JPS625531B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dual orthogonal polarization splitter that splits two orthogonal polarized waves in two frequency bands into two orthogonal polarized waves in each frequency band.

Note that here, in order to simplify the explanation, the explanation will be limited to two frequencies. Here, let the frequencies of the two frequency bands be _L and _H , respectively, and _H
＞Assume that there is a relationship of _L. In addition, the two orthogonal polarized waves (right-handed and left-handed circularly polarized waves in the case of circularly polarized waves) in each frequency band are designated as V _H , H _H , V _L , and H _L , with subscripts H, L
to distinguish frequency bands.

Figure ₁ is a block diagram showing an example of _the configuration of a dual- _polarization splitter. _{The L} wave is a tapered waveguide whose inner diameter changes linearly in the tube axis direction, 4 is a branch waveguide provided at 90 degree intervals around the tube axis of the tapered waveguide 3, and 5 is _{an H} waveguide. 6 is a waveguide dedicated to a low frequency band, and 7 is an orthogonal waveguide 2 composed of a tapered waveguide 3 and a branch waveguide 4.
It is a polarization splitter.

FIG. 2 is a diagram showing a joint portion between the tapered waveguide 3 and the branched waveguide 4. As shown in FIG. Although not shown in the figure, each branch waveguide 4 is provided with a low-pass filter that allows _{the L} wave to pass through but cuts off _{the H} wave.

Now, consider the case where _H and _L waves are incident on the tapered waveguide 3 from the main waveguide 1 side. _{The H} wave propagates to the high frequency band dedicated waveguide 5 without being coupled to the branch waveguide 4 due to the action of the low-pass filter. On the other hand, _{the L} wave is completely reflected by the shear characteristics of the tapered waveguide 3, and is coupled to each branch waveguide 4 through four coupling holes 2 provided at appropriate positions in the tapered waveguide 3. . This splitter has four branching waveguides 4 symmetrically arranged at 90 degree intervals around the tube axis, so it can split any polarized wave.

Therefore, when the coupling portion between the tapered waveguide 3 and the branch waveguide 4 in FIG. 2 is combined as shown in _{FIG .} 2
It operates as a duplexer 7 that can transfer polarized waves to a waveguide 6 dedicated to low frequency bands without changing the polarization state.

However, in the conventional orthogonal dual polarization splitter, the tapered waveguide 3 is constructed of a circular waveguide, and the inner diameter changes linearly, so the disadvantage is that the frequency characteristics are narrow for the following reasons. There is.

The reason for this is, first, that in this orthogonal dual polarization splitter, the third portion of the tapered waveguide is constituted by a circular waveguide. Therefore, it is necessary to design the tapered waveguide 3 so that higher-order modes are not generated when _{the H} wave passes through the tapered waveguide 3. The higher-order mode generated by the taper is the _TM11 ° mode in a circular waveguide, and the shearing frequency _cTM11 ° of this higher-order mode is _cTM11 °=365.49/D (GHz) (1).

Here, D is the diameter (mm) of the circular waveguide.

On the other hand, the cutoff frequency _cTE11 ° of the fundamental mode TE11 mode of the circular waveguide propagating through the main waveguide 1 is _cTE11 °= _175.78D /(GHz) (2). Therefore, the diameter D of the tapered waveguide 3 on the main waveguide 1 side needs to be selected so that the TE ₁₁ ° mode passes through at _L and the TM ₁₁ ° mode is slightly cut off at _H. Considering that the diameter D is constant, there is a relationship of _cTE11゜ < _L < f _H < _cTM11゜, so the ratio of _H / _L cannot be made more than 2.08 times, and the frequency characteristics of the duplexer are limited. ing.

Also, since the taper changes linearly,
Since the position of the equivalent reflection surface presented by the tapered waveguide 3 changes greatly between high frequency waves and low frequency waves among _{the L} waves, the optimum position of the coupling hole 2 changes depending on the frequency, and _{the L} wave It was not possible to improve the demultiplexing characteristics over a wide band.

_In order to eliminate these drawbacks, this invention constructs the tapered waveguide with a square waveguide and changes the taper in a curved manner, thereby making it possible to obtain a large _H / _L ratio. The purpose is to reduce the change in the position of the equivalent reflecting surface of the waveguide to obtain a wideband orthogonal dual polarization splitter, and will be described in detail below with reference to the drawings.

