JP4888143B2 - T-branch waveguide and array antenna - Google Patents

Description

  The present invention relates to a T-branch waveguide used for power distribution and synthesis in the microwave and millimeter wave bands, and an array antenna using the T-branch waveguide.

  An E-plane or H-plane T-branch waveguide is used for branching the waveguide for power distribution and synthesis. The E-plane T-branch waveguide is composed of a main waveguide and a branch waveguide having a rectangular cross section coupled to one E-plane of the main waveguide. The H-plane T-branch waveguide includes a main waveguide and a branch waveguide having a rectangular cross section coupled to one H-plane of the main waveguide. In any of the T-branch waveguides, reflection is large simply by connecting the waveguides. In general, impedance matching is performed at the coupling portion between the main waveguide and the branch waveguide in order to improve the reflection characteristics of the branch waveguide (see, for example, Patent Document 1 and Patent Document 2).

Japanese Patent Laid-Open No. 05-22006 (FIG. 1) Japanese Patent Laid-Open No. 05-160612 (FIGS. 5 and 6)

  Further, in order to change the distribution ratio of the H-plane T-branch waveguide, a method of changing the two branch waveguides to different heights before and after the connection portion between the main waveguide and the branch waveguide, A method of providing a matching iris around a connection port of a branching waveguide is known (see, for example, Patent Document 3).

Japanese Patent Laying-Open No. 2005-167879 (paragraph number 0002, FIG. 2)

  However, in the H-plane T-branch waveguide as in Patent Document 1, the configuration of the E-plane T-branch waveguide, the deterioration of reflection characteristics and phase characteristics are suppressed, and the distribution ratio of the E-plane T-branch waveguide is increased. No specific way to change is proposed. In the case of an H-plane T-branch waveguide, since the tube axis direction of the main waveguide and the tube axis direction of the branch waveguide are arranged on the same plane, when the electric wave to be fed is distributed in the horizontal plane from the vertical direction The arrangement space of the T-branch waveguide in the vertical direction becomes large.

  Further, in the branched waveguide as in Patent Document 2, since the bent-shaped side waveguide is provided at the branched portion, the size of the branched waveguide is increased at the bent portion, and the mounting space is restricted. . Further, since the branching direction of the branching waveguide is branched in the same direction as that of the main waveguide or in an acute angle with respect to the main waveguide, the branching direction is restricted. For this reason, it becomes difficult to install the branching waveguide in a limited space.

  Further, in the T-branch waveguide described in Patent Document 3 (paragraph number 0002), in order to make the height of the branch waveguide different, two branch waveguides having different heights from the main waveguide are used. However, there is a problem in that it is difficult to manufacture three different waveguides that intersect at one point and are coupled. In addition, in the other T-branch waveguide described in Patent Document 3 (FIG. 1), since a plurality of matching irises projecting into the waveguide are provided, the internal shape of the waveguide becomes complicated. There was a problem that it was difficult to manufacture. Patent Document 3 does not disclose a specific configuration for changing the distribution ratio in the E-plane T-branch waveguide.

  The present invention has been made to solve such a problem, and suppresses deterioration of reflection characteristics and phase characteristics, and is distributed unevenly from the main waveguide to the two branch waveguides. The object is to obtain a waveguide.

A T-branch waveguide according to the present invention includes a main waveguide, and a branch waveguide that is E-branched with a wide surface coupled to the rectangular cross section of the main waveguide,
The main waveguide is provided with a step on the wide surface so that the short side dimension of the waveguide in the coupling portion with the branching waveguide in the main waveguide is expanded.
The coupling portion of the branching waveguide with the main waveguide is provided with a conductive plate on the wide waveguide inner surface opposite to the wide surface to which the main waveguide is coupled. The central portion of the wide surface facing the wide surface of the wave tube is disposed at a position shifted from the tube axis of the main waveguide.

