Passband variable device, waveguide, and passband variable method

Abstract

To realize a passband variable filter of a high Q value.SOLUTION: A passband variable device 10 comprises: a waveguide 11 including a band-pass filter member 13 consisting of a plurality of resonance members 14 used as resonators and a coupling member 15 disposed between the resonance members 14 and used for coupling the resonators, and a passband variable member 16 consisting of one or more magnetic substance elements for varying a passband of the band-pass filter member 13 with a magnetic field applied from the outside of the waveguide 11; and a magnetic field application section 12 which applies a magnetic field for controlling effective permeability of the resonance member 14 in order to vary the passband of the band-pass filter member 13.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a passband tuning device, a waveguide, and a passband tuning method. [Background technology]

[0002] When constructing a microwave communication system, it is desirable to externally vary the passband of a waveguide having a band-pass filter (BPF).

[0003] As a related technique, Patent Document 1 discloses an agile-type microwave filter. The agile-type microwave filter of Patent Document 1 includes one or more ferrite resonators arranged in a waveguide. In addition, the center frequency of the agile-type microwave filter is shifted by changing the resonant frequency of the ferrite resonator of the agile-type microwave filter of Patent Document 1.

[0004] As a related technique, a magnetic resonator is disclosed in Patent Document 2. According to the magnetic resonator of Patent Document 2, a magnetic resonator is constructed by forming electrodes on the front and back surfaces of a substrate coated with a magnetic film having tensor permeability, and an external magnetic field is applied to the magnetic film by a permanent magnet, and the resonant frequency is adjusted by changing the magnitude of the external magnetic field.

[0005] As a related technique, Patent Document 3 discloses a planar filter in which a flat filter member and a tuning member are arranged facing each other with a predetermined distance between them. The filter member has a structure in which an input / output section made of a superconductor and multiple resonant elements are formed on a substrate. The tuning member has a structure in which multiple dielectric thin films and multiple electrodes for applying an electric field to these dielectric thin films are arranged on the surface of a magnetic plate whose magnetic permeability changes with an applied magnetic field.

[0006] Each of the dielectric thin films is disposed at a position facing a gap between the resonant elements of the filter member or a gap between the filter member and the input / output unit, and a voltage is applied between the electrodes to variably control the effective dielectric constant ε of the gap between the resonant elements or the gap between the resonant element and the input / output unit, thereby adjusting the skirt characteristic and ripple.

[0007] Furthermore, as a related technique, a variable inductor is disclosed in Patent Document 4. According to the variable inductor of Patent Document 4, a magnetic force is applied from the outside to a magnetic core around which a coil of the variable inductor is wound. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 05-037202 [Patent Document 2] Japanese Patent Application Publication No. 08-293704 [Patent Document 3] JP 2001-102808 A [Patent Document 4] Japanese Patent Application Publication No. 01-169012 Summary of the Invention [Problem to be solved by the invention]

[0009] However, in Patent Documents 1, 2 and 4, the passband frequency is adjusted using ferrite (magnetic material) as a resonator, so it is difficult to suppress loss within the ferrite and increase the Q value (reduce loss).

[0010] In addition, it is difficult to apply the planar filter of Patent Document 3 to a waveguide. Moreover, the planar filter of Patent Document 3 has a complex structure because a voltage application electrode is attached to the filter member and a refrigerator is required because a superconductor is used.

[0011] An example of an objective of the present disclosure is to realize a passband tunable filter with a high Q value. [Means for solving the problem]

[0012] In order to achieve the above object, a passband tunable device according to one aspect of the present disclosure includes: a waveguide having a band-pass filter member including a plurality of resonator members used as resonators and coupling members disposed between the resonator members and used to couple the resonators; and a passband variable member including one or more magnetic elements that varies a passband of the band-pass filter member by a magnetic field applied from outside the waveguide; a magnetic field applying means for applying the magnetic field to control the effective permeability of the resonator member in order to vary the passband of the bandpass filter member; The present invention is characterized by having the following.

[0013] In order to achieve the above object, a waveguide according to one aspect of the present invention comprises: an input terminal for introducing a first radio wave into the waveguide; a bandpass filter member including a plurality of resonator members used as resonators and coupling members disposed between the resonator members and used to couple the resonators; a passband variable member including one or more magnetic elements that varies a passband of the bandpass filter member by a magnetic field applied from outside the waveguide; an output terminal that outputs a second radio wave output from the band-pass filter member to the outside of the waveguide after the first radio wave is input to the band-pass filter member; The present invention is characterized by having the following.

