JP3017753B2 - Composite piezoelectric element - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a composite piezoelectric element in which a surface acoustic wave element and a quartz resonator are integrally combined.

(Technical background of the invention and its problems) Recently, the demand for ultra-small pagers,
For example, as shown in FIG. 2, the antenna 1 is connected to an antenna filter composed of a surface acoustic wave element 2, and a radio wave of a predetermined band is selected based on the sharp filtering characteristic. This output is mixed by the mixer 3 with a signal from the local oscillation circuit 4 based on the crystal resonator 5 and converted to an intermediate frequency.

The signal converted to the intermediate frequency is amplified by an amplifier 7 via a monolithic filter (MCF) 6 and decoded by a decoder 8. The decoder 8 is supplied with a signal from a timing circuit based on the crystal oscillator 9. Then, the speaker 10a is sounded by the decoded output of the decoder to notify the calling.

In such a configuration, in order to reduce the size and weight, the development of integrated circuit elements that operate at low voltage and low power consumption, the development of ultra-small circuit components, batteries, and the like, as well as surface acoustic wave elements used for input circuits, for example, Also, it is necessary to reduce the size of the crystal unit used for the local oscillation circuit.

For this reason, efforts have been made to reduce the size of surface acoustic wave devices and quartz resonators. However, it is difficult to make the shape extremely small with devices utilizing this kind of piezoelectric phenomenon in order to maintain electrical characteristics. In addition, in order to stably operate the device for a long period of time, the external shape cannot be reduced so much because the device is housed in an airtight container together with an inert gas or the like.

(Object of the Invention) The present invention has been made in view of the above circumstances, and the shape can be significantly reduced in size by integrating a surface acoustic wave element and a quartz oscillator, and the characteristics are also excellent. It is an object to provide a composite piezoelectric element.

(Summary of the Invention) The present invention forms a surface acoustic wave element on a plate surface of a quartz plate,
A quartz resonator is held on the back surface of the quartz plate.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the cross-sectional view shown in FIG.

In the figure, reference numeral 11 denotes a substrate formed by cutting a quartz crystal at a predetermined angle with respect to its crystal axis. On one side surface of the substrate 11, a surface acoustic wave element 12, for example, an interdigital electrode 12a is formed to form a surface acoustic wave filter adjusted to a desired filtering characteristic.

Also, a pair of holding members 11a are arranged at a predetermined interval on the other side plate surface of the substrate 11, where the crystal of the crystal is cut at a predetermined angle with respect to the crystal axis and polished to form an electrode on the plate surface. Thus, both ends of the crystal resonator 13 adjusted to a predetermined resonance frequency are held.

Then, the substrate 11 is housed in a container 15 via a lead terminal 14, the electrodes are led out, and the container 15 is hermetically sealed.

With such a configuration, since the surface acoustic wave does not propagate to the back surface of the substrate 11 on which the surface acoustic wave element 12 is formed, even if the crystal resonator 13 is provided here, there is no electrical adverse effect. .

Since the crystal resonator 13 and the substrate 11 holding the same are made of the same material, they have the same expansion coefficient due to temperature change, and do not exert stress on the crystal resonator 13 due to the difference in expansion coefficient. Properties can be obtained.

A quartz resonator is provided on the back surface of the substrate 11 of the surface acoustic wave element 12.
Since 13 is held, the shape can be remarkably reduced in size as compared with those individually sealed, and the number of members is reduced and the assembling process is simplified.

The present invention is not limited to the above embodiment. For example, a shield electrode may be provided on the other side plate surface of the substrate 11 to shield radiation from the crystal resonator 13.

The surface acoustic wave element 12 may be not only a filter but also, for example, a resonator used for a local oscillation circuit.
Of course, not only a resonator used for the frequency reference of the local oscillation circuit but also a monolithic filter or the like used for the intermediate frequency amplification stage may be used.

(Effects of the Invention) As described in detail above, according to the present invention, it is possible to provide a composite piezoelectric element that can be reduced in size, is easy to assemble, is inexpensive, and has good electrical characteristics.

[Brief description of the drawings]

 FIG. 1 is a side sectional view showing an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of a pager. 11 Crystal plate 12 Surface acoustic wave device 13 Crystal resonator 14 Lead terminal 15 Container

Claims (1)

(57) [Claims] 1. A surface acoustic wave device formed on one side surface of a quartz plate, a crystal resonator held by a holding member provided on the other side surface of the quartz plate, and a quartz resonator provided on the other side surface of the quartz plate. And a shield electrode for shielding radiation from the quartz resonator.