JPH02276302A - Array antenna exciting system - Google Patents

Abstract

PURPOSE:To obtain a desired Taylor type radiant pattern by finding the angular position of a zero point to supply the desired Taylor type radiant pattern, finding excitation amplitude and phase to form directional zero points at the angular position and that of an unrequired side lobe, and setting them at each antenna element. CONSTITUTION:First of all, an initial radiant pattern is formed. Next, the angu lar position of the zero point to supply the desired Taylor type radiant pattern is calculated. Then, the excitation amplitude ai (i=1-M; element number) and the excitation phase pi to form the directional zero point at the angular position of the zero point are found. After that, the unrequired side lobe with a level higher than that of the peak side lobe of an ideal Taylor type radiant pattern out of the side lobes of the radiant pattern obtained by setting the excitation amplitude ai at an amplitude controller (At1)-(AtM) and the excitation phase pi at a phase shifter (Pa1)-(PaM) is selected, and the numeric values of the excitation amplitude and phase to form the zero point of the radiant pattern of an array antenna can be found at the angular position of the unrequired side lobe and that of the zero point of the ideal Taylor type radiant pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to an array antenna capable of obtaining a desired low side lobe pattern.

[Prior Art] FIG. 5 shows, for example, an array antenna shown in 1988 IEICE Spring National Conference, B-118, "Formation of Low Sidelobe Pattern in Conformal Array Antenna", by Needle et al.

In the figure, (Ax >, (A2), ・
...(Ayo) is an element antenna arranged on a curved surface.

(p, t) , (p, a) , ..., (
p, m) are phase shifters.

(A, 1) , (A, 2) , ..., (A□
) is the amplitude controller. In an array antenna having such a configuration, in order to obtain a desired sidelobe level, it is necessary to set an appropriate excitation amplitude for each element antenna. Conventionally, this excitation amplitude A, (i=1 to M: element number)
is given by equation (1).

1, =T, ・W, /E, (θ, > (1)
However, T is the amplitude distribution given on the projection plane when the element antenna of the conformal array antenna is projected onto the plane orthogonal to the main beam axis direction.

Further, W is a weight for correcting the element density on the projection plane, and E, (θ,) is the amplitude of the i-th N element pattern in the main beam direction.

[Problems to be Solved by the Invention] In the conventional array antenna excitation method, the excitation amplitude A is determined as described above, so when T is given and Tiller distribution is given, the zero point of the Tiller-shaped radiation pattern is There is a problem that the desired sidelobe level cannot be obtained because the angular position shifts, and because the element antennas are arranged on two curved surfaces, the peak directional force t of the directivity of each element antenna is different, and unnecessary sidelobes are generated. There was a problem that occurred.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain an array antenna excitation method that can obtain a radiation pattern with a desired sidelobe level.

[Means for Solving the Problems] The array antenna excitation method according to the present invention first determines the angular position of the zero point of an ideal tiller-shaped radiation pattern and then applies the radiation pattern of the array antenna to the angular position of the zero point. Numerically find the excitation amplitude phase to form the zero point 1
Next, among the side lobes of the radiation pattern obtained by the excitation amplitude phase, select an unnecessary side lobe higher than the peak side lobe level of the ideal tiller-shaped radiation pattern, and select the angular position of the unnecessary side lobe and the ideal side lobe. The excitation amplitude phase for forming the zero point of the radiation pattern of the array antenna at the angular position of the zero point of the tiller-shaped radiation pattern is numerically determined.

[Operation] In the present invention, in the radiation pattern of the array antenna, the angular position of the zero point for giving a desired tiller-shaped radiation pattern is determined, and the directional zero point is formed at the angular position and the angular position of the unnecessary side lobe. A desired Tiller-shaped radiation pattern can be obtained by determining the excitation amplitude phase for each element antenna and setting the excitation amplitude phase to each element antenna.

[Embodiments of the invention] An embodiment of the present invention will be described below with reference to one drawing.

FIG. 1 is a flowchart showing a method of calculating excitation amplitude and phase of an array antenna according to an embodiment of the present invention.

The array antenna shown in the flowchart of FIG. 1 has the same configuration as the conventional array antenna shown in FIG.

First, an initial radiation pattern is formed using step tube 1.

In one embodiment of the present invention, each excitation amplitude is set so that the aperture distribution becomes a desired Tiller distribution on a plane perpendicular to the main beam axis. FIG. 2 shows the radiation pattern obtained in step 1 above.

