Patent ID: 12224473

DESCRIPTION OF EMBODIMENTS

To describe the invention in more detail, embodiments for carrying out the invention will be described below with reference to the accompanying drawings.

First Embodiment

FIG.1is a configuration diagram showing an antenna feeding circuit including a polarized waveguide filter1according to a first embodiment.

The antenna feeding circuit for satellite communication uses the polarized waveguide filter1so as to, for example, allow a signal in one frequency band out of signals in two frequency bands to pass through, and attenuate a signal in the other frequency band.

FIG.2is a perspective view showing the polarized waveguide filter1according to the first embodiment.

InFIG.2, a first rectangular waveguide11is installed in parallel to an X-Y plane.

An incident plane11aof the first rectangular waveguide11is a plane parallel to a Z-X plane, and the incident plane11ais a plane on which an electromagnetic wave which is a signal in a given frequency band is incident.

An exit plane11bof the first rectangular waveguide11is a plane parallel to the Z-X plane, and the exit plane11bis a plane from which the electromagnetic wave incident from the incident plane11aexits.

The exit plane11bof the first rectangular waveguide11is connected to a first edge surface13aof a rectangular cavity resonator13via a coupling unit12, and the electromagnetic wave incident from the incident plane11ais coupled to the rectangular cavity resonator13through a coupling hole12aof the coupling unit12.

The first rectangular waveguide11includes a third wall surface11c, a third wall surface11d, a fourth wall surface11e, and a fourth wall surface11f.

Each of the third wall surface11cand the third wall surface11dis a surface parallel to the X-Y plane, and each of the third wall surface11cand the third wall surface11dis a wide wall surface wider in area than each of the fourth wall surface11eand the fourth wall surface11f.

Each of the fourth wall surface11eand the fourth wall surface11fis a surface parallel to a Y-Z plane, and each of the fourth wall surface11eand the fourth wall surface11fis a narrow wall surface narrower in area than each of the third wall surface11cand the third wall surface11d.

The coupling unit12connects the exit plane11bof the first rectangular waveguide11to the first edge surface13aof the rectangular cavity resonator13.

The coupling unit12has the coupling hole12afor coupling the electromagnetic wave incident on the first rectangular waveguide11to the rectangular cavity resonator13.

The rectangular cavity resonator13is installed in parallel to the X-Y plane.

The first edge surface13aof the rectangular cavity resonator13is a surface parallel to the Z-X plane, and the first edge surface13ais connected to the exit plane11bof the first rectangular waveguide11via the coupling unit12.

A second edge surface13bof the rectangular cavity resonator13is a surface parallel to the Z-X plane, and faces the first edge surface13a. The second edge surface13bis connected to an incident plane15aof a second rectangular waveguide15via a coupling unit14.

The rectangular cavity resonator13excites each of a TE10 mode and a TE20 mode of the electromagnetic wave.

The rectangular cavity resonator13includes a first wall surface13c, a first wall surface13d, a second wall surface13e, and a second wall surface13f.

Each of the first wall surface13cand the first wall surface13dis a surface parallel to the X-Y plane, and each of the first wall surface13cand the first wall surface13dis a wide wall surface wider in area than each of the second wall surface13eand the second wall surface13f.

Each of the second wall surface13eand the second wall surface13fis a surface parallel to the Y-Z plane, and each of the second wall surface13eand the second wall surface13fis a narrow wall surface narrower in area than each of the first wall surface13cand the first wall surface13d.

The coupling unit14connects the second edge surface13bof the rectangular cavity resonator13to the incident plane15aof the second rectangular waveguide15.

The coupling unit14has a coupling hole14afor coupling the electromagnetic wave incident on the rectangular cavity resonator13to the second rectangular waveguide15.

The second rectangular waveguide15is installed in parallel to the X-Y plane.

The incident plane15aof the second rectangular waveguide15is a plane parallel to the Z-X plane, and the incident plane15ais connected to the second edge surface13bof the rectangular cavity resonator13via the coupling unit14.

An exit plane15bof the second rectangular waveguide15is a plane parallel to the Z-X plane, and the exit plane15bis a plane from which the electromagnetic wave incident from the incident plane15aexits.

The second rectangular waveguide15includes a third wall surface15c, a third wall surface15d, a fourth wall surface15e, and a fourth wall surface15f.

Each of the third wall surface15cand the third wall surface15dis a surface parallel to the X-Y plane, and each of the third wall surface15cand the third wall surface15dis a wide wall surface wider in area than each of the fourth wall surface15eand the fourth wall surface15f.

