JPS5972804A - Surface acoustic wave element - Google Patents

Abstract

PURPOSE:To obtain functions for mixture, conversion, etc. of frequency with just a single element by forming >=3 electrodes to a surface acoustic wave element containing inter-digital electrodes. CONSTITUTION:>=3 inter-digital electrodes 201-203 are provided in the traveling direction of a surface acoustic wave in contact with the surface 204 of a piezoelectric material. The signal voltage is impressed to the 1st electrode 201 to produce a surface acoustic wave, and another signal voltage is impressed to one other electrodes. Then a signal is extracted out of the transmitted surface acoustic wave of the remaining inter-digital electrode. When an oscilltor 205 is connected to these electrodes. the electrode spaces d1 and d2 oscillate with a frequency f0 to satisfy d1>d0>d2 or d1<d0<d2. Therefore the surface acoustic wave that is driven by the electrode 201 and passes through the electrode 202 receives modulation from the oscillator 205. As a result, the surface acoustic wave radiated from the electrode 201 and passed through the electrode 202 contains the frequecy f1+f0. Then the electrode 203 is oscillated with frequency f1+f0 or f1-f0 to obtain an electric signal of each frequency. In such a way, the functions are obtained for a signal mixer, a filter and a delay unit respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a surface acoustic wave element in which interdigital electrodes are formed on a piezoelectric substrate, or interdigital electrodes are formed on a solid substrate, and piezoelectric The present invention relates to a surface acoustic wave element formed with a thin film.

Conventional Structure and Problems The conventional surface acoustic wave element has a pair of interdigital electrodes 101 and 102 formed on a piezoelectric substrate 105, as shown in FIG. The electric signal is applied to the electrode 101 and converted into a surface acoustic wave 106, and this surface acoustic wave 106 is converted back into an electric signal by the electrode 102 and taken out from the terminal 104, and has the function of a filter and a delay device. It was something.

OBJECTS OF THE INVENTION It is an object of the present invention to realize a surface acoustic wave element having functions other than those described above and serving as a small multifunctional element by forming three or more electrodes on the surface acoustic wave element.

Structure of the Invention The present invention provides three or more interdigital electrodes in the surface acoustic wave propagation direction in contact with a piezoelectric material surface, applies a signal voltage to the first interdigital electrode to generate a surface acoustic wave, and It is constructed so that other signal voltages are applied to some of the interdigital electrodes, and signals are extracted from the transmitted surface acoustic waves from other electrodes, and functions such as frequency mixing and conversion are performed in one element. This can be realized by

DESCRIPTION OF EMBODIMENTS FIG. 2 shows an embodiment of the present invention, in which a surface acoustic wave element having the functions of a filter, a delay device, and a mixer, a fourth
The figure shows another embodiment of a surface acoustic wave element having the functions of a filter and a mixer and capable of obtaining two signals with different delay times.

In FIG. 2, 201 is an interdigital electrode that converts an input electrical signal of frequency f1 into a surface acoustic wave, 203 is an interdigital electrode that converts the surface acoustic wave into an electrical signal,
2o4 is a piezoelectric substrate with these electrodes provided on its surface. 202 is the oscillation frequency f of the oscillator 205. This is an interdigital electrode that resonates with the electrode 201.
The surface acoustic wave that has reached the surface acoustic wave 02 and the surface acoustic wave excited from the electrode 202 by the oscillator 205 are mixed by the electrode 202, and has a function as a so-called surface acoustic wave multiplier. This multiplication function will now be explained using diagrams.

FIG. 3 shows the interdigital electrode 202 in FIG.
This is an expanded version of Electrodes 202a and 202b are formed on a piezoelectric substrate 204 and are excited by an oscillator 206 having an internal resistance R. Electrode spacing d1
．． d2 is d when the oscillator 205 is not connected.
l-d2=d0, but when oscillator 205 is connected, dl,%-,1: and d2U frequency f. d
l>do, d2<do or dl<d. , d2〉do
takes the state of

Therefore, in FIG. 2, a surface acoustic wave excited by electrode 201 and passing through electrode 202 is modulated by oscillator 205. Furthermore, when the output resistance R of the oscillator 20E5 changes depending on the output voltage of the oscillator, this corresponds to changing the load on the surface acoustic wave through the electrodes 202a and 202b. The wave receives modulation from oscillator 205.

