POLARIZED SHALLOW FILTER AND ANTENNA POWER CIRCUIT

Abstract

Polarized waveguide filter (1), comprising: a first rectangular waveguide (11); a second rectangular waveguide (15); and a rectangular cavity resonator (13) for exciting a TE10 mode and a TE20 mode of an electromagnetic wave, wherein the rectangular cavity resonator has a first boundary surface (13a) connected to an electromagnetic wave exit plane (11b) of the first rectangular waveguide via a coupling unit (12), wherein the rectangular cavity resonator has a second boundary surface (13b) connected to an electromagnetic wave impact plane (15a) of the second rectangular waveguide via a coupling unit (14), wherein the second boundary surface faces the first boundary surface, wherein the rectangular cavity resonator has two first wall surfaces (13c, 13d) and two second wall surfaces (13e, 13f), each of which is narrower in area than the first wall surfaces, and wherein at least one projection (16a, 16b) is provided on at least one of the first two wall surfaces in such a way as to protrude from the rectangular cavity resonator in order to shift a resonance frequency of the TE10 mode and a resonance frequency of the TE20 mode by different amounts, and where a first direction is a direction orthogonal to each of the first boundary surface and the second boundary surface, and a second direction is orthogonal to the first direction; and wherein the projection is provided in a position in which a distance from the first edge surface is identical to a distance from the second edge surface, and in which a distance from one of the edge sections in the second direction of a corresponding first wall surface is one quarter of a dimension in the second direction of the corresponding first wall surfaces or three quarters of the dimension in the second direction of the corresponding first wall surfaces.

Description

TECHNICAL FIELD

[0001] The invention relates to a polarized waveguide filter comprising rectangular waveguides and a rectangular cavity resonator and an antenna feed circuit. STATE OF THE ART

[0002] An antenna feed circuit for satellite communications, etc., may use a polarized waveguide filter to allow a signal in one frequency band to pass through signals in two frequency bands and to attenuate a signal in the other frequency band.

[0003] The following Non-Patent Literature 1 discloses a polarized waveguide filter in which a plurality of rectangular cavity resonators are connected through a coupling hole.

[0004] In the polarized waveguide filter described in Non-Patent Literature 1, one of the plurality of rectangular cavity resonators excites two modes, a TE10 mode and a TE20 mode.

[0005] Furthermore, in the polarized waveguide filter described in Non-Patent Literature 1, by creating a bypass path in the one rectangular cavity resonator, an attenuation pole is generated that attenuates a signal in a given frequency band.

[0006] US 2009 / 0 201 106 A1 describes a resonator for suppressing harmonics.

[0007] CN 1 09 509 950 A describes a miniaturized dual-frequency waveguide filter.

[0008] US 2016 / 0 351 985 A1 describes a resonator for use in a rectangular waveguide filter. LIST OF CITIONSPATENT LITERATURE

[0009] Non-Patent Literature 1: “WR-3 Band Quasi-Elliptical Waveguide Filters Using Higher Order Mode Resonances,” IEEE, 2017 SUMMARY OF THE INVENTIONTECHNICAL TASK

[0010] In the polarized waveguide filter described in Non-Patent Literature 1, a frequency of the attenuation pole can be changed by adjusting a relative position of the rectangular cavity resonator that excites the two modes to one waveguide or a relative position of the rectangular cavity resonator that excites the two modes to another rectangular cavity resonator.

[0011] However, the tuning also slightly changes the resonance frequency of the TE20 mode, thus affecting the passband characteristics. Therefore, if the resonance frequency of the TE20 mode can be tuned separately, it becomes easy to create a damping pole at a desired frequency and easily tune to obtain the desired passband characteristics. The parameters that tune the resonance frequency of the TE20 mode are the dimensions of a cavity resonator. When the dimensions of the cavity resonator are changed, the frequencies of the two modes, the TE10 mode and the TE20 mode, change together.Namely, if the resonance frequency of the TE20 mode is increased by adjusting the dimensions of the rectangular cavity resonator that excites the two modes, the resonance frequency of the TE10 mode increases with the increase, resulting in the amount of shift in the resonance frequency of the TE20 mode being essentially the same as the amount of shift in the resonance frequency of the TE10 mode. If the resonance frequency of the TE20 mode is decreased by adjusting the dimensions of the rectangular cavity resonator that excites the two modes, the resonance frequency of the TE10 mode decreases with the decrease, resulting in the amount of shift in the resonance frequency of the TE20 mode being essentially the same as the amount of shift in the resonance frequency of the TE10 mode.Therefore, the polarized waveguide filter described in Non-Patent Literature 1 has the problem that it is difficult to adjust the resonance frequency of each of the TE10 mode and the TE20 mode by greatly shifting the resonance frequency of the TE20 mode compared to the TE10 mode.

[0012] The invention is intended to solve a problem as described above, and an object of the invention is to obtain a polarized waveguide filter and an antenna feed circuit that can make the amount of shift of the resonance frequency of the TE10 mode different from the amount of shift of the resonance frequency of the TE20 mode. TECHNICAL SOLUTION

[0013] This object is achieved by subject matter having the features according to the independent claims. Advantageous embodiments of the invention are the subject of the figures, the description, and the dependent claims.