Each of the fourth wall surface15eand the fourth wall surface15fis a surface parallel to the Y-Z plane, and each of the fourth wall surface15eand the fourth wall surface15fis a narrow wall surface narrower in area than each of the third wall surface15cand the third wall surface15d.

Here, it is assumed that a direction orthogonal to each of the first edge surface13aand the second edge surface13bis a first direction, and a direction orthogonal to the first direction is a second direction. The first direction is a direction parallel to a y-axis, and the second direction is a direction parallel to an x-axis.

In the polarized waveguide filter1shown inFIG.2, dimensions in the second direction of the first wall surfaces13cand13dare longer than dimensions in the second direction of the third wall surfaces11c,11d,15c, and15d.

A protrusion16ais provided on the first wall surface13cof the rectangular cavity resonator13in such a way as to protrude outward from the rectangular cavity resonator13. The inside of the protrusion16ais hollow, and the space inside the protrusion16ais continuous with the space inside the rectangular cavity resonator13.

The protrusion16ashifts the resonance frequency of the TE10 mode and the resonance frequency of the TE20 mode by respective amounts different from each other.

FIG.3is an explanatory diagram showing an installation position of each of the protrusion16aand a protrusion16b.

Pais, as shown inFIG.3, a position in which the protrusion16ais provided on the first wall surface13c, and the position Pais a position in which a distance di from the first edge surface13ais identical to a distance di from the second edge surface13b. The position in which the distances di are identical to each other which is used here is not limited to a position in which the two distances exactly match each other, and may be a position in which the two distances differ from each other within a range in which no practical problems occur.

In addition, the position Pais, as shown inFIG.3, a position in which a distance from the second wall surface13fwhich is one edge portion in the second direction of the first wall surface13cis one-quarter of a dimension d in the second direction of the first wall surface13c. The one-quarter position used here is not limited to a position in which the distance from the second wall surface13fis exactly one-quarter of the dimension d of the first wall surface13c, and the distance from the second wall surface13fmay be shifted from the one-quarter position of the dimension d of the first wall surface13cwithin a range in which no practical problems occur.

When the protrusion16ais installed in the position Pa, the protrusion16ashifts the resonance frequency of the TE20 mode to a high frequency side without shifting the resonance frequency of the TE10 mode almost at all.

The protrusion16bis provided on the first wall surface13cof the rectangular cavity resonator13in such a way as to protrude outward from the rectangular cavity resonator13. The inside of the protrusion16bis hollow, and the space inside the protrusion16bis continuous with the space inside the rectangular cavity resonator13.

The protrusion16bshifts the resonance frequency of the TE10 mode and the resonance frequency of the TE20 mode by respective amounts different from each other.

Pbis, as shown inFIG.3, a position in which the protrusion16bis provided on the first wall surface13c, and the position Pbis a position in which a distance di from the first edge surface13ais identical to a distance di from the second edge surface13b. The position in which the distances di are identical to each other which is used here is not limited to a position in which the two distances exactly match each other, and may be a position in which the two distances differ from each other within a range in which no practical problems occur.

In addition, the position Pbis, as shown inFIG.3, a position in which a distance from the second wall surface13fwhich is one edge portion in the second direction of the first wall surface13cis about three-fourths of the dimension d in the second direction of the first wall surface13c. The three-fourths position used here is not limited to a position in which the distance from the second wall surface13fis exactly three-fourths of the dimension d of the first wall surface13c, and the distance from the second wall surface13fmay be shifted from the three-fourths position of the dimension d of the first wall surface13cwithin a range in which no practical problems occur.

When the protrusion16bis installed in the position Pb, the protrusion16bshifts the resonance frequency of the TE20 mode to a high frequency side without shifting the resonance frequency of the TE10 mode almost at all.

Next, operations of the polarized waveguide filter1shown inFIG.2will be described.

In the first rectangular waveguide11, an electromagnetic wave which is a signal in a given frequency band is incident from the incident plane11a. The first rectangular waveguide11transmits a TE10 mode in a rectangular waveguide, as a fundamental mode.

The electromagnetic wave incident on the first rectangular waveguide11is coupled to the rectangular cavity resonator13through the coupling hole12aof the coupling unit12.

Since the dimensions in the second direction of the first wall surfaces13cand13dof the rectangular cavity resonator13are longer than the dimensions in the second direction of the third wall surfaces11cand11dof the first rectangular waveguide11, the rectangular cavity resonator13excites each of the TE10 mode and the TE20 mode of the electromagnetic wave.

