JPS60160702A - Mode coupler - Google Patents

Abstract

PURPOSE:To provide an excellent coupling characteristic by providing a ridge in a main waveguide so as to make the cut-off frequency of the basic mode and the harmonic mode nearly coincident with each other thereby widening the frequency band. CONSTITUTION:A coupling hole 3 is provided to rectangular sub-waveguides 2 orthogonal to each other and a circular main waveguide 1 provided with ridges 5 on its inner face and orthogonal to the waveguides 2 and a terminal 1' feeding a wave having a frequency band higher than the frequency band detected by a mode coupler is provided. The ridges 5 are decided so that the cut-off frequency of them is coincident, the cut-off frequency of the TE11 mode being a tracking reference signal and also a communication signal and of the TE21* mode being a difference signal for antenna own tracking is almost coincident and then the coupling of both the modes to the sub-waveguide is maximized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to an improvement in a mode coupler used when a self-tracking function is required in an earth station antenna used for satellite communication.

[Description of prior art]

Conventionally, a so-called high-order mode monopulse self-tracking method has been widely used for antenna self-tracking because of its excellent tracking accuracy.

As is well known, in this method, among the circular guided higher-order modes, the detection level is zero when the antenna captures the target, but when the antenna misses the target, the guided wave generates a certain detection level inside the tube. By detecting something that has the property of excitation and driving the antenna so that the detection level of this higher-order mode signal is zero, the antenna can accurately capture the target. This is what I did.

The higher-order modes used here are preferably as low-order as possible, so circular waveguide TMOI mode, TE, oz mode, TE21 mode, and TE21'
mode is widely used. When the arriving wave is linearly polarized, it is necessary to use a plurality of these modes, but when the arriving wave is circularly polarized, it is sufficient to detect one of these higher-order modes. The electric field distributions of these modes are shown in FIG.

Conventionally, methods for detecting a desired higher-order mode include (1) a method using a multi-hole type higher-order mode coupler, (2) a method of simultaneously detecting a higher-order mode using a coupling hole common to the basic meter mode, is widely used. In the method described in item (1) above, in order to increase the detection sensitivity of higher-order mode signals without affecting the fundamental mode, a large number of coupling holes are connected at intervals determined by the frequency used and the shape of the waveguide. It has the disadvantage of being expensive as it requires opening in the direction of the tube axis. Furthermore, since the axial length becomes extremely long, there may be an inherent limit to the fact that it cannot be accommodated in the antenna, especially when used in a low frequency band. A conventional example of the method according to item (2) is shown in FIGS. 2 (fat, fb) and (C). In the figure, the wave arriving at the main waveguide 1 is reflected by the short-circuit surface 4 and is reflected by the coupling hole 3.
The light is guided to the sub-waveguide 2 via the auxiliary waveguide 2, and is separated into each mode via the synthesis circuit shown in the figure fc). At this time, for example, T E u
If the distance from the coupling hole 3 to the short-circuit surface 4 is selected so that the degree of coupling is maximized in the mode, the cut-off frequency and phase constant of the T E x1 mode and the higher-order modes are different in the main waveguide, The disadvantage was that the binding of At the same time, there was also the drawback that the frequency band of the degree of coupling in the TE11 mode became narrow.

[Purpose of the invention]

The present invention solves the above-mentioned drawbacks, and solves the above-mentioned (second)
), mode coupling has a wide frequency band and good coupling characteristics so that the cutoff frequencies of the fundamental mode and higher-order modes are almost the same in the main waveguide. The purpose is to provide equipment.

[Features of the invention]

The present invention provides a ridge within the main waveguide.

That is, the present invention provides a main waveguide made of a circular waveguide or a circular Taber waveguide, and a main waveguide formed around the main waveguide through four coupling holes provided in the circumferential direction of the main waveguide. It is composed of four attached sub-waveguides and a hybrid synthesis circuit for synthesizing the sub-waveguides, and the output of the synthesis circuit is directed in the direction of the incoming circularly polarized wave. TE21, which is a difference signal for antenna self-tracking of
*It has a terminal for detecting the mode and a terminal for detecting the T E 11 mode, which is a tracking reference signal as well as a communication signal, and by providing a ridge in the main wave tube, the T E 11 mode and the TE21 mode can be detected. The cut-off frequencies of the two are almost the same.

” The two characteristics are based on the following background.

A waveguide loaded with S.7 diodes, for example, a rectangular waveguide with narrower spacing at the center of the H plane to concentrate the electric field distribution at the center, will lower the cutoff frequency of the rectangular fundamental T E 1o mode wave. It is known that the cut-off frequency of rectangular TE20 and TE30 modes can be simultaneously increased.

For this reason, Fuji waveguides are used for the purpose of expanding the usable band of waveguides. It is also used to widen the bandwidth of pyramidal horn antennas and conical horn antennas.

FIG. 3 shows an example of changes in the cutoff frequency of each mode when a ridge is loaded in a circular waveguide. In the same figure, the horizontal axis is normalized by the radius a of the circular waveguide or shows the height h of the Fuji, and the vertical axis is normalized by the cutoff frequency f co of the circular T E 1x mode when there is no Fuji or loaded with Fuji. The cutoff frequency fc of each mode is shown in the case of FIG. The value of the ridge width W normalized by the waveguide radius a is 0.3 in the figure.

