JP2010226469A - Band pass filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a band pass filter which can be made more small-sized and lightweight than the prior arts. <P>SOLUTION: The band pass filter 1 includes: a metallic case 2 including a plurality of cavity inner walls 51-56 forming a plurality of cavities, respectively; a plurality of resonators 21-26 installed in the cavities; an input terminal 3 for inputting an electromagnetic wave from the outside of the case to excite the plurality of resonators; and an output terminal 4 for outputting the electromagnetic wave passed through the plurality of resonators to the outside of the case. The cavities have the plurality of cavity inner walls with openings 61-65 for electromagnetically coupling resonators forming neighboring preceding and following stages, and have conductive partitions 66-70 each being formed with a slit 71, which are held in the openings respectively. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a band-pass filter that suppresses electromagnetic waves in unnecessary frequency bands.

  Conventionally, communication lines such as telephone, mobile communication, and television relay use microwaves, and these communication lines include a base station for transmitting and receiving microwaves as radio waves. In this base station, a band-pass filter for passing only radio waves in a desired frequency band and removing unnecessary radio waves is installed.

  Conventionally, as this type of band-pass filter, one having a dielectric resonator having a low-loss characteristic is known (for example, see Patent Document 1).

  As shown in FIG. 11, the conventional band-pass filter 101 includes a plurality of dielectric resonators 121 to 126 installed in a closed space formed by a main body 102a and a lid portion 102b of a conductive casing 102. I have. These dielectric resonators 121 to 126 are separated from each other by hollow inner walls 151 to 156 constituting a part of the casing, and are electromagnetically coupled via coupling windows 161 to 165.

  The conductive casing 102 is provided with input / output terminals 103 and 104 to which a coupling probe is connected. Microwaves propagated from the outside of the casing 102 are dielectric resonators by the coupling probe. The dielectric resonator 121 is magnetically coupled to generate an electric field inside the dielectric resonator 121 to excite the dielectric resonator 121.

  With such a configuration, in the conventional band pass filter, since the dielectric resonators 121 to 126 have high Q values, the insertion loss before and after the pass band is rapidly increased.

  Here, the bandwidth of the band-pass filter changes according to the amount of coupling between adjacent dielectric resonators, and the bandwidth decreases as the amount of coupling between the dielectric resonators decreases. It has become. For this reason, in order to narrow the bandwidth, the cross-sectional area of the coupling window between adjacent dielectric resonators is reduced, or the distance between adjacent dielectric resonators is increased.

JP 2007-274572 A

  However, the band-pass filter shown in Patent Document 1 has a housing formed by a die casting method in which a metallic block is machined with a mill or a molten metal is filled into a mold, resulting in production limitations. Depending on the desired bandwidth, the cross-sectional area of the coupling window may not be sufficiently narrowed. Therefore, in order to narrow the bandwidth of the band pass filter, it is necessary to increase the distance between adjacent dielectric resonators, and as a result, there is a problem that the band pass filter is enlarged.

  The present invention has been made to solve the conventional problems, and an object of the present invention is to provide a band-pass filter that can be made smaller and lighter than the conventional one.

  The bandpass filter according to the present invention includes a metallic housing having a plurality of cavity inner walls that respectively form a plurality of cavities, a plurality of resonators installed in the cavity, and an electromagnetic wave input from the outside of the housing. In the band-pass filter comprising: an input terminal for exciting the plurality of resonators; and an output terminal for outputting the electromagnetic waves that have passed through the plurality of resonators to the outside of the housing. It has an opening for electromagnetically coupling the resonators forming the steps before and after the mating, and includes a conductive partition plate in which a slit is formed and held in the opening.

  With this configuration, the band-pass filter of the present invention can reduce the amount of coupling without increasing the interval between adjacent resonators by coupling adjacent resonators through slits. Therefore, it is possible to realize a band-pass filter that can be made smaller and lighter than before. Also, by preparing a plurality of partition plates having different slit sizes, the coupling amount of adjacent resonators can be adjusted only by replacing the partition plates. As compared with the case where the coupling window is formed by the above, the coupling amount can be easily adjusted.