FIG.4is an explanatory diagram showing an electric field distribution of resonance of the TE10 mode of the electromagnetic wave, andFIG.5is an explanatory diagram showing an electric field distribution of resonance of the TE20 mode of the electromagnetic wave.

The electromagnetic wave incident on the rectangular cavity resonator13is coupled to the second rectangular waveguide15through resonance of each of the TE10 mode and the TE20 mode and through the coupling hole14aof the coupling unit14.

The electromagnetic wave incident on the second rectangular waveguide15exits outside from the exit plane15b.

By the rectangular cavity resonator13exciting each of the TE10 mode and the TE20 mode of the electromagnetic wave, a path corresponding to the TE10 mode and a path corresponding to the TE20 mode are created inside the rectangular cavity resonator13.

By the creation of two paths, i.e., the path corresponding to the TE10 mode and the path corresponding to the TE20 mode, inside the rectangular cavity resonator13, an attenuation pole that depends on a difference between the two paths is created inside the rectangular cavity resonator13.

The protrusions16aand16bare provided on the first wall surface13cof the rectangular cavity resonator13.

The position Pain which the protrusion16ais provided is, as shown inFIG.3, a position in which a distance di from the first edge surface13ais roughly identical to a distance di from the second edge surface13b.

In addition, the position Pain which the protrusion16ais provided is, as shown inFIG.3, a position in which a distance from the second wall surface13fis about one-quarter of the dimension d in the second direction of the first wall surface13c.

The position Pbin which the protrusion16bis provided is, as shown inFIG.3, a position in which a distance di from the first edge surface13ais roughly identical to a distance di from the second edge surface13b.

In addition, the position Pbin which the protrusion16bis provided is, as shown inFIG.3, a position in which a distance from the second wall surface13fis about three-fourths of the dimension d in the second direction of the first wall surface13c.

Each of the position Paand the position Pbis, as shown inFIG.5, a position in which the electric field of the TE20 mode is large.

Each of the position Paand the position Pbis, as shown inFIG.4, off a position in which the electric field of the TE10 mode is large.

Thus, when the protrusions16aand16bare provided on the first wall surface13cof the rectangular cavity resonator13, the resonance frequency of the TE20 mode is shifted to a high frequency side, while the resonance frequency of the TE10 mode does not change almost at all.

By the shift in the resonance frequency of the TE20 mode to the high frequency side, the frequency of an attenuation pole created inside the rectangular cavity resonator13changes.

In the polarized waveguide filter1shown inFIG.2, the two protrusions16aand16bare provided on the first wall surface13cof the rectangular cavity resonator13. However, this is merely an example, and as shown inFIG.6, two protrusions16cand16dmay be provided on the first wall surface13dof the rectangular cavity resonator13, in addition to the two protrusions16aand16bprovided on the first wall surface13cof the rectangular cavity resonator13.

FIG.6is a configuration diagram showing the protrusions16aand16bprovided on the first wall surface13cof the rectangular cavity resonator13and the protrusions16cand16dprovided on the first wall surface13d.

A position Pc in which the protrusion16cis provided on the first wall surface13dis, as with the position Pa, a position in which a distance di from the first edge surface13ais roughly identical to a distance di from the second edge surface13b.

In addition, the position Pc in which the protrusion16cis provided is, as with the position Pa, a position in which a distance from the second wall surface13fis about one-quarter of the dimension d in the second direction of the first wall surface13d.

A position Pain which the protrusion16dis provided on the first wall surface13dis, as with the position Pb, a position in which a distance di from the first edge surface13ais roughly identical to a distance di from the second edge surface13b.

In addition, the position Pain which the protrusion16dis provided is, as with the position Pb, a position in which a distance from the second wall surface13fis about three-fourths of the dimension d in the second direction of the first wall surface13d.

By providing the two protrusions16cand16din addition to the two protrusions16aand16b, the amount of the shift in the resonance frequency of the TE20 mode to the high frequency side can be increased over a case in which only the protrusions16aand16bare provided.

In the polarized waveguide filter1shown inFIG.2, the two protrusions16aand16bare provided on the first wall surface13c. In the polarized waveguide filter1shown inFIG.6, the two protrusions16aand16bare provided on the first wall surface13c, and the two protrusions16cand16dare provided on the first wall surface13d.

However, they are merely examples, and as shown inFIG.7or8, only one of the protrusions16aand16bmay be provided on the first wall surface13c. In addition, only one of the protrusions16cand16dmay be provided on the first wall surface13d.

Thus, on the first wall surfaces13cand13dthere may be provided one protrusion in total or there may be provided three or four protrusions in total.

FIG.7is a configuration diagram showing the protrusion16aprovided on the first wall surface13cof the rectangular cavity resonator13.