[0014] A polarized waveguide filter disclosed herein comprises: a first rectangular waveguide; a second rectangular waveguide; and a rectangular cavity resonator for exciting a TE10 mode and a TE20 mode of an electromagnetic wave, wherein the rectangular cavity resonator has a first edge surface connected to an electromagnetic wave exit plane of the first rectangular waveguide via a coupling unit, wherein the rectangular cavity resonator has a second edge surface connected to an electromagnetic wave incident plane of the second rectangular waveguide via a coupling unit, the second edge surface facing the first edge surface.The rectangular cavity resonator has two first wall surfaces and two second wall surfaces, each of which is narrower in area than the first wall surfaces, and wherein at least one protrusion for shifting a resonance frequency of the TE10 mode and a resonance frequency of the TE20 mode by mutually different amounts is provided on at least one of the two first wall surfaces so as to protrude from the rectangular cavity resonator. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0015] According to the invention, the polarized waveguide filter is formed in which the rectangular cavity resonator has the two first wall surfaces and the two second wall surfaces, each of which is narrower in area than the first wall surfaces, and wherein the protrusion for shifting the resonant frequency of the TE10 mode and the resonant frequency of the TE20 mode by respective amounts different from each other is provided on at least one of the two first wall surfaces so as to protrude from the rectangular cavity resonator. Thus, the polarized waveguide filter according to the invention can make the amount of shift of the resonant frequency of the TE10 mode excited by the rectangular cavity resonator different from the amount of shift of the resonant frequency of the TE20 mode excited by the rectangular cavity resonator. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a configuration diagram showing an antenna feeding circuit including a polarized waveguide filter 1 according to a first embodiment. Fig. 2 is a perspective view showing the polarized waveguide filter 1 according to the first embodiment. Fig. 3 is an explanatory diagram showing the installation position of each of a projection 16a and a projection 16b. Fig. 4 is an explanatory diagram showing an electric field distribution of resonance of a TE10 mode of an electromagnetic wave. Fig. 5 is an explanatory diagram showing an electric field distribution of resonance of a TE20 mode of an electromagnetic wave. Fig. 6 is a configuration diagram showing the protrusions 16a and 16b provided on a first wall surface 13c of a rectangular cavity resonator 13, and protrusions 16c and 16d provided on a first wall surface 13d. Fig. 7 is a configuration diagram showing the protrusion 16a provided on the first wall surface 13c of the rectangular cavity resonator 13. Fig. 8 is a configuration diagram showing the protrusion 16b provided on the first wall surface 13c of the rectangular cavity resonator 13. Fig. 9 is an explanatory diagram showing an installation position of the projection 16a. Fig. 10 is a configuration diagram showing protrusions 16e and 16f provided in second wall surfaces 13e and 13f of the rectangular cavity resonator 13. Fig. 11 is a configuration diagram showing a polarized waveguide filter 1 according to a second embodiment. Fig. 12 is a configuration diagram showing a polarized waveguide filter 1 according to a third embodiment. Fig. 13 is a configuration diagram showing another polarized waveguide filter 1 according to the third embodiment. Fig. 14 is an explanatory diagram showing a polarized waveguide filter 1 in which a metal block B1 is coupled to a metal block B2. Fig. 15 is an explanatory diagram showing a polarized waveguide filter 1 in which a metal block B1 is coupled to a metal block B2. Fig. 16 is a configuration diagram showing a polarized waveguide filter 1 according to a fourth embodiment. Fig. 17 is a configuration diagram showing another polarized waveguide filter 1 according to the fourth embodiment. Fig. 18 is a configuration diagram showing a polarized waveguide filter 1 according to a fifth embodiment. DESCRIPTION OF EMBODIMENTS

[0016] In order to describe the invention in more detail, embodiments for implementing the invention are explained below with reference to the accompanying drawings. First embodiment.

[0017] Fig. 1 is a configuration diagram showing an antenna feeding circuit including a polarized waveguide filter 1 according to a first embodiment.

[0018] The antenna feed circuit for satellite communication uses the polarized waveguide filter 1 to allow, for example, a signal in one frequency band to pass among signals in two frequency bands and to attenuate a signal in the other frequency band.

[0019] Fig. 2 is a perspective view showing the polarized waveguide filter 1 according to the first embodiment.

[0020] In Fig. 2, a first rectangular waveguide 11 is installed parallel to an XY plane.

[0021] An incident plane 11a of the first rectangular waveguide 11 is a plane parallel to a ZX plane, and the incident plane 11a is a plane on which an electromagnetic wave, which is a signal in a given frequency band, is incident.

[0022] An exit plane 11b of the first rectangular waveguide 11 is a plane parallel to the ZX plane, and the exit plane 11b is a plane from which the electromagnetic wave incident from the incident plane 11a exits. The exit plane 11b of the first rectangular waveguide 11 is connected to a first edge surface 13a of a rectangular cavity resonator 13 via a coupling unit 12, and the electromagnetic wave incident from the incident plane 11a is coupled into the rectangular cavity resonator 13 via a coupling hole 12a of the coupling unit 12.

[0023] The first rectangular waveguide 11 comprises a third wall surface 11c, a third wall surface 11d, a fourth wall surface 11e and a fourth wall surface 11f.

[0024] The third wall surface 11c and the third wall surface 11d are each a surface parallel to the XY plane, and each of the third wall surface 11c and the third wall surface 11d is each a wide wall surface that is wider in area than each of the fourth wall surface 11e and the fourth wall surface 11f.

[0025] Each of the fourth wall surface 11e and the fourth wall surface 11f is a surface parallel to a YZ plane, and each of the fourth wall surface 11e and the fourth wall surface 11f is a narrow wall surface narrower in area than each of the third wall surface 11c and the third wall surface 11d.

[0026] The coupling unit 12 connects the exit plane 11b of the first rectangular waveguide 11 with the first edge surface 13a of the rectangular cavity resonator 13.

[0027] The coupling unit 12 has the coupling hole 12a for coupling the electromagnetic wave incident on the first rectangular waveguide 11 into the rectangular cavity resonator 13.

[0028] The rectangular cavity resonator 13 is installed parallel to the XY plane.

[0029] The first edge surface 13a of the rectangular cavity resonator 13 is a surface parallel to the ZX plane, and the first edge surface 13a is connected to the exit plane 11b of the first rectangular waveguide 11 via the coupling unit 12.

[0030] A second edge surface 13b of the rectangular cavity resonator 13 is a surface parallel to the ZX plane, facing the first edge surface 13a. The second edge surface 13b is connected to an incident plane 15a of a second rectangular waveguide 15 via a coupling unit 14.

[0031] The rectangular cavity resonator 13 excites each of a TE10 mode and a TE20 mode of the electromagnetic wave.

[0032] The rectangular cavity resonator 13 comprises a first wall surface 13c, a first wall surface 13d, a second wall surface 13e and a second wall surface 13f.

[0033] Each of the first wall surface 13c and the first wall surface 13d is a surface parallel to the XY plane, and each of the first wall surface 13c and the first wall surface 13d is a wide wall surface that is wider in area than each of the second wall surface 13e and the second wall surface 13f.

[0034] Each of the second wall surface 13e and the second wall surface 13f is a surface parallel to the YZ plane, and each of the second wall surface 13e and the second wall surface 13f is a narrow wall surface narrower in area than each of the first wall surface 13c and the first wall surface 13d.

[0035] The coupling unit 14 connects the second edge surface 13b of the rectangular cavity resonator 13 with the incident plane 15a of the second rectangular waveguide 15.