As can be seen from the figure, the cutoff frequency of the TE21 mode decreases as the ridge height h increases, as does the TE11 mode, and matches that of the T E u mode at point A in the figure. Therefore, by loading a circular waveguide with a shape near point A, the cutoff frequencies of the T E u mode and the T E 21'' mode can be made almost the same.

[Explanation based on examples]

Embodiments of the present invention will be described below with reference to the attached FIGS. 4 and 5.

Figure 4 (Circular main wave tube 1 with aluminum beam 5 provided on the inner surface)
Coupling holes 3 are provided between the rectangular sub-waveguides 2 and 2, which are orthogonal to each other, and terminals 1' for feeding power in a frequency band higher than the frequency band detected by this mode coupler are provided. Figure 4(b) is a BB arrow view of fa1 diagram, fC
Figure 1 is a BB cross-sectional view. The ridge 5 is A in FIG. 3 above.
It is determined to satisfy the condition indicated by the dot, that is, the cutoff frequencies match. As a result, the cutoff frequencies of the T E 11 and TE21 modes are almost the same, and the coupling of both modes to the sub waveguide 2 can be maximized.

The signal detected by the sub-waveguide 2 is separated into each mode by the combining circuit shown in FIG. 2 (C1).

FIG. 5 shows a case where the main waveguide is a circular tapered waveguide. In this case, the inner diameter changes in accordance with the change in the axial direction, but the shape of the ridge 5 must be changed in accordance with the inner diameter at the rear of the coupling hole (3) so as to maintain the condition at point A in FIG. 3.

In this case, as in the case of FIG. 4, the signal detected by the width waveguide 2 is separated into each mode by the combining circuit shown in FIG. 2 (C1).

Note that in FIGS. 4 and 5, the terminal 1' is used to feed power to a frequency band higher than fl, for example, f2, which is detected by the present mode coupler, but in this case, f2 is supplied to the sub waveguide 2. A filter or the like having a characteristic of blocking f is provided, and f
2, it is necessary to make the coupling hole equal to the short circuit surface.

Furthermore, the reason why both ends of the ridge 5 are tapered in both FIGS. 4 and 5 is to prevent deterioration of the VSWR characteristic of the wave passing through the main waveguide 1 due to loading of the ridge 5.

〔Effect of the invention〕

As explained above, if the ridge waveguide is used as the main waveguide of the TE21 high-order mode monopulse antenna self-tracking method, the cutoff frequencies of the TE11 mode and the TE21'' mode will almost match, and the phase of both modes will be As a result, the short-circuit surface where the coupling of the T E 1! mode is maximum is equal to the short-circuit surface where the coupling of the TE21 mode is maximum, and the frequency band of the mode coupler can be expanded and the This has a remarkable effect on improving the degree of next mode coupling.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the electric field distribution of each mode used in the high-order mode monopulse antenna self-tracking method. FIG. 2 is a diagram showing a conventional mode coupler. (Al is an external view, (BL is a vertical cross-sectional view, (C1 is a block diagram of a composite circuit. Radius of waveguide, fco...
Cutoff frequency of TE11 mode when no ridge is loaded, fc...cutoff frequency, h...ridge height, W...ridge width, A...T E u mode and T
The point where the cutoff frequency of E2 mode matches. FIG. 4 is a diagram showing an embodiment of the present invention in which the main waveguide is a circular waveguide. ta+ is an external view, (bl is an external view in the BB direction, and (C) is a BB sectional view. Figure 5 shows an embodiment of the present invention, in which the main waveguide is a circular tapered waveguide. Figure. 1... Main wave tube, 1'... Terminal that feeds a frequency band higher than the frequency band detected by this mode coupler, 2...
Sub-waveguide, 3... Coupling hole, 4... Short circuit surface, 5...
Ridge, 6... Hybrid, 7... 90" phase shifter, 8... Non-disjunctive terminator, 9... TEu mode right-handed circularly polarized wave output terminal, 10... T E 1x mode One drive left-handed circularly eccentric output terminal, 11...TE12 Mode output terminal. Patent applicant: NEC Corporation Representative, Patent attorney: Naotaka Ide (a) TE++ mode (b) TMo+ mode (C) T
E2+ mode (d) TE21″+-do Ryo 1 Figure M2 (b) Right 2 figure (C) Oj O, 20, 3Q, 4 o, sh/a 33 Figure claw 4 Mouth (a) Figure 4 ( b) Atsushi Figure 4 (C) Figure 5

Claims (1)

[Scope of claims] four width waveguides attached to the width waveguide, and a synthesis circuit consisting of a hybrid for synthesizing the width waveguides, and further, a terminal for detecting the T E 2-mode at the output of the synthesis circuit. and a terminal for detecting the T E u mode, in the mode coupler, the main waveguide is configured to substantially match the cut-off frequency of the T E 'u mode and the cut-off frequency of the T E 2-mode. A mode coupler characterized in that it is configured with a ridge.