JPS5847088B2 - solid state signal processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid-state signal processing device for processing various electrical signals by providing interdigital electrodes on a piezoelectric body and utilizing elastic waves propagating on the surface of the piezoelectric body. The present invention aims to provide a device that can process electrical signals by controlling the irradiation or the amount of light irradiation.

Conventionally, in signal processing devices using surface acoustic waves, the processing functions that involve light mainly involve mutual interference between light waves and surface waves, such as optical modulation devices, optical deflection devices, and even There are image input/output devices, etc.

However, to date, no device has been known that utilizes light and, regardless of the above-mentioned mutual interference, exhibits a completely different function than before irradiation with light.

The present invention provides interdigital electrodes provided on a piezoelectric body as input/output electrodes for electric signals and surface acoustic waves, arranged in regions with different sound velocities, and a photoconductive thin film on the propagation path of the surface waves. By providing an electro-mechanical coupler in the form of a charged electrode and controlling the irradiation of light onto this photoconductive thin film, a solid-state signal having the function of processing multiple signals with a single device is created. This is a realization of a processing device.

Hereinafter, the configuration of the device based on the present invention will be explained using the drawings.

1 at b respectively show the basic construction of the device according to the invention.

In the figure, 1 and 2 have surface wave velocities of Vl +
The region of the piezoelectric body where V'2 (V2 > Vl) is shown.

The broken lines indicate cases where the substances are chemically identical and differ only in the speed of sound, or cases where the substances are chemically different substances.

Of course, if the difference in sound speed is due to a difference in piezoelectric coupling, the surface acoustic wave mode to be used will also be different, and as in the case of ferroelectric piezoelectric ceramics, the interdigital electrode finger length direction, plate thickness direction, Depending on the wave propagation direction and the respective polarization between the electrode fingers, Prusstein-Griaev waves (CB-G waves), Rayleigh waves or pseudo-Raleigh waves (
PR wave).

Reference numerals 3 and 4 indicate interdigital electrodes for inputting and outputting electric signals and as electrodes for transmitting and receiving surface acoustic waves.

In particular, the electrode 4 has a pitch (λ1
λ2) is selected so that it has the following relationship.

Reference numeral 5 denotes an electro-mechanical coupler in the form of a charged electrode, which is provided in the middle of the electrodes 3.4 so that the length direction of each electrode finger is parallel to the other, and the spacing between them also satisfies the relationship of equation (1). It is being

Reference numerals 6 and 6' denote photoconductive thin films, which are provided on the charged electrodes so as to cover all the electrode fingers of the coupler 5 on the region 2 or 1.

However, if the piezoelectric region 1.2 is made of a photoconductive thin film such as CdS or ZnO, then the photoconductive thin films 6, 6 are not required in each case.

FIGS. 2a and 2b each show a different configuration of the device from that described above.

In the figure, 10, 100, and 20, 200 are regions of the piezoelectric material having different surface wave velocities, and correspond to regions 1 and 2 in FIG. 1, respectively.

30, 300 is an interdigital electrode, FIG. 1a. b electrode 3
corresponds to

40, 400, and 50.500 are also interdigital electrodes and correspond to electrode 4 in FIG.

60,600 is an electro-mechanical coupler, which is the coupler 5 in FIG.
corresponds to

70°700 is a photoconductive thin film, similar to thin film 6.6' in Figure 1.
corresponds to

In a device with this configuration, the electrodes 40, 50, or 40
0.500 may be considered to be that the electrodes 4 shown in FIG. 1 are arranged separately in regions where the speed of sound differs from each other.

Therefore, they may be electrically connected in parallel, or may be used by appropriately switching them individually.

Of course, the pitch of each electrode is selected so as to satisfy the relationship of equation (1).

In the apparatus shown in FIGS. 1 and 2, if the piezoelectric material can also serve as a photoconductor, the light beam is appropriately focused and locally connected to the coupler 6. ff, 70, or 700 or the coupler 6 of the package of this device.
．． It is desirable to provide a small window or slit above 6', 70, or 700 so that only the shaded area is irradiated with light.

Furthermore, the electrode structure for surface acoustic wave transmission and reception is not subject to any restrictions, except for the conditions shown in equation (1) above, and there are no restrictions on the electrode structure for surface acoustic wave transmission and reception. It is possible to change the shape of the electrode structure.

Now, it will be explained below that the solid-state device having the above-mentioned configuration has the function of processing a plurality of signals with a single device.

Generally, it can be considered that the transmission characteristics of the elastic surface waves transmitted and received between interdigital electrodes are determined by the width of the transfer function of each electrode and the distance between the electrodes.

First, the case of the configuration shown in FIG. 1a will be explained.

When the electrode 3 is used as a transmitting electrode and the electrode 4 is used as a receiving electrode, when the photoconductive thin film 6 is not irradiated with light, the overall transmission characteristic F(e) is expressed by the following equation.

When light is irradiated onto the photoconductive thin film 6 and the electro-mechanical coupler 5 is short-circuited, the surface wave is not received in the portion of the receiving electrode 4 above the region 2, so that equation (2) is satisfied. is expressed as follows.

From this, it can be seen that in the frequency domain, both the amplitude and the phase change.

Furthermore, in the time domain, for example, when one pulse signal sent from the electrode 3 is not irradiated with light, it is received as two consecutive signals with a constant time delay rd2Ll--=1. What used to be one becomes one by irradiation with light.

Therefore, by controlling the light irradiation, it is possible to easily vary the phase, select the delay time, vary the amplitude, and encode the human input signal.

Of course, it is clear that the same effect can be expected with the configuration shown in FIG.

However, the transmitting and receiving electrodes 34 are compatible, and when the speed of sound changes to vl by the photoconductive thin film device, the photoconductive thin film 6 of the electro-mechanical coupler 5 is provided. The pitch λ'2 of the portions may be selected so as to satisfy the following relationship.

Next, the apparatus having the configuration shown in FIG. 2a will be explained.

When the electrode 30 is used as a transmitting electrode and the electrodes 40 and 50 are used as receiving electrodes, when the entire surface of the photoconductive thin film 70 is irradiated with light,
Whether the electrodes 40 and 50 are used separately or connected in parallel, the continuous wave signal applied to the electrode 30, for example, by intermittent irradiation with light, as compared to the state of no irradiation. An encoded output signal consisting of a pulse train can be extracted from.

When the photoconductive thin film 70 is irradiated locally with light, the distance between each input and output electrode via the electro-mechanical coupler 60 can be effectively changed. Like the device shown in FIG. 1, it can have various signal processing functions as described above.

This is shown more specifically in Figure 2 bm.

As is clear from the above explanation, the solid-state signal processing device according to the present invention works as a multifunctional device that can perform all of the signal processing functions using a desk device by controlling light irradiation. be.

[Brief explanation of drawings]

FIG. 1 a+b and FIG. 2 a+b are diagrams showing the basic configuration of a solid-state signal processing device according to the present invention, respectively.

Claims (1)

[Claims] 1. A piezoelectric body having a plurality of regions with different sound velocities, each region being provided with interdigital electrodes with a center frequency near the center frequency of a human signal, and a surface acoustic wave that can be transmitted and received between the electrodes. An electro-mechanical coupler in the form of a charged electrode is provided on the propagation path of the electro-mechanical coupler, and the photoconductive film on the electro-mechanical coupler is controlled to be irradiated with light effective for conduction. A solid-state signal processing device characterized in that it performs signal processing by.