Waveguide connection structure, determination method thereof, manufacturing method thereof, and waveguide switch using same

Provided is a waveguide connection structure 1 in which two waveguides 10 and 20 respectively formed with waveguide paths 11 and 21 face each other, in which a choke groove 25 having a depth corresponding to a leakage prevention target frequency is provided, at the end face 20a of the waveguide 20, in a band-shaped region whose center is a center of the waveguide path 21, and which is bounded by an inner ellipse and an outer ellipse, the minor radius of the outer ellipse is longer than the minor radius of the inner ellipse by a length corresponding, and the choke groove 25 includes two groove portions 25a and 25b that are in contact with the inner ellipse and the outer ellipse and are located on the longer side of the rectangle, in the band-shaped region.

TECHNICAL FIELD

The present invention relates to a waveguide connection structure, a determination method thereof, a manufacturing method thereof, and a waveguide switch using the same.

BACKGROUND ART

In order to cope with mobile traffic, which is expected to further increase in the future, there is a strong demand for the use of millimeter wave and terahertz wave bands for wireless communication, which are capable of achieving transmission speeds on the order of several tens of Gbps, and for example, the use of 252 to 325 GHz is considered in IEEE802.15.3d.

For example, a rectangular waveguide with inner dimensions of 0.864 mm×0.432 mm is used as a propagation path for propagating electromagnetic waves in the WR-3 band (220 to 325 GHZ). As a choke flange for coupling such rectangular waveguides, a choke flange having a structure in which a rectangular choke groove is formed in order to prevent leakage of electromagnetic waves from the waveguide opening is known (for example, See Patent Document 1).

FIG.13shows a waveguide connection structure in the related art in which a waveguide90for the WR-3 band having rectangular choke grooves92-1to92-3formed around the opening of the waveguide path91on the flange surface is coupled with a waveguide80with a flat flange surface with a predetermined gap g.

FIG.14is an enlarged view of the triple choke grooves92-1to92-3shown inFIG.13. The choke grooves92-1to92-3are rectangular frame-shaped continuous grooves each having a predetermined width and a predetermined depth, and are provided concentrically with respect to the center position of the opening of the waveguide path91. The depth of each of the choke grooves92-1to92-3and a distance from the end of the opening of the waveguide path91to the inner side of the nearest choke groove92-1are each set to λg/4, where λg is the guide wavelength.

RELATED ART DOCUMENT

Patent Document

DISCLOSURE OF THE INVENTION

Problem that the Invention is to Solve

FIG.15Ais a perspective view showing a waveguide connection structure in the related art in which two rectangular waveguides80′ and90′ without choke grooves formed therein face each other in parallel with a predetermined gap g. A waveguide path81′ is formed in the waveguide80′, and a waveguide path91′ is formed in the waveguide90′. The waveguides80′ and90′ correspond to WR-3 waveguides having the WR-3 band as the transmission band.

FIG.15Bshows a simulation result of the in-plane electric field distribution when the operating frequency is 280 GHz and the gap g is 300 μm, in the structure ofFIG.15A. InFIG.15B, a rectangle indicating the position of the waveguide path91′ and an ellipse and a circle indicating the position of the equiphase surface (wave front) of the electromagnetic wave are superimposed on the image of the simulation result.

According to the simulation result ofFIG.15B, the equiphase surface of the electromagnetic wave emitted from the waveguide path91′ and leaking into the void in the gap g is substantially circular (for example, wf1in the figure) at a position away from the center of the waveguide path91′ by one wavelength or more, but has a shape close to an ellipse (for example, wf2in the figure) at a position near the center of the waveguide path91′. Further, it can be seen that the electric field of the electromagnetic wave leaking into the void in the gap g spreads like a fan, and is strongest in the direction perpendicular to the longer side of the opening of the rectangle of the waveguide path91′.

However, in the choke flange in the related art as shown inFIGS.13and14, the shapes of the choke grooves92-1to92-3do not correspond to the electric field that spreads like a fan, so that there is a problem that the leakage of electromagnetic waves cannot be suppressed within a practically allowable range due to the existence of such an unnecessary resonance mode, in the WR-3 band. The unnecessary resonance mode in this choke flange is such that the electromagnetic waves reflected by the straight choke grooves92-1to92-3interfere with each other between the waveguide path91′ and the choke grooves92-1to92-3, without canceling out the waves incident on the choke grooves92-1to92-3.

The present invention has been made in order to solve such problems in the related art, and an object of the present invention is to provide a waveguide connection structure, a determination method thereof, a manufacturing method thereof, and a waveguide switch using the same which are capable of effectively suppressing the leakage of electromagnetic waves from a connection point of two facing waveguides.

