JP4105017B2 - Waveguide type dielectric filter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a waveguide type dielectric filter used in a high frequency region such as the GHz band, and relates to a waveguide type dielectric filter capable of obtaining a desired attenuation pole.
[0002]
[Prior art]
[Patent Document 1]
US Patent No. 5926079 [Patent Document 2]
Japanese Patent Laid-Open No. 6-177607
By coupling a plurality of dielectric waveguide resonators, various types of waveguide dielectric filters can be realized. FIG. 10 shows such a waveguide-type dielectric filter. The resonator block 21 includes three resonators 22A, 22B, and 22C, and an iris is formed between the resonators to adjust the coupling. is doing. Conductor strips extending from the bottom surfaces of the resonators 22A and 22C at the input / output ends to the end surfaces are used as the input electrode 25 and the output electrode 26, respectively. The dielectric is exposed only on both sides of the input / output electrodes and a part of the end face in contact with them, and the other entire surface is covered with a conductor film. In this example, a short dielectric portion having input / output electrodes formed on the bottom surface is formed outside the resonators at both ends.
[0004]
The above dielectric can be mounted on a planar circuit such as a printed circuit board. The inventors have proposed this mounting structure in Japanese Patent Application No. 2001-216919. However, conventional waveguide dielectric filter structures have been unable to generate an attenuation pole required as a filter in an arbitrary band. In order to improve the selection characteristics as a filter, it is necessary to obtain attenuation poles on the high band side or low band side or both of the pass band.
[0005]
[Problems to be solved by the invention]
The present invention provides a structure for obtaining an arbitrary attenuation pole in a monolithic waveguide type dielectric filter, and realizes a polarized type waveguide dielectric filter with a simple and highly productive structure. Is. In addition, when the wave tube type dielectric filter is mounted on a planar circuit formed on a printed circuit board or other wiring board, the discontinuity between the input / output terminals of the filter and the signal lines of the board is reduced as much as possible. The loss caused by the reflection and radiation of the electromagnetic field is reduced.
[0006]
[Means for Solving the Problems]
The present invention solves the above problems by adding a resonator. That is, in a waveguide type dielectric filter in which a plurality of dielectric waveguides are integrally formed in a dielectric block, a plurality of dielectric waveguides constituting the filter are formed in the dielectric block. A dielectric waveguide for forming an attenuation pole is formed on at least one side of the dielectric waveguide, and an input / output dielectric is disposed between the dielectric waveguides. One end of the dielectric waveguide is pulled out to the bottom surface of the input / output dielectric. Characterized in that the other end of the branch has an input / output electrode with a conductor strip extending to the bottom surface of the dielectric waveguide constituting the filter and the bottom surface of the dielectric waveguide to form an attenuation pole It is.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The basic components of the waveguide dielectric filter according to the present invention are as follows.
(1) A dielectric block in which a dielectric constituting a plurality of resonators constituting a filter unit and a dielectric waveguide resonator disposed at least on one end side are integrally formed. The bond is adjusted,
(2) In the meantime, an input / output electrode comprising a conductor strip formed on the bottom surface of the dielectric as a polarized orthogonal input / output structure and reaching the bottom surface of the resonator on both sides and extending to the side end surface of the dielectric;
(3) A conductor film that covers the surface of the dielectric block except for both sides of the input / output electrode and the portion of the end face that contacts the input / output electrode, and is connected to the ground potential.
[0008]
Resonance modes and waveguides of a waveguide resonator constituting a polarized input / output structure in which input / output electrodes are connected to signal lines of a wiring board such as a printed circuit board and a signal from the wiring board generates an attenuation pole Coupled to the resonant mode inside the filter. Between the resonator forming the input and output electrodes, the waveguide resonator generating the attenuation pole, and the resonator forming the filter, the filter and the resonator generating the pole are reduced by narrowing the width of the dielectric. Adjust the bond between.
[0009]
【Example】
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a waveguide type dielectric filter according to the present invention having a three-element polarized input / output structure. Resonators 12A, 12B, and 12C constituting a three-element filter are disposed in a substantially rectangular parallelepiped dielectric block 11, and the coupling is adjusted by an iris formed by forming a groove from the side. In this example, a resonator 13 for forming a polarized input / output structure, that is, an attenuation pole is arranged on the input side, and a dielectric 14 serving as an input / output unit is arranged therebetween. On the bottom surface of the dielectric serving as the input / output unit, the input electrode 15 extends from the side end surface to the inside and branches off at the bottom surface of the dielectric 14, and extends to the resonator 13 that forms the filter unit direction and the attenuation pole. An output electrode 16 extending on the opposite end face is formed on the opposite side of the filter.
[0010]
In order to adjust the coupling between the resonator for obtaining the filter part and the attenuation pole and the dielectric of the polarized input / output structure, in order to narrow the width of the connecting part of the filter part and the polarized input / output structure, Grooves are formed from In order to prevent loss due to radiation from the polarized input / output structure to the input side, the dielectric of the input / output portion of the polarized input / output structure is also narrowed.
[0011]
