JPS5927528B2 - Centrally fed slot array antenna device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a centrally fed slot array antenna (hereinafter referred to as CF).
(abbreviated as A) device.

Conventionally, the CFA apparatus shown in FIGS. 1 and 2 is known.

In FIG. 1 and FIG. 2, 1 is a power supply line, which is connected to a transmitter (or receiver).

The energy of the electromagnetic waves supplied through the feeder line 1 is divided equally on the left and right sides at the branching section 2, and the energy is divided equally between the left and right arrays 3,
4.

A plurality of slot elements 5 are provided in each of these arrays 3 and 4, and the electromagnetic waves are radiated into space by these slot elements 5 and combined.

A flare 6 is used to form a pattern in a plane perpendicular to the arrays 3 and 4.

The CFA device shown in FIG. 1 does not take into account interference outside the waveguide between the left and right arrays 3.4, and therefore has the disadvantage that antenna performance is degraded due to the interference.

Generally, in CFA, the equal phase planes of the left and right arrays are designed to be continuous at the central feeding part, but this effort has mainly focused on the behavior of electromagnetic waves within the waveguide, which can be handled computationally. In reality, the interference between the left and right arrays, which cannot be calculated, is ignored or only corrected to a certain extent using experimental methods.

In addition, in CFA, in order to achieve the aperture amplitude distribution, elements with high radiation efficiency are placed near the central feeding section.
Inevitably, interference will increase.

In this way, the above-mentioned interference is a troublesome thing that cannot be calculated and its influence cannot be ignored.

As a result of this interference in the CFA, the phase distribution over the entire surface of the CFA has a phase difference in the phase plane at the feeding section, as shown in FIG.

This step can be considered to be caused by the phase distribution being subjected to phase modulation by a function having a period of 1/2 of the total length of the antenna, and therefore a large side lobe is generated near the main rope of the radiation pattern.

The generation of this side lobe is particularly problematic when the CFA is used as a radar antenna.

In this way, in CFA, although the interference between the left and right arrays is a detriment to the realization of practical directional characteristics, it is impossible to handle it in theoretical calculations that take this into account. It becomes necessary to use some means to reduce interference.

The present invention is intended to reduce the interference between the arrays described above with a simple configuration, and a plate or plate having an electromagnetic field shielding effect is placed outside the central feeding part of the perforated waveguide of the slot antenna array. A shield member made of blocks or the like is provided.

An embodiment of the present invention will be described in detail below with reference to FIGS. 4 and 5.

In Figures 4 and 5, 1 is a power supply line, 2 is a branch part,
3 and 4 are arrays, 5 is a slot element, and 6 is a flare, which are similar to those described with respect to FIGS. 1 and 2.

Reference numeral 7 denotes the above-mentioned shield member, which is attached so as to be in close contact with the flare 6 and the waveguides constituting the arrays 3 and 4.

Although the shape of the shield member 7 is a simple plate, it is effective to some extent, but it is possible to increase the thickness of the plate and provide one or more grooves 9 at the end, as shown in the shield member indicated by reference numeral 8 in FIG. By selecting its depth so that 9 acts as a choke structure, a great shielding effect is obtained.

A CFA apparatus provided with the above-mentioned shield member 8 is shown in FIG. 7 as another embodiment.

In FIG. 7, 1 is a feeder line, 2 is a branch, 3 and 4 are arrays, 5 is a slot element, and 6 is a flare, which are similar to those explained in FIGS. 1 and 2. be.

The shield member 8 includes the flare 6, the array 3,
It is attached so as to be in close contact with the waveguide constituting part 4.

FIG. 8 is an actual measurement example showing the effect of the shield member.
An experiment was conducted using an element array, and the coupling amounts of conventional structure A, B when using shield member 7, and C1 when using shield member 8 are shown.

When the shield member 8 was used, an interference reduction effect of about 16 dB was obtained.

Furthermore, although coupling of about -14 dB is observed in A of FIG. 5 above, the phase error due to this coupling is estimated to be about 15 degrees at maximum.

In the case of C, this error is 3° or less. The interference between the left and right arrays is treated as a step in the phase plane at the central feeding section, and the radiation pattern is calculated by changing the size of the step. The results are shown in FIGS. 9 and 10.

FIG. 9 shows a case where the level difference is 15°, and FIG. 10 shows a case where the level difference is 5°.

When these two are compared, a clear difference in sidelobe level is recognized, and this difference is the effect of the shield member.

[Brief explanation of the drawing]

Figure 1 is a front view showing the conventional example, and Figure 2 is A-A in Figure 1.
3 is a graph showing a step in the phase plane due to interference at the power feeding section, FIG. 4 is a front view showing an embodiment of the present invention, and FIG. 5 is a cross section taken along the line A-A in FIG. 4. 6 is a perspective view of the main part of another embodiment, FIG. 7 is a partially cutaway perspective view of another embodiment, FIG. 8 is a graph showing the interference reduction effect by the shield member, and FIG. The figure and FIG. 10 are graphs showing the results of pattern simulation. 1: Flare, 7, 8: Shield member, 9: Groove.

Claims (1)

[Scope of Claims] 1. In a waveguide slot antenna device having a feeding point at the center of the array, outside the waveguide feeding portion and at a position where the element group constituting the array is divided near the feeding point, A centrally fed slot array antenna device characterized in that a shielding member made of a plate or block having an electromagnetic field shielding effect is installed. 2. One or more grooves whose front edge of the shield member crosses the antenna aperture surface perpendicular to the antenna array axis and have a depth in the depth direction of the antenna aperture within the thickness width of the front edge end surface of the shield member. 2. The center-fed slot array antenna device according to claim 1, wherein the slot array antenna device is provided in a direction transverse to the antenna aperture.