FIG. 3 shows an embodiment of the present invention in which the tapered waveguide 3 is configured with square polarization.

The tapered shape in the figure has a square side length a
(z) with respect to the distance z in the tube axis direction a(z)=a1+(a2-a1) {1/2(1-cosπz/L)} ⁿ ...(3) a1 One side of a square waveguide with a small cross-sectional shape Length a2 Length of one side of a square waveguide with a large cross-sectional shape L Length of a tapered waveguide z Distance from the cross-sectional area of size a1 n Changes as a positive real number. The operating principle is similar to the conventional one. The higher-order mode generated in the square tapered waveguide 3 is TM□ ₂₁ mode (or TM□ ₁₂ mode)
This corresponds to the TM ₁₁ ° mode of the circular waveguide, and the shearing frequency _cTM21 □ ₂₁ is _cTM21 □ ₂₁ = 335.19/a ₂ (GHz) (4). Here, the unit of a ₂ is mm.

On the other hand, the fundamental wave TE□ ₁₀ (or
The cutoff frequency _cTE10 □ ₁₀ of the TE□ ₀₁ ) mode is _cTE10 □ ₁₀ = 149.9/a ₂ (GHz)...(5). Therefore, in the duplexer according to the present invention, _{the H} / _L ratio can be up to 2.236 times, and a duplexer with a wider band than the conventional duplexer can be obtained.

Moreover, in the tapered waveguide 3 of this invention, a(z)
Compared to a conventional tapered waveguide with the same taper length L, in which a(z) changes linearly, the tapered waveguide 3 exhibits _a The change in position of the equivalent reflective surface becomes smaller.

Therefore, the coupling hole 2 for demultiplexing _{the L} wave
The optimum position of the L wave does not change greatly depending on the frequency, and _{the L} wave demultiplexing characteristics can be improved over a wide band.

Note that the above describes the case where two tapered waveguides 3 are directly coupled by four branch waveguides 4, but the branch waveguides 4 may be connected after being appropriately coupled or branched using a hybrid circuit. You may do so. Also
It is clear that when the bandwidth of _L is narrow, a conventional tapered waveguide provided in the waveguide section dedicated to the low frequency band may be used.

As described above, the orthogonal dual polarization splitter according to the present invention achieves a large _H / _L ratio by using a square tapered waveguide and by changing the length of one side of the square in a curved manner. It has the advantage that two orthogonal polarized waves in two frequency bands can be separated, and that _{the L} separation characteristics can be made good over a wide band.

[Brief explanation of the drawing]

Figure 1 is a configuration block diagram of a conventional dual-polarization splitter, Figure 2 is a structural diagram showing a conventional coupling section between a tapered waveguide and a branching waveguide, and Figure 3 is a diagram showing a configuration of a conventional dual polarization splitter. FIG. 3 is a structural diagram of a coupling portion between a tapered waveguide and a branched waveguide, showing an example. In the figure, 1 is a main waveguide, 2 is a coupling hole, 3 is a tapered waveguide, 4 is a branch waveguide, 5 is a waveguide dedicated to high frequency bands, 6 is a waveguide dedicated to low frequency bands, and 7 is a waveguide dedicated to low frequency bands. This is a splitter for two orthogonal polarized waves. It should be noted that the same or corresponding parts in the figures are indicated by the same reference numerals.

Claims (1)

[Claims] 1. Orthogonality of two frequency bands propagating through the main waveguide 2.
Of the polarized waves, two orthogonal polarized waves in the low frequency band are transmitted to four branch waveguides provided in the tapered waveguide section using the shear characteristics of the tapered waveguide provided in the main waveguide. The wave is split into the waveguide, and then the split waves are combined again into the four branch waveguides, and the wave is sent to the low frequency band dedicated waveguide in the same polarization state as the one propagating in the main wave. In the broadband orthogonal dual polarization splitter to be transferred, the cross-sectional shape of the tapered waveguide is a square, and the length of one side of the square is a( z ).
However, for the distance z in the tube axis direction, a( z )=a1+(a2-a1) {1/2(1-cosπz/L)} ^nwhere a1 is the length of one side of the square waveguide with a small cross-sectional shape a2 Length of the side of a square waveguide with a large cross-sectional shape L Length of the tapered waveguide N Positive real number z A tapered waveguide that changes with the distance from the cross-sectional position of size a1 is used. Dual orthogonal polarization splitter.