Note that a tiller distribution of -50 dB was given as the desired tiller distribution. In the radiation pattern shown in Figure 2 above, -
The reason why a sidelobe level of 50 dB is not obtained is that the angular position of the zero point of the desired tiller-shaped radiation pattern is shifted.

Therefore, a side lobe level of -50 dB is obtained in the following steps. Step 2 calculates the angular position of the zero to give the desired tiller-shaped radiation pattern. '' The angular position U of the zero point is generally given by equation (2).

U = 5[A” + (n-0, 5>2/A2+(5-
0,5>21”2 (2) However.

n = number of zero points, n = nth zero point A = log (b+ (b2-1)"" ＞/π201
ogb=sidelobe level (dB) Next, in step 3, the excitation amplitude phase for forming a directional zero point at the angular position of the zero point is determined. That is, the excitation amplitude a, (i=1 to M; element number), and excitation phase p that minimize F in equation (3) are determined.

However, E, (θ) = contribution 1 of each element in the U direction
n
nHere, a method for numerically determining the excitation amplitude a and the excitation phase p has been described, but the excitation amplitude a and the excitation phase p may also be determined by a plane wave synthesis method.

Next, in step 4, the excitation amplitude ai is controlled by the amplitude controllers (A, 1) to (8) shown in FIG. 5, and the excitation phase pi is controlled by the phase shifters (P, l) to (P . Here, we select zero points at appropriate intervals in the unnecessary sidelobes,
Excitation amplitude a that minimizes F in equation (4), (i=l~M
;X
(element number) and excitation phase p.

However, "ik (θ) = contribution in the direction of zero in the unnecessary sidelobe.Here, we have described a method for numerically obtaining the excitation amplitude a and the excitation phase p, but the excitation amplitude a and the excitation phase ρ , may be obtained by plane wave synthesis method.

Next, in step 5, the excitation amplitude ai is controlled by amplitude controllers (At t ) to (At, ) shown in FIG. 5, and the excitation phase pi is controlled by phase shifters (P, l) to (P, y), a low sidelobe pattern as shown in FIG. 4 is formed.

[Effects of the Invention] As described above, according to the present invention, in the radiation pattern of an array antenna, the angular position of the zero point for providing a desired tiller-shaped radiation pattern is determined.

Find the excitation amplitude phase to form a directivity zero point at the above angular position and the angular position of the unnecessary sidelobe.

By setting the above excitation amplitude phase for each element antenna, a desired Tiller-shaped radiation pattern can be obtained.

Furthermore, since a low sidelobe pattern can be uniquely formed, there is an effect that the excitation amplitude phase that provides a desired Tiller-shaped radiation pattern can be found in a short required calculation time.

[Brief explanation of drawings]

Fig. 1 is a flowchart showing the excitation amplitude phase calculation method of this invention, Fig. 2 is a tiller-shaped radiation pattern diagram in which the angular positions of the zero points are shifted, and Fig. 3 is obtained when the angular positions of the zero points are aligned. Tiller type radiation pattern diagram, FIG. 4 is a tiller type radiation pattern diagram obtained by the present invention,
FIG. 5 is a diagram of an antenna for explaining a conventional calculation method of excitation amplitude phase. In the figure, (At >, (A2), ・
...(Am) is an element antenna arranged on a curved surface. (P, 1), (P, 2), ..., (P,
, ) is a phase shifter. (A, 1) , (Atz) , ..., (
AtII> is an amplitude controller. Note that the same reference numerals in each figure indicate the same or equivalent parts. Figure 1.

Claims (1)

[Claims] In an excitation method that determines the excitation amplitude phase of an array antenna consisting of multiple element antennas arranged on a curved surface,
Find the angular position of the zero point of the ideal Taylor-shaped radiation pattern, then numerically find the excitation amplitude phase for forming the zero point of the radiation pattern of the array antenna at the angular position of the zero point, and then Among the sidelobes of the radiation pattern obtained by the amplitude phase, select an unnecessary sidelobe higher than the peak sidelobe level of the ideal Taylor-shaped radiation pattern, and calculate the angular position of the unnecessary sidelobe and the ideal Taylor-shaped radiation pattern. An array antenna excitation method characterized in that an excitation amplitude phase for forming a zero point of the radiation pattern of the array antenna is numerically determined at the angular position of the zero point of the radiation pattern of the array antenna.