[0036] The coupling unit 14 has a coupling hole 14a for coupling the electromagnetic wave incident on the rectangular cavity resonator 13 into the second rectangular waveguide 15.

[0037] The second rectangular waveguide 15 is installed parallel to the XY plane.

[0038] The incident plane 15a of the second rectangular waveguide 15 is a plane parallel to the ZX plane, and the incident plane 15a is connected to the second edge surface 13b of the rectangular cavity resonator 13 via the coupling unit 14.

[0039] An exit plane 15b of the second rectangular waveguide 15 is a plane parallel to the ZX plane, and the exit plane 15b is a plane from which the electromagnetic wave incident from the incident plane 15a exits.

[0040] The second rectangular waveguide 15 comprises a third wall surface 15c, a third wall surface 15d, a fourth wall surface 15e and a fourth wall surface 15f.

[0041] Each of the third wall surface 15c and the third wall surface 15d is a surface parallel to the XY plane, and each of the third wall surface 15c and the third wall surface 15d is a wide wall surface that is wider in area than each of the fourth wall surface 15e and the fourth wall surface 15f.

[0042] Each of the fourth wall surface 15e and the fourth wall surface 15f is a surface parallel to the YZ plane, and each of the fourth wall surface 15e and the fourth wall surface 15f is a narrow wall surface narrower in area than each of the third wall surface 15c and the third wall surface 15d.

[0043] Here, it is assumed that a direction orthogonal to each of the first edge surface 13a and the second edge surface 13b is 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.

[0044] In the Fig. 2, dimensions in the second direction of the first wall surfaces 13c and 13d are longer than dimensions in the second direction of the third wall surfaces 11c, 11d, 15c and 15d.

[0045] A protrusion 16a is provided on the first wall surface 13c of the rectangular cavity resonator 13 so as to protrude from the rectangular cavity resonator 13. The inside of the protrusion 16a is hollow, and the space inside the protrusion 16a is connected to the space inside the rectangular cavity resonator 13.

[0046] The projection 16a shifts the resonance frequency of the TE10 mode and the resonance frequency of the TE20 mode by different amounts.

[0047] Fig. 3 is an explanatory diagram showing an installation position of the projection 16a and a projection 16b.

[0048] P a is, as in Fig. 3, a position in which the projection 16a is provided on the first wall surface 13c, and the position P ais a position where a distance d1 from the first edge surface 13a is identical to a distance d1 from the second edge surface 13b. The position used here where the distances d1 are identical to each other is not limited to a position where the two distances exactly coincide with each other, but may be a position where the two distances differ from each other within a range where no practical problems arise.

[0049] In addition, the position P a , as in Fig. 3, a position where a distance from the second wall surface 13f, which is an edge portion in the second direction of the first wall surface 13c, is one-quarter of a dimension d in the second direction of the first wall surface 13c. The one-quarter position used here is not limited to a position where the distance from the second wall surface 13f is exactly one-quarter of the dimension d of the first wall surface 13c, and the distance from the second wall surface 13f may be shifted from the one-quarter position of the dimension d of the first wall surface 13c within a range where no practical problems arise.

[0050] When the projection 16a is in position P a is installed, the protrusion 16a shifts the resonance frequency of the TE20 mode to a high frequency side, almost without shifting the resonance frequency of the TE10 mode.

[0051] The protrusion 16b is provided on the first wall surface 13c of the rectangular cavity resonator 13 so as to protrude from the rectangular cavity resonator 13. The inside of the protrusion 16b is hollow, and the space inside the protrusion 16b is continuous with the space inside the rectangular cavity resonator 13.

[0052] The projection 16b shifts the resonance frequency of the TE10 mode and the resonance frequency of the TE20 mode by different amounts.

[0053] P b is, as in Fig. 3, a position in which the projection 16b is provided on the first wall surface 13c, and the position P bis a position where a distance d1 from the first edge surface 13a is identical to a distance d1 from the second edge surface 13b. The position used here where the distances d1 are identical to each other is not limited to a position where the two distances exactly coincide with each other, but may be a position where the two distances differ from each other within a range where no practical problems arise.

[0054] In addition, the position P b , as in Fig. 3, a position where a distance from the second wall surface 13f, which is an edge portion in the second direction of the first wall surface 13c, is approximately three-quarters of the dimension d in the second direction of the first wall surface 13c. The three-quarter position used here is not limited to a position where the distance from the second wall surface 13f is exactly three-quarters of the dimension d of the first wall surface 13c, and the distance from the second wall surface 13f may be shifted from the three-quarter position of the dimension d of the first wall surface 13c within a range where no practical problems arise.

[0055] When the projection 16b is in position P b is installed, the protrusion 16b shifts the resonance frequency of the TE20 mode to a high frequency side, almost without shifting the resonance frequency of the TE10 mode.

[0056] Next, the functions of the Fig. 2 shown polarized waveguide filter 1 is described.

[0057] In the first rectangular waveguide 11, an electromagnetic wave, which is a signal in a given frequency band, is incident from the incident plane 11a. The first rectangular waveguide 11 transmits a TE10 mode in a rectangular waveguide as a fundamental mode.

[0058] The electromagnetic wave incident on the first rectangular waveguide 11 is coupled into the rectangular cavity resonator 13 through the coupling hole 12a of the coupling unit 12.

[0059] Since the dimensions in the second direction of the first wall surfaces 13c and 13d of the rectangular cavity resonator 13 are longer than the dimensions in the second direction of the third wall surfaces 11c and 11d of the first rectangular waveguide 11, the rectangular cavity resonator 13 excites each of the TE10 mode and the TE20 mode of the electromagnetic wave.

[0060] Fig. 4 is an explanatory diagram showing an electric field distribution of resonance of the TE10 mode of the electromagnetic wave, and Fig. 5 is an explanatory diagram showing an electric field distribution of resonance of the TE20 mode of the electromagnetic wave.

[0061] The electromagnetic wave incident on the rectangular cavity resonator 13 is coupled into the second rectangular waveguide 15 through resonance of each of the TE10 mode and the TE20 mode and through the coupling hole 14a of the coupling unit 14.

[0062] The electromagnetic wave impinging on the second rectangular waveguide 15 exits from the exit plane 15b.

[0063] By exciting each of the TE10 mode and the TE20 mode of the electromagnetic wave in the rectangular cavity resonator 13, a path corresponding to the TE10 mode and a path corresponding to the TE20 mode are generated inside the rectangular cavity resonator 13.