  In addition, an array antenna that includes a subarray antenna in which a plurality of antenna elements are arranged and distributes power to the subarray antenna may be configured using the T-branch waveguide.

  According to the present invention, it is possible to obtain an E-plane T-branch waveguide having good reflection characteristics and unequal distribution from the main waveguide to the two branching waveguides in equal phase.

Embodiment 1 FIG.
FIGS. 1A and 1B are views showing an example of a waveguide slot array antenna using a T-branch waveguide according to Embodiment 1 of the present invention, and FIG. FIG. 1 and FIG. 1B are rear views of the antenna. In FIG. 1B, a power supply circuit provided on the back surface of the antenna is illustrated, and a transmitter / receiver connected to the power supply circuit and a signal processor of the antenna are not illustrated.

  In the figure, the waveguide slot array antenna includes a radiation waveguide 2 provided with a plurality of radiation slots 1 and a waveguide feeding circuit 4 that feeds the radiation waveguide 2. The radiating slot 1 provided in each radiating waveguide 2 constitutes an antenna element in which a plurality of slots are arranged in a staggered manner in a one-dimensional direction. A plurality of the radiation waveguides 2 are arranged in parallel in a direction orthogonal to the arrangement direction of the radiation slots 1 to form a subarray (subarray antenna) 3. A plurality of subarrays 3 are arranged in a two-dimensional plane (up, down, left and right in the drawing) to constitute a slot array antenna.

  The radiating waveguide 2 and the waveguide feeding circuit 4 are each provided with an oblique slot 5 arranged in a one-dimensional direction. The radiating waveguide 2 and the waveguide feeding circuit 4 are connected to each other with their diagonal slots 5 attached to each other. Of course, the radiating waveguide 2 and the waveguide feeding circuit 4 are connected by penetrating a rectangular hole in either the radiating waveguide 2 or the waveguide feeding circuit 4 and providing an oblique slot 5 on the other. You may do it. Feeding to each sub-array 3 is performed by a waveguide feeding circuit 4, and excitation of the radiating waveguide 2 is performed via an oblique slot 5. The waveguide feeding circuit 4 is constituted by a T-branch waveguide.

  In general, since the number of radiation slots 1 for each subarray 3 is not constant, the E-plane T-branch needs to be unequal. In addition, even when the number of radiation slots 1 for each subarray 3 is the same, in order to provide an aperture distribution such as a tailor distribution, the T-branch waveguides 6 and 23 on the H plane need to be unequally distributed. In the example of FIGS. 1A and 1B, the E-plane T-branch waveguide surrounded by the broken line 7 is unevenly distributed. The E-plane T-branch waveguide 7 distributes electromagnetic waves input from a direction perpendicular to the antenna aperture plane (the direction of the drawing in the drawing) within a horizontal plane (up and down in the drawing). In the following description, only the E-plane T-branch waveguide 7 will be described in detail.

  FIG. 2 is a diagram showing a configuration of an unequal distribution type E-plane T-branch waveguide according to the first embodiment of the present invention. 2A is a perspective view, and FIG. 2B is a cross-sectional view taken along a plane horizontal to the electric field direction of the waveguide (a plane parallel to the narrow side of the short side of the waveguide rectangular cross section). FIG.

  In the figure, it is constituted by a main waveguide 11 having a rectangular cross section and a side waveguide 12 having a rectangular cross section coupled to one E surface of the main waveguide 11. The side waveguide 12 constitutes a branching waveguide. The main waveguide 11 has a first terminal 8 at one end and a connection terminal 20 at the other end. The side waveguide 12 has one end as the second terminal 9 and the other end as the third terminal 10, and a connection port 21 is provided on one E surface (a wide surface on the long side of the waveguide rectangular cross section). The first terminal 8 is an input port, and the second terminal 9 and the third terminal 10 are output ports. The connection terminal 20 of the main waveguide 11 is connected to the connection port 21 of the side waveguide 12. At this time, the main waveguide 11 and the side waveguide 12 are connected so that their central axes (tube axes) are orthogonal.

