JPH04304002A - Dielectric filter - Google Patents

Abstract

PURPOSE:To reduce the axial length of a dielectric unit, that is, an integrally forming filter than that of a conventional structure by adjusting the stray capacitance so as to obtain a desired frequency thereby reducing the axial length L of a dielectric block 14. CONSTITUTION:A dielectric unit 12 includes a dielectric block 14 on which two dielectric coaxial resonators are formed, and a board 18 projecting from an open end face 16 of the dielectric block 14 in the axial direction of the dielectric block 14 and formed integrally. A stray capacitance is formed between a capacitor electrode 28a formed on the board 18 and a ground electrode 26 formed to a lower side of the board 18 and between a capacitor electrode 28b formed on the board 18 and the ground electrode 26 respectively. The frequency adjustment of the integrally formed filter 10 is implemented by adjusting the stray capacitance.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter, and more particularly to an integrally molded dielectric filter in which a plurality of dielectric coaxial resonators are formed in one dielectric block.

0002

2. Description of the Related Art Conventionally, there has been an integrally molded filter 1 as shown in FIG. 11 as a dielectric filter used in a BPF (band pass filter) or BEF (band elimination filter). The integrally molded filter 1 includes a dielectric block 2 in the form of a housing, a dielectric bushing 4 is fitted into a through hole 3 of the block, and is coupled to a bonding substrate (not shown) by a metal pin 5 inserted into the dielectric bushing 4. Ru. The frequency was adjusted by adjusting the axial length L of the dielectric block 2 or by adding electrodes to the open end surface 6.

0003

[Problems to be Solved by the Invention] In such an integrally molded filter 1, the frequency adjustment range is narrow in the method of adding electrodes to the open end surface 6, so in order to adjust the frequency over a wide range, the length L must be adjusted. The desired frequency was set using the following method. That is, the length L is determined by the frequency, and depending on the value of the set frequency, the length L becomes longer, that is, the integrally molded filter 1 becomes larger. moreover,
Since the integrally molded filter 1 is coupled to the bonding substrate by the metal pins 5, the length of the entire structure in the axial direction is further increased, resulting in an increase in size.

[0004] Therefore, the main object of the present invention is to provide a dielectric filter that can be miniaturized.

[0005]

[Means for Solving the Problems] The present invention provides a dielectric filter in which a dielectric coaxial resonator is composed of one dielectric block, in which a substrate for forming at least a stray capacitance for frequency adjustment is connected to the dielectric block. This dielectric filter is characterized in that it is integrally formed so as to protrude from the open end side of the dielectric filter.

[0006]

[Operation] A relatively large stray capacitance is formed by the substrate, and the frequency can be adjusted thereby, so that even if the axial length of the dielectric block is set short, the desired frequency can be set.

[0007]

According to the present invention, the length of the dielectric block in the axial direction can be shortened, so that the dielectric filter can be made smaller than before. The above objects of this invention,
Other objects, features and advantages will become more apparent from the following detailed description of the embodiments with reference to the drawings.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, an integrally molded filter 10 of this embodiment is used as a BPF, for example, and includes a dielectric unit 12. As shown in FIG. The dielectric unit 12 is
It includes a housing-like dielectric block 14 in which two dielectric coaxial resonators are formed, and an open end surface 16 of the dielectric block 14.
The substrate 18 protrudes from the side in the axial direction of the dielectric block 14.
is formed. The dielectric block 16 and the substrate 18 are integrally formed so that the lower surface and both axial side surfaces of the dielectric block 14 and the substrate 18 are flush with each other.

Furthermore, the open end surface 16 of the dielectric block 14
There are two through holes 22a and 2 from the short circuit end surface 20 to
2b is formed. The bottom surfaces of the through holes 22a and 22b are formed flush with the top surface of the substrate 18, and therefore the cross-sectional shapes of the through holes 22a and 22b are substantially semicylindrical. An inner conductor (
(not shown) is formed. Further, an outer conductor, that is, a ground electrode 26 is formed on the outer peripheral surfaces of the dielectric block 14 and the substrate 18, except for the open end surface 16, the upper surface of the substrate 18, and the front side surface 24. Therefore, two dielectric coaxial resonators are formed in one dielectric block 14.

Two opposing capacitor electrodes 28a and 28b are formed on the upper surface of the substrate 18. Further, capacitor electrodes 28a and 28b are formed to extend to through holes 22a and 22b, respectively, and are connected to the inner conductor, respectively. Capacitor electrodes 28a and 28b
By opposing each other, a coupling capacitance C1 shown in the equivalent circuit of FIG. 3 is formed. Capacitor electrodes 28a and 2
8b and a ground electrode 26 formed on the lower surface of the substrate 18, stray capacitances C2 and C3 are formed, respectively. Further, input/output electrodes 30a and 30b are formed from both ends of the upper surface of the substrate 18 to part of the lower surface as shown in FIG. An external Q (Qe) capacitor C4 is formed by the capacitor electrode 28a facing the input/output electrode 30a, and a Qe capacitor C5 is formed by the capacitor electrode 28b facing the input/output electrode 30b.

Note that the earth electrode 26 and the input/output electrode 30a
and 30b are formed with a gap therebetween so as to be electrically insulated. In this integrated filter 10, the frequency is adjusted by stray capacitances C2 and C3. Therefore, even if the axial length L of the dielectric block 14 is set short, a desired frequency can be set by adjusting the stray capacitances C2 and C3. Therefore, since the axial length L of the dielectric block 14 can be shortened, the axial length of the dielectric unit 12 can be shortened, and the integrally molded filter 10 can be made smaller. That is, the integrally molded filter 1
0 can be made shorter than the conventional structure (total length in the axial direction when the integrally molded filter is bonded to the bonding substrate).

