JPS6224982Y2 - - Google Patents

Description

[Detailed description of the invention] This invention utilizes the length vibration of a rectangular plate-shaped ceramic piezoelectric vibrator, and arranges the electrode surfaces of a series resonator and a parallel resonator on a plane, and resonators are placed on both sides of the opposing electrodes. This is a π-terminal ladder type ceramic filter with a conductor that contacts near the vibration nodes to serve as an input terminal, an output terminal, and a ground terminal.

Ladder-type ceramic filters with a three-element π-end configuration that combine piezoelectric vibrators in series and in parallel and have bandpass characteristics are used in intermediate frequency amplification circuits for radios and various other wireless devices. Piezoelectric vibrators that utilize peripheral vibration of a square plate are widely used in this type of filter because they are easy to manufacture.

A conventional three-element π-end configuration ladder type ceramic filter has a configuration as shown in FIG. 1, and an equivalent circuit shown in FIG. 2. In Fig. 1, series resonator 1
an input terminal 5 having an auxiliary terminal 9 between the series resonator 1 and the parallel resonator 2, an output terminal 6 having an auxiliary terminal 10 between the series resonator 1 and the parallel resonator 3, and the parallel resonators 2 and 3. is press-contacted with a bridge terminal 8, and the ground terminal 7 is bonded to the bridge terminal 8. Conventional devices of this type have a complicated structure and include a large number of parts such as the bridge terminal 8 and auxiliary terminals 9 and 10, which are disadvantageous in that they are not only expensive due to component costs but also require time to assemble.

The present invention eliminates this drawback by arranging three resonators on a plane and providing conductors on both sides of each resonator, thereby making it possible to obtain a small-sized ceramic filter with a small number of parts and easy assembly.

In the ceramic filter of the present invention, as shown in Fig. 3, the series resonator 1 is a rectangular plate-shaped piezoelectric vibrator that vibrates in the longitudinal direction, and the parallel resonators 2 and 3 suppress spurious vibrations. Therefore, the series resonator 1 is a rectangular plate-shaped piezoelectric vibrator having different widths. The material for a rectangular plate-shaped piezoelectric vibrator that utilizes vibration in the longitudinal direction must have a high coupling coefficient, but the length dimension is approximately the same as the side length compared to a square plate-shaped vibrator that utilizes peripheral vibration. 80%, and the width dimension can be less than half the length, resulting in a significant reduction in material costs. In addition, in order to improve the characteristics as a filter by setting the capacitance of the parallel resonators 2 and 3 to about 10 times the capacitance of the series resonator 1, the parallel resonators 2 and 3 are
Use one with a larger area and a smaller thickness.
In order to form the equivalent circuit of FIG. 2, this ceramic filter has a series resonator 1 and parallel resonators 2 and 3 arranged in a plane as shown in FIG. The element 1 and the parallel resonator 2 are brought into contact near the vibration nodes to serve as an input terminal, and the conductor 7 is brought into contact near the vibration nodes of the parallel resonator 3 to serve as one of the ground terminals. On the other electrode surface of the resonator that is in contact with the conductors 5 and 7, the conductor 6 is brought into contact near the vibration nodes of the series resonator 1 and the parallel resonator 3 to serve as an output terminal, and the conductor 7' are brought into contact near the vibration nodes of the parallel resonator 2 to form a ground terminal. The conductors 7 and 7' are bonded together to form a common ground terminal. Each of the above-mentioned conductors is constructed by cutting a single metal plate into the shape shown in the figure, and finally cut along the line X-X' to separate each terminal.

The filter thus assembled is housed in an insulating case 11 as shown in FIG. 4, and the conductors 5, 6 and 7, 7' serve as input terminals, output terminals and ground terminals.

As another example of the present invention, as shown in FIG. 5, a conductive synthetic resin such as conductive rubber is bonded to the contact points of the conductors 5 and 7 near the nodes of the resonators.
Further, the conductor 5' and the conductor 5, which do not contact any of the resonators, and the conductors 7 and 7' are assembled by pressure bonding when the resonator is sealed in the insulating case. Figure 6 shows a filter assembled in this way with a conductor 5
and 5' are joined to form an input terminal, and conductor 6
becomes an output terminal, and conductors 7 and 7' are joined to form a ground terminal.

As described above, the filter of the present invention has a bridge terminal 8 and an auxiliary terminal 9, 1 more than the conventional filter.
0 is no longer required, and since the input terminal 5, output terminal 6, and ground terminals 7 and 7' are made on the same surface, it can be constructed in the form of two lead frames, reducing component costs and assembly costs. . Furthermore, in terms of external dimensions, each resonator is composed only of piezoelectric vibrators that vibrate in the longitudinal direction, so the area is approximately the same and the thickness is about half that of a conventional ceramic filter, making it compact. In addition, since each resonator is held in place by conductive synthetic resin, it has excellent impact resistance, and by widening the contact area of the conductor with each resonator, unnecessary spurious waves from each resonator are reduced. There are advantages.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional ladder-type ceramic filter with three elements at the π end configuration, and Figure 2 is a three-element π-edge configuration.
3 is an equivalent circuit diagram of a ladder type ceramic filter with an end configuration. FIG.
FIG. 5 is an assembled diagram of another example of the present invention, and FIG. 6 is an assembled diagram of FIG. 5. In the figure, 1...Series resonator, 2, 3...Parallel resonator, 5...Input terminal conductor, 6...Output terminal conductor, 7, 7'... Earth terminal conductor.

Claims (1)

[Scope of utility model registration request] A series resonator 1 and parallel resonators 2 and 3, each consisting of a rectangular plate-shaped ceramic piezoelectric vibrator having length vibration and having electrode surfaces on opposing surfaces, are arranged on a plane, and the series resonator 1 and the parallel resonator A conductor 5 is brought into contact with one surface of the parallel resonator 2 to serve as an input terminal, and a conductor 7 is brought into contact with one surface of the parallel resonator 3 to serve as a ground terminal.
A conductor 6 is brought into contact with the other surface of the output terminal to serve as an output terminal.
Further, there is a ladder type ceramic filter having a three-element π-end configuration in which a conductor 7' is brought into contact with the other surface of the parallel resonator 3 to serve as a ground terminal.