JPS5866401A - Electronic scanning antenna - Google Patents

Abstract

PURPOSE:To disperse a quantized phase error that produces a large side lobe in a specific direction, by supplying the electric power to an array antenna from a waveguide slot antenna with a change of the feeding phase. CONSTITUTION:The output of a signal transmitter 7 is radiated again from element antennas 1a-1n via a waveguide slot array antenna 10, wave receiving antennas 9a-9n and phase shifters 2a-2n. The oscillating amplitude and the phase are controlled by the length (l) and the deflection degree (d) of a slot 13 formed at the antenna 10. Therefore the phase degree of a phase shifter 2i is set at -alpha{i-(n+1)/2}<2m>, and the slot length (l) with which the sum of susceptances of slots 13 is set at 0 is selected so that an input signal is equal to[alpha{i - (n+1)/2}<2m>-betai]B. Here B is the minimum unit phase angle, alpha is a constant, beta is a constant corresponding to the beam scanning angle, (n) is the number of elements of an antenna, (i) is the array number of the element antenna, (m) is a natural number, and[X]B is the digital phase degree quantized with B which is most approximate to X.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic scanning antenna with multiple phase shifters.

Figure 1 shows a conventional electronic scanning antenna.
la) to (1n) are element 7 antennas, (2L) to (2n
) is a phase shifter, and (Sa) to (3n) are phase shifter drive circuits.

(4a) to (4n) are power feeding transmission lines, and (5) is a control circuit.

+61 #- is the transmit/receive switch, (7) is the transmitter, +81
It is a Fi receiver. This electronic scanning antenna has a control circuit (
5) to the phase shifter drive circuits (3a) to (3n).
Send to.

The phase shift amount of each phase shifter (2a) to (2n) is changed to the phase shifter (21!
According to the arrangement order of L) to (2n), as shown in FIG. 2A.

− Set to make a numerical change (dotted line).

As shown in FIG. 2B, the beam direction 0 is controlled.

Conventionally, in beam scanning 2π in this type of antenna, digital phase changes are performed using an electronic computer using a phase angle of B-/2PCP-bits as the minimum unit. A phase error (quantized phase error) in the range of 10B/2 as shown in FIG. 3 occurs, and this has the disadvantage that large side lobes occur in a specific direction in the radiation pattern of the electronic scanning antenna.

In order to eliminate the above-mentioned conventional drawbacks, the electronic scanning antenna according to the present invention changes the feeding phase so as to disperse the quantization phase error that causes a large sidelobe in a specific direction.

FIG. 4 shows an embodiment of the present invention, which will be described in detail below.

In Fig. 4, (la) to (tn) are Vi element antennas, (2a) to (2n) are phase shifters, (3a) to (
3n) is a phase shifter drive circuit, (5) is a control circuit, (6) is a transmitting/receiving switch, (7) is a transmitter, (8) is a receiver, (
9a) to (9n) are wave receiving element antennas for receiving power supplied through space; (II is a waveguide slot array antenna, which is approximately the same as the entire element antenna group that constitutes array antenna I) It has a structure in which a plurality of slots are cut in the wall surface of a rectangular waveguide.This waveguide slot array antenna αI
Fi is a power distribution-order radiator that distributes and supplies power to the array antenna Oυ through space. That is, the radiation power from the waveguide slot array antenna OI is transmitted to each receiving element antenna (9a) to (9) of the array antenna αυ.
n), passes through phase shifters (2a) to (2n), and is radiated into space again from each element antenna (1a) to (1n). Further, Q3 is a radio wave absorber that absorbs power that is not irradiated to the array antenna 011 and eliminates unnecessary reflections.・FIG. 5 is a front view of the waveguide slot array antenna On, and this waveguide slot array antenna Qlj has a metal plate a9 at the end.
This is a standing wave feeding system short-circuited with a thrower on the wide wall of the rectangular waveguide.
(13 is cut at an interval λg/2 (λg is the wavelength within the waveguide).

In this device, the phase of the long signal of the phase shifter (21) related to the first element antenna (11) is adjusted to 1 using the waveguide slot array antenna 01, for example, using the phase of the transmitter output end as a reference. , and adjust as shown in equation (1).

1α+ 1- (-2-!-) ) 2m...
...Madashi Hata, α is an arbitrary constant, i-1, 2,...n.

m is a natural number (1, 2,...).

When the phase shifter (21) is set as shown in equation (2) using the control signal from the control circuit (5), the phase of the signal supplied to the element antenna (11) is determined as shown in equation (3). becomes.

However, the symbol EX)B is closest to X.

This means that a digital phase amount quantized by B is taken. β is a constant corresponding to the beam scanning angle.