  Furthermore, the bandpass filter according to the present invention is characterized in that the resonator is constituted by a dielectric resonator formed of a dielectric.

  With this configuration, the bandpass filter of the present invention is composed of dielectric resonators having a plurality of resonators each having a high Q value, so that insertion loss before and after the passband is drastically reduced while being small and lightweight. Can be increased.

  Furthermore, the bandpass filter according to the present invention is characterized in that the resonator is constituted by a semi-coaxial metal resonator formed of a columnar metal having conductivity.

  With this configuration, the bandpass filter of the present invention has a plurality of resonators each composed of a semi-coaxial metal resonator, and thus can have a low loss characteristic while being small and light.

  Further, in the bandpass filter according to the present invention, the inner walls of the plurality of cavities include at least two or more of the plurality of resonators, and electromagnetically different from the resonators forming the front and rear stages. It has the opening part couple | bonded with this, It is characterized by the above-mentioned.

  With this configuration, the bandpass filter according to the present invention generates the interlaced coupling in which two resonators other than the preceding and following stages are coupled in addition to the coupling of the two resonators that form the adjacent preceding and following stages. Insertion loss before and after can be rapidly increased, and radio waves outside the desired frequency band can be reliably attenuated. In addition, since the insertion loss before and after the pass band increases rapidly, the number of resonators installed in the housing can be reduced.

  The present invention can provide a band-pass filter that can be made smaller and lighter than conventional ones.

It is a perspective view which shows typically the structure of the band pass filter in the 1st Embodiment of this invention. It is sectional drawing in the filter part of the 1st line of FIG. It is a perspective view which shows the partition plate in the 1st Embodiment of this invention. It is a top view which shows the partition plate in the 1st Embodiment of this invention. It is a perspective view which shows typically the structure of the band pass filter in the 2nd Embodiment of this invention. It is sectional drawing in the filter part of the 1st line of FIG. It is sectional drawing which shows the other shape of a semi-coaxial metal resonator. It is a circuit diagram which shows the structure of the bandpass filter in the 3rd Embodiment of this invention. It is a perspective view which shows typically the structure of the band pass filter in the 3rd Embodiment of this invention. It is a perspective view which shows typically the other shape example of a partition plate. It is a perspective view which shows the structure of the conventional band pass filter typically.

  Hereinafter, bandpass filters according to embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
A bandpass filter according to a first embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the band-pass filter 1 according to the present embodiment functions as a six-stage filter, and is formed by a metal casing 2 having a substantially rectangular parallelepiped shape and a cylindrical dielectric. Dielectric resonators 21 to 26, an input terminal 3 for inputting electromagnetic waves to the dielectric resonator 21, and an output terminal 4 for outputting electromagnetic waves from the dielectric resonator 26.

  The housing 2 includes a housing body 2a and a lid portion 2b. The housing body 2a has a plurality of cavity inner walls 51 to 56 that respectively form a plurality of cylindrical cavities. These cylindrical cavities are shielded by the lid 2b. The casing 2 is formed by, for example, a manufacturing method such as a die casting method in which a conductive block is processed by milling or a molten metal is filled in a mold.

  The dielectric resonators 21 to 26 are installed in a plurality of cavities with a predetermined space from the inner walls 51 to 56 of the cavities. In the present embodiment, the case where the cavities have the same radius and depth in the inner walls 51 to 56 will be described, but they may be different from each other.

  Here, the dielectric resonators 21 to 26 shown in FIG. 1 are arranged in two rows of three in the housing body 2a. In the case of this arrangement, the volume of the housing 2 is compact, and the input terminal 3 and the output terminal 4 can be installed on the same side surface of the housing 2, but the positions of the input terminal 3 and the output terminal 4 are suitable. It is not limited to this. These dielectric resonators 21 to 26 may be arranged other than in two rows, and may be arranged in a zigzag shape or in one row, for example.