  An E-plane step 16 (first step) and an E-plane step 17 (second step) are provided around the connection port 21 of the side waveguide 12 (around the coupling portion). The E surface step 16 is arranged on the second terminal side of the side waveguide 12 so that the step surface forms a step on one E surface (wide surface) of the main waveguide 11. The E plane step 16 is provided so that the E plane dimension indicating the length of the short side of the waveguide in the main waveguide 11 is enlarged around the connection port 21. The E surface step 17 is arranged on the third terminal side of the side waveguide 12 so that the step surface forms a step on the other E surface (wide surface) of the main waveguide 11. The E plane step 16 is provided so that the E plane dimension indicating the length of the short side of the waveguide in the main waveguide 11 is enlarged around the connection port 21. That is, E surface steps 16 and 17 are arranged on the E surface opposite to each other in the main waveguide 11 so as to face each other. The E plane steps 16 and 17 are different from each other in the step width, that is, the height of the step in the direction of the short side of the waveguide with respect to the E plane of the main waveguide 11 (t1 and t2 in the figure). In the example shown in FIG. 2, the width t2 of the E-plane step 17 is larger than the width t1 of the E-plane step 16.

  Further, a metal block 18 is provided which is in contact with the tube wall of the side waveguide 12 and protrudes from the E surface of the side waveguide 12 on the side opposite to the E surface on the connection port 21 side, and constitutes a conductive plate. Yes. The block 18 is arranged at a position where the central portion thereof is shifted from the center line 15 (tube axis) of the main waveguide 11 by d toward the third output terminal 10 side. That is, the block 18 has an E surface direction (that is, an E surface step) of the main waveguide 10 in which the height of the step is lower at the center of the wide surface with respect to the tube axis (center line 15) of the main waveguide 10. 17 direction). In FIG. 2, there is a relationship of d = | d1-d2 | / 2.

Next, the operation will be described.
The millimeter wave or microwave band RF signal input from the first terminal 8 is distributed to the second terminal 9 and the third terminal 10 and output. As described above, in the T-branch waveguide shown in FIG. 2, the E plane step 17 on the third terminal 10 side is set to an appropriate width, and the E plane step 16 on the second terminal 9 side is set. The width t1 is made smaller than the width t2 of the E-plane step 17 on the third terminal 10 side by an appropriate size. This magnitude is set so as to strengthen the signal on the second terminal 9 side and weaken the signal on the third terminal 10 side. Further, the block 18 is arranged at a position shifted by an appropriate distance d on the third terminal 10 side from the center line (tube axis) 15 of the main waveguide 11. This distance d is set so that the output signals of the second terminal 9 and the third terminal 10 after distribution have substantially equiphase characteristics.

Thus, in order to prevent the passing phase difference from deviating from the ideal state when the E-plane step is installed asymmetrically at the junction of the E-plane T-branch waveguide, the block 18 is provided with the width of the step of the E-plane step. The phase of the signal distributed by the branching waveguide is adjusted by moving in the direction in which the signal is small. As a result, the T-branch waveguide of this embodiment has good reflection characteristics, and can obtain an E-plane T-branch waveguide that is equally distributed from the main waveguide to the two branch waveguides. it can. Since this E-plane T-branch waveguide can distribute the feed signal from the vertical direction to the horizontal plane, when feeding the waveguide slot array antenna from the vertical direction, Compared to the case of using, the arrangement space in the vertical direction (antenna thickness direction) of the feeder circuit can be reduced.

FIG. 3A is a diagram illustrating the reflection characteristics of the first terminal 8. In the figure, the horizontal axis represents frequency, and the vertical axis represents signal amplitude [dB].
The reflection characteristics of the embodiment are indicated by solid lines, and the reflection characteristics of the conventional example are indicated by broken lines. It can be seen that the reflection characteristics are greatly improved in the embodiment. The conventional example here is one in which the 16 E plane step, the 17 E plane step, and the block 10 are not provided in the E plane T branching waveguide.