Means for Solving the Problem

In order to solve the above-described problems, a waveguide connection structure according to the present invention is a waveguide connection structure including two waveguides having end faces each of which is formed with at least one waveguide path, the end faces face each other in parallel with a predetermined gap, in which a choke groove having a depth corresponding to ¼ of a guide wavelength corresponding to a leakage prevention target frequency is provided at the end face of at least one of the two waveguides, in a band-shaped region surrounding an opening of a rectangle of the at least one waveguide path, the band-shaped region is a region whose center is a center of the rectangle, and which is bounded by an inner ellipse and an outer ellipse whose major axis direction is parallel to a longer side of the rectangle, a minor radius of the inner ellipse corresponds to ¼ of the guide wavelength, a minor radius of the outer ellipse is longer than the minor radius of the inner ellipse by a length corresponding to ¼ of the guide wavelength, and the choke groove includes two groove portions that are in contact with the inner ellipse and the outer ellipse and are located on the longer side of the rectangle, in the band-shaped region.

In other words, the waveguide connection structure according to the present invention is a structure in which a choke groove of a shape that covers a region having a strong electric field of an electromagnetic wave leaking into a predetermined gap between two waveguides is formed on the end face of at least one of the two waveguides. With this configuration, the waveguide connection structure according to the present embodiment can effectively suppress the leakage of electromagnetic waves from a connection point of two facing waveguides.

Further, in the connection structure according to the present invention, the choke groove further includes two groove portions that are in contact with the inner ellipse and the outer ellipse and are located on the shorter side of the rectangle, in the band-shaped region, and the four groove portions may be separated from each other by four non-groove portions along the diagonal direction of the rectangle within the band-shaped region.

With this configuration, the waveguide connection structure according to the present invention can suppress the leakage of electromagnetic waves to less than-25 dB, over the entire operating frequency range of a WR-3 waveguide (fractional bandwidth of about 40%), for example, with respect to a predetermined gap up to about 1/10 wavelength of the guide wavelength.

Further, a determination method of a waveguide connection structure according to the present invention is a determination method of a waveguide connection structure in which end faces of two waveguides respectively formed with at least one waveguide path face each other in parallel with a predetermined gap, a choke groove having a depth corresponding to ¼ of a guide wavelength corresponding to a leakage prevention target frequency is provided at the end face of at least one of the two waveguides, in a band-shaped region surrounding an opening of a rectangle of the at least one waveguide path, the band-shaped region is a region whose center is a center of the rectangle, and which is bounded by an inner ellipse and an outer ellipse whose major axis direction is parallel to a longer side of the rectangle, a minor radius of the inner ellipse corresponds to ¼ of the guide wavelength, a minor radius of the outer ellipse is longer than the minor radius of the inner ellipse by a length corresponding to ¼ of the guide wavelength, and the choke groove includes two groove portions that are in contact with the inner ellipse and the outer ellipse and are located on the longer side of the rectangle, in the band-shaped region, the determination method including: an electromagnetic field analysis step of, by using, as an analysis model, an analysis waveguide connection structure in which end faces of two analysis waveguides, which respectively have waveguide paths of the same shape as the waveguide paths and are not formed with choke grooves, face each other in parallel with a predetermined gap, when an electromagnetic wave of the leakage prevention target frequency propagates from one to the other of the two analysis waveguides which are not formed with the choke grooves, acquiring a shape of an equiphase surface of electromagnetic waves leaking from the predetermined gap by electromagnetic field analysis; an ellipse shape acquisition step of acquiring a minor radius and a major radius of an equiphase surface separated by a distance corresponding to ¼ of the guide wavelength in a direction perpendicular to the longer side of the rectangle from the center of the rectangle, among the equiphase surfaces acquired in the electromagnetic field analysis step; an inner ellipse shape determination step of determining the minor radius and the major radius of the equiphase surface acquired in the ellipse shape acquisition step as the minor radius and a major radius of the inner ellipse; and an outer ellipse shape determination step of determining values obtained by respectively adding a distance corresponding to ¼ of the guide wavelength to the minor radius and the major radius of the inner ellipse determined in the inner ellipse shape determination step as the minor radius and a major radius of the outer ellipse.

With this configuration, in the determination method of a waveguide connection structure according to the present invention, the shape of the equiphase surface of the electromagnetic waves of the leakage prevention target frequency propagating from one to the other of the two analysis waveguides is acquired by electromagnetic field analysis, so that it is possible to determine the range of the band-shaped region R on the end face of at least one of the two waveguides.