[0064] By generating two paths, i.e., the path corresponding to the TE10 mode and the path corresponding to the TE20 mode, inside the rectangular cavity resonator 13, an attenuation pole is generated inside the rectangular cavity resonator 13 which depends on a difference between the two paths.

[0065] The projections 16a and 16b are provided on the first wall surface 13c of the rectangular cavity resonator 13.

[0066] The position P a, in which the projection 16a is provided, is, as in Fig. 3, a position in which a distance d1 from the first edge surface 13a is approximately identical to a distance d1 from the second edge surface 13b.

[0067] In addition, the position P a , in which the projection 16a is provided, as in Fig. 3, a position in which a distance from the second wall surface 13f is about a quarter of the dimension d in the second direction of the first wall surface 13c.

[0068] The position P a , in which the projection 16b is provided, is, as in Fig. 3, a position in which a distance d1 from the first edge surface 13a is approximately identical to a distance d1 from the second edge surface 13b.

[0069] In addition, the position P b , in which the projection 16b is provided, as in Fig. 3, a position in which a distance from the second wall surface 13f is about three-quarters of the dimension d in the second direction of the first wall surface 13c.

[0070] Each from position P a and the P b is, as in Fig. 5, a position where the electric field of the TE20 mode is large.

[0071] Each from position P a and P b is, as in Fig. 4, outside a position where the electric field of the TE10 mode is large.

[0072] Thus, when the protrusions 16a and 16b are provided on the first wall surface 13c of the rectangular cavity resonator 13, the resonance frequency of the TE20 mode is shifted toward the high-frequency side, while the resonance frequency of the TE10 mode remains almost unchanged. Shifting the resonance frequency of the TE20 mode toward the high-frequency side changes the frequency of a damping pole generated inside the rectangular cavity resonator 13.

[0073] In the Fig. 2, the two projections 16a and 16b are provided on the first wall surface 13c of the rectangular cavity resonator 13. However, this is only an example, and as shown in Fig. 6, two projections 16c and 16d may be provided on the first wall surface 13d of the rectangular cavity resonator 13 in addition to the two projections 16a and 16b provided on the first wall surface 13c of the rectangular cavity resonator 13.

[0074] Fig. 6 is a configuration diagram showing the protrusions 16a and 16b provided on a first wall surface 13c of the rectangular cavity resonator 13, and the protrusions 16c and 16d provided on a first wall surface 13d.

[0075] A position P c , in which the projection 16c is provided on the first wall surface 13d, is like the position P a a position in which a distance d1 from the first edge surface 13a is approximately identical to a distance d1 from the second edge surface 13b.

[0076] In addition, the position P c, in which the projection 16c is provided, such as the position P a a position in which a distance from the second wall surface 13f is about a quarter of the dimension d in the second direction of the first wall surface 13d.

[0077] A position P d , in which the projection 16d is provided on the first wall surface 13d, is like the position P b a position in which a distance d1 from the first edge surface 13a is approximately identical to a distance d1 from the second edge surface 13b.

[0078] In addition, the position P d , in which the projection 16d is provided, such as the position P b a position in which a distance from the second wall surface 13f is about three-quarters of the dimension d in the second direction of the first wall surface 13d.

[0079] By providing the two protrusions 16c and 16d in addition to the two protrusions 16a and 16b, the amount of shift of the resonance frequency of the TE20 mode to the high frequency side can be increased compared to a case where only the protrusions 16a and 16b are provided.

[0080] In the Fig. 2, the two projections 16a and 16b are provided on the first wall surface 13c. In the case of the Fig. 6, the two projections 16a and 16b are provided on the first wall surface 13c and the two projections 16c and 16d are provided on the first wall surface 13d.

[0081] However, these are only examples, and as in Fig. 7 or Fig. 8, only one of the projections 16a and 16b may be provided on the first wall surface 13c. Furthermore, only one of the projections 16c and 16d may be provided on the first wall surface 13d.

[0082] Thus, a total of one projection may be provided on the first wall surfaces 13c and 13d, or a total of three or four projections may be provided.

[0083] Fig. 7 is a configuration diagram showing the protrusion 16a provided on the first wall surface 13c of the rectangular cavity resonator 13.

[0084] Fig. 8 is a configuration diagram showing the protrusion 16b provided on the first wall surface 13c of the rectangular cavity resonator 13.

[0085] In the Fig. 7 shown polarized waveguide filter 1, the position P awhere the protrusion 16a is provided, a position where a distance from the second wall surface 13f is approximately one-quarter of the dimension d in the second direction of the first wall surface 13d. Thus, when the protrusion 16a is provided on the first wall surface 13c, the resonance frequency of the TE20 mode shifts toward a high-frequency side, while the resonance frequency of the TE10 mode almost does not change at all.

[0086] It is assumed that the position P a in which the projection 16a is provided, for example, as in Fig. 9, is a position in which a distance from the second wall surface 13f is one-half of the dimension d in the second direction of the first wall surface 13d. When the position P aIn the region where the protrusion 16a is provided, the one-half position of the dimension d of the first wall surface 13d is used, the resonance frequency of the TE10 mode is shifted to a high-frequency side, while the resonance frequency of the TE20 mode almost does not change at all. The one-half position used here is not limited to a position where the distance from the second wall surface 13f is exactly one-half of the dimension d of the first wall surface 13c, and the distance from the second wall surface 13f can be shifted from the one-half position of the dimension d of the first wall surface 13c within a range where no practical problems arise.

[0087] Fig. 9 is an explanatory diagram showing an installation position of the projection 16a.

[0088] The position P a , in which the projection 16a is provided, is, as in Fig. 9, a position in which a distance d1 from the first edge surface 13a is approximately identical to a distance d1 from the second edge surface 13b. The position used here, in which the distances d1 are identical to each other, is not limited to a position in which the two distances exactly coincide with each other, but may be a position in which the two distances differ from each other within a range in which no practical problems arise.

[0089] In the first embodiment described above, the polarized waveguide filter 1 is configured in which the protrusions 16a and 16b, which shift the resonance frequency of the TE10 mode and the resonance frequency of the TE20 mode by mutually different amounts, are provided on one or more first wall surfaces among the two first wall surfaces 13c and 13d of the rectangular cavity resonator 13 so as to protrude from the rectangular cavity resonator 13. Thus, the polarized waveguide filter 1 can make the amount of shift of the resonance frequency of the TE10 mode excited by the rectangular cavity resonator 13 different from the amount of shift of the resonance frequency of the TE20 mode excited by the rectangular cavity resonator 13.