[0014] Furthermore, in order to achieve the above object, a passband control method according to one aspect of the present invention includes: a band-pass filter member including a plurality of resonant members used as resonators, a coupling member disposed between the resonant members and used to couple the resonators, and a pass-band variable member including one or more magnetic elements that varies a pass-band of the band-pass filter member in response to a magnetic field applied from outside the waveguide; applying the magnetic field to the waveguide to control an effective permeability of the resonant members in order to vary the pass-band of the band-pass filter member; It is characterized by: Effect of the Invention

[0015] One aspect is that a passband tunable filter with a high Q value can be realized. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram illustrating an example of a passband variable device. [Diagram 2] FIG. 2 is an exploded perspective view illustrating an example of a waveguide according to the first embodiment. [Diagram 3] FIG. 3 is a top view and a side view for explaining an example of a waveguide in the first embodiment. [Figure 4] FIG. 4 is a diagram for explaining an example of transmission characteristics of the waveguide in the first embodiment. [Diagram 5] FIG. 5 is an exploded perspective view illustrating an example of a waveguide according to the second embodiment. [Figure 6] FIG. 6 is a top view and a side view for explaining an example of a waveguide according to the second embodiment. [Figure 7] FIG. 7 is a diagram for explaining an example of transmission characteristics of a waveguide in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment will be described with reference to the drawings. In the drawings described below, elements having the same or corresponding functions are denoted by the same reference numerals, and repeated description thereof may be omitted.

[0018] (Embodiment) The configuration of a passband variable device 10 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram for explaining an example of a passband variable device.

[0019] [Device configuration] A passband variable device 10 shown in Fig. 1 is a device that realizes a passband variable filter with a high Q value. As shown in Fig. 1, the passband variable device 10 includes a waveguide 11 and a magnetic field application unit 12 (12a, 12b).

[0020] 1, the waveguide 11 has a band-pass filter member 13, a passband variable member 16, an input terminal 17, and an output terminal 18. The band-pass filter member 13 is composed of two or more resonant members 14 and one or more coupling members 15.

[0021] Specifically, the waveguide 11 has a band-pass filter member 13 composed of a plurality of resonant members 14 used as resonators and coupling members 15 arranged between the resonant members 14 and used to couple the resonators, and a passband variable member 16 composed of one or more magnetic elements that varies the passband of the band-pass filter member 13 by a magnetic field applied from outside the waveguide 11.

[0022] The bandpass filter member 13 has two or more resonant members 14 and one or more coupling members 15. A bandpass filter is a bandpass filter.

[0023] The resonator members 14 are metallic members used as resonators. The coupling members 15 are metallic members disposed between the resonator members 14 and used to couple the resonators. The strength of the coupling is determined by the shape of the coupling members 15.

[0024] The passband (first passband) of the bandpass filter is determined by the shape of the resonant member 14, the shape of the coupling member 15, the distance between the resonant member 14 and the coupling member 15, etc. The first passband is the passband when no magnetic field is applied.

[0025] The passband variable member 16 is disposed inside the waveguide 11, near the bandpass filter member 13. The passband variable member 16 is disposed at a position where a first passband of the bandpass filter member can be changed to a preset second passband when a magnetic field of a preset strength is applied to the passband variable member 16. The second passband is a passband that is changed from the first passband when a magnetic field is applied.

[0026] The passband variable member 16 is not used as a resonator. Therefore, although the direction and strength of the electric field centered on the resonator change depending on the presence or absence of the passband variable member 16 (ferrite), the semi-coaxial resonance mode itself does not change.

[0027] The passband variable member 16 has one or more magnetic elements (ferrite). One ferrite may be provided for the plurality of resonator members 14, or one ferrite may be provided for each of the plurality of resonator members 14.

[0028] The magnetic field applying section 12 (12a, 12b) applies a magnetic field for controlling the effective magnetic permeability of the resonator member 14 in order to vary the pass band of the band-pass filter member 13.

[0029] The magnetic field applying unit 12 applies a magnetic field using, for example, a magnet or an electromagnet, and changes the pass frequency, or the pass bandwidth, or both.

[0030] When magnets are used as the magnetic field application unit 12, the strength of the magnetic field is changed by changing the number of magnets. Also, the strength of the magnetic field is changed by changing the distance between the magnets and the waveguide 11. The magnets are placed outside the waveguide 11 and near the passband variable member 16.