  The dielectric resonators 21 to 26 are fixed to the bottom surface 2c (see FIG. 2) of the housing 2 by known means such as screws so that the longitudinal directions thereof are parallel to each other. These dielectric resonators 21 to 26 are respectively supported by a low dielectric constant support 31, and the electromagnetic waves excited by the dielectric resonators 21 to 26 are the metals constituting the cavity inner walls 51 to 56. It is not attenuated by the wall. The inner surface of the casing 2 in which the dielectric resonators 21 to 26 are installed may be subjected to a treatment such as silver plating in order to increase the no-load Q of the dielectric resonators 21 to 26.

  In the hollow inner walls 51 to 56 of the housing main body 2a, openings 61 to 65 for inserting a partition plate to be described later are formed between two dielectric resonators that form steps adjacent to each other.

  The band pass filter 1 may have a plurality of frequency adjustment screws 41 to 46 for adjusting the resonance frequencies of the dielectric resonators 21 to 26 in the lid portion 2b. In this case, as shown in FIG. 2, the center axis of each frequency adjusting screw is installed so as to overlap the extension line of the center axis of each dielectric resonator. By adjusting the distance between the frequency adjusting screws 41 to 46 and the dielectric resonators 21 to 26, the resonance frequencies of the dielectric resonators 21 to 26 can be changed.

  Further, since the frequency adjusting screws 41 to 46 for the respective dielectric resonators 21 to 26 are installed in the same direction, the band pass filter 1 can be made small and light.

  The input terminal 3 has a loop-shaped inner conductor 3a. The inner conductor 3 a of the input terminal 3 is provided in a cavity formed by the cavity inner wall 51, and inputs electromagnetic waves propagated from an external circuit to the dielectric resonators 21 to 26.

  Similarly, the output terminal 4 is provided in a cavity formed by the cavity inner wall 56, and outputs electromagnetic waves that have passed through the dielectric resonators 21 to 26 to an external circuit. Similarly to the input terminal 3, the output terminal 4 has a loop-shaped internal conductor (not shown).

  The band-pass filter 1 further includes conductive partition plates 66 to 70 between two dielectric resonators that form adjacent stages before and after each other. In the following description, the partition plate 66 will be described as an example when it is not necessary to distinguish the partition plates 66 to 70 in particular.

  As shown in FIG. 3, the partition plate 66 has slits 71 formed therein. The slit 71 functions as a coupling window for coupling adjacent dielectric resonators. Therefore, the slit 71 is preferably shaped so that the longitudinal direction of the slit 71 is perpendicular to the direction of the electric field distributed between adjacent dielectric resonators.

  The partition plates 66 to 70 are respectively held in the openings 61 to 65, and the partition plates 66 to 70 have a surface with respect to a plane including the central axes of the two adjacent dielectric resonators. Is installed vertically. Further, as shown in FIG. 4, screw holes 72 are formed in the partition plates 66 to 70, and are fixed to the openings 61 to 65 of the housing 2 by screws. The partition plates 66 to 70 may be fixed to the openings 61 to 65 of the housing 2 by a known method such as welding or soldering. Moreover, you may form in the opening parts 61 thru | or 65 the groove part by which the partition plates 66 thru | or 70 are each fitted.

  When electromagnetic waves are input from the external circuit to the bandpass filter 1 having the above-described configuration via the input terminal 3, the electromagnetic waves are excited in the dielectric resonator 21. At this time, the TE01δ mode is excited in the dielectric resonator 21 by adjusting the diameter of the dielectric resonator 21 and the distance from the cavity inner wall 51. The electromagnetic wave excited in the dielectric resonator 21 excites the dielectric resonator 22 through the slit 71 of the partition plate 66. In this case, an electric field that is substantially parallel to the circumference of each of the dielectric resonators 21 and 22 is distributed around the dielectric resonator 21 and the dielectric resonator 22 in the horizontal plane. Therefore, the slit 71 of the partition plate 66 is formed so that the longitudinal direction thereof is parallel to the height direction of the dielectric resonators 21 and 22. Similarly, the slits 71 of the partition plates 67 to 70 are formed so that the longitudinal direction thereof is parallel to the height direction of the dielectric resonator.