[0090] As in Fig. 10, by providing protrusions 16e and 16f in the second wall surfaces 13e and 13f of the rectangular cavity resonator 13 in such a manner as to protrude toward the inside of the rectangular cavity resonator 13, 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.

[0091] Fig. 10 is a configuration diagram showing the protrusions 16e and 16f provided in the second wall surfaces 13e and 13f of the rectangular cavity resonator 13.

[0092] However, the positions where the protrusions 16e and 16f are provided are respectively outside each of the position where the electric field of the TE10 mode is large and the position where the electric field of the TE20 mode is large, and there is no large difference between them.

[0093] Thus, by providing the protrusions 16e and 16f in the second wall surfaces 13e and 13f of the rectangular cavity resonator 13, 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.

[0094] When the protrusions 16e and 16f are provided in the second wall surfaces 13e and 13f, the difference between the resonance frequency of the TE10 mode after the shift and the resonance frequency of the TE20 mode after the shift is not large compared to a case where the protrusions 16a and 16b are provided on the first wall surface 13c. Therefore, when the protrusions 16e and 16f are provided in the second wall surfaces 13e and 13f, the amount of frequency change of an attenuation pole generated inside the rectangular cavity resonator 13 is small compared to a case where the protrusions 16a and 16b are provided on the first wall surface 13c.

[0095] It should be noted that when the protrusions 16a and 16b are provided on the first wall surface 13c, a power loss of a signal in a given frequency band, etc., can be reduced compared to a case where the protrusions 16e and 16f are provided in the second wall surfaces 13e and 13f. Second embodiment.

[0096] In a second embodiment, a polarized waveguide filter 1 is described in which a dimension of a protrusion 16a in a direction in which the protrusion 16a protrudes from a rectangular cavity resonator 13 differs from a dimension of a protrusion 16b in a direction in which the protrusion 16b protrudes from the rectangular cavity resonator 13. The directions in which the protrusions 16a and 16b protrude from the rectangular cavity resonator 13 are directions parallel to a Z-axis.

[0097] Fig. 11 is a configuration diagram showing the polarized waveguide filter 1 according to the second embodiment. In Fig. 11 have the same reference numerals as in Fig. 2 and Fig. 3 refer to the same or corresponding parts, so that a description is omitted.

[0098] The dimension of the projection 16b in the direction in which the projection 16b protrudes from the rectangular cavity resonator 13 is longer than the dimension of the projection 16a in the direction in which the projection 16a protrudes from the rectangular cavity resonator 13.

[0099] Each of the protrusion 16a and the protrusion 16b shifts the resonance frequency of the TE20 mode to a high frequency side.

[0100] However, since the dimension in the projecting direction is longer in the protrusion 16b than in the protrusion 16a, the amount of displacement to the high frequency side resulting from the provision of the protrusion 16b is larger than the amount of displacement to the high frequency side resulting from the provision of the protrusion 16a.

[0101] By making the dimension of the projection 16b in the outward direction different from the dimension of the projection 16a in the outward direction, the amount of displacement toward the high frequency side can be changed. Third embodiment.

[0102] In the Fig. 1, the projections 16a and 16b are shown, each having a cylindrical shape.

[0103] In a third embodiment, a polarized waveguide filter 1 is described in which projections 16a and 16b each have a rectangular parallelepiped shape.

[0104] In the Fig. 1, the projections 16a and 16b are shown, each having a cylindrical shape. However, this is only an example, and as shown in Fig. 12, the projections 16a and 16b may each have a rectangular parallelepiped shape.

[0105] Fig. 12 is a configuration diagram showing the polarized waveguide filter 1 according to the third embodiment. In Fig. 12 have the same reference numerals as in Fig. 2 and Fig. 3 refer to the same or corresponding parts, so that a description is omitted.

[0106] In the Fig. In the polarized waveguide filter 1 shown in Figure 12, the protrusions 16a and 16b each have a rectangular parallelepiped shape, and the lengths of the protrusions 16a and 16b in a direction parallel to the Y-axis are longer than the lengths of the protrusions 16a and 16b in a direction parallel to the X-axis. Such a rectangular parallelepiped shape is hereinafter referred to as a "horizontally oriented rectangular parallelepiped shape."

[0107] In a case where the projections 16a and 16b each have a cylindrical shape, the resonance frequency of the TE10 mode almost does not change at all even if the projection 16a is at the position P a on the first wall surface 13c and the projection 16b at the position P b on the first wall surface 13c.

[0108] On the other hand, in a case where the projections 16a and 16b each have a horizontally oriented rectangular parallelepiped shape, if the projection 16a is in the position P a on the first wall surface 13c and the projection 16b in the position P bprovided on the first wall surface 13c, not only is the resonance frequency of the TE20 mode 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 shift of the resonance frequency of the TE10 mode to the high-frequency side is very small compared to the amount of shift of the resonance frequency of the TE20 mode to the high-frequency side. Thus, a change in the resonance frequency resulting from the provision of the protrusions 16a and 16b, each having a horizontally oriented rectangular parallelepiped shape, substantially corresponds to a change in only the resonance frequency of the TE20 mode.

[0109] In the Fig. In the polarized waveguide filter 1 shown in Figure 12, the projections 16a and 16b each have a horizontally oriented rectangular parallelepiped shape.

[0110] However, this is only an example, and as in Fig. As shown in Figure 13, the protrusions 16a and 16b may each have a rectangular parallelepiped shape, and the lengths of the protrusions 16a and 16b in the direction parallel to the Y-axis may be shorter than the lengths of the protrusions 16a and 16b in the direction parallel to the X-axis. Such a rectangular parallelepiped shape is hereinafter referred to as a "horizontally oriented rectangular parallelepiped shape."

[0111] Fig. 13 is a configuration diagram showing another polarized waveguide filter 1 according to the third embodiment.

[0112] When the protrusions 16a and 16b each have a cylindrical shape, by providing the protrusions 16a and 16b on the first wall surface 13c, the resonance frequency of the TE20 mode is shifted to a high frequency side.

[0113] When the protrusions 16a and 16b each have a vertically oriented rectangular parallelepiped shape, by providing the protrusions 16a and 16b on the first wall surface 13c, the resonance frequency of the TE20 mode is shifted to a higher frequency side than in a case where the protrusions 16a and 16b each have a cylindrical shape.