Further, a manufacturing waveguide connection structure according to the present invention is a manufacturing method of a waveguide connection structure in which end faces of two waveguides respectively formed with at least one waveguide path face each other in parallel with a predetermined gap, a choke groove having a depth corresponding to ¼ of a guide wavelength corresponding to a leakage prevention target frequency is provided at the end face of at least one of the two waveguides, in a band-shaped region surrounding an opening of a rectangle of the at least one waveguide path, the band-shaped region is a region whose center is a center of the rectangle, and which is bounded by an inner ellipse and an outer ellipse whose major axis direction is parallel to a longer side of the rectangle, a minor radius of the inner ellipse corresponds to ¼ of the guide wavelength, a minor radius of the outer ellipse is longer than the minor radius of the inner ellipse by a length corresponding to ¼ of the guide wavelength, and the choke groove includes two groove portions that are in contact with the inner ellipse and the outer ellipse and are located on the longer side of the rectangle, in the band-shaped region, the manufacturing method including: an electromagnetic field analysis step of, by using, as an analysis model, an analysis waveguide connection structure in which end faces of two analysis waveguides, which respectively have waveguide paths of the same shape as the waveguide paths and are not formed with choke grooves, face each other in parallel with a predetermined gap, when an electromagnetic wave of the leakage prevention target frequency propagates from one to the other of the two analysis waveguides which are not formed with the choke grooves, acquiring a shape of an equiphase surface of electromagnetic waves leaking from the predetermined gap by electromagnetic field analysis; an ellipse shape acquisition step of acquiring a minor radius and a major radius of an equiphase surface separated by a distance corresponding to ¼ of the guide wavelength in a direction perpendicular to the longer side of the rectangle from the center of the rectangle, among the equiphase surfaces acquired in the electromagnetic field analysis step; an inner ellipse shape determination step of determining the minor radius and the major radius of the equiphase surface acquired in the ellipse shape acquisition step as the minor radius and a major radius of the inner ellipse; an outer ellipse shape determination step of determining values obtained by respectively adding a distance corresponding to ¼ of the guide wavelength to the minor radius and the major radius of the inner ellipse determined in the inner ellipse shape determination step as the minor radius and a major radius of the outer ellipse; a choke groove formation step of forming the choke groove in the band-shaped region defined by the minor radii and the major radii of the inner ellipse and the outer ellipse determined in the inner ellipse shape determination step and the outer ellipse shape determination step; and a waveguide arrangement step of arranging the two waveguides such that the end faces of the two waveguides face each other in parallel with the predetermined gap.

That is, in the manufacturing method of the waveguide connection structure according to the present embodiment, the choke groove is formed in the band-shaped region of the end face of at least one of the two waveguides determined by the above determination method, and the two waveguides are disposed such that the end faces of the two waveguides face each other in parallel with the predetermined gap therebetween. With this configuration, the manufacturing method of a waveguide connection structure according to the present embodiment can manufacture the waveguide connection structure capable of effectively suppressing the leakage of electromagnetic waves from a connection point of two facing waveguides.

Further, a waveguide switch according to the present invention includes a base portion; a first fixed waveguide block which is fixed to the base portion, and in which at least one waveguide path surrounded by a metal wall is formed so as to penetrate from a first end face to a second end face; a second fixed waveguide block which is fixed to the base portion and has a third end face parallel to the second end face of the first fixed waveguide block, and in which at least one waveguide path surrounded by a metal wall is formed so as to penetrate from the third end face to a fourth end face; a movable waveguide block which has a fifth end face facing the second end face of the first fixed waveguide block with a predetermined gap in parallel and a sixth end face facing the third end face of the second fixed waveguide block with a predetermined gap in parallel, in which a plurality of waveguide paths surrounded by metal walls are formed penetrating from the fifth end face to the sixth end face, and which is supported by the base portion so as to be slidable parallel to the second end face of the first fixed waveguide block and the third end face of the second fixed waveguide block; and a driving device that is provided on the base portion and slides the movable waveguide block, in which the movable waveguide block is slid with respect to the first fixed waveguide block and the second fixed waveguide block, and any one of the plurality of waveguide paths of the movable waveguide block is selectively connected to between any one of the at least one waveguide path of the first fixed waveguide block and any one of the at least one waveguide path of the second fixed waveguide block, in different plurality of positions, a choke groove having a depth corresponding to ¼ of a guide wavelength corresponding to a leakage prevention target frequency is provided, in a band-shaped region surrounding at least one opening among an opening of the at least one waveguide path on a second end face side of the first fixed waveguide block, an opening of the at least one waveguide path on a third end face side of the second fixed waveguide block, and openings of the plurality of waveguide paths on a fifth end face side and a sixth end face side of the movable waveguide block, and the band-shaped region is a region whose center is a center of a rectangle, and which is bounded by an inner ellipse and an outer ellipse whose major axis direction is parallel to a longer side of the rectangle, a minor radius of the inner ellipse corresponds to ¼ of the guide wavelength, a minor radius of the outer ellipse is longer than the minor radius of the inner ellipse by a length corresponding to ¼ of the guide wavelength, and the choke groove includes two groove portions that are in contact with the inner ellipse and the outer ellipse and are located on the longer side of the rectangle, in the band-shaped region.