Further, the coupling capacitance C1 can be arbitrarily set by changing the distance between the opposing portions of the capacitor electrodes 28a and 28b. Therefore, unlike the conventional method in which the coupling coefficient is uniquely determined by electric or magnetic coupling through coupling holes, slits, etc., the coupling coefficient can be set arbitrarily, resulting in a greater degree of freedom in design and higher precision. Furthermore, the number of parts can be reduced without requiring a bonding board, dielectric bushing, metal pin, etc. as in the conventional case, thereby reducing costs and improving mass productivity.

Referring to FIG. 4, an integrally molded filter 40 of another embodiment is also used as a BPF, and is different from the integrally molded filter 10 of FIG. 1 only in the formation locations of input and output electrodes. , the other configurations are the same. That is, the input/output electrodes 42a and 42b of the integrally molded filter 40 are connected to the capacitor electrode 28a on the upper surface of the substrate 18.
and 28b are formed on the lower surface of the substrate 18. Strictly speaking, the location where the ground electrode 44 is formed is also changed in detail as shown in FIGS. 4 and 5 in order to electrically insulate it from the input/output electrodes 42a and 42b.

In this integrally molded filter 40, a coupling capacitance C6 shown in the equivalent circuit of FIG. 6 is formed between capacitor electrodes 28a and 28b.
8b and the ground electrode 44, each stray capacitance C7
and C8 are formed. Furthermore, the capacitor electrode 28
A Qe capacitor C9 is formed between the capacitor electrode 28b and the input/output electrode 42a, and a Qe capacitor C10 is formed between the capacitor electrode 28b and the input/output electrode 42b. This embodiment also provides the same effects as the previous embodiment.

Referring to FIG. 7, another embodiment of an integrally molded filter 50 is used as a BEF. The integrally molded filter 50 includes a dielectric unit 12 similar to the embodiment described above, and the two through holes 22a and 22b of the dielectric block 16 are provided with coupling terminals 52a and 52.
b is inserted and electrically connected to the inner conductor. Further, on the outer peripheral surfaces of the dielectric block 14 and the substrate 18, except for the open end surface 16, the upper surface and the front side surface 24 of the substrate 18,
An outer conductor or ground electrode 54 is formed. Therefore, two dielectric coaxial resonators are formed in one dielectric block 14.

On the upper surface of the substrate 18, for example, chip-shaped capacitors 56a and 56b are arranged. The tips of coupling terminals 52a and 52b are connected to the electrodes on the upper surface of capacitors 56a and 56b, respectively, and the electrodes on the lower surface of capacitors 56a and 56b are connected to the coil 58.
connected by. Input/output terminals 60a and 60b are connected to electrodes on the lower surfaces of capacitors 56a and 56b, respectively. Therefore, capacitor 56
a and 56b form Qe capacitances C11 and C12 shown in FIG. is formed. Further, the coil 58 forms a coupling inductor L, and magnetically couples the input/output terminals 60a and 60b. This embodiment also provides the same effects as the previous embodiment.

In each of the above embodiments, the dielectric unit 12 was formed by integrally molding the dielectric block 14 and the substrate 18, but as shown in FIG. It may also be formed by bonding the substrate 18 to the end surface 16. Alternatively, the dielectric unit may be formed by laminating a dielectric block 62 onto a substrate 64 such that one end 66 of the substrate 64 protrudes, as shown in FIG. Note that the dielectric block and the substrate shown in FIGS. 9 and 10 may be made of different materials.

Furthermore, in each of the embodiments described above, the present invention was applied to a two-stage integral filter in which two dielectric coaxial resonators were formed in one dielectric block. It can also be applied to discrete dielectric filters that form one dielectric coaxial resonator in a dielectric block and three or more stage dielectric filters that form three or more dielectric coaxial resonators in one dielectric block. Needless to say.

Furthermore, if coupling holes and slits are used in conjunction with each dielectric coaxial resonator, the degree of freedom in design can be further increased. Further, the cross-sectional shape of the through-hole in the dielectric block may be circular, square, or the like in addition to the semicylindrical shape.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a bottom view of the embodiment of FIG. 1;

FIG. 3 is an equivalent circuit diagram of the embodiment of FIG. 1;

FIG. 4 is a perspective view showing another embodiment of the invention.

FIG. 5 is a bottom view of the embodiment of FIG. 4;

FIG. 6 is an equivalent circuit diagram of the embodiment of FIG. 4;

FIG. 7 is a perspective view showing another embodiment of the invention.

FIG. 8 is an equivalent circuit diagram of the embodiment of FIG. 7;

FIG. 9 is an illustrative view showing one embodiment of a method for manufacturing a dielectric unit.

FIG. 10 is an illustrative view showing another aspect of the dielectric unit manufacturing method.

FIG. 11 is a perspective view showing a prior art.

[Explanation of symbols]

10, 40, 50...Integrated filter 12
...Dielectric units 14, 62
...Dielectric blocks 18, 64
…substrate

Claims (1)

[Claims] 1. A dielectric filter in which a dielectric coaxial resonator is constituted by one dielectric block, wherein a substrate for forming at least a stray capacitance for frequency adjustment protrudes from an open end side of the dielectric block. A dielectric filter characterized by being integrally formed.