JP3306331B2 - Dielectric filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a dielectric filter, and more particularly to a coaxial TEM resonator type dielectric filter in which two dielectric substrates are bonded.

[0002]

2. Description of the Related Art Dielectric resonators (filters), multilayer LC filters, and the like have come to be used as filters that can be used in the hundreds of MHz band for mobile communication devices and the like. In particular, a dielectric filter combined with a coaxial TEM resonator is used in various fields as a filter and a duplexer because a high Q is obtained.

There are two types of dielectric filters: one that connects a plurality of dielectric resonators alone, and one that forms a plurality of resonators integrally by forming a plurality of through holes in a dielectric block. Further, a structure in which a dielectric substrate having a concave groove and a flat dielectric substrate are bonded to each other is also adopted.

FIG. 2 is a perspective view showing a dielectric filter having such a bonding structure. A flat dielectric substrate 22 is bonded to the surface of the dielectric substrate 21 having the concave groove 20 having the concave groove 20 with an adhesive 23 such as glass, and an inner conductor 25 is formed in a through hole that can be bonded. Then, the outer conductor 26 is formed on the surface where the through hole does not open. Although not shown, a short-circuit conductor is formed on one end surface of the through hole. An input / output terminal electrode 28 is formed so as to be surrounded by the outer conductor 26, thereby forming a dielectric filter in which a plurality of dielectric resonators are integrated.

[0005]

In a dielectric filter in which a plurality of dielectric resonators are integrated to form a block, the resonance frequency of the resonator at the center in the structure becomes higher,
It is necessary to correct this. In order to lower the resonance frequency, it is necessary to increase the size (length) of the resonator or to increase the dielectric constant of the dielectric material in that portion. In order to change the dimensions, operations such as polishing of the dielectric are required, and in order to increase the dielectric constant, diffusion treatment of the additive material is required.

The present invention provides a dielectric filter capable of adjusting the resonance frequency between resonators without adding a step such as mechanical processing or heat treatment.

[0007]

The present invention solves the above-mentioned problems by lowering the effective permittivity of the dielectric in the portion of the dielectric resonator at both ends and increasing the resonance frequency of the resonator at both ends. Things.

That is, a first dielectric substrate having three or more parallel grooves, and a second dielectric substrate adhered to the surface of the first dielectric substrate where the grooves are formed by an adhesive. An inner conductor is formed in the concave groove of the first dielectric substrate and on the surface facing the concave groove of the second dielectric substrate, and the first dielectric substrate and the second dielectric substrate are bonded. In a dielectric filter in which an outer conductor is formed on a surface that is not formed and an end surface on which the concave groove does not open, and a short-circuit conductor is formed on one of the open end surfaces of the concave groove, the first dielectric on the surface of the second dielectric substrate is provided. A layer having a lower dielectric constant than the first dielectric substrate and the second dielectric substrate is formed in portions facing the concave grooves at both ends of the substrate, and a part of the inner conductor is formed on the layer having a low dielectric constant. It is characterized by being formed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS When glass is used as a material having a low dielectric constant, it can be used as an adhesive material for a dielectric substrate and a low dielectric constant layer. A low dielectric constant layer is formed in the portion, and the effective dielectric constant of the resonator portion is reduced, so that the resonance frequency can be increased.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of the present invention. A dielectric filter is formed using a dielectric substrate having a dielectric constant of about 90, and is obtained by bonding a dielectric substrate 11 having a concave groove 10 and a flat dielectric substrate 12 to each other. Groove 10
Are formed in parallel with the surface of the first dielectric substrate 11. First dielectric substrate 11 and second dielectric substrate 12
Bonding with the glass substrate 13 is performed by applying a glass paste to the bonding surface of the dielectric substrate, and then pressing and heat-treating the glass paste.

The glass layer 13 used as the adhesive is formed not only on the bonding surface between the first dielectric substrate 11 and the second dielectric substrate 12, but also on the first dielectric substrate 11 of the second dielectric substrate 12. Are also formed on the surface of the portion opposite to the concave grooves 10a and 10c at both ends of the substrate. The glass layer 13 is not formed on the portion facing the central groove 10b.

