JPS5839401B2 - circular array antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circular array antenna formed by arranging a plurality of circularly polarized antennas on the circumference.

In conventional array antennas of this type, the reference excitation direction of the circularly polarized antennas is the same for all of the circularly polarized antennas.

Here, this conventional circular array antenna will be explained using FIG. 1.

In Figure 1, 12 turnstile antennas (Tu
rnstile antennas) 1 are arranged on a circumference 2 at equal intervals, that is, at intervals of 30°, forming a circular array antenna 3.

Each turnstile antenna 1 has a phase difference of 900 2
It consists of two dipole antennas 4 and 5.

If the direction of one dipole antenna, for example the dipole antenna 4, is taken as the reference excitation direction of each turnstile antenna 1, then all the reference excitation directions coincide with the X-axis direction as shown in FIG.

Since the conventional circular array antenna 3 is configured as described above, first, each of the turnstile antennas 1 generates elliptically polarized waves due to unbalanced power supply, that is,
If the axial ratio of the circularly polarized waves is poor, the poor axial ratio of the circularly polarized waves of the circular array antenna 3 as a whole is maintained.

This is obvious when viewed in the axial direction of the circular array antenna 3 (the Z-axis direction perpendicular to the plane of the paper in Figure 1), but on the other hand, even if each turnstile antenna 1 is a pure circularly polarized wave, it When viewed in the direction, it becomes elliptical polarization, but in this case, if the observation direction is kept at a constant angle from the Z-axis direction and rotated in the circumferential direction, the axial ratio will obviously change at a period of 90°. .

This is a so-called phased array antenna in which the circular array antennas 3 are concentrically stacked in multiple stages and beams are scanned electronically.
When applied to na), it also results in variations in the axial ratio during beam scanning in the circumferential direction.

As described above, the conventional circular array antenna 3 generally has the disadvantage that the axial ratio is degraded and the fluctuation is large.

In order to eliminate these conventional drawbacks, the present invention installs the turnstile antennas as circularly polarized antennas with their reference excitation directions spatially rotated sequentially, and also sets a phase amount corresponding to this spatial rotation angle. The power supply phase to each turnstile antenna is compensated, and as a result, a circular array antenna with excellent polarization characteristics is provided.

The present invention will be explained below with reference to figures showing embodiments thereof.

In FIG. 2, 12 turnstile antennas 1a
j1bjlCj... are similarly arranged along the circumference 2 at angular intervals of 300, forming a circular array antenna 6.

In the two orthogonal dipole antennas 4 and 5 that constitute each of the turnstile antennas, the dipole antenna 5 is delayed in phase by 90 degrees with respect to the dipole antenna 4.
(vertical direction toward the front of the paper in the figure), each turnstile antenna emits right-handed circularly polarized waves, that is, counterclockwise in FIG. 2.

The reference excitation direction of each of the turnstile antennas, that is, the dipole antenna 4, is spatially rotated sequentially by 30° counterclockwise as shown in FIG. Phase amounts corresponding to angles, that is, 0°, -300° -600, . . . are given as the feeding phases, respectively.

Since this invention is configured as described above, each turnstile antenna la
, ib, ic, ... are elliptically polarized waves, there is no effect on the right-handed circularly polarized wave component because the spatial rotation of the polarization plane is compensated by the feeding phase. However, for unnecessary left-handed circularly polarized components, the polarization rotation angle is clearly equivalent to 6.
Those shifted by 0.00 are combined over the entire circumference and are canceled out, and in the end, only the desired right-handed circularly polarized wave is generated as a whole, and the axes of each circularly polarized antenna ia, ib, lc,... The poor ratio is improved.

In addition, it is undeniable that the wave will generally be elliptically polarized when observed in a direction other than the Z-axis direction, but even in this case, the observation direction can be rotated in the circumferential direction with a constant angle from the Z-axis direction. Since the axial ratio does not change, even when applied to a phased array antenna, it is possible to achieve constant polarization characteristics for beam scanning in the circumferential direction.

FIG. 3 shows another embodiment of the invention, which is the turnstile antenna la shown in FIG.

Helical antenna 7a instead of 1b, 1c,...
A circular array antenna 8 is constructed using t7bt7Cj....

If the reference excitation direction of the helical antenna 7a is, for example, the X-axis direction, then the reference excitation directions of the respective helical antennas are sequentially rotated counterclockwise by 30 degrees as shown in FIG. A phase amount corresponding to the angle is given as the feeding phase.

Fig. M4 shows still another embodiment of the present invention, in which circular aperture antennas 9a, 9b, 9c are used as circularly polarized antennas.
, . . . are used to construct the circular array antenna 10.

Each circular aperture antenna has a circular waveguide 11 and a dielectric plate 1.
2 and generates circularly polarized waves.

If the reference excitation direction of the circular aperture antenna is, for example, the direction of the dielectric plate 12 in the plane of the paper in FIG.
They are arranged rotated by 0.

In addition, although the case of right-handed polarization has been described above, the present invention is not limited to this, and can be similarly implemented in the case of left-handed polarization.

Further, the present invention may be used not only for transmission but also for reception.

Furthermore, the circularly polarized antenna is not limited to the one in the example.
The same method can be implemented using any circularly polarized antenna such as a spiral antenna, circularly polarized horn antenna, or cross slot antenna.

Further, the number of circularly polarized antennas to be arranged is not limited to 12, and may be any number.

Further, the circular array antenna according to the present invention can be implemented by stacking concentrically in multiple stages on a flat or curved surface.

As described above, in this invention, the reference excitation direction of each circularly polarized antenna arranged on the circumference is sequentially rotated, and by compensating this spatial rotation angle with the feeding phase,
In order to provide a circular array antenna with excellent polarization characteristics,
When this is applied to communications antennas or radar antennas, the effect is significantly greater.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of a conventional circular array antenna, Figure 2
FIG. 3 is a schematic diagram showing another embodiment of the invention; FIG. 4 is a schematic diagram showing still another embodiment of the invention. It is. In the figure, 1, 1a. 1 b + 1 c +... is a turnstile antenna, 3 is a circular array antenna, 4 and 5 are dipole antennas, 7a y 7t) +
7C+...Helical antenna% 9a+9bt9c
t... is a circular aperture antenna, 11 is a circular waveguide, 12
is a dielectric plate. In the drawings, the same or corresponding parts are designated by the same reference numerals.

Claims (1)

[Claims] 1. In a circular array antenna consisting of a plurality of circularly polarized antennas arranged along the circumference, the reference excitation direction of each of the circularly polarized antennas is sequentially rotated, and each of the circularly polarized antennas is rotated in its spatial direction. A circular array antenna characterized by suppressing the generation of unnecessary backflow circularly polarized waves by exciting with a feeding phase corresponding to the rotation angle.