In addition, a conductor pattern (exposed narrower than the waveguide resonator) is formed on the side end face with a part of the dielectric exposed. The other surface is covered with a dielectric film (the end surface and the bottom surface with the input / output electrodes have exposed portions of the dielectric), and the adjacent conductive films are connected to each other. Yes. In this example, the output electrode 16 is formed without a polarized input / output structure. As shown in FIG. 2, the input / output electrodes are mounted on the wiring boards 18 and 19 and connected to a signal line by a conductor strip formed on the surface thereof. Since the conductor strip and the input / output electrode form one continuous conductor strip, radiation due to mismatch of the input / output portions can be suppressed.
[0012]
Electricity of a conventional three-element waveguide dielectric filter described in Japanese Patent Application No. 2001-216919 of the prior application and a waveguide dielectric filter having a three-element polarized input / output structure according to the present invention. A comparison of characteristics (transmission characteristics) is shown in FIG. In this example, it can be seen that the waveguide type dielectric filter according to the present invention has an attenuation pole on the high side of the pass band, and the attenuation characteristic near the attenuation pole is greatly improved as compared with the conventional filter.
[0013]
Another embodiment of the present invention will be described. FIG. 4 shows a polarized input / output structure with a two-stage resonator on the input side, and is structurally the same as that shown in FIG. Further, FIG. 6 is arranged on both the input and output sides, so that attenuation poles can be multistaged. The frequency and the like of the attenuation pole can be adjusted by adjusting the shape and coupling state of the resonator serving as the polarized input / output structure. The coupling adjustment between the resonators constituting the filter can also be performed by a through hole or the like. 5 and 7 show examples of the conductor patterns of the input / output electrodes. FIG. 5 shows a case where a resonator for obtaining an attenuation pole is added only on one side as shown in FIG. 4, and FIG. Are arranged on both sides. FIG. 8 shows a conductor pattern of a wiring board to be mounted, in which a dielectric input / output electrode and a strip line of the wiring board are continuously formed in the same shape and discontinuity is eliminated. Needless to say, the present invention can be applied not only to a filter but also to a duplexer.
[0014]
A three-stage filter having the structure shown in FIG. 1 was prototyped as an actual sample. When the dielectric size was 45.5 mm in length, 10.2 mm in width, and 3.2 mm in thickness, a filter with an attenuation pole appearing at the high frequency side of the passband with a central frequency of 3.45 GHz was obtained. The characteristics are shown in FIG. 9, and it was confirmed that the return loss characteristics in the passband were good and could be used sufficiently as a filter.
[0015]
【The invention's effect】
The effects of the present invention are listed as follows.
1. Since the input / output conductor pattern is formed in a continuous form as if the signal line on the wiring board (printed circuit board) was extended, the waveguide resonance caused by the bottom conductor pattern connected to the signal line The electromagnetic field inside the filter is coupled with the fundamental resonance mode of the waveguide resonator that generates the attenuation pole and the waveguide resonator of the filter unit, and as a result, coupling with an external circuit occurs. It is possible to realize a polarized filter with
2. Since the input / output terminals of the filter are on the same plane as the signal lines of a planar circuit such as a printed circuit board, the continuity between the signal lines of the printed circuit board and the input / output terminals of the filter is well maintained, and high-frequency signals generated by discontinuities Therefore, it can be mounted on a wiring board such as a printed board, and a low-loss element can be obtained.
3. Since the width of the portion where the dielectric is exposed in the conductor pattern on the side surface is narrower than that of the waveguide resonator, the cut-off waveguide is used for the frequency of the fundamental resonance mode of the resonator and the resonator to obtain the attenuation pole. Thus, low loss can be realized.
4). By adopting a structure that has high continuity with the input / output signal lines and the signal lines are terminated at the bottom of the resonator, the pattern on the printed circuit board on which the filter is mounted does not change the electrical termination position of the conductor pattern on the bottom Any pattern is acceptable. For example, if the filter according to the present invention is mounted on a continuous T-branch strip line, it is not necessary to re-create a conductor pattern on the substrate even when the filter dimensions are slightly changed, which is highly convenient.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an embodiment of the present invention. FIG. 2 is a perspective view showing a mounting method on a substrate. FIG. 3 is an explanatory view of characteristics of a waveguide type dielectric filter according to the present invention. FIG. 5 is a bottom view showing an embodiment of the present invention. FIG. 6 is a perspective view showing another embodiment of the present invention. FIG. 7 is another embodiment of the present invention. FIG. 8 is a perspective view showing another embodiment of the present invention. FIG. 9 is an explanatory view of the characteristics of the waveguide type dielectric filter according to the present invention. FIG.
11: Dielectric block
12: Resonator
13: Polarized input / output structure (resonator)
14: Input / output section
15: Input electrode
16: Output electrode
18, 19: Wiring board

Claims (2)

In a waveguide type dielectric filter in which a plurality of dielectric waveguides are integrally formed in a dielectric block,
The dielectric block is formed with a plurality of dielectric waveguide resonators constituting a filter, and a dielectric waveguide resonator for forming an attenuation pole is formed at least on one end,
The bottom surface of the dielectric placed between the waveguide resonator at the input / output end and the dielectric waveguide to form the attenuation pole extends inward from the side end surface and branches in the opposite direction, with one entering A waveguide-type dielectric comprising an input / output electrode with a conductor strip extending to the bottom surface of the waveguide resonator at the output end and the other end to the bottom surface of the waveguide resonator for forming an attenuation pole filter.   2. A waveguide type dielectric according to claim 1, wherein conductor strips are formed on the wiring board so as to face at least one of the branched input / output electrodes, and the input / output electrodes are mounted on the wiring board and connected to the conductor strips. filter.

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