[0114] In both the horizontally oriented rectangular parallelepiped shape and the vertically oriented rectangular parallelepiped shape, the places where orthogonal planes intersect among a plurality of planes of a rectangular parallelepiped may be rounded.

[0115] In addition, in six planes of the rectangular cavity resonator 13, six planes of the first rectangular waveguide 11 or six planes of the second rectangular waveguide 15, the points where the orthogonal planes of the six planes intersect may also be rounded.

[0116] If it is possible to round off the points where planes intersect, a construction is possible in which a cutting process is to be carried out by means of a drill.

[0117] As in Fig. 14 or Fig. As shown in Fig. 15, the polarized waveguide filter 1 may be formed by coupling a metal block B1 that has been subjected to a cutting process using a drill with a metal block B2 that has been subjected to a cutting process using a drill.

[0118] Fig. 14 and Fig. 15 are explanatory diagrams showing polarized waveguide filters 1 each having a metal block B1 and a metal block B2 coupled to each other.

[0119] Between the Fig. 14 and Fig. 15, the position of a coupled plane of the metal block B1 and the metal block B2 is different, and the position of the coupling unit 12 relative to the first edge surface 13a of the rectangular cavity resonator 13 is different. Fourth embodiment.

[0120] In a fourth embodiment, a polarized waveguide filter 1 with an external resonator 22 is described.

[0121] Fig. 16 is a configuration diagram showing the polarized waveguide filter 1 according to the fourth embodiment. In Fig. 16 denote the same reference numerals as in the Fig. 2 and Fig. 3 the same or corresponding parts, so that a description is omitted.

[0122] The coupling unit 21 connects the second wall surface 13e of the rectangular cavity resonator 13 with an incident plane 22a of the second rectangular waveguide 22.

[0123] The coupling unit 21 has a coupling hole 21a for coupling an electromagnetic wave incident on the rectangular cavity resonator 13 into the external resonator 22. The external resonator 22 is installed parallel to the XY plane.

[0124] The incident plane 22a of the external resonator 22 is a plane parallel to the YZ plane, and the incident plane 22a is connected to the second wall surface 13e of the rectangular cavity resonator 13 via the coupling unit 21.

[0125] When an electromagnetic wave is incident from the incident plane 22a, an attenuation pole having a frequency different from a frequency of an attenuation pole generated inside the rectangular cavity resonator 13 is generated inside the external resonator 22.

[0126] The frequency of the damping pole generated inside the external resonator 22 is determined by a length of the external resonator 22 in a direction parallel to the x-axis and a length of the external resonator 22 in a direction parallel to the y-axis.

[0127] In the Fig. In the polarized waveguide filter 1 shown in Fig. 16, by including the external resonator 22 in addition to an attenuation pole generated inside the rectangular cavity resonator 13, an attenuation pole having a frequency different from the frequency of the attenuation pole generated inside the rectangular cavity resonator 13 is generated.

[0128] In the Fig. In the polarized waveguide filter 1 shown in Figure 16, the external resonator 22 has a rectangular parallelepiped shape. However, this is only an example, and as shown in Fig. 17, a shape on the XY plane of an external resonator 23 may be, for example, trapezoidal.

[0129] Fig. 17 is a configuration diagram showing another polarized waveguide filter 1 according to the fourth embodiment.

[0130] An incident plane 23a of the external resonator 23 is a plane parallel to the YZ plane, and the incident plane 23a is connected to the second wall surface 13e of the rectangular cavity resonator 13 via the coupling unit 21.

[0131] An edge surface 23b is a surface parallel to the YZ plane facing the impact plane 23a.

[0132] A length of the impact plane 23a in a direction parallel to the y-axis is shorter than a length of the edge surface 23b in the direction parallel to the y-axis. The lengths in the direction parallel to the y-axis are lengths in the first direction.

[0133] When an electromagnetic wave is incident from the incident plane 23a, an attenuation pole having a frequency different from a frequency of an attenuation pole generated inside the rectangular cavity resonator 13 is generated inside the external resonator 23.

[0134] The frequency of the damping pole generated inside the external resonator 23 is determined by a length of the external resonator 23 in a direction parallel to the x-axis, a length of the incident plane 23a in a direction parallel to the y-axis, and a length of the edge surface 23b in the direction parallel to the y-axis.

[0135] When a shape on the XY plane of the external resonator 23 is trapezoidal, the number of parameters that determine a frequency of a damping pole generated inside the external resonator 23 increases compared to a case where the external resonator 22 has a rectangular parallelepiped shape, and thus flexibility in design improves.

[0136] In the Fig. 16 and Fig. In the polarized waveguide filters 1 shown in Fig. 17, the incident plane 22a of the external resonator 22 or the incident plane 23a of the external resonator 23 is connected to the second wall surface 13e of the rectangular cavity resonator 13 via the coupling unit 21.

[0137] However, this is only an example, and an incident plane 22a of an external resonator 22 or an incident plane 23a of an external resonator 23 may be connected to the second wall surface 13f of the rectangular cavity resonator 13 via a coupling unit (not shown). Thus, the polarized waveguide filter 1 may include two external resonators 22 or two external resonators 23. Furthermore, the polarized waveguide filter 1 may include one external resonator 22 and one external resonator 23. Fifth embodiment.

[0138] In a fifth embodiment, a polarized waveguide filter 1 comprising a second rectangular cavity resonator 32 is described.

[0139] Fig. 18 is a configuration diagram showing the polarized waveguide filter 1 according to the fifth embodiment. In Fig. 18 denote the same reference numerals as in the Fig. 2 and Fig. 3 identical or corresponding parts, so no description is required.

[0140] The Fig. The polarized waveguide filter 1 shown in Fig. 18 comprises two rectangular cavity resonators, the rectangular cavity resonator 13 and the second rectangular cavity resonator 32. However, this is only an example, and the polarized waveguide filter 1 may include three or more rectangular cavity resonators.

[0141] A coupling unit 31 connects the exit plane 15b of the second rectangular waveguide 15 to a third edge surface 32a of the second rectangular cavity resonator 32.

[0142] The coupling unit 31 has a coupling hole 31a for coupling an electromagnetic wave incident on the second rectangular waveguide 15 into the second rectangular cavity resonator 32.