With this configuration, the waveguide switch according to the present invention uses the above-described waveguide connection structure for the movable portion (movable waveguide block), thereby improving the return loss and insertion loss of the switch over a wide band, and can suppress the unintended leakage of electromagnetic waves in the gap between the first fixed waveguide block and the movable waveguide block and the gap between the second fixed waveguide block and the movable waveguide block.

Further, the waveguide switch according to the present invention uses the above-described waveguide connection structure for the movable waveguide block, so that the gap between the first fixed waveguide block and the movable waveguide block and the gap between the second fixed waveguide block and the movable waveguide block can be made wider than before, and the machining accuracy is relaxed and the resistance to aging is improved.

Advantage of the Invention

The present invention provides a waveguide connection structure, a determination method thereof, a manufacturing method thereof, and a waveguide switch using the same which are capable of effectively suppressing the leakage of electromagnetic waves from a connection point of two facing waveguides.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of a waveguide connection structure, a determination method thereof, a manufacturing method thereof, and a waveguide switch using the same according to the present invention will be described below with reference to the drawings.

As shown inFIG.1, the waveguide connection structure1of the present embodiment has a structure in which end faces10band20aof two waveguides10and20face each other in parallel with a predetermined gap g. A waveguide path11is formed in the waveguide10, and a waveguide path21is formed in the waveguide20. For example, the waveguides10and20have inner dimensions of 0.864 mm×0.432 mm, and correspond to WR-3 waveguides having the transmission band of the WR-3 band (220 to 325 GHZ). A plurality of waveguide paths may be formed in the waveguides10and20, like the first fixed waveguide block40and the movable waveguide block60which will be described later.

In either one or both of the end face10bof the waveguide10and the end face20aof the waveguide20, in the band-shaped region R surrounding the opening of the rectangle of the waveguide path21, a choke groove25is provided to prevent leakage of electromagnetic waves from the gap g between the end faces10band20a. The choke groove25provided in the end face20aof the waveguide20will be mainly described later. The band-shaped region R is a region bounded by an inner ellipse e1and an outer ellipse e2whose major axis direction is parallel to the longer side of the opening of the rectangle of the waveguide path21, as indicated by oblique lines inFIG.2. The centers of the inner ellipse e1and the outer ellipse e2are equal to the center of the opening of the rectangle of the waveguide path21.

The inner wall surfaces of the groove portions25ato25dforming the choke groove25are perpendicular to the end face20a. Further, the depth of the groove portions25ato25dcorresponds to ¼ of the guide wavelength λg corresponding to the leakage prevention target frequency. In the present embodiment, the leakage prevention target frequency is 272.5 GHZ, which is the center frequency of the WR-3 band (220 to 325 GHZ). In this case, the guide wavelength λg is approximately 1.43 mm. Here, the depth corresponding to ¼ of the guide wavelength λg refers to a depth within a range of ±20% of ¼ of the guide wavelength λg. In addition, the leakage prevention target frequency is not limited to the above values, and may be any frequency within the WR-3 band or other desired frequency band according to the sizes of the waveguide10and the waveguide20.

The minor radius rs1of the inner ellipse e1has a length corresponding to ¼ of the guide wavelength λg. The minor radius rs2of the outer ellipse e2is longer than the minor radius rs1of the inner ellipse e1by a length corresponding to ¼ of the guide wavelength λg. Here, the length corresponding to ¼ of the guide wavelength λg refers to a length within a range of ±20% of ¼ of the guide wavelength λg.

FIGS.3A to3Care diagrams showing an arrangement example of the choke grooves25formed in the band-shaped region R. In terms of geometrical optics, when a curved mirror along the equiphase surface of an electromagnetic wave is placed on the propagation path of the electromagnetic wave, the reflected wave of the electromagnetic wave reflected by the curved mirror traces the traveling direction of the incident wave of the electromagnetic wave incident on the curved mirror in the opposite direction. Therefore, when an elliptical curved mirror (choke groove25) along the equiphase surface of the radiation wave that leaks from the waveguide path21into the void and does not directly enter the waveguide path11is formed at a position where the phase shift is π/2 (¼ wavelength) from the center of the opening of the waveguide path21, the reflected wave of the radiation wave at the choke groove25becomes opposite in phase to the incident wave of the radiation wave and the waves cancel out each other. In other words, it is estimated that the choke groove25can suppress unnecessary radiation waves.