[0031] When an electromagnet is used as the magnetic field application unit 12, the strength of the magnetic field is changed by changing the value of the current flowing through the electromagnet. Also, the strength of the magnetic field is changed by changing the distance between the electromagnet and the waveguide 11. The electromagnet is disposed outside the waveguide 11 and in the vicinity of the passband variable member 16.

[0032] [Effects of the embodiment] As described above, in the embodiment, a bandpass filter is formed using the resonant member 14 and the coupling member 15, and the effective permeability of the resonant member 14 is varied using the passband variable member 16 which is not a resonator, thereby realizing a passband variable filter with a high Q value.

[0033] In other words, since ferrite is not used as a resonator, a variable passband filter with a high Q value can be realized even among waveguides having a variable passband filter of the magnetic field control type.

[0034] In addition, since ferrite has a large dielectric loss tangent (tan δ), its use in a resonator would result in large loss. However, since ferrite is not used as a resonator, the loss due to the dielectric loss tangent can be reduced. EXAMPLES

[0035] The waveguide 20 in the first embodiment will be described with reference to Figs. 2, 3 and 4. The waveguide 20 in the first embodiment corresponds to the waveguide 11 in Fig. 1. Fig. 2 is an exploded perspective view for explaining an example of the waveguide in the first embodiment. Fig. 3 is a top view and a side view for explaining an example of the waveguide in the first embodiment. Fig. 4 is a diagram for explaining an example of the transmission characteristics of the waveguide in the first embodiment.

[0036] 2 and 3, the waveguide 20 has a housing 21 (a first housing 21a and a second housing 21b), a band-pass filter member 13 (a plurality of resonant members 14 and a plurality of coupling members 15), a passband variable member 16, an input terminal 17, and an output terminal 18. In the first embodiment, one passband variable member 16 is arranged for the plurality of resonant members 14.

[0037] The waveguide 20 may be, for example, a rectangular waveguide, a circular waveguide, a ridged waveguide, etc. In the first embodiment, a rectangular waveguide is used for explanation. However, the shape of the waveguide 20 is not limited to a rectangular waveguide.

[0038] 2 and 3, the housing 21 is divided into two parts in the Z-axis direction, a first housing 21a and a second housing 21b. The first housing 21a and the second housing 21b are joined together.

[0039] The first housing 21a has a passband variable member 16 and posts 22 (22a, 22b).

[0040] 2 and 3, the passband variable member 16 is a rectangular plate, the length of which in the longitudinal direction is equal to or longer than the length from the input terminal 17 to the output terminal 18, and the length of which in the lateral direction is shorter than the length of the inner wall of the waveguide 20. However, the shape of the plate is not limited to a rectangle, and may be any shape that covers all of the resonant members 14.

[0041] The passband variable member 16 is positioned so that the first passband of the bandpass filter member 13 can be varied to a preset second passband when a magnetic field for controlling the effective permeability of the resonator member 14 is applied with a preset strength.

[0042] 2 and 3, the pillars 22a and 22b fix the passband variable member 16 to a predetermined position. One end of the pillar 22a is fixed to an end (a portion near the end) of the upper surface of the first housing 21a on the input terminal 17 side, and one end of the pillar 22b is fixed to an end (a portion near the end) of the upper surface of the first housing 21a on the output terminal 18 side. The other end of the pillar 22a is fixed to an end (a portion near the end) of the input terminal 17 side of the passband variable member 16, and the other end of the pillar 22b is fixed to an end (a portion near the end) of the output terminal 18 of the passband variable member 16.

[0043] 3, the number of support posts 22 is two, but is not limited to two. Furthermore, the support posts 22 may be fixed using screws or by welding.

[0044] The length L1 of the posts 22a and 22b shown in FIG. 3 may be a length at which the passband variable member 16 comes into contact with the resonant member 14, or may be a length at which the passband variable member 16 does not come into contact with the resonant member 14.

[0045] The second housing 21b has a plurality of resonant members 14, a plurality of coupling members 15, an input terminal 17, and an output terminal 18. The resonant members 14, the coupling members 15, the input terminal 17, and the output terminal 18 are provided on the inner side wall of the second housing 21b.

[0046] In the example of Figs. 2 and 3, the resonant member 14 is a rectangular metal flat plate. The shape of the resonant member 14 is not limited to a rectangular shape. In the example of Figs. 2 and 3, the coupling member 15 is a rectangular metal flat plate. The shape of the coupling member 15 is not limited to a rectangular shape. The input terminal 17 and the output terminal 18 are metal flat plates. The shapes of the input terminal 17 and the output terminal 18 are not limited to the shapes shown in Figs. 2 and 3.