  Further, in FIG. 1, the openings 61 to 65 have shapes that support both side surfaces and the lower surface of the partition plates 66 to 70, but the present invention is not limited to this, and the openings 61 to 65 have the shape of the partition plate 66. The shape which supports only the both side surfaces of thru | or 70 may be sufficient. In this case, the bottom of the partition plate 66 is directly supported by the bottom surface 2 c of the housing 2.

  By having the configuration as described above, the bandpass filter 1 according to the present embodiment increases the interval between adjacent dielectric resonators by coupling adjacent dielectric resonators via the slits 71. The amount of coupling can be reduced. Therefore, the band pass filter 1 that can be made smaller and lighter than before can be realized. Also, by preparing a plurality of partition plates having different slit sizes, the coupling amount of adjacent dielectric resonators can be adjusted by exchanging the partition plates. The amount of coupling can be easily adjusted as compared with the case where the coupling window is formed by processing.

  In addition, the bandpass filter 1 according to the present embodiment includes a dielectric resonator having a plurality of resonators each having a high Q value, so that insertion loss before and after the passband is reduced while being small and lightweight. It can be increased rapidly.

  Further, since it is not necessary to form a coupling window directly in the housing 2, a complicated manufacturing process for the housing is not required, and the manufacturing time is shortened. Moreover, since the process of forming the slit in the partition plate can be performed independently of the production of the housing, for example, the partition plate is manufactured only by the process of forming the slit in the metal plate, and as a result, the partition plate The production time is short. And since a partition plate can be easily installed in a housing | casing by a screw stop etc., as a result, the time which manufactures the whole band pass filter will be shortened.

  Furthermore, since the slit functioning as a coupling window is formed in the partition plate independently of the casing, the shape of the coupling window can be easily changed as compared with the prior art. That is, it is possible to easily adjust the degree of coupling only by exchanging the partition plate. In addition, it becomes easy not only to change the direction of the slit in the longitudinal direction according to the mode of the electromagnetic wave excited by the dielectric resonator, but also as described later, the bandpass filter is a semi-coaxial metal resonator, etc. Even when a resonator other than the dielectric resonator is provided, it is easy to change the shape of the slit according to the mode of the electromagnetic wave excited by the resonator.

  Therefore, it is possible to increase the degree of freedom with respect to the shape of the slit compared to the conventional band-pass filter that processes the housing by milling to form a coupling window or directly welds a plate that functions as a partition to the housing. It becomes.

  Furthermore, if the cross-sectional area of the opening is made narrower, the partition plate held in the opening can be reduced in size. Therefore, even when preparing various partition plates having slits of various shapes, the partition plate is manufactured. Therefore, the material required for this can be reduced, and as a result, the manufacturing cost can be reduced.

  In the above description, the case where the dielectric resonators 21 to 26 are respectively installed in a plurality of cylindrical cavities formed in the housing 2 has been described. However, the dielectric resonators 21 to 26 may be installed in a cavity having a shape other than a cylindrical shape.

  In this case, for example, one cavity where the six dielectric resonators 21 to 26 are installed is formed in the housing 2. Then, the six dielectric resonators are appropriately partitioned by a partition plate in which slits are formed.

  In the above-described embodiment, the case where the bandpass filter includes the dielectric resonator has been described. However, the present invention is not limited to this, and the bandpass filter is not limited to this as in the second embodiment described below. A semi-coaxial metal resonator may be provided.

(Second Embodiment)
A bandpass filter according to a second embodiment of the present invention will be described with reference to FIGS.

  The configuration of the bandpass filter 81 according to the second embodiment is substantially the same as the configuration of the bandpass filter 1 according to the first embodiment described above, and each component is shown in FIG. The same reference numerals as those in the first embodiment will be used, and only differences will be described in detail.

  As shown in FIG. 5, the band-pass filter 81 according to the present embodiment functions as a six-stage filter, and includes a metal casing 82 having a substantially rectangular parallelepiped shape, and a cylindrical semi-coaxial metal resonance. 83 to 88, an input terminal 5 for inputting electromagnetic waves to the semi-coaxial metal resonator 83, and an output terminal 6 for outputting electromagnetic waves from the semi-coaxial metal resonator 88.

