JPS60201712A - Comb-line filter - Google Patents

Abstract

PURPOSE:To simplify the structure with a thin and flat design for a comb-line filter by producing a Stonley wave on the interfacial boundary between an isotropic elastic material and a piezoelectric material to form an ultrasonic delay line and at the same time constituting a capacitor with said elastic material and material. CONSTITUTION:Input and output transducers 23 and 24 and a capacitor 25 for formation of a comb-line filter are produced with a 3-layer structure of a thin metallic film 27, a piezoelectric material 22 and a metallic thin film 28. The transducer 23 is excited with impression of signal voltage. Then the vibration of an ultrasonic wave, i.e., a Stonley wave is transmitted only on the interfacial boundary between an isotropic elastic material 21 and the material 22. Then the transducer 24 is excited and the voltage is produced in response to the vibration of the transducer 24.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a comb filter mainly used in video equipment such as TVs and VTRs.

Conventional configuration and problems thereof Figures 1 (&) and (b) respectively show circuits with a comb-shaped film configuration. 1 is an ultrasonic delay line, 2 is an impedance constituting a comb filter, and 3 and 4 are matching impedances of the ultrasonic delay line 1.

A combination of the ultrasonic delay line 1 and the impedance 2 constituting the comb filter is collectively referred to as a comb filter.

FIG. 2 shows a conventional example of a comb filter. 5 is an ultrasonic delay medium, 6 is an electrode, 7 is a piezoelectric vibrator for input, 8 is a piezoelectric vibrator for output, 9 is an electrode, 10 is solder or epoxy resin, 11 is an electrode, and 12 is an ultrasonic wave 13 is a lead wire for A/L, 14 is a lead wire for input, 15 is a lead wire for output, 16 is a terminal pin for earth, 17 is a terminal pin for input, 18 is an output terminal. 19 is a resistor for forming a comb-shaped filter, and 20 is a case.

The operating principle of the conventional comb filter is that by applying a signal voltage to the input terminal pin 17, the piezoelectric vibrator 7
is excited, propagates inside and on the surface of the ultrasonic delay medium 5 as a transverse wave (SH wave), reaches the output piezoelectric vibrator 8 with a certain delay time, and vibrates. This vibration is combined with a delayed signal at the output terminal pin 18, where each signal passes from the input terminal pin 17 through the comb filter forming resistor 19, thereby exhibiting a comb characteristic. The comb filter forming resistor 19 may be a capacitor. A comb-shaped filter with this structure requires built-in components for the comb-shaped filter, so the case 20 becomes thicker, and the lead wires 13 to 16 are thicker.
, the method of connecting the comb filter components becomes complicated.

OBJECTS OF THE INVENTION In view of the above-mentioned drawbacks, an object of the present invention is to provide a comb-shaped filter that has a simplified structure and a thin planar structure.

Structure of the Invention In order to achieve the above object, the present invention provides at least one pair of a first electrode, a second electrode, one of the first electrodes and a second electrode, on a portion of an isotropic elastic substrate. Provide a conductor to join the
A thin film of piezoelectric material is formed on the electrode and the isotropic elastic substrate at a portion where the ultrasonic wave propagates, and a third electrode is provided on the piezoelectric material formed on the electrode, and a third electrode is provided on the piezoelectric material formed on the electrode. This configuration includes a conductor that electrically connects the piezoelectric material on the top and the piezoelectric material on the second electrode.

A stone IJ-wave is generated on the interface between an isotropic elastic body and a piezoelectric material, and this sound wave forms an ultrasonic delay line.
By constructing the capacitor for the cross-shaped filter using an isotropic elastic material and a piezoelectric material, it has a planar structure and can be made thinner.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention is shown in FIGS. 3(a) and 3(b), respectively.

21 is an isotropic elastic body, 22 is a piezoelectric material, 23 is an input transducer, 24 is an output transducer, 26 is a capacitor for forming a comb filter, and 26 is a conductor connecting the transducers 23, 24 and the capacitor 25. FIG. 4 (tL), (■) respectively show an example of a transducer, a capacitor, and a structure for joining a transducer and a capacitor. Reference numerals 27 and 28 designate a thin metal film that constitutes a transducer and a capacitor for forming a cross-shaped filter, and also connects the transducer and the capacitor. The transducers 23, 24 and the capacitor 25 for the comb filter configuration are made of metal thin films 27. Piezoelectric material22. Metal thin film 2
This can be realized by having a three-layer structure of 8. Then, when a signal voltage is applied to the input transducer 23, it is excited, the vibration propagates only on the interface between the isotropic elastic body 21 and the piezoelectric material 22, and the output transducer 24 vibrates.
A voltage is generated according to this vibration. The ultrasonic wave used in this structure is a Stoneley wave that vibrates and propagates only on the interface when two types of material abrasive constants satisfy a certain condition. The comb-shaped filter condenser 26 has the same structure as the transducers 23 and 24, so it vibrates, but this vibration does not propagate to the surroundings, and merely uses the capacitance of the piezoelectric material. do not have. In addition, Fig. 3 (a
) and Figure 4 (IIL) are configuration examples of Figure 1 (a),
FIG. 3(b) and FIG. 4 (b3 is an example of the configuration of FIG. 1(b)).

Effects of the Invention By implementing the comb filter of the present invention, the following effects can be obtained.

■ A capacitor that constitutes an ultrasonic delay line and a comb filter at the same time can be obtained.

■ Can be made thinner.

■ Simple structure.

[BRIEF DESCRIPTION OF THE DRAWINGS] Figures 1(e-) and (b) are block diagrams of a general comb filter, Figure 2 is a partially cutaway front view of a conventional comb filter, and Figure 3(a) is a diagram of a conventional comb filter. ) and (b) are plan views showing embodiments of the comb filter of the present invention, and FIG. 4 (&), respectively.
, (b) are side views of the same essential parts. 21... Isotropic elastic body, 22... Piezoelectric material, 23... Input transducer, 24...
...Output transducer, 25...
Capacitor for comb filter configuration, 26... Conductor for junction, 27.28... Metal thin film.

Claims (2)

[Claims] (1) A first electrode for configuring one or more pairs of input and output quadrature transducers, a second electrode for configuring a capacitor, one of the first electrodes and the second electrode on a part of the isotropic elastic substrate. A conductor is provided to connect the electrodes, a piezoelectric material is formed on the electrode and the isotropic elastic substrate at a portion that serves as an ultrasonic propagation route, and a third conductor is formed on the piezoelectric material formed on the electrode.
What is claimed is: 1. A comb-shaped filter characterized in that a conductor is provided to electrically connect a piezoelectric material on the first electrode and a piezoelectric material on the second electrode. (2) The comb filter according to claim 1, wherein one of the two conductors connected to the first electrode is separated from the second electrode.