JPS5919403A - Converter of polarized wave - Google Patents

Abstract

PURPOSE:To obtain a small elliptically polarized wave rate over a wide frequency band, by forming plural grooves vertical to a guide axis on an inner wall of a circular waveguide and loading an iris at symmetrical position. CONSTITUTION:Plural number of circular grooves 2 having d1 depth and (w) width vertical to the guide axis (taken as the (z) axis) of the circular waveguide 1 having 2R inner diameter are formed on the inner wall of the circular waveguide 1. Further, the iris 4 as a phase shift element is loaded to a position symmetrical to the inner wall of the circular waveguide 1 and the guide axis, i.e. one plane including the (z) axis. Then, the depth d1 of the grooves 2 of the iris 4 becomes deeper into a depth d2. The difference of the phase constant in the polarized wave converter toward the (x) and (y) shows a gradual change to frequencies with the iris 4 and the groove 2, allowing to improve the frequency characteristics of the elliptically polarized wave rate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a broadband, small elliptical polarization converter that can convert a small elliptical polarization into a small elliptical polarization.

Polarization converters are used as part of the radiation feeding device for aperture antennas in wireless communications. A circular polarizer as such a polarization converter converts linearly polarized waves into circularly polarized waves or circularly polarized waves into linearly polarized waves within a waveguide. Circularly polarized waves are obtained by providing a phase difference of 90 degrees in a direction inclined at 45 degrees with respect to the plane of polarization of the incident linearly polarized waves. Conventionally, when using this method, a circular waveguide with a smooth inner wall surface is used, while an iris using flat glass or metal fins is used as a phase shift element to provide a phase difference of 9Q degrees. I've been exposed to it.

Among the above-mentioned phase shift elements, glass has problems in terms of mechanical strength and electrical loss. On the other hand, metal phase shift elements are more advantageous than glass in terms of mechanical strength and electrical loss. Under these circumstances, there is an increasing demand for improvements in the polarization characteristics of circular polarizers, and circularly polarized waves with small elliptical polarization over a wide band that can be converted into elliptically polarized waves close to circularly polarized waves over a wide band are increasing. Equipment is desired.

Examples of conventional phase shift elements using metal include an iris and the like. This is as mentioned above.

It is loaded into a circular waveguide with a smooth inner wall surface.

The phase difference between two orthogonal waves generated by this polarization converter is
If the phase constant of the mode in which the electric field is perpendicular to the iris is βl, and the phase constant of the mode in which the electric field is perpendicular to the smooth waveguide wall perpendicular to this is β2, then the difference between these phase constants depends on Δβ - β1 - β2. .

The length t of the polarization converter is determined so that the product (Δβx7) of this phase constant difference Δβ and the length t of the polarization converter is 90 degrees.

Here, βl varies depending on the iris structure (the distance between adjacent irises, the thickness of the iris, the depth of the groove, etc.). On the other hand, β; is determined by the cutoff wavelength of a smooth circular waveguide, and has the following frequency characteristics (expressed in wave numbers).

β;-(k kc) (1) In this case, the cutoff wavelength depends only on the diameter of one circular waveguide. In other words, since the frequency characteristic of β depends only on the waveguide diameter, the method of widening the band of the polarizer depends only on the selection of the structural parameters of the iris, which has a small elliptical polarization coefficient. The drawback was that there was a limit to the broadband polarization converter.

An object of the present invention is to provide a polarization converter having a small elliptical polarization over a wider frequency band.

According to the present invention, a plurality of grooves are formed perpendicularly to the tube axis of the circular waveguide on the inner wall surface of one circular waveguide, and a plurality of grooves including the tube 1+11 are formed on the inner wall surface of the circular Jl waveguide. A polarization converter is obtained, which is characterized in that an iris is mounted on an iris device that is symmetrical about two 31' planes.

Next, embodiments of the present invention will be described with reference to the drawings.

