratio (r) with the monopulse characteristic derived from the antenna characteristic of the array antenna, characterized in that the phase angles of the individual antenna elements are adjusted such that one line is left alternately with respect to the main antenna beam direction for each line or after results in a right-tilted receive direction, and that the receive signals are combined for each line, and that the sum channel (S _Σ ) of the monopulse processing is generated by combining the signals of all lines of the array antenna, the signals of the left and right pivoted lines with the same sign are received, and that the difference channel (S _Δ ) of the monopulse processing is generated by the combination of the signals of all lines of the array antenna, wherein the signals of the left and right pivoted lines received with opposite signs.

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