FIG.3Ashows an example in which the choke groove25includes two groove portions25aand25b. The two groove portions25aand25bare in contact with the inner ellipse e1and the outer ellipse e2in the band-shaped region R, and are located on the longer side of the opening of the rectangle of the waveguide path21. These two groove portions25aand25bare separated from each other in the band-shaped region R by two non-groove portions26aand26blocated on the shorter sides of the opening of the rectangle of the waveguide path21. That is, the choke groove25shown inFIG.3Ahas a shape that covers the region having a strong electric field that spreads like a fan, as shown in the simulation result ofFIG.15B. Compared with the structures shown inFIGS.3B and3C, the structure shown inFIG.3Arequires less area for the choke groove25, so that the manufacturing cost and the number of man-hours can be reduced.

FIG.3Bshows an example in which the choke groove25includes four groove portions25a,25b,25c, and25d. This is equivalent to the configuration of choke groove25shown inFIG.1. Similar to that shown inFIG.3A, the two groove portions25aand25bare in contact with the inner ellipse e1and the outer ellipse e2in the band-shaped region R, and are located on the longer sides of the opening of the rectangle of the waveguide path21. Further, the two groove portions25cand25dare in contact with the inner ellipse e1and the outer ellipse e2in the band-shaped region R, and are located on the shorter side of the opening of the rectangle of the waveguide path21. These four groove portions25ato25dare separated from each other in the band-shaped region R by four non-groove portions27a,27b,27c, and27dalong the diagonal direction of the opening of the rectangle of the waveguide path21.

FIG.3Cshows an example in which the choke groove25is formed in the entire band-shaped region R. In the configuration in which the choke groove25is formed in the entire band-shaped region R, compared with the configuration ofFIG.3A or3Bin which the choke groove25is formed only in a part of the band-shaped region R, better frequency characteristics (return loss S11and insertion loss S21) can be obtained in a narrower frequency range.

The upper part ofFIG.4shows an example of the dimensions of the choke groove25shown inFIG.3B. The lower part ofFIG.4shows a cross section including the centers of the openings of the waveguide paths11and21of the waveguide connection structure1.

The minor radius rs1of the inner ellipse e1is 0.4 mm, and is a distance corresponding to ¼ of the guide wavelength λg of the WR-3 band. The major radius of the inner ellipse e1is 0.6 mm. The minor radius rs2of the outer ellipse e2is 0.76 (=0.4+λg/4) mm. The major radius of the outer ellipse e2is 0.96 (=0.6+λg/4) mm. The angles formed by the extending directions of the four non-groove portions27a,27b,27c, and27dwith respect to the major radii of the inner ellipse e1and the outer ellipse e2are all 26.5°. The width of the four non-groove portions27a,27b,27c, and27dis 0.1 mm. Each of the four groove portions25ato25dhas a depth of 0.36 (=λg/4) mm. A gap g between the end faces10band20ais 0.1 mm.

FIGS.5A and5Bshow simulation results of the return loss S11and the insertion loss S21between the waveguide paths11and21in the structure ofFIG.4.FIG.5Bis an enlarging graph of the vicinity of 0 dB inFIG.5A. In this simulation, it is assumed that an electromagnetic wave is incident from the waveguide10on the port P1side shown inFIG.4Btoward the waveguide20on the port P2side.

As shown inFIG.5A, the frequency range in which the return loss S11is less than −15 dB is 200.0 to 336.4 GHZ, and it is confirmed that the return loss S11is suppressed to less than −15 dB over a wide frequency range including the WR-3 band (220 to 325 GHz, fractional bandwidth of about 40%). Further, as shown inFIG.5B, it is confirmed that the insertion loss S21shows a good value (close to 0 dB) higher than −0.5 dB over the WR-3 band. Further, as shown inFIG.5C, it is confirmed that the leakage of electromagnetic waves from between the waveguide paths11and21in the structure ofFIG.4is suppressed to less than −25 dB over the WR-3 band.

Even when the port P1side is the waveguide20and the port P2side is the waveguide10, the return loss S11and the insertion loss S21between the waveguide paths11and21do not change.

In the above simulation, the gap g between the end faces10band20ais assumed to be 0.1 mm, but it has been confirmed that the return loss S11in the frequency range including the WR-3 band can be suppressed to less than-15 dB, even with a gap g of 0.15 mm, which corresponds to about 1/10 wavelength of the guide wavelength λg (=1.43 mm) at 272.5 GHZ, which is the center frequency of the WR-3 band.

FIGS.6A and6Bshow simulation results of the return loss S11and the insertion loss S21between the waveguide paths11and21, in a structure in which similar choke grooves are provided not only on the end face20aof the waveguide20but also on the end face10bof the waveguide10. For comparison,FIGS.6A and6Bshow the return loss S11and the insertion loss S21in a structure in which the choke groove25is provided only on the end face20aof the waveguide20, with broken lines.