FIG.8is a configuration diagram showing the protrusion16bprovided on the first wall surface13cof the rectangular cavity resonator13.

In the polarized waveguide filter1shown inFIG.7, the position Pain which the protrusion16ais provided is a position in which a distance from the second wall surface13fis about one-quarter of the dimension d in the second direction of the first wall surface13d. Thus, when the protrusion16ais provided on the first wall surface13c, the resonance frequency of the TE20 mode is shifted to a high frequency side, while the resonance frequency of the TE10 mode does not change almost at all.

It is assumed that the position Pain which the protrusion16ais provided is, for example, as shown inFIG.9, a position in which a distance from the second wall surface13fis one-half of the dimension d in the second direction of the first wall surface13d. When the position Pain which the protrusion16ais provided is the one-half position of the dimension d of the first wall surface13d, the resonance frequency of the TE10 mode is shifted to a high frequency side, while the resonance frequency of the TE20 mode does not change almost at all. The one-half position used here is not limited to a position in which the distance from the second wall surface13fis exactly one-half of the dimension d of the first wall surface13c, and the distance from the second wall surface13fmay be shifted from the one-half position of the dimension d of the first wall surface13cwithin a range in which no practical problems occur.

FIG.9is an explanatory diagram showing an installation position of the protrusion16a.

The position Pain which the protrusion16ais provided is, as shown inFIG.9, a position in which a distance di from the first edge surface13ais identical to a distance di from the second edge surface13b. The position in which the distances di are identical to each other which is used here is not limited to a position in which the two distances exactly match each other, and may be a position in which the two distances differ from each other within a range in which no practical problems occur.

In the above-described first embodiment, the polarized waveguide filter1is formed in which the protrusions16aand16bthat shift the resonance frequency of the TE10 mode and the resonance frequency of the TE20 mode by respective amounts different from each other are provided on one or more first wall surfaces out of the two first wall surfaces13cand13dof the rectangular cavity resonator13, in such a way as to protrude outward from the rectangular cavity resonator13. Thus, the polarized waveguide filter1can make the amount of the shift in the resonance frequency of the TE10 mode which is excited by the rectangular cavity resonator13different from the amount of the shift in the resonance frequency of the TE20 mode which is excited by the rectangular cavity resonator13.

As shown inFIG.10, by providing protrusions16eand16fin the second wall surfaces13eand13fof the rectangular cavity resonator13in such a way as to protrude toward the inner side of the rectangular cavity resonator13, each of the resonance frequency of the TE10 mode and the resonance frequency of the TE20 mode can be shifted to a high frequency side.

FIG.10is a configuration diagram showing the protrusions16eand16fprovided in the second wall surfaces13eand13fof the rectangular cavity resonator13.

However, positions in which the protrusions16eand16fare provided are off each of the position in which the electric field of the TE10 mode is large and the position in which the electric field of the TE20 mode is large, and there is not much difference between them.

Thus, by providing the protrusions16eand16fin the second wall surfaces13eand13fof the rectangular cavity resonator13, not only the resonance frequency of the TE20 mode is shifted to a high frequency side, but also the resonance frequency of the TE10 mode is shifted to a high frequency side.

When the protrusions16eand16fare provided in the second wall surfaces13eand13f, compared with a case in which the protrusions16aand16bare provided on the first wall surface13c, a difference between the resonance frequency of the TE10 mode after shifting and the resonance frequency of the TE20 mode after shifting is not large. Hence, when the protrusions16eand16fare provided in the second wall surfaces13eand13f, compared with a case in which the protrusions16aand16bare provided on the first wall surface13c, the amount of the change in the frequency of an attenuation pole created inside the rectangular cavity resonator13is small.

Note that when the protrusions16aand16bare provided on the first wall surface13c, a loss in the power of a signal in a given frequency band, etc., can be reduced over a case in which the protrusions16eand16fare provided in the second wall surfaces13eand13f.

Second Embodiment

In a second embodiment, a polarized waveguide filter1will be described in which a dimension of a protrusion16ain a direction in which the protrusion16aprotrudes outward from a rectangular cavity resonator13differs from a dimension of a protrusion16bin a direction in which the protrusion16bprotrudes outward from the rectangular cavity resonator13. The directions in which the protrusions16aand16bprotrude outward from the rectangular cavity resonator13are directions parallel to a Z-axis.

FIG.11is a configuration diagram showing the polarized waveguide filter1according to the second embodiment. InFIG.11, the same reference signs as those ofFIGS.2and3indicate the same or corresponding portions and thus description thereof is omitted.