[0047] In the example of FIG. 4, the waveguide 20 of the first embodiment has a plate thickness of the resonator member 14 and the coupling member 15 of 0.3 mm (millimeters) and a first passband of 7.5 GHz (gigahertz).

[0048] The example of Fig. 4 is a graph showing the transmission characteristics when the magnetic field application unit 12 applies magnetic field strengths of 5 [kA / m] (kiloamperes per meter), 50 [kA / m], 100 [kA / m], 200 [kA / m], and 300 [kA / m] to the waveguide 20 of Example 1. In the graph of Fig. 4, the vertical axis represents the attenuation of the transmission signal (S parameter: S12) in [dB] (decibels), and the horizontal axis represents the signal frequency [GHz].

[0049] In the example of Fig. 4, it is shown that the first passband changes to the second passband due to the strength of the magnetic field. That is, in the example of Fig. 4, it can be seen that the center frequency and the passband width change according to the strength of the magnetic field by changing the strength of the magnetic field.

[0050] [Effects of Example 1] As described above, in the first embodiment, a bandpass filter is formed using the resonant member 14 and the coupling member 15, and the effective permeability of the resonant member 14 is varied using the passband variable member 16 that is not a resonator, thereby realizing a passband variable filter with a high Q value.

[0051] In other words, since ferrite is not used as a resonator, a variable passband filter with a high Q value can be realized even among waveguides having a variable passband filter of the magnetic field control type.

[0052] In addition, since ferrite has a large dielectric loss tangent (tan δ), its use in a resonator would result in large loss. However, since ferrite is not used as a resonator, the loss due to the dielectric loss tangent can be reduced. EXAMPLES

[0053] The waveguide 30 in the second embodiment will be described with reference to Figs. 5, 6 and 7. The waveguide 30 in the second embodiment corresponds to the waveguide 11 in Fig. 1. Fig. 5 is an exploded perspective view for explaining an example of the waveguide in the second embodiment. Fig. 6 is a top view and a side view for explaining an example of the waveguide in the second embodiment. Fig. 7 is a diagram for explaining an example of the transmission characteristics of the waveguide in the second embodiment.

[0054] 5 and 6, the waveguide 30 has a housing 31 (a third housing 31a and a fourth housing 31b), a band-pass filter member 13 (a plurality of resonant members 14 and a plurality of coupling members 15), a plurality of passband variable members 16, an input terminal 17, and an output terminal 18. In the second embodiment, one passband variable member 16 is disposed for each of the plurality of resonant members 14.

[0055] The waveguide 30 may be, for example, a rectangular waveguide, a circular waveguide, a ridged waveguide, etc. In the second embodiment, a rectangular waveguide is used for explanation. However, the shape of the waveguide 30 is not limited to a rectangular waveguide.

[0056] 5 and 6, the housing 31 is divided into two parts in the Z-axis direction, a third housing 31a and a fourth housing 31b. The third housing 31a and the fourth housing 31b are joined together.

[0057] The fourth housing 31b has a plurality of resonant members 14, a plurality of coupling members 15, an input terminal 17, and an output terminal 18. The resonant members 14, the coupling members 15, the input terminal 17, and the output terminal 18 are provided on the inner side wall of the second housing 21b.

[0058] 5 and 6, the passband variable members 16 are circular magnetic flat plates (disk-shaped plates). However, the shape of the passband variable members 16 is not limited to a circular shape. Each passband variable member 16 is disposed on the resonator member 14. The passband variable members 16 and the resonator member 14 are bonded together using, for example, an adhesive.

[0059] The passband variable member 16 is positioned so that the first passband of the bandpass filter member 13 can be varied to a preset second passband when a magnetic field for controlling the effective permeability of the resonator member 14 is applied with a preset strength.

[0060] In the example of Figs. 5 and 6, the resonant member 14 is a rectangular metal flat plate. The shape of the resonant member 14 is not limited to a rectangular shape. In the example of Figs. 5 and 6, the coupling member 15 is a rectangular metal flat plate. The shape of the coupling member 15 is not limited to a rectangular shape. The input terminal 17 and the output terminal 18 are metal flat plates. The shapes of the input terminal 17 and the output terminal 18 are not limited to the shapes shown in Figs. 5 and 6.