Due to the above action, the surface acoustic waves radiated from the electrode 201 and passed through the electrode 202 contain a frequency of f1±fo, and the surface acoustic wave that passes through the electrode 203 has a frequency of f, +fo, or fl-f.

By causing resonance, electrical signals of each frequency component can be obtained. Therefore, as described above, a surface acoustic wave element having the functions of a signal mixer, a filter, and a delay device can be realized on the same substrate.

In FIG. 4, 301 is an interdigital electrode that converts an input electrical signal of frequency f1 into a surface acoustic wave, 302 is an interdigital electrode that resonates at the oscillation frequency 10 of the oscillator 306, and the electrode 301 is excited by the electrode 306.
The surface acoustic waves reaching the electrode 3 and the oscillator 306
The surface acoustic waves excited from 02 are mixed by electrode 302. Electrodes 303 and 304 have a frequency of 11-f
.

Alternatively, it is an interdigital electrode that resonates with f1+fo. The spacing between the electrodes 303 and 304 and the electrode 302 is 11 o and 12 o, respectively, and when the propagation velocity of the surface acoustic wave on the piezoelectric substrate is V, td=l, /v-12/v
Frequencies f1-f with a time difference of. Or f1+fo
electrical signals are obtained as outputs of electrodes 303 and 304. Therefore, as described above, it is possible to realize a surface acoustic wave element having functions as a signal mixer and a filter and capable of obtaining two signals having different delay times on the same substrate.

The surface acoustic wave elements described above in FIGS. 2 and 4 are as follows:
Compared to conventional devices having these functions, it is possible to reduce the size, improve reliability, and reduce costs. Furthermore, since these surface acoustic wave elements do not require a DC power source, they do not require wiring for a power source and can provide a power-saving element with a simple configuration, compared to other processing circuits that perform frequency mixing.

Effects of the Invention The present invention provides three or more interdigital electrodes in the direction of surface acoustic wave propagation in contact with a piezoelectric material surface, applies a signal voltage to the first interdigital electrode, and applies a signal voltage to one of the other interdigital electrodes. By applying a different signal voltage to some things and extracting signals from others,
In addition to conventional signal delay and filter functions, this device can achieve many functions such as frequency mixing and frequency conversion functions using this, and has great effects on miniaturization and improved reliability. It is something.

[Brief explanation of the drawing]

Fig. 1 is a top view of a conventional surface acoustic wave element, Fig. 2 is a top view of an embodiment of the present invention, Fig. 3 is an enlarged perspective view thereof, and Fig. 4 is a top view of a conventional surface acoustic wave element.
The figure is a top view of another embodiment of the invention. 201.202.203...Interdigital electrode, 204...Piezoelectric substrate, 205...
...Oscillator, 206...Input terminal, 2o7...
...output terminal. Name of agent Patent attorney Toshio Nakao and one other person Figure 1 Figure 2 2θ, 2 204 03 2 (H Figure 3

Claims (3)

[Claims] (1) Three or more interdigital electrodes are provided in the direction of surface acoustic wave propagation in contact with the piezoelectric material surface, a signal voltage is applied to the first interdigital potential to generate surface acoustic waves, and the other interdigital electrodes are A surface acoustic wave element characterized in that a signal voltage is applied to some of the elements, and a signal is extracted from the surface acoustic waves transmitted from the other elements. (2) A first signal voltage is applied to the first interdigital electrode, a second signal voltage is applied to the second interdigital electrode to perform frequency mixing, and the frequency is mixed by the third interdigital electrode. 2. The surface acoustic wave device according to claim 1, wherein the surface acoustic wave device is configured to selectively extract signals of different frequencies. (3) Applying the first signal type pressure to the first interdigital electrode and applying the second signal voltage to the second interdigital electrode to perform frequency mixing; The electrodes are arranged at different distances from the second interdigital electrode, and the third. 2. The surface acoustic wave device according to claim 1, wherein the surface acoustic wave device is configured to obtain two signals with different delay times from the fourth interdigital electrode.