The dimension of the protrusion16bin the direction in which the protrusion16bprotrudes outward from the rectangular cavity resonator13is longer than the dimension of the protrusion16ain the direction in which the protrusion16aprotrudes outward from the rectangular cavity resonator13.

Each of the protrusion16aand the protrusion16bacts to shift the resonance frequency of the TE20 mode to a high frequency side.

However, since the dimension in the outward protruding direction is longer in the protrusion16bthan the protrusion16a, the amount of the shift to the high frequency side resulting from the provision of the protrusion16bis larger than the amount of the shift to the high frequency side resulting from the provision of the protrusion16a.

By making the dimension of the protrusion16bin the outward protruding direction different from the dimension of the protrusion16ain the outward protruding direction, the amount of the shift to the high frequency side can be changed.

Third Embodiment

In the polarized waveguide filter1shown inFIG.1, there are shown the protrusions16aand16beach having a cylindrical shape.

In a third embodiment, a polarized waveguide filter1will be described in which protrusions16aand16beach have a rectangular parallelepiped shape.

In the polarized waveguide filter1shown inFIG.1, there are shown the protrusions16aand16beach having a cylindrical shape. However, this is merely an example, and for example, as shown inFIG.12, the protrusions16aand16bmay each have a rectangular parallelepiped shape.

FIG.12is a configuration diagram showing the polarized waveguide filter1according to the third embodiment. InFIG.12, the same reference signs as those ofFIGS.2and3indicate the same or corresponding portions and thus description thereof is omitted.

In the polarized waveguide filter1shown inFIG.12, the protrusions16aand16beach have a rectangular parallelepiped shape, and lengths of the protrusions16aand16bin a direction parallel to the Y-axis are longer than lengths of the protrusions16aand16bin a direction parallel to the X-axis. Such rectangular parallelepiped shape is hereinafter referred to as “horizontally oriented rectangular parallelepiped shape”.

In a case where the protrusions16aand16beach have a cylindrical shape, even if the protrusion16ais provided in the position Paon the first wall surface13cand the protrusion16bis provided in the position Pbon the first wall surface13c, the resonance frequency of the TE10 mode does not change almost at all.

On the other hand, in a case where the protrusions16aand16beach have a horizontally oriented rectangular parallelepiped shape, if the protrusion16ais provided in the position Paon the first wall surface13cand the protrusion16bis provided in the position Pbon the first wall surface13c, then not only the resonance frequency of the TE20 mode is shifted to a high frequency side, but also the resonance frequency of the TE10 mode is slightly shifted to a high frequency side. However, the amount of the shift in the resonance frequency of the TE10 mode to the high frequency side is very small compared with the amount of the shift in the resonance frequency of the TE20 mode to the high frequency side. Thus, a change in resonance frequency resulting from the provision of the protrusions16aand16beach having a horizontally oriented rectangular parallelepiped shape substantially corresponds to a change in only the resonance frequency of the TE20 mode.

In the polarized waveguide filter1shown inFIG.12, the protrusions16aand16beach have a horizontally oriented rectangular parallelepiped shape.

However, this is merely an example, and as shown inFIG.13, the protrusions16aand16bmay each have a rectangular parallelepiped shape, and the lengths of the protrusions16aand16bin the direction parallel to the Y-axis may be shorter than the lengths of the protrusions16aand16bin the direction parallel to the X-axis. Such rectangular parallelepiped shape is hereinafter referred to as “vertically oriented rectangular parallelepiped shape”.

FIG.13is a configuration diagram showing another polarized waveguide filter1according to the third embodiment.

When the protrusions16aand16beach have a cylindrical shape, by providing the protrusions16aand16bon the first wall surface13c, the resonance frequency of the TE20 mode is shifted to a high frequency side.

When the protrusions16aand16beach have a vertically oriented rectangular parallelepiped shape, by providing the protrusions16aand16bon the first wall surface13c, the resonance frequency of the TE20 mode is shifted to a higher frequency side than that of a case in which the protrusions16aand16beach have a cylindrical shape.

In either of the horizontally oriented rectangular parallelepiped shape and the vertically oriented rectangular parallelepiped shape, locations where orthogonal planes among a plurality of planes of a rectangular parallelepiped intersect may be rounded.

In addition, in six planes of the rectangular cavity resonator13, six planes of the first rectangular waveguide11, or six planes of the second rectangular waveguide15, too, locations where orthogonal planes among the six planes intersect may be rounded.

If locations where planes intersect are allowed to be rounded, then a design in which a cutting process using a drill is to be performed is possible.