  FIG. 3B shows an example of the frequency characteristic of the amplitude of the signal distributed from the first terminal 8 to the second terminal 9 and the third terminal 10. In the figure, the horizontal axis represents frequency, the vertical axis represents signal amplitude [dB], the amplitude of the second terminal 9 is port 2, and the amplitude of the third terminal 10 is port 3.

  In an ideal equal distribution, the signals of the second terminal 9 and the third terminal 10 are both -3 dB. However, in the T-branch waveguide according to the first embodiment, the signal at the second terminal 9 is large (about −2.6 [dB]), and the signal at the third terminal 10 is small (−3.5 [ dB]), and it can be seen that unequal distribution characteristics are obtained.

  Next, FIG. 3C shows the phase characteristics of the passing signals distributed from the first terminal 8 to the second terminal 9 and the third terminal 10, respectively. In the figure, the vertical axis represents the frequency, and the horizontal axis represents the passing phase difference. In an ideal E-plane T-branch, the passing phase difference between the output signal of the first terminal 8 and the output signal of the second terminal 9 is 180 °. Here, in order to explain the effect of the phase characteristic of the T-branch waveguide according to this embodiment, the phase characteristic when the block 18 is not moved is shown by a broken line in the figure as a comparative reference. As shown in the figure, when the block is not moved, a phase difference of about 4 ° is generated. On the other hand, by shifting this block to the port 3 side, it is understood that substantially equiphase characteristics are obtained. .

  In the above description, an example in which a T-branch waveguide is used as an unequal distributor for input signals has been described. However, a T-branch waveguide may be used as a synthesizer for unequal synthesis. In this case, needless to say, RF signals having different power amplitudes input to the second terminal 9 and the third terminal 10 are combined and output to the first terminal 8.

It is a figure which shows the structure of the waveguide slot array antenna by Embodiment 1 of this invention. It is a figure which shows the structure of the T branch waveguide by Embodiment 1 of this invention. It is a figure which shows the (a) reflection amplitude characteristic of T branching waveguide, and (b) passage amplitude characteristic, and (c) passage phase characteristic by Embodiment 1 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Radiation slot, 2 Radiation waveguide, 3 Subarray, 4 Waveguide feeding circuit, 5 Diagonal slot, 8 1st terminal, 9 2nd terminal, 10 3rd terminal, 11 Main waveguide, 12 Side conduction Wave tube (branch waveguide), 15 Main waveguide centerline (tube axis), 16 E-plane step, 17 E-plane step, 18 block (conductive plate).

Claims (4)

A main waveguide;
A broad waveguide coupled to the rectangular cross section of the main waveguide, and a branched waveguide that is E-branched,
Said main waveguide, as waveguide short side dimension of the connecting portion between the branch waveguide in the main waveguide expands, Rutotomoni step is provided on the wide surface, opposite broad surfaces of the main waveguide On the other hand, the height of the step differs between the step on the one wide surface opposite to the step on the other wide surface in the coupling portion with the branch waveguide ,
The coupling portion of the branching waveguide with the main waveguide is provided with a conductive plate on a wide surface in the waveguide opposite to the wide surface to which the main waveguide is coupled,
The conductive plate is disposed at a position where a central portion of the wide surface of the conductive plate facing the wide surface of the branching waveguide is shifted from the tube axis of the main waveguide.
A T-branch waveguide characterized by that.   The conductive plate is arranged such that a center portion of the wide surface is shifted toward the wide surface side of the main waveguide having a lower step height with respect to the tube axis of the main waveguide. The T-branch waveguide according to claim 1. A sub-array antenna in which a plurality of antenna elements are arranged,
An array antenna, wherein power is distributed to the sub-array antenna by the T-branch waveguide according to claim 1 or 2.   4. The array antenna according to claim 3, wherein the antenna element is a slot antenna.

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