JPH0370301A - Array antenna exciting system - Google Patents

Abstract

PURPOSE:To obtain a desired Taylor radiation pattern even when the direction of a major beam is changed by obtaining an excited amplitude phase attaining a desired synthesis radiation pattern with a specific exciting element antenna selected among plural element antennas contributing the major beam direction. CONSTITUTION:An array antenna consists of element antennas A1-Am arranged on a curved face, variable amplifiers At1-AtM, phase shifters Pa1-Pam, switches SW1-SWM, and an exciting amplitude phase arithmetic device 1 operating the excited amplitude phase. Every time the major beam direction is changed, the excited element antenna is selected among element antennas contributing the major beam direction so as to attain symmetrical element arrangement around the major beam axis and the exciting amplitude phase is obtained to attain a desired synthesis radiation pattern by the exciting element antenna. Thus, even when the direction of the major beam is changed, the desired Taylor radiation pattern is obtained.

Description

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

[Prior art] Figure 8 shows Japanese Patent Application No. 198032 filed earlier by the present inventors.
Similarly, FIG. 9 shows the array antenna excitation method shown in Japanese Patent Application No. 1-98032.

(AI >, (A2 >, ..., (AM)
is an element antenna arranged on a curved surface, (P, 1)
, (P,2)..., (P,,) is a phase shifter, (
A, I), (A, 2)..., (A, M) are variable amplitude amplifiers. 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 phase for each element antenna. In the conventional example shown in FIG. 8, first, in step 1, an initial radiation pattern is formed. In this conventional example, each excitation amplitude is set so that the aperture distribution becomes a desired Tiller distribution on a plane perpendicular to the main beam axis.

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 (1).

U = n [A” + (n-0,5>” /A 2
+ (n-0,5>” ko 1'2 (1
) 1 day.

stone - number of zeros, n = nth zero A = log (b+ (b” -1> ””)
/yr201 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. In other words, the excitation amplitude a that minimizes F in equation (2), (i=1~M:
number), excitation phase p.

1 seek.

However, E, (θ) - contribution of each element in the U direction l n
Next, in step 4, the excitation amplitude ai is changed to the variable amplitude amplifiers (A, ) to (Atat) shown in FIG. 9, and the excitation phase pi is changed to the phase shifter (p, 1> to (P, , ). If unnecessary side lobes higher than the set side lobe level occur in the radiation pattern obtained at this time, select zero points at appropriate intervals in the unnecessary side lobes, and use Equation (3,). The excitation amplitude a, (i+
−1 to M:l element number) and excitation phase P are determined.

(3) However, E, (θ〉−Contribution in the zero point k direction in the unnecessary side lobe) Next, in step 5, the above excitation amplitude ai is set to the variable amplitude amplifiers (A, □) to (A□) shown in FIG. 9, By setting the excitation phase pi to the phase shifter (P, 1) to <p-+*) also shown in FIG. 9, a desired low sidelobe pattern is formed.

[Problems to be Solved by the Invention] In the conventional array antenna excitation method, the excitation amplitude phase is determined as described above for all the element antennas contributing to the main beam direction, so when the main beam is scanned, the first
As shown in FIG. This was done to solve the problem.

The purpose of this 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 1] The array antenna excitation method according to the present invention is characterized in that each time the main beam direction of the composite radiation pattern of two or more element antennas changes, the element antenna to be excited is , from among the element antennas that contribute to the direction, so that the element arrangement is symmetrical about the main beam axis, and receive only the radio waves incident on the selected element or only from the selected element. The purpose is to find the excitation amplitude phase that radiates radio waves and makes one desired combined radiation baton.

[Function 1] In this invention, when the main beam direction changes, the element antenna to be excited is selected from among the element antennas that contribute to the main beam direction, so that the element arrangement is symmetrical about the main beam axis. By selecting and determining the excitation amplitude phase that makes the desired vicarious radiation pattern by the excitation element antenna, the desired Taylor-shaped radiation pattern can be obtained even if the direction of the main beam changes.

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

FIG. 1 is a flowchart 1 showing a method of calculating the excitation amplitude phase of an array antenna according to an embodiment of the present invention. Now, the array antenna shown in the flowchart of Fig. 1 has a configuration as shown in Fig. 2, and in Fig. 9, (SWX),
..., (s, m) are switches, (1> is an excitation amplitude phase calculation device that calculates the above excitation amplitude phase. Regarding the calculation of the excitation amplitude phase calculation device listed in L, use the flowchart in Fig. 1. I will explain.

First, the main beam direction is set to θ-0°. If θ=0°, start from step 2 of the flowchart in FIG. Step 2 forms an initial radiation pattern. 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.6 Figure 3 shows the radiation pattern obtained in step 2 above. . Note that the desired tiller distribution is -50 dB.
gave the Tiller distribution of . The reason why a -50 dB sidelobe level is not obtained in the radiation pattern shown in FIG. 3 is that the angular position of the zero point of the desired tiller-shaped radiation pattern is shifted. Therefore, a sidelobe level of -50 dB is obtained in the following steps. Step 3
Then, calculate the angular position of the zero point to give the desired tiller-shaped radiation pattern. The angular position U of the zero point is generally given by equation (4).

U = n [A2+ (n-0,5>2A2+ (n
-0,5>21”2 (4) However.

Agency - Number of zeros, n = 11th zero A = log (b+ (b"-1)"")/π201
ogb=sidelobe level (dB) Next, in step 4, the excitation amplitude phase for forming a directional zero point is determined based on the angular position of the zero point. In other words, F in equation (5)
Excitation amplitude a that minimizes (i = 1 to M: element number),
Excitation phase p.