As shown inFIG.14or15, the polarized waveguide filter1can be formed by coupling a metal block B1having been subjected to a cutting process using a drill to a metal block B2having been subjected to a cutting process using a drill.

FIGS.14and15are explanatory diagrams showing polarized waveguide filters1each having a metal block B1and a metal block B2coupled together.

BetweenFIGS.14and15, the position of a coupled plane of the metal block B1and the metal block B2is different, and the position of the coupling unit12relative to the first edge surface13aof the rectangular cavity resonator13is different.

Fourth Embodiment

In a fourth embodiment, a polarized waveguide filter1including an external resonator22will be described.

FIG.16is a configuration diagram showing the polarized waveguide filter1according to the fourth embodiment. InFIG.16, the same reference signs as those ofFIGS.2and3indicate the same or corresponding portions and thus description thereof is omitted.

A coupling unit21connects the second wall surface13eof the rectangular cavity resonator13to an incident plane22aof the external resonator22.

The coupling unit21has a coupling hole21afor coupling an electromagnetic wave incident on the rectangular cavity resonator13to the external resonator22.

The external resonator22is installed in parallel to the X-Y plane.

The incident plane22aof the external resonator22is a plane parallel to the Y-Z plane, and the incident plane22ais connected to the second wall surface13eof the rectangular cavity resonator13via the coupling unit21.

When an electromagnetic wave is incident from the incident plane22a, an attenuation pole is created inside the external resonator22at a frequency different from a frequency of an attenuation pole created inside the rectangular cavity resonator13.

The frequency of the attenuation pole created inside the external resonator22is determined by a length of the external resonator22in a direction parallel to the x-axis and a length of the external resonator22in a direction parallel to the y-axis.

In the polarized waveguide filter1shown inFIG.16, by including the external resonator22, in addition to an attenuation pole created inside the rectangular cavity resonator13, an attenuation pole is created at a frequency different from a frequency of the attenuation pole created inside the rectangular cavity resonator13.

In the polarized waveguide filter1shown inFIG.16, the external resonator22has a rectangular parallelepiped shape. However, this is merely an example, and for example, as shown inFIG.17, a shape on the X-Y plane of an external resonator23may be trapezoidal.

FIG.17is a configuration diagram showing another polarized waveguide filter1according to the fourth embodiment.

An incident plane23aof the external resonator23is a plane parallel to the Y-Z plane, and the incident plane23ais connected to the second wall surface13eof the rectangular cavity resonator13via the coupling unit21.

An edge surface23bis a surface parallel to the Y-Z plane, and faces the incident plane23a.

A length of the incident plane23ain a direction parallel to the y-axis is shorter than a length of the edge surface23bin the direction parallel to the y-axis. The lengths in the direction parallel to the y-axis are lengths in the first direction.

When an electromagnetic wave is incident from the incident plane23a, an attenuation pole is created inside the external resonator23at a frequency different from a frequency of an attenuation pole created inside the rectangular cavity resonator13.

The frequency of the attenuation pole created inside the external resonator23is determined by a length of the external resonator23in a direction parallel to the x-axis, a length of the incident plane23ain a direction parallel to the y-axis, and a length of the edge surface23bin the direction parallel to the y-axis.

When a shape on the X-Y plane of the external resonator23is trapezoidal, the number of parameters that determine a frequency of an attenuation pole created inside the external resonator23increases over a case in which the external resonator22has a rectangular parallelepiped shape, and thus, flexibility in design improves.

In the polarized waveguide filters1shown inFIGS.16and17, the incident plane22aof the external resonator22or the incident plane23aof the external resonator23is connected to the second wall surface13eof the rectangular cavity resonator13via the coupling unit21.

However, this is merely an example, and an incident plane22aof an external resonator22or an incident plane23aof an external resonator23may be connected to the second wall surface13fof the rectangular cavity resonator13via a coupling unit (not shown). Thus, the polarized waveguide filter1may include two external resonators22or two external resonators23. In addition, the polarized waveguide filter1may include one external resonator22and one external resonator23.

Fifth Embodiment

In a fifth embodiment, a polarized waveguide filter1including a second rectangular cavity resonator32will be described.

FIG.18is a configuration diagram showing the polarized waveguide filter1according to the fifth embodiment. InFIG.18, the same reference signs as those ofFIGS.2and3indicate the same or corresponding portions and thus description thereof is omitted.

The polarized waveguide filter1shown inFIG.18includes two rectangular cavity resonators, the rectangular cavity resonator13and the second rectangular cavity resonator32. However, this is merely an example, and the polarized waveguide filter1may include three or more rectangular cavity resonators.