An inner conductor 15 is formed in a through hole formed by the concave groove of the dielectric block integrated by the glass layer 13. An outer conductor 16 is formed on the surface where the through hole does not open, and a terminal electrode 18 insulated from the outer conductor is formed on a part thereof. The terminal electrode may be capacitively coupled to the inner conductor, or may be directly connected. Although not shown, a conductor film is also formed on one end face where the through-hole is opened to form a short-circuit conductor.

As described above, the glass layer 13 exists in a part around the inner conductors 15a and 15c at both ends, and the center inner conductor 15b
There is no glass layer around. The periphery of the central inner conductor 15b is surrounded by a material having a high dielectric constant constituting the dielectric substrate. In contrast, the inner conductors 15a, 15c at both ends
Since there is a material having a dielectric constant as low as about 10 in a part of the surrounding area, the effective dielectric constant of this part is reduced.

The resonance frequency of a dielectric resonator is determined by its size and dielectric constant. The lower the dielectric constant, the higher the resonance frequency. By changing the dielectric constant and thickness of the glass layer, it becomes possible to match the resonance frequency to be matched.

The above effect can be obtained by forming a low dielectric constant layer around a part of the inner conductor at both ends, so that the material is not limited to glass. However, it is desirable to use the adhesive as it is as the low dielectric constant material from the viewpoint of man-hours. Further, even when there are four or more resonators, the resonance frequency can be matched with the same structure as described above.

[0017]

According to the present invention, the resonance frequency can be adjusted by interposing a low dielectric constant layer, and a block type dielectric filter having desired characteristics can be obtained.

Further, since an adhesive can be used as the low dielectric constant layer, the number of steps can be reduced to a minimum, and there is an advantage that no particular cost increase occurs.

[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 conventional dielectric filter.

[Explanation of symbols]

 11, 12, 21, 22: Dielectric substrate 13, 23: Adhesive (glass layer) 15, 25: Inner conductor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01P 1/20-1/219 H91P ^7/ 00-7/10

Claims (3)

(57) [Claims] 1. A first dielectric substrate having three or more parallel concave grooves, and a second dielectric substrate adhered to the surface of the first dielectric substrate on which the concave grooves are formed by an adhesive. An inner conductor is formed in the concave groove of the first dielectric substrate and on the surface facing the concave groove of the second dielectric substrate, and the first dielectric substrate and the second dielectric substrate are bonded. An outer conductor is formed on the non-opened surface and the open end of the groove, and a short-circuit conductor is formed on one of the open ends of the groove, wherein the first dielectric on the surface of the second dielectric substrate is provided. A layer having a lower dielectric constant than the first dielectric substrate and the second dielectric substrate is formed in portions facing the concave grooves at both ends of the substrate, and a part of the inner conductor is formed on the layer having a low dielectric constant. A dielectric filter characterized by being formed. 2. A first dielectric substrate having three or more parallel grooves, and a second dielectric substrate adhered to the surface of the first dielectric substrate on which the grooves are formed by an adhesive. An inner conductor is formed in the concave groove of the first dielectric substrate and on the surface facing the concave groove of the second dielectric substrate, and the first dielectric substrate and the second dielectric substrate are bonded. An outer conductor is formed on a surface not formed and an end face where the groove is not opened, and a short circuit conductor is formed on one of the end faces where the groove is opened, wherein the first dielectric substrate and the second dielectric substrate The adhesive is made of a material having a lower dielectric constant than the first dielectric substrate and the second dielectric substrate, and faces the concave grooves at both ends of the first dielectric substrate on the surface of the second dielectric substrate. The adhesive layer is also formed on the adhesive layer, and a part of the inner conductor is formed on the adhesive layer. Body filter. 3. The dielectric filter according to claim 2, wherein the adhesive is glass.