1
Find 1.

Element number B) and excitation phase p are determined.

However, E, (θ) - contribution of each element in the U direction 1 n
nHere,
The above excitation amplitude a and the excitation phase p are expressed as follows:
1 We have described the method of calculating value, but the excitation S amplitude a,
and excitation phase p, are found by the plane wave synthesis method.
1. Even the first one is good.

Next, in step 5, the excitation amplitude ai is changed to the variable amplitude device (A, 1) to (A, ,;) shown in FIG. 2, and the excitation phase pi is changed to the variable amplitude device (P, , ) to By setting (P, , ), a radiation pattern as shown in FIG. 4 can be obtained. In the figure, unnecessary side lobes higher than the set side lobe level -50 dB occur. Here, zero points are selected at appropriate intervals in the unnecessary side lobe, and the excitation amplitude a, (i=l
~M;X
1 (6) However, E, (θ) - the contribution of the zero point k direction in the unwanted sidelobe Here, the above excitation amplitude a and excitation phase p are expressed as
Although the method of finding one value has been described, the excitation fFA amplitude a and the excitation phase p may also be found by a plane wave synthesis method.

Next, in step 6, the excitation amplitude ai is set using variable amplitude generators <A, ) to (A□) shown in FIG.
By setting the phase shifters (p-+) to (p-x) shown in the figure, a low sidelobe pattern as shown in FIG. 5 is formed.

Next, the main beam direction is set to θ-60°. When θ=60°, start from step 1 of flowchart 1- in FIG. In step l, the element antenna to be excited is
The element antennas contributing to the main beam direction are selected so that the element arrangement is symmetrical about the main beam axis, and the element antennas other than the excited element antenna are non-excited by the switch. In other words, the element antenna to be excited in FIG. 2 can be selected from (i+j> to (M). Then, steps 2 to 6 above
The excitation amplitude phase that makes the combined radiation pattern of the excited element antenna a desired one is determined. FIG. 6 shows a radiation pattern obtained by this example, in which the main beam direction θ is 60°.

Further, the set value of the sidelobe level is -50 dB. On the other hand, FIG. 7 was created for comparison with FIG. 6, and shows that the element antennas to be excited are selected from (i to k) to (M), that is, the arrangement of the excited elements is asymmetrically selected from step 2 above. This is the radiation pattern when the excitation amplitude phase that makes the desired composite radiation pattern by the above-mentioned excited element antenna is determined by 6, and the main beam direction θ is 60°.
It is. Also, the setting value of the sidelobe level is -50d
It is B. As can be seen by comparing FIG. 6 and FIG. 7, the desired radiation pattern is obtained in FIG. 6 obtained in this embodiment.

[Effects of the Invention] As described above, according to the present invention, each time the main beam direction changes, the element antenna to be excited is selected from among the element antennas that contribute to the main beam direction, with the element antenna centered around the main beam axis. By selecting the arrangement so that it is symmetrical and finding the excitation amplitude phase that makes the desired combined radiation pattern by the excitation element antenna, the desired tiller-shaped radiation pattern can be obtained even if the direction of the main beam changes. .

[Brief explanation of drawings]

Fig. 1 is a flowchart showing the calculation method of the excitation amplitude phase of this invention, Fig. 2 is a diagram of an antenna for explaining this invention, and Fig. 3 is a tiller-shaped radiation pattern diagram in which the angular position of the zero point is shifted. , FIG. 4 is a tiller-shaped radiation pattern diagram obtained when the angular positions of the zero points are matched, and FIG. 5 is a tiller-shaped radiation pattern diagram when the main beam direction θ is Oo. Fig. 6 is a tiller-shaped radiation pattern diagram according to the present invention in which the main beam direction θ is 60°, and Fig. 7 is a diagram of the tiller-shaped radiation pattern according to the present invention with the main beam direction θ set at 60°.
0°, Tiller-shaped radiation pattern diagram when the arrangement of excited elements is asymmetrical, Figure 8 is a flowchart showing the conventional calculation method of excitation amplitude phase, and Figure 9 explains the conventional calculation method of excitation amplitude phase. Figure 5 No. 10 of the antenna for
The figure shows an arrangement of element antennas that contribute to the main beam direction. In the figure, (AI), (A2 >, ・
...(A,) is an element antenna arranged on a curved surface. (p, t) , (P, 2) , ..., (P,
, ) is a phase shifter. (Atl) , (At2) , ..., (
At, ) is a variable amplitude generator, (s, ), (3,2), ---
, (sw,) is a switch, and (1> is an excitation amplitude phase calculation device. In each figure, the same reference numerals indicate the same or corresponding parts. The first is.

Claims (1)

[Claims] Excitation amplitude of an array antenna consisting of a plurality of element antennas arranged on a curved surface, a switch connected to each element antenna, a phase shifter connected to the switch, and a variable amplitude amplifier connected to the phase shifter. With the excitation method that determines the phase, unnecessary side lobes that are higher than the peak side lobe level of the ideal Taylor radiation pattern among the side lobes that are at ±90 degrees or more when the main beam direction of the above array antenna is set to 0 degrees. An array antenna excitation method that numerically determines 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 ideal Taylor-shaped radiation pattern within ±90 degrees above. In the excitation amplitude phase calculation device,
Each time the main beam direction of the composite radiation pattern of the plurality of element antennas changes, select the element antenna to be excited from among the element antennas that contribute to the main beam direction so that the element arrangement is symmetrical about the main beam axis. The excitation amplitude is selected so that only the radio waves incident on the selected element is received or the radio wave is emitted only from the selected element, and a desired composite radiation pattern is obtained using the array antenna excitation method. An array antenna excitation method characterized by determining the phase.