Wave transmission lines and networks – Coupling networks – Wave filters including long line elements
Patent
1992-09-25
1994-04-19
Ham, Seungsook
Wave transmission lines and networks
Coupling networks
Wave filters including long line elements
333207, H01P 1205, H05K 346
Patent
active
053049675
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a dielectric filter used in various types of radio equipment such as portable or automobile telephones, and in other similar electronic devices.
BACKGROUND ART
High frequency filters have conventionally been used in various types of radio and other electronic equipment. Among those high frequency filters, there is a dielectric filter using dielectric resonators.
The conventional dielectric filter will be described with reference to a concrete example shown in the accompanying drawings.
First Prior-Art Example
FIGS. 7, 8, and 9A to 9C are drawings showing a first prior-art example, in which FIG. 7 is a perspective view (of the main body only) of a high frequency filter, FIG. 8 is a perspective view (of the main body and a metal case) of the high frequency filter, and FIGS. 9A to 9C show circuit examples of the high frequency filter.
In those figures, IN denotes an input terminal, OUT an output terminal, C.sub.0 a coupling capacitor, 1 and 2 dielectric resonators, 3 a circuit board (interstage circuit board), 4 and 5 conductor patterns, 6 a metal case, and 7 and 8 external terminals.
As shown in FIG. 7, this dielectric filter has two dielectric resonators 1 and 2 arranged side by side, a circuit board 3 provided integrally with those resonators at one end in the longitudinal direction thereof, and a necessary circuit element mounted on the circuit board 3. For the circuit board 3, a dielectric substrate is utilized, for example, and on which conductor patterns 4 and 5 are formed by thick film printing. One end of each of above-mentioned conductor patterns 4 and 5 formed on the circuit board substrate 3 are connected respectively to the conductors of the dielectric resonators 1 and 2, and the other ends thereof are formed as the input terminal IN and the output terminal OUT, respectively. A coupling capacitor C0 as the above-mentioned circuit element, for example, is mounted between the conductor patterns 4 and 5.
In this example, the coupling capacitor C.sub.0 is mounted as a discrete part, however this coupling capacitor C.sub.0 may be formed utilizing the thin film patterns on the circuit board 3. The dielectric filter shown in FIG. 7 is constituted only by the main body, but this dielectric filter is usually used by being covered with a metal case 6 as shown in FIG. 8.
This metal case 6 is provided with external terminals 7 and 8, which will be connected to the input terminal IN and the output terminal OUT on the main body side, respectively. To attach the metal case 6 to the main body, the metal case 6 is moved in the arrow direction shown in FIG. 8 so that one end portion of the dielectric resonators 1 and 2 is inserted into the inside of the metal case 6. In other words, the above-mentioned insertion is done so that a part of the dielectric resonators 1 and 2 are positioned inside the metal case 6. Under this condition, the circuit board 3 is covered by the metal case 6.
The circuit construction of the above-mentioned dielectric filter is as shown in FIG. 9A. This circuit serves as a band pass filter as it is formed by connecting the coupling capacitor C.sub.0 between the input terminal IN and the output terminal OUT, and a dielectric resonator 1 between the input terminal IN and the ground, and the dielectric resonator 2 between the output terminal OUT and the ground.
This high frequency filter is sometimes made as a polar band pass filter or a band rejection filter by adding some other element or elements as shown in FIGS. 9B and 9C. In the case of a polar band pass filter shown in FIG. 9B, a coil L is connected in parallel with the coupling capacitor C.sub.0 as shown in FIG. 9A. In the case of a band rejection filter shown in FIG. 9C, a capacitor C1 is connected between the input terminal IN of the circuit 9A and the dielectric resonator 1, and a capacitor C.sub.2 between the output terminal OUT and the dielectric resonator 2.
In order to make those dielectric filters, the coil L or the capacitors C.sub.1 and C.sub.2 mentioned above are mounted
REFERENCES:
patent: 4757288 (1988-07-01), West
patent: 5006956 (1991-04-01), Kawakita et al.
patent: 5036301 (1991-07-01), Takao et al.
patent: 5115373 (1992-05-01), Takeda
patent: 5196813 (1993-03-01), Nakakubo
Ham Seungsook
TDK Corporation
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