  The housing body 82a has a plurality of cavity inner walls 51 to 56 that respectively form a plurality of cylindrical cavities. These cylindrical cavities are shielded by the lid portion 82b. The casing 82 in the present embodiment is also manufactured by a die casting method or the like in which a conductive block is processed by milling or a molten metal is filled in a mold, similarly to the casing 2 according to the first embodiment. Is formed.

  The semi-coaxial metal resonators 83 to 88 are installed in a plurality of cavities so as to be separated from the cavity inner walls 51 to 56 with a predetermined space.

  The semi-coaxial metal resonators 83 to 88 are configured by a cylindrical resonance element formed of a metal such as brass, brass, aluminum, or invar, for example. Further, the semi-coaxial metal resonators 83 to 88 may be subjected to processing such as silver plating in order to increase the no-load Q. Similarly, the inner surface of the casing 82 in which the semi-coaxial metal resonators 83 to 88 are installed is also subjected to a treatment such as silver plating in order to increase the no-load Q of the semi-coaxial metal resonators 83 to 88. Also good.

  Further, as shown in FIG. 6, the inner conductor 5 a is parallel to the longitudinal direction of the semi-coaxial metal resonator 83 in the cavity. Here, the tip of the internal conductor 5a may be soldered to the bottom surface 82c of the casing 82 as a ground. Or the front-end | tip of the internal conductor 5a may be formed so that a front-end | tip may be in an open state, without contacting the bottom face 82c. Moreover, you may comprise so that the front-end | tip of the internal conductor 5a may be soldered to the semi-coaxial metal resonator 83. FIG.

  Returning to FIG. 5, openings 61 to 65 are formed in the hollow inner walls 51 to 56 of the casing main body 82 a, similarly to the casing main body 2 a in the first embodiment.

  Further, the band pass filter 81 includes partition plates 73 to 77 formed in the same manner as the partition plates 66 to 70 in the first embodiment, and these partition plates 73 to 77 have openings 61 to 65. Are to be held respectively. Further, the partition plates 73 to 77 are fixed to the openings 61 to 65 of the housing 82 by screws, similarly to the partition plates 66 to 70 in the first embodiment shown in FIG.

  When electromagnetic waves are excited in the semi-coaxial metal resonators 83 to 88, an electric field that is substantially parallel to the longitudinal direction of each of the semi-coaxial metal resonators 83 to 88 is distributed around the semi-coaxial metal resonators 83 to 88. . Therefore, the slits 78 of the partition plates 73 to 77 are preferably formed so that the longitudinal direction is perpendicular to the longitudinal direction of the semi-coaxial metal resonators 73 to 77.

  As described above, the band-pass filter 81 according to the present embodiment couples adjacent semi-coaxial metal resonators via the slits 78, thereby increasing the coupling amount without increasing the interval between adjacent semi-coaxial metal resonators. Can be reduced. Therefore, the band pass filter 81 which can be reduced in size and weight as compared with the conventional one can be realized. Further, the band pass filter 81 according to the present embodiment has a plurality of resonators each composed of a semi-coaxial metal resonator, and thus can have a low loss characteristic while being small and light. Also, in the band pass filter 81 according to the present embodiment, the same effect as that of the band pass filter 1 according to the first embodiment described above can be obtained.

  In the above description, the case where any of the semi-coaxial metal resonators 83 to 88 has a cylindrical shape has been described. However, the semi-coaxial metal resonator may have a shape other than a cylindrical shape.

  FIG. 7 is a cross-sectional view schematically showing another example of the shape of the semi-coaxial metal resonator of the present invention, and is a view of the resonator in the first row from the input terminal 3 side. As shown in FIG. 7, the semi-coaxial metal resonator 89 has a step shape. The semi-coaxial metal resonator may have a shape such as a prism.