[0143] The second rectangular cavity resonator 32 is installed parallel to the XY plane.

[0144] The third edge surface 32a of the second rectangular cavity resonator 32 is a surface parallel to the ZX plane, and the third edge surface 32a is connected to the exit plane 15b of the second rectangular waveguide 15 via the coupling unit 31.

[0145] A fourth edge surface 32b of the second rectangular cavity resonator 32 is a surface parallel to the ZX plane and faces the third edge surface 32a. The fourth edge surface 32b is connected to an incident plane 34a of a third rectangular waveguide 34 via a coupling unit 33.

[0146] The second rectangular cavity resonator 32 excites each of the TE10 mode and the TE20 mode of the electromagnetic wave.

[0147] The second rectangular cavity resonator 32 includes a fifth wall surface 32c, a sixth wall surface 32e and a sixth wall surface 32f.

[0148] The fifth wall surface 32c is a surface parallel to the XY plane, and the fifth wall surface 32c is a wide wall surface that is wider in area than each of the sixth wall surface 32e and the sixth wall surface 32f.

[0149] Fig. 18 is a drawing of the polarized waveguide filter 1 viewed from a front direction of the sheet, and when the front direction of the sheet is an upper side of the polarized waveguide filter 1, the fifth wall surface 32c is an upper surface of the second rectangular cavity resonator 32. Although in Fig. 18, a bottom surface of the second rectangular cavity resonator 32 is not shown, the bottom surface of the second rectangular cavity resonator 32 is another fifth wall surface facing the fifth wall surface 32c.

[0150] Each of the sixth wall surface 32e and the sixth wall surface 32f is a surface parallel to the YZ plane, and each of the sixth wall surface 32e and the sixth wall surface 32f is a narrow wall surface that is narrower in area than the fifth wall surface 32c.

[0151] The coupling unit 33 connects the fourth edge surface 32b of the second rectangular cavity resonator 32 to the incident plane 34a of the third rectangular waveguide 34.

[0152] The coupling unit 33 has a coupling hole 33a for coupling the electromagnetic wave incident on the second rectangular cavity resonator 32 into the third rectangular waveguide 34.

[0153] The third rectangular waveguide 34 is installed parallel to the XY plane.

[0154] The incident plane 34a of the third rectangular waveguide 34 is a plane parallel to the ZX plane, and the incident plane 34a is connected to the fourth edge surface 32b of the second rectangular cavity resonator 32 via the coupling unit 33.

[0155] An exit plane 34b of the third rectangular waveguide 34 is a plane parallel to the ZX plane, and the exit plane 34b is a plane from which the electromagnetic wave incident from the incident plane 34a exits.

[0156] The third rectangular waveguide 34 includes a seventh wall surface 34c, an eighth wall surface 34e and an eighth wall surface 34f.

[0157] The seventh wall surface 34c is a surface parallel to the XY plane, and the seventh wall surface 34c is a wide wall surface that is wider in area than each of the eighth wall surface 34e and the eighth wall surface 34f.

[0158] Fig. 18 is a drawing of the polarized waveguide filter 1 viewed from a front direction of the sheet, and when the front direction of the sheet is the top side of the polarized waveguide filter 1, the seventh wall surface 34c is a top surface of the third rectangular waveguide 34. Although in Fig. 18, a bottom surface of the third rectangular waveguide 34 is not shown, the bottom surface of the third rectangular waveguide 34 is another seventh wall surface facing the seventh wall surface 34c.

[0159] Each of the eighth wall surface 34e and the eighth wall surface 34f is a surface parallel to the YZ plane, and each of the eighth wall surface 34e and the eighth wall surface 34f is a narrow wall surface that is narrower in area than the seventh wall surface 34c.

[0160] In the Fig. 18, a dimension in the second direction of the fifth wall surface 32c is longer than each of dimensions in the second direction of the third wall surfaces 11c, 11d, 15c and 15d and a dimension in the second direction of the seventh wall surface 34c.

[0161] A protrusion 35a is provided on the fifth wall surface 32c of the second rectangular cavity resonator 32 so as to protrude. The inside of the protrusion 35a is hollow, and the space within the protrusion 35a is continuous with the space within the second rectangular cavity resonator 32.

[0162] The projection 35a shifts the resonance frequency of the TE10 mode and the resonance frequency of the TE20 mode by different amounts from each other.

[0163] A protrusion 35b is provided on the fifth wall surface 32c of the second rectangular cavity resonator 32 so as to protrude. The inside of the protrusion 35b is hollow, and the space within the protrusion 35b is continuous with the space within the second rectangular cavity resonator 32.

[0164] The projection 35b shifts the resonance frequency of the TE10 mode and the resonance frequency of the TE20 mode by different amounts from each other.

[0165] In the Fig. In the polarized waveguide filter 1 shown in Figure 18, the two protrusions 35a and 35b are provided on the fifth wall surface 32c. However, this is only an example, and a protrusion projecting from the second rectangular cavity 32 may also be provided on the bottom surface of the second rectangular cavity resonator 32 facing the fifth wall surface 32c.

[0166] The total number of protrusions provided on the fifth wall surface 32c and protrusions provided on the bottom surface of the second rectangular cavity resonator 32 may be any number between one and four inclusive.

[0167] Next, the functions of the Fig. 18 shown polarized waveguide filter 1 is described.

[0168] It is assumed that a length of the rectangular cavity resonator 13 in a direction parallel to the x-axis is identical to a length of the second rectangular cavity resonator 32 in the direction parallel to the x-axis, and a length of the rectangular cavity resonator 13 in a direction parallel to the y-axis is identical to a length of the second rectangular cavity resonator 32 in the direction parallel to the y-axis.

[0169] Furthermore, it is assumed that the installation positions of the projections 16a and 16b with respect to the first wall surface 13c of the rectangular cavity resonator 13 are identical to installation positions of the projections 35a and 35b with respect to the fifth wall surface 32c of the second rectangular cavity resonator 32.

[0170] It is also assumed that dimensions of the projections 16a and 16b in an outward direction are identical to dimensions of the projections 35a and 35b in an outward direction.

[0171] When the lengths, positions, and dimensions described above are satisfied, a frequency of an attenuation pole generated inside the second rectangular cavity resonator 32 is identical to a frequency of an attenuation pole generated inside the rectangular cavity resonator 13. Thus, the Fig. 18 shown polarized waveguide filter 1 achieve a greater amount of attenuation than the one shown in Fig. 2 polarized waveguide filters 1 shown.