A coupling unit31connects the exit plane15bof the second rectangular waveguide15to a third edge surface32aof the second rectangular cavity resonator32.

The coupling unit31has a coupling hole31afor coupling an electromagnetic wave incident on the second rectangular waveguide15to the second rectangular cavity resonator32.

The second rectangular cavity resonator32is installed in parallel to the X-Y plane.

The third edge surface32aof the second rectangular cavity resonator32is a surface parallel to the Z-X plane, and the third edge surface32ais connected to the exit plane15bof the second rectangular waveguide15via the coupling unit31.

A fourth edge surface32bof the second rectangular cavity resonator32is a surface parallel to the Z-X plane, and faces the third edge surface32a. The fourth edge surface32bis connected to an incident plane34aof a third rectangular waveguide34via a coupling unit33.

The second rectangular cavity resonator32excites each of the TE10 mode and the TE20 mode of the electromagnetic wave.

The second rectangular cavity resonator32includes a fifth wall surface32c, a sixth wall surface32e, and a sixth wall surface32f.

The fifth wall surface32cis a surface parallel to the X-Y plane, and the fifth wall surface32cis a wide wall surface wider in area than each of the sixth wall surface32eand the sixth wall surface32f.

FIG.18is a drawing of the polarized waveguide filter1viewed from a front direction of the paper, and when the front direction of the paper is a top side of the polarized waveguide filter1, the fifth wall surface32cis a top surface of the second rectangular cavity resonator32. Although, inFIG.18, a bottom surface of the second rectangular cavity resonator32is not shown, the bottom surface of the second rectangular cavity resonator32is another fifth wall surface facing the fifth wall surface32c.

Each of the sixth wall surface32eand the sixth wall surface32fis a surface parallel to the Y-Z plane, and each of the sixth wall surface32eand the sixth wall surface32fis a narrow wall surface narrower in area than the fifth wall surface32c.

The coupling unit33connects the fourth edge surface32bof the second rectangular cavity resonator32to the incident plane34aof the third rectangular waveguide34.

The coupling unit33has a coupling hole33afor coupling the electromagnetic wave incident on the second rectangular cavity resonator32to the third rectangular waveguide34.

The third rectangular waveguide34is installed in parallel to the X-Y plane.

The incident plane34aof the third rectangular waveguide34is a plane parallel to the Z-X plane, and the incident plane34ais connected to the fourth edge surface32bof the second rectangular cavity resonator32via the coupling unit33.

An exit plane34bof the third rectangular waveguide34is a plane parallel to the Z-X plane, and the exit plane34bis a plane from which the electromagnetic wave incident from the incident plane34aexits.

The third rectangular waveguide34includes a seventh wall surface34c, an eighth wall surface34e, and an eighth wall surface34f.

The seventh wall surface34cis a surface parallel to the X-Y plane, and the seventh wall surface34cis a wide wall surface wider in area than each of the eighth wall surface34eand the eighth wall surface34f.

FIG.18is a drawing of the polarized waveguide filter1viewed from a front direction of the paper, and when the front direction of the paper is the top side of the polarized waveguide filter1, the seventh wall surface34cis a top surface of the third rectangular waveguide34. Although, inFIG.18, a bottom surface of the third rectangular waveguide34is not shown, the bottom surface of the third rectangular waveguide34is another seventh wall surface facing the seventh wall surface34c.

Each of the eighth wall surface34eand the eighth wall surface34fis a surface parallel to the Y-Z plane, and each of the eighth wall surface34eand the eighth wall surface34fis a narrow wall surface narrower in area than the seventh wall surface34c.

In the polarized waveguide filter1shown inFIG.18, a dimension in the second direction of the fifth wall surface32cis longer than each of dimensions in the second direction of the third wall surfaces11c,11d,15c, and15dand a dimension in the second direction of the seventh wall surface34c.

A protrusion35ais provided on the fifth wall surface32cof the second rectangular cavity resonator32in such a way as to protrude outward. The inside of the protrusion35ais hollow, and the space inside the protrusion35ais continuous with the space inside the second rectangular cavity resonator32.

The protrusion35ashifts the resonance frequency of the TE10 mode and the resonance frequency of the TE20 mode by respective amounts different from each other.

A protrusion35bis provided on the fifth wall surface32cof the second rectangular cavity resonator32in such a way as to protrude outward. The inside of the protrusion35bis hollow, and the space inside the protrusion35bis continuous with the space inside the second rectangular cavity resonator32.

The protrusion35bshifts the resonance frequency of the TE10 mode and the resonance frequency of the TE20 mode by respective amounts different from each other.