The radiation pattern 2 of the electronic scanning antenna as a whole is expressed by equation (4), where the antenna element spacing is X and the propagation constant is k, and the main lobe where equation (4) is the maximum is The direction is expressed by equation (5).

xe’α(1-(″”-))2m However, 1 is the excitation amplitude of the first element antenna.

It is.

Furthermore, the electronic phase error caused by the discontinuity listed in equation (4) (if β is 0, D is also O), but as shown in Figure 6, there are 9 curves that are different from the conventional electronic phase error. Next door.

The inclination and direction are distributed to the left and right.

That is, side lobes due to quantization phase errors can be dispersed from a specific direction and become small, and large side lobes occurring in a specific direction can be reduced.

1 is the excitation amplitude with respect to the deviation d of the waveguide wall surface of the slot αJ from the center line a◆.

Figure TB is the excitation phase versus slot length t. That is, the excitation amplitude expressed by equation (4) is:

This can be realized by adjusting the slot 00 deviation amount d,
The excitation phase expressed by equation (1) can be achieved by adjusting the slot length t. Furthermore.

By selecting the deviation amount d so that the sum of the conductances of each slot, which is proportional to the excitation amplitude, is 1, and at the same time selecting the slot length t, so that the sum of the susceptances of each slot, which is proportional to the excitation phase, is O. The excitation amplitude can be increased without deteriorating the input standing wave ratio of the waveguide slot array antenna α.

An array antenna with arbitrary phase distribution can be constructed.

Therefore, in FIG. 4, the distance between the waveguide slot array antenna 01 and the array antenna aυ is selected according to the excitation amplitude two-phase distribution.

Power is received on the array antenna αD side. According to numerical and experimental studies, this optimal distance is achieved at 32 or less, where λ is the wavelength of the radio waves used.

Further, according to the embodiment of the present invention, the antenna for distributing power is constructed of a series-fed array antenna consisting of a plurality of radiating elements, so the construction can be significantly simplified.
Furthermore, the entire element antenna group and the series-fed array antenna can be made approximately the same size, allowing efficient power distribution.

Although the present invention has been described with respect to the case where they are arranged in a straight line, it goes without saying that it can be similarly applied to the case where they are arranged in two planes.

Further, in the embodiment, a case has been described in which a waveguide slot array antenna of a standing wave feeding type using a rectangular waveguide is used, but the present invention is not limited thereto. It can be implemented using a tube slot array antenna, and it can also be implemented using a slot 7L antenna with a slot cut in the narrow wall of a rectangular waveguide, a circular waveguide slot array antenna, or a coaxial cable. It can also be implemented using a slot array antenna in which slots are cut in the conductor.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a conventional electronic traveling antenna, and FIG. 2 is a diagram explaining its directional characteristics. Arri in the same figure is a chart showing the amount of phase shift of each phase shifter, B in the same figure is a directivity characteristic diagram of a magnetron fixed antenna, and FIG. 3 is a chart showing electronic phase errors in a conventional antenna. FIG. 4 is a schematic diagram showing an embodiment of the present invention, FIG. 5 is a configuration diagram of a waveguide slot array antenna used in this invention, and FIG. 6 is a diagram showing electronic phase error in the antenna of this invention. , Figure 7 explains the excitation amplitude phase characteristics of the slot, where A is a diagram showing the excitation amplitude, and Figure B is a diagram showing the excitation phase. (la) to (1n) are element antennas, (2a) to (2n) are phase shifters, (35L)
~(3n) is a phase shifter drive circuit, (5) is a control circuit, (6
) is the transmission/reception switching circuit, (7) is the transmitter, (8) Fi receiver, (9a) to (9n) are the receiving element antennas, a
o is a waveguide slot array antenna, ao is an array antenna, and az is a radio wave/absorber. Note that in FIG. 1, the same or corresponding parts are designated by the same reference numerals. Agent Patent Attorney Makoto Kuzuno - Figure 3 One-way joint 1; Figure 2 (l15) Figure 4 jI5 Figure θ 1

Claims (1)

[Claims] A plurality of element antennas, a plurality of phase shifters provided in each of the plurality of element antennas, a phase shifter drive circuit provided in each of the plurality of phase shifters, and the phase shifter. It is equipped with a control circuit that gives a control signal corresponding to the beam direction to the drive circuit, and uses a series-fed slot array antenna consisting of a plurality of radiating elements as an antenna that distributes power to each element antenna. In an electronic scanning antenna in which the main beam direction is controlled by producing a required amount of phase shift in an incoming microwave signal, the phase shift is used to reduce sidelobes caused by quantization phase errors during beam scanning. The amount of phase shift of the device is [α(1-(“-')
12m - β1]3 and the input signal phase of each phase shifter to be 11-(±1 > ) 2m, the sum of the susceptances of each slot proportional to the excitation phase is The slot length t was selected such that 0. An electronic scanning antenna characterized by using a series-fed slot array antenna.