[0061] In the example of FIG. 7, the waveguide 30 of the second embodiment has a plate thickness of the resonator member 14 and the coupling member 15 of 0.3 mm, and a first passband of 7.5 GHz.

[0062] The example of Fig. 7 is a graph showing the transmission characteristics when the magnetic field application unit 12 applies magnetic field strengths of 5 [kA / m] (kiloamperes per meter), 50 [kA / m], 100 [kA / m], 200 [kA / m], and 300 [kA / m] to the waveguide 30 of Example 2. In the graph of Fig. 4, the vertical axis represents the attenuation of the transmission signal (S parameter: S12) in [dB] (decibels), and the horizontal axis represents the frequency of the signal in [GHz].

[0063] In the example of Fig. 7, it is shown that the first passband changes to the second passband due to the strength of the magnetic field. That is, in the example of Fig. 7, it can be seen that the center frequency and the passband width change according to the strength of the magnetic field by changing the strength of the magnetic field.

[0064] [Effects of Example 2] As described above, in the second embodiment, a bandpass filter is formed using the resonant member 14 and the coupling member 15, and the effective permeability of the resonant member 14 is varied using the passband variable member 16 which is not a resonator, thereby realizing a passband variable filter with a high Q value.

[0065] In other words, since ferrite is not used as a resonator, a variable passband filter with a high Q value can be realized even among waveguides having a variable passband filter of the magnetic field control type.

[0066] In addition, since ferrite has a large dielectric loss tangent (tan δ), its use in a resonator would result in large loss. However, since ferrite is not used as a resonator, the loss due to the dielectric loss tangent can be reduced.

[0067] Furthermore, in addition to the passband variable member 16 for the resonator member 14, one passband variable member for the coupling member 15 is disposed in the vicinity of the coupling member 15 for each coupling member 15. Then, in addition to the magnetic field (first magnetic field) applied to the passband variable member 16, a magnetic field (second magnetic field) is applied to the passband variable member for the coupling member 15, thereby changing the passband width. [Note] The following supplementary notes are further disclosed regarding the above-described embodiments. A part or all of the above-described embodiments can be expressed by (Supplementary Note 1) to (Supplementary Note 15) described below, but are not limited to the following descriptions.

[0068] (Appendix 1) a waveguide having a band-pass filter member including a plurality of resonator members used as resonators and coupling members disposed between the resonator members and used to couple the resonators; and a passband variable member including one or more magnetic elements that varies a passband of the band-pass filter member by a magnetic field applied from outside the waveguide; a magnetic field applying means for applying the magnetic field to control the effective permeability of the resonator member in order to vary the passband of the bandpass filter member; A variable passband device having the above configuration.

[0069] (Appendix 2) the passband variable member is disposed at a position within the waveguide where a first passband of the band-pass filter member can be varied to a second passband that is set in advance when a magnetic field of a preset strength is applied to the passband variable member; 2. A passband tunable device as described in appendix 1.

[0070] (Appendix 3) One of the passband variable members is disposed for a plurality of the resonator members. 3. A passband tunable device as described in appendix 2.

[0071] (Appendix 4) the passband variable member is a rectangular flat plate, the length of the passband variable member in the longitudinal direction is equal to or greater than the length from the input terminal to the output terminal, and the length of the passband variable member in the lateral direction is shorter than the length of the inner lateral direction of the waveguide; 4. A passband tunable device as described in appendix 3.

[0072] (Appendix 5) The passband variable member is disposed for each of the plurality of resonator members. 3. A passband tunable device as described in appendix 2.

[0073] (Appendix 6) The passband variable member is a circular flat plate. 6. A passband tunable device as described in appendix 5.

[0074] (Appendix 7) The magnetic field applying means comprises one or more magnets. 7. A passband tunable device according to any one of claims 1 to 6.

[0075] (Appendix 8) The magnetic field applying means comprises one or more electromagnets. 7. A passband tunable device according to any one of claims 1 to 6.

[0076] (Appendix 9) an input terminal for introducing a first radio wave into the waveguide; a bandpass filter member including a plurality of resonator members used as resonators and coupling members disposed between the resonator members and used to couple the resonators; a passband variable member including one or more magnetic elements that varies a passband of the bandpass filter member by a magnetic field applied from outside the waveguide; an output terminal that outputs a second radio wave output from the band-pass filter member to the outside of the waveguide after the first radio wave is input to the band-pass filter member; A waveguide having

[0077] (Appendix 10) disposing the passband variable member at a position within the waveguide where a first passband of the band-pass filter member can be varied to a second passband that is set in advance when a magnetic field of a preset strength is applied to the passband variable member; 10. The waveguide of claim 9.