  In the above-described embodiment, the case where the dielectric resonators 21 to 26 or the semi-coaxial metal resonators 83 to 88 are coupled in two adjacent resonators, that is, the front and rear stages are described. Without being limited thereto, the resonator may be coupled to resonators other than the preceding and following stages as in the third embodiment described below.

(Third embodiment)
A bandpass filter according to a third embodiment of the present invention will be described with reference to FIGS.

  The configuration of the bandpass filter 90 according to the third embodiment is substantially the same as the configuration of the bandpass filter 1 according to the first embodiment described above, and each component is shown in FIG. The same reference numerals as those in the first embodiment will be used, and only differences will be described in detail.

  In FIG. 8, an arrow A between the dielectric resonators 21 to 26 indicates an electromagnetic wave between two adjacent dielectric resonators that form the front and back stages of the dielectric resonators 21 to 26. Represents a strong bond.

  Bandpass filter 90 in the present embodiment includes a partition plate having a slit for electromagnetically coupling dielectric resonator 21 and dielectric resonator 26 in addition to the partition plate between adjacent dielectric resonators. For example, a partition plate between the dielectric resonators that do not form the front and rear stages is provided, and the coupling indicated by the arrow B in FIG. 8 occurs. Hereinafter, the coupling between the resonators that do not form the front and back stages as indicated by the arrow B is referred to as interlaced coupling.

  A band-pass filter having a dielectric resonator that forms interlaced coupling has a transmission characteristic including a transmission zero in the transition region between the pass band and the cutoff band, and functions as a band-pass filter having a steep cut characteristic. To do. In addition, by appropriately selecting the set and the number of resonators to be interlaced, the transmission characteristics can have transmission zeros only on the high frequency side or the low frequency side with respect to the pass frequency band.

  As shown in FIG. 9, the bandpass filter 90 having interlaced coupling includes partition plates 92 and 93 between two dielectric resonators constituting the front and rear stages and between two dielectric resonators in which interlaced coupling is performed. To be installed. Further, the partition plate installed between the two dielectric resonators to be interlaced is different from the partition plate installed between the two dielectric resonators constituting the front and rear stages in the size and shape of the slit. By adjusting the size and shape of the slit, it is possible to adjust the transmission characteristics such as the frequency at which the transmission zero occurs.

  As described above, the band-pass filter 90 of the present invention not only has the effect of the dielectric filter 1 according to the first embodiment described above, but also two dielectric resonators that form adjacent stages. In addition to the coupling of 21 to 26, the interlace coupling in which two resonators other than the preceding and following stages are coupled is generated, so that the insertion loss before and after the passband can be rapidly increased by forming the transmission zero point, and the desired frequency Out-of-band radio waves can be reliably attenuated. In addition, since the insertion loss before and after the pass band increases rapidly, the number of resonators installed in the housing 2 can be reduced.

  In the above description, the case where the bandpass filter includes the dielectric resonators 21 to 26 or the semi-coaxial metal resonators 83 to 88 has been described. However, the present invention is not limited to this. The present invention may be applied to a band pass filter including a semi-coaxial metal resonator or other types of known resonators. In this case, since the electric field distribution between the resonators differs depending on the type of two adjacent resonators, the longitudinal direction of the slits formed in each partition plate may need to be different from each other. In the conventional band pass filter, in order to make the longitudinal directions of the coupling windows different from each other, a complicated manufacturing process for manufacturing the housing is required. By using the plate, it is possible to easily change the longitudinal direction of the coupling window.

  In the above description, the case where the band-pass filter 1 includes the six dielectric resonators 21 to 26 or the six semi-coaxial metal resonators 83 to 88 has been described. However, the band pass filter 1 only needs to include at least two dielectric resonators or at least two semi-coaxial metal resonators. The number of required dielectric resonators or the number of semi-coaxial metal resonators is appropriately changed according to the use of the band pass filter.

  In the above description, the case where the dielectric resonators 21 to 26 or the semi-coaxial metal resonators 83 to 88 are mainly installed in the housing 2 has been described. However, the present invention is not limited to this. In addition, a circuit having a function other than a filter, such as an amplifier circuit or a modulation / demodulation circuit, may be formed.