Referring to FIGS. 1 to 4, the polarization converter according to one embodiment of the present invention has a tube axis (Z-axis and depth a perpendicular to )
A corrugated circular waveguide formed by forming a plurality of circumferential grooves 2 having a width W is used. P is one period of the cork-1 circular waveguide. Furthermore, in the polarization converter of this embodiment, there are two more points.

An iris 4 as a phase shift element is mounted on the inner wall surface of the two-circular waveguide l at a position symmetrical with respect to a plane including the tube axis, that is, the Z axis. By providing the iris 4 in this manner, the depth of the groove 2 in the iris 4 portion is deeper than dl<d2. In FIGS. 1 to 4, reference numeral 3 denotes a metal fin formed by providing a groove 2 and an iris 4 in the circular waveguide 1.

Note that FIGS. 1 to 4 are for the purpose of simplifying the explanation.

Although the pitch of the iris 4 was made to match the pitch of the corrugate, in principle it is not necessary that the two be the same. for example,
It is also possible to form the iris 4 by sandwiching a plurality of grooves 2.

The polarization converter of this embodiment is as shown in FIG.

The yz plane and the xz plane are placed at 45 degrees with respect to the plane of the incident linearly polarized wave E. In Figure 2,
EX, , Ey are the components of the incident linearly polarized wave E in the X direction and the X direction, and the phase constants in the polarizer are respectively β8. Let it be β7.

Hereinafter, the effects of the polarization converters of the two embodiments will be explained with reference to FIGS. 5 and 6. In Figures 5 and 6, R
indicates R in FIG.

(5) In Fig. 5, curve A is the phase constant β9 due to the iris 4, curve B is the phase constant β2° due to the circular waveguide with a smooth inner wall surface, and curve C is the phase constant β2° due to the circular waveguide with a smooth inner wall surface. The phase constant β8 according to (d+/R<1) is respectively expressed.

Difference in phase constant Δβ(−β;
-βy) tends to decrease as one frequency becomes higher, as shown by the curve in the -Δβ chart in FIG.

However, according to the present invention, a circular waveguide in which a cork 1 groove 2 with a depth of d/R<1 was formed on the inner wall surface was used instead of the conventional circular waveguide having a smooth inner wall surface. In the polarization converter, the phase constant β8 is used as shown in curve C in Figure 5.
shows a characteristic in which Δβ-β8-β2 increases as one frequency becomes higher, compared to β of curve B in FIG. The characteristic of this Δβ-β knee β2 is shown by curve E in FIG. As a result, the difference in the phase constant between the iris 4 and the corrugated groove 2 in the polarization converter of the present invention, Δβ−β, is expressed as (6) for one frequency, as shown by the curve F in FIG. Shows gradual changes.

Δβ is a quantity directly proportional to the phase difference, and the fact that the frequency characteristic of Δβ is flat indicates that the frequency characteristic of elliptical polarization is good. Improving the frequency characteristics of elliptical polarization using a polarization converter equipped with an iris in a circular waveguide with an inner wall surface,
Bandwidth can be expanded.

As explained above, according to the present invention, a polarization converter having a small elliptical polarization coefficient over a wide frequency band can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a polarization converter according to an embodiment of the present invention;
Figure 2 is a diagram showing the left end face of the polarization converter in Figure 1;
Fig. 3 is a cross-sectional view of the polarization converter shown in Fig. 1 taken along the y--z plane, and Fig. 4 is a cross-sectional view of the polarization converter shown in Fig. 1.
A cross-sectional view when cut along the z-x plane, FIG. 5 is a diagram for explaining the relationship between the wave number and phase constant β of the polarization converter in FIG. 1, and FIG. FIG. 3 is a diagram for explaining the relationship between the wave number of the polarization converter and the phase constant difference Δβ. 1...Circular waveguide, 2...Groove, 3...Metal fin,
4...Iris.

Claims (1)

[Claims] 1 A plurality of grooves are formed perpendicularly to the tube axis of the circular waveguide on the inner wall surface of the circular waveguide, and a plurality of grooves are formed on the inner wall surface of the circular waveguide with respect to one plane including the tube axis. A polarization converter characterized by having irises mounted in symmetrical positions.