JPS641965B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circularly polarized plane array antenna using a radial waveguide used in the GHz band.

A planar array antenna using such a radial waveguide has the advantage of a simple structure of a feeding system, and the following have been mainly proposed in the past.

That is, FIG. 1 shows a structure in which a radial waveguide is cut in the axial direction, and a circular plate 3 having a circular opening 2 having the same cross section as the waveguide 1 is connected to the tip of a circular power feeding waveguide 1. , and a circular plate 4 without an opening is further disposed at a certain interval above the circular plate. The disks 3 and 4 serve as lower and upper conductors constituting a radial waveguide.
A matched load 5 is connected to the end of the radial waveguide.

FIG. 2 shows a front view of the radial waveguide, with the opening 2 of the feeding circular waveguide 1 in the center and the matching load 5 around the periphery.

FIG. 3 shows an antenna with a cross-shaped slot 6 in the upper conductor 4 of the radial waveguide. The cruciform slots are arranged axially symmetrically and concentrically. The arrows in FIG. 3 indicate the direction of the current flowing in the upper conductor 4 of the radial waveguide when the feeding waveguide 1 is excited in the TE ₁₁ mode, which is the fundamental mode of the circular waveguide. In the case of Figure 3, slots 6-1 and 6-3, which have the same direction as the current, are not excited, but slots 6-2 and 6-4 are excited, and radio waves with longitudinal polarization are emitted. . Note that although the slots 6-5 and 6-6 in the diagonal direction are both excited, the combined radiated radio wave has vertical polarization.

It is clear that using the antenna shown in Figure 3, if the feeding circular waveguide is further rotated by 90 degrees and excited in the TE ₁₁ mode, and the phase difference between them is set to 90 degrees, a circularly polarized wave antenna will be obtained.

However, since this antenna uses a circular waveguide for power feeding, the waveguide becomes larger as the frequency decreases (for example, at 1.5GHz, the diameter is approximately 17mm).
cm), and further has the disadvantage that a circularly polarized wave generator must be added to the feeding waveguide 1 in order to use it as a circularly polarized antenna.

The present invention provides a radiating element consisting of a set of approximately V-shaped slots on a predetermined spiral line on the upper conductor of a circular waveguide fed by a conventionally used coaxial line. To provide a circularly polarized plane array antenna with a simple structure that improves characteristics by making the circularly polarized waves radiated from each radiating element in phase by sequentially arranging them in the same direction, and omitting a circularly polarized wave generator. It is.

Hereinafter, details of the present invention will be explained with reference to FIG. 4 and subsequent figures including examples.

FIG. 4 shows an example of a feeding circuit used in the antenna according to the present invention, in which the inner conductor 7-1 and the outer conductor 7
A conventional coaxial line 7 consisting of -2 is used. The inner conductor 7-1 of this coaxial line is connected to the upper conductor 4 of the radial waveguide, which is composed of upper and lower disc-shaped conductors 4 and 3 arranged oppositely at equal intervals. A conductor disk 8 is inserted for alignment with the wave path. Further, the outer conductor 7-2 is connected to the lower conductor 3. 5 is a matching load connected to the end of the waveguide, and this load 5 can be omitted for practical purposes. This is because, as will be explained later, when power is supplied by arranging a slot in the waveguide, the power is attenuated by emitting radio waves at the slot, so even if it is reflected back at the end of the waveguide, there is no substantial negative effect. This is because it has no effect.

Unlike the case shown in FIG. 3, a current having only a radial component flows through the radial waveguide fed by the coaxial line.

FIG. 5 is a diagram showing the principle of the antenna according to the present invention. Figure 5 is a front view of Figure 4;
The arrows on the xy axes indicate the direction of the current flowing in the upper conductor 4 of the radial waveguide at a certain moment. This current propagates in the radial direction, and the wavelength of the most fundamental propagation mode, which uniformly spreads from the center in the radial direction with the same intensity, is λ _g .
This wavelength varies slightly with radial position due to the nature of the Betzel function.

In FIG. 5, δ is on the x-axis from the center o of the upper conductor 4.
At a _first point _p1 located at a distance _of ,
One of the slots 9-1 is arranged in a substantially V-shape with an inclination of about 45 degrees to the x-axis.

In this way, each of them is approximately
It is well known that circularly polarized waves are radiated by a pair of slots tilted at 45°, spaced apart from each other by 1/4×λ _g , and oriented in opposite directions.

