JPH0722814A - filter - Google Patents

Abstract

PURPOSE:To prevent the degradation of filter characteristic due to the reduction of Q of a resonator by eliminating the earth pattern on the rear side of a substrate corresponding to a circuit pattern part. CONSTITUTION:A substrate 1 provided with an earth pattern 4 on the rear side, plural resonators 2 and 3 mounted on the front side of this substrate 1, and a circuit pattern 5 which is provided on the front side of the substrate 1 to connect the input/output terminals 8 of these resonators 2 and 3 through a capacity element, an inductance element 7, or the like are provided. The earth pattern 4 on the rear side of the substrate 1 facing the circuit pattern 5 is eliminated. Therefore, the floating capacity between the circuit pattern 5 on the front side of the substrate 1 and the earth pattern 4 on the rear side is remarkably reduced. Consequently, Q of resonators 2 and 3 is not reduced practically, and thereby, the degradation of the filter characteristic is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter used for an antenna duplexer or the like.

[0002]

2. Description of the Related Art A conventional filter of this type includes a substrate provided with a ground pattern on the back side, a plurality of resonators mounted on the front side of the substrate, and input / output terminals of these resonators. And a circuit pattern provided on the front surface side of the substrate so as to be connected via a capacitance element or an inductance element.

[0003]

A problem with the above-mentioned conventional device is that the Q of the resonator is lowered and the filter characteristics are deteriorated. That is, stray capacitance is formed between the circuit pattern provided on the front surface side of the substrate and the ground pattern on the back surface side. This is because the Q of the substrate is lower than the Q of the resonator, and as a result, A capacitor having a low Q is connected in parallel to the resonator, which lowers the Q of the resonator and deteriorates the filter characteristics.

Therefore, an object of the present invention is to prevent deterioration of filter characteristics due to a decrease in Q of the resonator.

[0005]

In order to achieve this object, the present invention eliminates the ground pattern on the back surface side of the substrate facing the circuit pattern portion.

[0006]

With the above arrangement, the stray capacitance between the circuit pattern on the front surface side of the substrate and the ground pattern on the rear surface side becomes extremely small, so that the Q of the resonator does not substantially decrease, and the filter The deterioration of the characteristics is prevented.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. 1 to 3, reference numeral 1 denotes a glass epoxy substrate, and behind the surface thereof are five dielectric coaxial resonators (hereinafter referred to as resonators) 2 serving as receiving filters and a transmitting filter. The four dielectric coaxial resonators (hereinafter referred to as resonators) 3 are fixed to the ground pattern 4 of the substrate 1 by soldering so as to form one row in the lateral direction. A circuit pattern 5 is provided in front of the surface of the substrate 1, and the capacitance element 6 and the inductance element 7 shown in FIG. 4 are mounted on the circuit pattern 5. The lead wires of the plurality of inductance elements 7 are wound in a cylindrical shape, and are mounted in parallel so that their opening directions are not aligned. The input / output terminal 2a of the resonator 2 is directly soldered to the circuit pattern 5, and the input / output terminal 3a of the resonator 3 is
It is soldered to the circuit pattern 5 via the capacitor 6. With the above mounting structure, the electrical circuit connection is as shown in FIG.

In FIG. 4, 8 is an input / output terminal to which the antenna 9 is connected, 10 is a terminal to which a transmission output is supplied, and 11 is a receiving terminal. These terminals 8, 1
As shown in FIG. 1, 0 and 11 are provided separately from the front center of the substrate 1 and the left and right. That is, in FIG. 4, the resonator 2 and the capacitor 6 provided between the input / output terminal 8 and the terminal 11 constitute a reception filter, and the resonator 3 and the capacitor 6 between the input / output terminal 8 and the terminal 10 are connected. The inductance element 7 constitutes a transmission filter. FIG. 3 shows the back side of the substrate 1, and the ground pattern 12 is provided on almost the entire surface. However, the circuit pattern 5 of the capacitor 6 group of the reception filter in FIG.
The portion corresponding to is an opening 13 from which the ground pattern 12 is removed. Therefore, the stray capacitance between the group of capacitors 6 of the reception filter and the circuit pattern 5 and the ground pattern 12 on the back side thereof becomes extremely small,
The Q of the reception filter portion does not decrease and the filter characteristic is high. That is, when a large stray capacitance is formed here, the stray capacitance 14 is directly connected in parallel to the resonator 2 as shown in FIG. This stray capacitance 1
Since No. 4 is formed of a glass epoxy type substrate having a low Q, its Q is low and if it is directly connected to the resonator 2, the Q of the resonator 2 becomes extremely low, and as a result, the filter characteristics are deteriorated. It will end up. On the transmission filter side, the stray capacitance 15 is connected in parallel to the resonator 3, but is connected via the capacitor 6, so that the Q of the resonator 3 is not directly lowered.

In FIG. 3, the side 13a of the opening 13 is shown.
A strip-shaped ground pattern 12a is also provided between the substrate and the end surface of the substrate 1.
This is because the isolation characteristic between the input / output terminal 8 and the terminal 11 is not deteriorated.

[0010]

As described above, according to the present invention, the substrate having the ground pattern on the back side, the plurality of resonators mounted on the front side of the substrate, and the input and output terminals of these resonators are provided. And a circuit pattern provided on the front surface side of the substrate so as to connect between them via a capacitive element or an inductance element, and the ground pattern on the back surface side of the substrate facing the circuit pattern portion is deleted. Since the stray capacitance between the circuit pattern on the front surface side of the substrate and the ground pattern on the back surface side becomes extremely small, the Q of the resonator does not substantially decrease and deterioration of the filter characteristics is prevented. is there.

[Brief description of drawings]

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

FIG. 2 is a front view of an embodiment of the present invention.

FIG. 3 is a back view of an embodiment of the present invention.

FIG. 4 is an electric circuit diagram of an embodiment of the present invention.

FIG. 5 is an electric circuit diagram showing a comparative example of one embodiment of the present invention.

[Explanation of symbols] 1 substrate 2 resonator 3 resonator 4 ground pattern 5 circuit pattern 6 capacitor 7 inductance element 8 input / output terminal 9 antenna 10 terminal 11 terminal 12 ground pattern 13 opening

Front page continuation (72) Inventor Shoji Tanaka 55-12, Ozumi, Osamu, Tanabe-cho, Tsuzuki-gun, Kyoto Prefecture Matsushita Nitto Electric Co., Ltd.

Claims (2)

[Claims] 1. A substrate having a ground pattern on the back side, a plurality of resonators mounted on the front side of the substrate, and a capacitance element or an inductance element between the input and output terminals of these resonators. And a circuit pattern provided on the front surface side of the substrate so as to be connected via the ground pattern on the back surface side of the substrate facing the circuit pattern portion. 2. A window-shaped ground pattern deletion portion is formed on the back surface of the substrate, and a strip-shaped ground pattern is provided between a side edge of the ground pattern of this ground pattern removal portion and a substrate end surface facing the ground pattern. The filter according to claim 1, wherein an earth terminal connected to the strip-shaped earth pattern is provided on the end surface of the substrate.