Compared to the configuration in which the choke groove is provided only on the end face20aof the waveguide20, in the configuration in which the choke grooves are provided both on the end face10bof the waveguide10and the end face20aof the waveguide20, it is confirmed that in a wider frequency range, the return loss S11can be suppressed to less than −15 dB, and the insertion loss S21exhibits good values higher than −0.5 dB.

Hereinafter, an example of a determination method of a waveguide connection structure (steps S1to S4below) and a manufacturing method (steps S1to S6below) will be described with reference toFIG.7. The determination method of the present embodiment is executed by a control device such as a microcomputer or a personal computer including a CPU, a ROM, a RAM, a HDD, and the like.

First, by using, as an analysis model, an analysis waveguide connection structure in which the end faces of two analysis waveguides, which respectively have waveguide paths of the same shape as the waveguide paths11and21of the two waveguides10and20and are not formed with choke grooves, face each other in parallel with a predetermined gap g, when an electromagnetic wave of a leakage prevention target frequency propagates from one to the other of the two analysis waveguides which are not formed with the choke grooves, the shapes of equiphase surfaces of the electromagnetic wave leaking from the predetermined gap g are acquired by electromagnetic field analysis (electromagnetic field analysis step S1). For example, the two analysis waveguides correspond to waveguides80′ and90′ shown inFIG.15A. In the following description, the waveguide90′ is the waveguide20before the choke groove is formed, and the waveguide path91′ has the same shape as the waveguide path21.

Next, the minor radius and the major radius of an equiphase surface separated by a distance corresponding to ¼ of the guide wavelength λg in the direction perpendicular to the longer side of the rectangle from the center of the opening of the rectangle of the waveguide path91′ of the waveguide90′, among the equiphase surfaces acquired in the electromagnetic field analysis step S1are acquired (ellipse shape acquisition step S2).

Next, the minor radius and the major radius of the equiphase surface acquired in the ellipse shape acquisition step S2are determined as the minor radius and the major radius of the inner ellipse e1(inner ellipse shape determination step S3).

Next, values obtained by respectively adding a distance corresponding to ¼ of the guide wavelength λg to the minor radius and the major radius of the inner ellipse e1determined in the inner ellipse shape determination step S3are determined as the minor radius and the major radius of the outer ellipse e2(outer ellipse shape determination step S4).

Next, the waveguide20is completed by forming the choke groove25in the band-shaped region R of the waveguide90′ defined by the minor radii and the major radii of the inner ellipse e1and the outer ellipse e2determined in the inner ellipse shape determination step S3and the outer ellipse shape determination step S4(choke groove formation step S5).

Next, the two waveguides10and20are arranged such that the end face10bof the waveguide10and the end face20aof the waveguide20face each other in parallel with a predetermined gap g (waveguide arrangement step S6). This completes the waveguide connection structure.

The configuration of a waveguide switch100including the waveguide connection structure1according to the embodiment of the present invention will be described below. In general, a gap is required around a moving unit such as a waveguide switch, but there is a lower limit to the size of the allowable gap due to restrictions on machining accuracy. Further, the gap may be widened due to abrasion of the sliding unit of the mechanism that supports the moving unit. As the operating frequency (the shorter the wavelength) increases, the gap of the same size becomes substantially wider with respect to the wavelength, so that leakage of electromagnetic waves increases. The waveguide switch100of the present embodiment suppresses leakage of electromagnetic waves in such gaps around the moving unit.

FIG.8is an exploded perspective view,FIG.9is a side view, andFIG.10is a plan view of the waveguide switch100including the waveguide connection structure1according to the embodiment of the invention. In addition, in these figures, orthogonal axes of X, Y, and Z are shown such that the direction of each part can be easily understood.

As shown inFIGS.8to10, the waveguide switch100includes a base portion31, a first fixed waveguide block40, a second fixed waveguide block50, a movable waveguide block60, and a driving device70. The first fixed waveguide block40, the second fixed waveguide block50, and the movable waveguide block60correspond to the waveguide10or the waveguide20having the WR-3 band shown inFIG.1or the like as a transmission band.

The base portion31is formed in a plate shape having a rectangular outer shape, the first fixed waveguide block40is fixed to one end side of the upper surface31aof the base portion31, and the second fixed waveguide block50is fixed to the other end side.

The first fixed waveguide block40is formed in a rectangular parallelepiped shape, and at least one (three in this example) waveguide paths41,42, and43having a predetermined diameter surrounded by metal walls are formed so as to penetrate from the first end face40ato the second end face40bon the opposite side. Here, the waveguide paths41to43are formed at the same height from the upper surface31aof the base portion31, in a direction perpendicular to the first end face40aand the second end face40b, in parallel with each other with a predetermined gap.