In the polarized waveguide filter1shown inFIG.18, the two protrusions35aand35bare provided on the fifth wall surface32c. However, this is merely an example, and a protrusion that protrudes outward may also be provided on the bottom surface of the second rectangular cavity resonator32that faces the fifth wall surface32c.

The total number of protrusions provided on the fifth wall surface32cand protrusions provided on the bottom surface of the second rectangular cavity resonator32may be any number between one and four, inclusive.

Next, operations of the polarized waveguide filter1shown inFIG.18will be described.

It is assumed that a length of the rectangular cavity resonator13in a direction parallel to the x-axis is identical to a length of the second rectangular cavity resonator32in the direction parallel to the x-axis, and a length of the rectangular cavity resonator13in a direction parallel to the y-axis is identical to a length of the second rectangular cavity resonator32in the direction parallel to the y-axis.

In addition, it is assumed that installation positions of the protrusions16aand16bwith respect to the first wall surface13cof the rectangular cavity resonator13are identical to installation positions of the protrusions35aand35bwith respect to the fifth wall surface32cof the second rectangular cavity resonator32.

Furthermore, it is assumed that dimensions of the protrusions16aand16bin an outward direction are identical to dimensions of the protrusions35aand35bin an outward direction.

When the above-described lengths, positions, and dimensions are satisfied, a frequency of an attenuation pole created inside the second rectangular cavity resonator32is identical to a frequency of an attenuation pole created inside the rectangular cavity resonator13. Thus, the polarized waveguide filter1shown inFIG.18can obtain a larger amount of attenuation than that of the polarized waveguide filter1shown inFIG.2.

When the installation positions of the protrusions16aand16bwith respect to the first wall surface13cof the rectangular cavity resonator13differ from the installation positions of the protrusions35aand35bwith respect to the fifth wall surface32cof the second rectangular cavity resonator32, or when the dimensions of the protrusions16aand16bin the outward direction differ from the dimensions of the protrusions35aand35bin the outward direction, a frequency of an attenuation pole created inside the second rectangular cavity resonator32differs from a frequency of an attenuation pole created inside the rectangular cavity resonator13. Thus, the polarized waveguide filter1shown inFIG.18can increase the number of attenuation poles over the polarized waveguide filter1shown inFIG.2.

Note that also when the number of protrusions provided on the first wall surface13cof the rectangular cavity resonator13differs from the number of protrusions provided on the fifth wall surface32cof the second rectangular cavity resonator32, a frequency of an attenuation pole created inside the second rectangular cavity resonator32differs from a frequency of an attenuation pole created inside the rectangular cavity resonator13.

In addition, also when the dimensions of the rectangular cavity resonator13differ from the dimensions of the second rectangular cavity resonator32, a frequency of an attenuation pole created inside the second rectangular cavity resonator32differs from a frequency of an attenuation pole created inside the rectangular cavity resonator13.

Note that in the invention of this application, a free combination of the embodiments, modifications to any component of each of the embodiments, or omissions of any component in each of the embodiments are possible within the scope of the invention.

INDUSTRIAL APPLICABILITY

The invention is suitable for a polarized waveguide filter including rectangular waveguides and a rectangular cavity resonator, and an antenna feeding circuit.

REFERENCE SIGNS LIST

1: polarized waveguide filter,11: first rectangular waveguide,11a: incident plane,11b: exit plane,11c: third wall surface,11d: third wall surface,11e: fourth wall surface,11f: fourth wall surface,12: coupling unit,12a: coupling hole,13: rectangular cavity resonator,13a: first edge surface,13b, second edge surface,13c: first wall surface,13d: first wall surface,13e: second wall surface,13f: second wall surface,14: coupling unit,14a: coupling hole,15: second rectangular waveguide,15a: incident plane,15b: exit plane,15c: third wall surface,15d: third wall surface,15e: fourth wall surface,15f: fourth wall surface,16a,16b,16c,16d,16e,16f: protrusion,21: coupling unit,21a: coupling hole,22: external resonator,22a: incident plane,23: external resonator,23a: incident plane,23b: edge surface,31: coupling unit,31a: coupling hole,32: second rectangular cavity resonator,32a: third edge surface,32b: fourth edge surface,32c: fifth wall surface,32e: sixth wall surface,32f: sixth wall surface,33: coupling unit,33a: coupling hole,34: third rectangular waveguide,34a: incident plane,34b: exit plane,34c: seventh wall surface,34e: eighth wall surface,34f: eighth wall surface, and35a,35b: protrusion.