  Moreover, in the above description, the case where the rectangular slit was formed in the partition plate was demonstrated. However, the partition plate may be formed with slits or openings having a shape other than a rectangle. FIG. 10 is a perspective view schematically showing another example of the shape of the partition plate of the present invention. As shown in FIG. 10A, the partition plate may be formed with a cross-shaped slit. Moreover, as shown in FIG.10 (b), the circular opening may be formed in the partition plate. That is, the slit or opening formed in the partition plate may have any shape as long as a desired coupling amount is obtained between the two resonators.

  The band pass filter may be provided with a coupling adjusting screw for adjusting the degree of coupling between the resonators. The coupling adjusting screw is installed between the resonators adjacent to each other among the dielectric resonators 21 to 26 or the semi-coaxial metal resonators 83 to 88.

  In this case, the partition plate is formed with a through hole that communicates with the slit and whose longitudinal direction is perpendicular to the longitudinal direction of the slit, and the coupling adjusting screw is inserted into the through hole. As a result, the coupling adjustment screw slides in a direction perpendicular to the longitudinal direction of the slit, and the cross-sectional area of the slit is adjusted according to the insertion depth of the coupling adjustment screw. The degree is adjusted.

  The coupling adjusting screw may be configured by a coupling degree adjusting rod having a fixing portion for fixing at a desired insertion depth. Further, by using a male screw instead of the coupling degree adjusting rod and forming a female screw on the partition plate, the coupling degree between the dielectric resonators 21 to 26 may be adjusted by the screw feeding mechanism.

  In the above description, the case where the coupling adjustment screw is installed between the resonators has been described. However, the coupling adjustment screw does not necessarily need to be installed between all the resonators, and may be installed in the housing as necessary.

  In the above description, the case where the frequency adjusting screws 41 to 46 are installed on the dielectric resonators 21 to 26 or the semi-coaxial metal resonators 83 to 88 has been described. However, the frequency adjusting screw does not necessarily have to be installed on all of these resonators. In addition, when the frequency adjustment of the band pass filter is unnecessary, the frequency adjustment screw may not be installed in the housing.

  As described above, the band-pass filter according to the present invention has an effect that it can be made smaller and lighter than before, and is useful as a band-pass filter that suppresses electromagnetic waves in unnecessary frequency bands.

DESCRIPTION OF SYMBOLS 1 Band pass filter 2 Case 2a Case main body 2b Cover part 2c Bottom surface 3 Input terminal 3a Internal conductor 4 Output terminal 5 Input terminal 5a Internal conductor 6 Output terminal 21 thru | or 26 Dielectric resonator 31 Support body 41 thru | or 46 Frequency adjustment screw 51 to 56 Cavity inner walls 61 to 65 Openings 66 to 70 Partition plate 71 Slit 72 Screw holes 73 to 77 Partition plate 78 Slit 81 Band pass filter 82 Housing 82c Bottom surface 83 to 88 Semicoaxial metal resonator 89 Semicoaxial metal resonator 90 Band pass filter 92, 93 Partition plate

Claims (4)

A metallic housing having a plurality of cavity inner walls each forming a plurality of cavities;
A plurality of resonators installed in the cavity;
An input terminal for inputting electromagnetic waves from the outside of the housing to excite the plurality of resonators;
In a band pass filter comprising: an output terminal that outputs electromagnetic waves that have passed through the plurality of resonators to the outside of the housing;
The inner walls of the plurality of cavities have openings for electromagnetically coupling the resonators forming the steps before and after the adjacent ones,
A bandpass filter comprising a conductive partition plate in which a slit is formed and held in the opening.   The bandpass filter according to claim 1, wherein the resonator includes a dielectric resonator formed of a dielectric.   The bandpass filter according to claim 1, wherein the resonator is a semi-coaxial metal resonator formed of a columnar metal having conductivity.   The plurality of cavity inner walls have openings for electromagnetically coupling at least two or more of the plurality of resonators with resonators different from the resonators forming the front and rear stages. The band-pass filter according to claim 1, wherein the band-pass filter is provided.

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