[0078] (Appendix 11) One of the passband variable members is disposed for a plurality of the resonator members. 11. The waveguide of claim 10.

[0079] (Appendix 12) the passband variable member is a rectangular flat plate, the length of the passband variable member in the longitudinal direction is equal to or greater than the length from the input terminal to the output terminal, and the length of the passband variable member in the lateral direction is shorter than the length of the inner lateral direction of the waveguide; 12. The waveguide of claim 11.

[0080] (Appendix 13) The passband variable member is disposed for each of the plurality of resonator members. 11. The waveguide of claim 10.

[0081] (Appendix 14) the passband variable member is a circular flat plate; 14. The waveguide of claim 13.

[0082] (Appendix 15) a band-pass filter member including a plurality of resonant members used as resonators, a coupling member disposed between the resonant members and used to couple the resonators, and a pass-band variable member including one or more magnetic elements that varies a pass-band of the band-pass filter member in response to a magnetic field applied from outside the waveguide; applying the magnetic field to the waveguide to control an effective permeability of the resonant members in order to vary the pass-band of the band-pass filter member; Passband control method.

[0083] Although the invention has been described above with reference to the embodiments, the invention is not limited to the above-described embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the invention within the scope of the invention. [Industrial Applicability]

[0084] According to the above description, a passband tunable filter with a high Q value can be realized, which is useful in fields requiring a waveguide having a passband tunable filter. [Explanation of symbols]

[0085] 10 Variable passband device 11, 20, 30 waveguide 12, 12a, 12b Magnetic field application unit 13 Bandpass filter components 14 Resonating members 15 Connecting members 16 Variable passband components 17 Input terminal 18 Output terminal 21 Case 21a First enclosure 21b Second Case 22, 22a, 22b posts 31 Case 31a Third Case 31b Fourth Case

Claims

1. a waveguide having a band-pass filter member including a plurality of metallic resonator members used as resonators and coupling members disposed between the resonator members and used to couple the resonators; and a pass-band variable member including one or more magnetic elements that varies a pass band of the band-pass filter member by a magnetic field applied from outside the waveguide; a magnetic field applying means for applying the magnetic field to control the effective permeability of the resonator member in order to vary the passband of the bandpass filter member; A variable passband device having the above configuration.

2. The magnetic field applying means comprises one or more magnets.

2. The passband tunable device according to claim 1.

3. The magnetic field applying means comprises one or more electromagnets.

2. The passband tunable device according to claim 1.

4. an input terminal for introducing a first radio wave into the waveguide; a bandpass filter member including a plurality of resonator members made of metal and used as resonators, and a coupling member disposed between the resonator members and used to couple the resonators; a passband variable member including one or more magnetic elements, the passband of which is variable by controlling an effective permeability of the resonant member of the bandpass filter member by a magnetic field applied from outside the waveguide; an output terminal that outputs a second radio wave output from the band-pass filter member to the outside of the waveguide after the first radio wave is input to the band-pass filter member; A waveguide having

5. disposing the passband variable member at a position within the waveguide where a first passband of the bandpass filter member can be varied to a second passband that is set in advance when a magnetic field of a preset strength is applied; 5. The waveguide of claim 4.

6. One of the passband variable members is disposed for a plurality of the resonator members.

6. The waveguide of claim 5.

7. the passband variable member is a rectangular flat plate, the length of the passband variable member in the longitudinal direction is equal to or greater than the length from the input terminal to the output terminal, and the length of the passband variable member in the lateral direction is shorter than the length of the inner lateral direction of the waveguide; 7. The waveguide of claim 6.

8. The passband variable member is disposed for each of the plurality of resonator members.

6. The waveguide of claim 5.

9. The passband variable member is a circular flat plate.

9. The waveguide of claim 8.

10. a band-pass filter member including a plurality of resonant members made of metal used as resonators, a coupling member disposed between the resonant members and used to couple the resonators, and a pass-band variable member including one or more magnetic elements that varies a pass-band of the band-pass filter member in response to a magnetic field applied from outside the waveguide; and applying the magnetic field to the waveguide to control the effective permeability of the resonant members in order to vary the pass-band of the band-pass filter member; Passband control method.

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