[0172] When the installation positions of the projections 16a and 16b with respect to the first wall surface 13c of the rectangular cavity resonator 13 differ from the installation positions of the projections 35a and 35b with respect to the fifth wall surface 32c of the second rectangular cavity resonator 32, or when the dimensions of the projections 16a and 16b in the outward direction differ from the dimensions of the projections 35a and 35b in the outward direction, a frequency of an attenuation pole generated inside the second rectangular cavity resonator 32 differs from a frequency of an attenuation pole generated within the rectangular cavity resonator 13. Thus, the Fig. 18 shown polarized waveguide filter 1 the number of attenuation poles compared to the one in Fig. 2 shown polarized waveguide filter 1.

[0173] It should be noted that even if the number of protrusions provided on the first wall surface 13c of the rectangular cavity resonator 13 is different from the number of protrusions provided on the fifth wall surface 32c of the second rectangular cavity resonator 32, a frequency of an attenuation pole generated inside the second rectangular cavity resonator 32 is different from a frequency of an attenuation pole generated inside the rectangular cavity resonator 13.

[0174] Even if the dimensions of the rectangular cavity resonator 13 are different from the dimensions of the second rectangular cavity resonator 32, a frequency of an attenuation pole generated inside the second rectangular cavity resonator 32 is different from a frequency of an attenuation pole generated inside the rectangular cavity resonator 13.

[0175] It should be noted that in the invention of this application, a free combination of the embodiments, modifications to any component of any of the embodiments, or omission of any component in any of the embodiments are possible within the scope of the invention. INDUSTRIAL APPLICABILITY

[0176] The invention is suitable for a polarized waveguide filter comprising rectangular waveguides and a rectangular cavity resonator, and an antenna feed circuit. LIST OF REFERENCE SYMBOLS

[0177] 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, and 35a, 35b: projection.

Claims

[1] Polarized waveguide filter (1), comprising: a first rectangular waveguide (11); a second rectangular waveguide (15); and a rectangular cavity resonator (13) for exciting a TE10 mode and a TE20 mode of an electromagnetic wave, wherein the rectangular cavity resonator has a first edge surface (13a) connected to an electromagnetic wave exit plane (11b) of the first rectangular waveguide via a coupling unit (12), wherein the rectangular cavity resonator has a second edge surface (13b) connected to an electromagnetic wave incident plane (15a) of the second rectangular waveguide via a coupling unit (14), wherein the second edge surface faces the first edge surface, wherein the rectangular cavity resonator has two first wall surfaces (13c, 13d) and two second wall surfaces (13e, 13f), each of which is narrower in area than the first wall surfaces, and wherein at least one projection (16a, 16b) for shifting a resonance frequency of the TE10 mode and a resonance frequency of the TE20 mode by mutually different amounts is provided on at least one of the two first wall surfaces so as to protrude from the rectangular cavity resonator, and wherein a first direction is a direction orthogonal to each of the first edge surface and the second edge surface, and a second direction is orthogonal to the first direction; and wherein the projection is provided in a position in which a distance from the first edge surface is identical to a distance from the second edge surface, and in which a distance from one of edge portions in the second direction of a corresponding one of the first wall surfaces is one-quarter of a dimension in the second direction of the corresponding one of the first wall surfaces or three-quarters of the dimension in the second direction of the corresponding one of the first wall surfaces. [2] A polarized waveguide filter according to claim 1, wherein each of the first rectangular waveguide and the second rectangular waveguide has two third wall surfaces (11c, 11d, 15c, 15d) and two fourth wall surfaces (11e, 11f, 15e, 15f), each of which is narrower in area than the third wall surfaces, and a dimension of each of the first wall surfaces in the second direction is longer than dimensions in the second direction of the respective third wall surfaces. [3] A polarized waveguide filter according to claim 1, wherein the at least one projection comprises a plurality of projections provided on the at least one of the first wall surfaces, and dimensions of the respective projections in a direction in which the projections protrude from the rectangular cavity resonator are different from each other. [4] A polarized waveguide filter according to claim 1, wherein the projection has a cylindrical shape. [5] A polarized waveguide filter according to claim 1, wherein the projection has a rectangular parallelepiped shape. [6] A polarized waveguide filter according to claim 2, wherein at least one of the second wall surfaces of the rectangular cavity resonator is connected to an external resonator (22, 23) via a coupling unit (21). [7] A polarized waveguide filter according to claim 6, wherein the external resonator (22) has a rectangular parallelepiped shape. [8] A polarized waveguide filter according to claim 6, wherein a dimension in the first direction of a first side of the external resonator (23) is shorter than a dimension in the first direction of a second side of the external resonator (23), the first side being connected to a corresponding one of the second wall surfaces of the rectangular cavity resonator via the coupling unit, the second side facing the first side. [9] A polarized waveguide filter according to claim 1, comprising: a third rectangular waveguide (34); and a second rectangular cavity resonator (32) for exciting the TE10 mode and the TE20 mode of the electromagnetic wave, wherein the second rectangular cavity resonator has a third edge surface (32a) connected to an electromagnetic wave exit plane (15b) of the second rectangular waveguide via a coupling unit (31), wherein the second rectangular cavity resonator has a fourth edge surface (32b) connected to an electromagnetic wave incident plane (34a) of the third rectangular waveguide via a coupling unit (33), wherein the fourth edge surface faces the third edge surface, wherein the second rectangular cavity resonator has two fifth wall surfaces (32c) and two sixth wall surfaces (32e, 32f), each of which is narrower in area than the fifth wall surfaces, and wherein at least one protrusion (35a, 35b) for shifting a resonance frequency of the TE10 mode and a resonance frequency of the TE20 mode by amounts different from each other is provided on at least one of the two fifth wall surfaces so as to protrude from the second rectangular cavity resonator. [10] A polarized waveguide filter according to claim 9, wherein the third rectangular waveguide has two seventh wall surfaces (34c) and two eighth wall surfaces (34e, 34f), each of which is narrower in area than the seventh wall surfaces, and a dimension in the second direction of each of the fifth wall surfaces is longer than dimensions in the second direction of the respective third wall surfaces (11c, 11d, 15c, 15d) and dimensions in the second direction of the respective seventh wall surfaces. [11] An antenna feed circuit comprising the polarized waveguide filter according to any one of claims 1 to 10.

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