The diameters and heights of these waveguide paths41to43are the same as the waveguide path51of the second fixed waveguide block50, which will be described later. The waveguide path42is formed on a line passing through the center of the waveguide path51. The other two waveguide paths41and43are disposed such that the extension line passing through the center position of their openings sandwiches the extension line passing through the center position of the opening of the waveguide path51symmetrically.

On the other hand, the second fixed waveguide block50is formed in a rectangular parallelepiped shape having the same outer shape as the first fixed waveguide block40, is fixed to the base portion31in a state of facing the third end face50ain parallel with a predetermined distance therebetween, in the second end face40bof the first fixed waveguide block40, and at least one (one in this example) waveguide path51surrounded by a metal wall is formed so as to penetrate from the third end face50ato the fourth end face50bon the opposite side. The diameter and height of this waveguide path51are the same as those of the waveguide paths41to43of the first fixed waveguide block40. Further, the waveguide path51is formed on a line passing through the center of the waveguide path42in a direction perpendicular to the third end face50aand the fourth end face50b.

The movable waveguide block60is supported so as to be slidable parallel to the second end face40band the third end face50a, between the second end face40bof the first fixed waveguide block40and the third end face50aof the second fixed waveguide block50, on the upper surface31aof the base portion31. The movable waveguide block60is formed in a rectangular parallelepiped shape having a length slightly shorter (for example, 200 μm) than the distance between the second end face40bof the first fixed waveguide block40and the third end face50aof the second fixed waveguide block50and approximately the same height as the first and second fixed waveguide blocks40and50, and approximately the same height as the first and second fixed waveguide blocks40and50, and a plurality of (in this example, three corresponding to the number of waveguide paths41to43formed in the first fixed waveguide block40) waveguide paths61,62, and63surrounded by metal walls are formed to penetrate from the fifth end face60ato the sixth end face60b. Here, the fifth end face60afaces the second end face40bof the first fixed waveguide block40in parallel with a gap g (for example, g=100 μm), and the sixth end face60bfaces the third end face50aof the second fixed waveguide block50in parallel with the gap g (for example, g=100 μm).

The diameters and heights of the waveguide paths61to63of the movable waveguide block60are the same as those of the waveguide paths41to43of the first fixed waveguide block40and the waveguide path51of the second fixed waveguide block50. The waveguide path62is formed in a direction perpendicular to the fifth end face60aand the sixth end face60b. The other two waveguide paths61and63are formed obliquely with respect to the fifth end face60aand the sixth end face60b. These plurality of waveguide paths61to63surrounded by metal walls are provided with different passband characteristics within the millimeter wave band, by a known method such as arranging a resonance plate or a dielectric resonator inside.

In the position shown inFIG.10(hereinafter referred to as the “neutral position”), the opening of the central waveguide path62on the fifth end face60aside is aligned concentrically with the opening of the waveguide path42of the first fixed waveguide block40on the second end face40bside, and the opening of the central waveguide path62on the sixth end face60bside is aligned concentrically with the opening of the waveguide path51of the second fixed waveguide block50on the third end face50aside. Therefore, in the neutral position ofFIG.10, the waveguide path42of the first fixed waveguide block40and the waveguide path51of the second fixed waveguide block50are connected via the waveguide path62of the movable waveguide block60.

In the neutral position, the opening positions of the waveguide paths61to63on the side of the fifth end face60aare spaced outward by L from the opening position of the waveguide path42of the first fixed waveguide block40, and the opening positions of the waveguide paths61to63on the side of the sixth end face60bare spaced apart by L on both sides from the opening position of the waveguide path51of the second fixed waveguide block50.

Therefore, as shown inFIG.11, at the first position where the movable waveguide block60is slid in the width direction (X direction) by −L from the neutral position, the opening position of the waveguide path41on the second end face40bside of the first fixed waveguide block40and the opening position of one waveguide path61on the fifth end face60aside of the movable waveguide block60match, the opening position of the waveguide path51on the third end face50aside of the second fixed waveguide block50and the opening position of the waveguide path61on the sixth end face60bside of the movable waveguide block60match, and the waveguide path41of the first fixed waveguide block40and the waveguide path51of the second fixed waveguide block50are connected via the waveguide path61.

Further, as shown inFIG.12, at the second position where the movable waveguide block60is slid in the width direction by L from the neutral position, the opening position of the waveguide path43on the second end face40bside of the first fixed waveguide block40and the opening position of the waveguide path63on the fifth end face60aside of the movable waveguide block60match, the opening position of the waveguide path51on the third end face50aside of the second fixed waveguide block50and the opening position of the waveguide path63on the sixth end face60bside of the movable waveguide block60match, and the waveguide path43of the first fixed waveguide block40and the waveguide path51of the second fixed waveguide block50are connected via the waveguide path63.