Now, the antenna according to the present invention has a pair of slots _9-1 and 9- which constitute the radiating element 91 on the x-axis.
Next, on the upper conductor 4, radiating elements 9 ₂ , 9 ₃ , . Points p ₁ , p ₂ , p ₃ , . . . on a spiral line s assumed as follows are arranged in the same direction one after another.

The spiral line s starts from point p ₁ and passes sequentially through a second point p ₂ , a third point p _{3 , .} . . and reaches an end point p ₅ . The position of the second point p ₂ is determined by spatially rotating the first point p ₁ by 90 degrees counterclockwise and moving it onto the y-axis, and moving 1/4× in the radial direction from the center o on this y-axis. This is the position shifted by the dimension of λ _g . This shift on the y-axis is done spatially by 90 degrees in order to make the circularly polarized waves radiated from a pair of slots 9-1 and 9-2 and 9-3 and 9-4 in phase. This is because it is necessary to temporally delay the phase by 90° by the degree of rotation.

The position of the third point _p3 is also determined in the same manner as above. That is, the second point p ₂ is spatially rotated 90 degrees counterclockwise and moved onto the x-axis, and the position is shifted from the center o in the radial direction on this x-axis by a dimension of 1/2 × λ _g . It is.

The position of the fourth point p ₄ is similarly determined on the y-axis, and since the last point p ₅ has been rotated 360° counterclockwise with respect to the first point p ₁ , the corresponding phase angle is 360°. It is shifted radially on the x-axis by λ _g to retard it by °. In addition, in the case of FIG. 5, the rotation direction of the circularly polarized wave is counterclockwise.

Although the circularly polarized radiating element is shown in FIG. 5 as a set of slots axially inclined at 45 degrees, this angle need not be exactly 45 degrees. Also, since it is sufficient for a pair of slots to maintain an angle of 90 degrees to each other, it is not necessary to have a completely axially symmetrical V-shape.
An extension of one slot may cross the other slot.

Figure 6 shows an actual planar array antenna.
This is an embodiment _of the antenna according to the present invention, in which radiating elements 9 ₁ , 9 ₂ , 9 ₃ , .

FIG. 7 shows an embodiment in which the direction of rotation of the polarized waves of the radiated radio waves is clockwise, but since the operating principle is exactly the same as that in FIG. 5, the explanation will be omitted.

FIG. 8 shows the case where the front surface of the slot is covered with an insulating cover 10 for snow and waterproof purposes. These insulators include PE, FRP, polystyrene, polyurethane, PVO, etc.

According to the present invention, the structure is simple, can be constructed at low cost, and has good characteristics, so that it will have great practical effects in the future.

[Brief explanation of drawings]

Figure 1 is a central longitudinal sectional view of a planar array antenna using a conventional radial waveguide, Figure 2 is a front view of the same waveguide, Figure 3 is a front view of the same slotted waveguide, and Figures 4 and below are This is related to a specific example of the circularly polarized planar array antenna according to the present invention, and FIG. 4 is a cutaway perspective view showing a waveguide and coaxial line to illustrate a feeding circuit used therein, and FIG. 6 is a front view illustrating the current direction in the same slotted waveguide, FIG. 6 is a front view of another embodiment, FIG. 7 is a front view of still another embodiment, and FIG. 8 is a perspective view of one with a cover. 2...Opening, 3...Lower conductor, 4...Upper conductor, 5...
Matching load, 7... Coaxial line, 8... Conductor disk, o... Center, x, y... Axis, λ _g ... Wavelength, p ₁ , p ₂ ,......
Point, 9-1, 9-2,... ...Slot, 10...
cover.

Claims (1)

[Claims] 1 The wavelength of the propagation mode that spreads uniformly from the center in the radial direction with the same intensity, which is the most basic propagation mode in a radial waveguide consisting of upper and lower disc-shaped conductors arranged oppositely at equal intervals, is λ _g Then, a first point on the radial axis of the upper conductor is located at a distance of δ from its center, and a point δ+ from the center on an axis perpendicular to this axis.
A second point at a distance of 1/4 x λ _g , δ + 1/2 on the same axis as the first point and on the opposite side of the first point.
A third point at a distance of ×λ _g , a fourth point on the same axis as the second point and a distance of δ+3/4×λ _g from the center to the opposite side of the second point, and a first point. On the same axis and in the same direction as the fifth point located at a distance of δ + λ _g from the center, and on a spiral line that sequentially passes through a group of points determined in the same manner, 1/4 × λ _g for each on the orthogonal line.
The radiating element is composed of a pair of slots arranged with a center spacing of Circularly polarized planar array antenna.