In this manner, the movable waveguide block60slides with respect to the first fixed waveguide block40and the second fixed waveguide block50, and any of the waveguide paths61to63is selectively connected to between any of the waveguide paths41to43of the first fixed waveguide block40and the waveguide path51of the second fixed waveguide block50, in different positions (neutral position, first position, and second position).

This example has a symmetrical structure in which the waveguide path51of the second fixed waveguide block50is located on the extension line of the line passing through the center of the waveguide path42of the first fixed waveguide block40, and at the neutral position, the three waveguide paths61to63of the movable waveguide block60are also line-symmetrical with respect to the extension line. On the other hand, an asymmetrical structure in which the waveguide path51of the second fixed waveguide block50is not on the extension line of the line passing through the center of the waveguide path42of the first fixed waveguide block40is also possible, and in this case, the three waveguide paths61to63of the movable waveguide block60are also disposed asymmetrically.

The movable waveguide block60is slidably supported by the driving device70provided on the base portion31. Although the structure of the driving device70is arbitrary, for example, a structure that converts the rotary motion of the stepping motor into linear motion and transmits the motion to the support member that supports the movable waveguide block60from the lower surface side of the base portion31. In this case, the position and movement distance of the movable waveguide block60are detected by a sensor, an encoder, or the like, and the movable waveguide block60may be controlled to be able to selectively move to at least the neutral position inFIG.10, the first position inFIG.11, and the second position inFIG.12.

The choke groove25as shown in any ofFIGS.3A to3Cis provided in a band-shaped region R surrounding at least one opening among the openings of the waveguide paths41to43on the second end face40bside of the first fixed waveguide block40, the opening of the waveguide path51on the third end face50aside of the second fixed waveguide block50, and the openings of the plurality of waveguide paths61to63on the fifth end face60aside and the sixth end face60bside of the movable waveguide block60.

As described above, the waveguide connection structure1according to the present embodiment has a structure in which a choke groove25having a shape that covers a region having a strong electric field of the electromagnetic wave leaking into the predetermined gap g between the waveguide10and the waveguide20is formed in one or both of the end face10band the end face20a. With this configuration, the waveguide connection structure1according to the present embodiment can effectively suppress leakage of electromagnetic waves from the connection point of the two waveguides10and20facing each other.

Further, the waveguide connection structure1according to the present embodiment may be a structure in which the four groove portions25ato25dforming the choke groove25are separated from each other by four non-groove portions27ato27dalong the diagonal direction of the opening of the rectangle of the waveguide path11or the waveguide path21, in the band-shaped region R. With this configuration, the waveguide connection structure1according to the present embodiment can suppress the return loss S11to less than-15 dB, over the entire operating frequency range of a WR-3 waveguide (fractional bandwidth of about 40%), for example, with respect to a predetermined gap g up to about 1/10 wavelength of the guide wavelength.

Further, in the determination method of the waveguide connection structure1according to the present embodiment, the shape of the equiphase surface of the electromagnetic waves of the leakage prevention target frequency propagating from one to the other of the two analysis waveguides is acquired by electromagnetic field analysis, so that it is possible to determine the range of the band-shaped region R on either one or both of the end face10band the end face20aof the two waveguides10and20.

Further, in the manufacturing method of the waveguide connection structure1according to the present embodiment, the choke groove25is formed in the band-shaped region R of either one or both of the end face10band the end face20adetermined by the above determination method, and the two waveguides10,20are disposed such that the end faces10band20aface each other in parallel with a predetermined gap g therebetween. With this configuration, the manufacturing method of the waveguide connection structure1according to the present embodiment can manufacture the waveguide connection structure1capable of effectively suppressing the leakage of electromagnetic waves from a connection point of two facing waveguides10and20.

Further, the waveguide switch100according to the present embodiment uses the above-described waveguide connection structure1for the moving unit (movable waveguide block60), thereby improving the return loss and insertion loss of the switch over a wide band, and can suppress the unintended leakage of electromagnetic waves in the gap between the first fixed waveguide block40and the movable waveguide block60and the gap between the second fixed waveguide block50and the movable waveguide block60.

Further, the waveguide switch100according to the present invention uses the above-described waveguide connection structure1for the moving unit (the movable waveguide block60), so that the gap between the first fixed waveguide block40and the movable waveguide block60and the gap between the second fixed waveguide block50and the movable waveguide block60can be made wider than before, and the machining accuracy is relaxed and the resistance to aging is improved.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS