Hitachi, Ltd.

Katashi Hazama

Jun Yamada

Akitsuna Yuhara

Kiyoharu Kishimoto

Hitoshi Yanagihara

Yoshihiko Noro

Takeshi Murakami

Akira Shibata

Nobuhiro Tokushuku

Kuniaki Miura

Kentaro Hanma

Shinya Iida

Masaki Yoshii

Michiyori Miura

Hideo Abe

Naotake Ebinuma

An optical disc consists of a base plate, a reflective thin layer, and a protective thin layer. The optical disc has a sample mark area having two sample marks, one of which is off-set on one side of a track, another of which is off-set at an opposite side of a track. These sample marks are produced by an injection molding with replica technique. At the time of the injection molding, additional pressure moves soft injected plastic resin, which causes double transcription of the sample marks. For preventing the double transcription, groove areas are provided on opposite sides of the sample mark area. The groove areas provide an anchor effect at the time of injection molding.

Optical information medium with sample mark area and multiple

In a FM luminance signal circuit of a signal reproducing circuit of a video tape recorder,

Signal reproducing circuit for a video tape recorder

A surface acoustic wave device, a method for manufacturing the same and a manufacturing equipment therefor are disclosed. In the surface acoustic wave device having functional elements such as input and output interdigital electrodes of Al, Al-Si alloy or Al-Cu-Si alloy thin film strips and a grating type reflector, arranged on a piezoelectric substrate and any other bus conductors arranged on the same substrate, at least a portion of the functional elements and the bus conductors having a high frequency metal strip having a line width of no more than 2 .mu.m, at least the metal strip having the width of no more than 2 .mu.m has a film thickness of no less than 0.25 .mu.m at least a portion thereof but no more than an upper limit of an effective film thickness determined by a required characteristic of the surface acoustic wave device, whereby a transfer characteristic of the surface acoustic wave device is compensated and controlled, for example, a reflection efficiency of a grating type reflector is improved or a loss due to a D.C. resistance of the input and output electrodes is reduced.

Surface acoustic wave device and method for manufacturing the same

A surface acoustic wave device on a piezoelectric substrate comprises an interdigital transducer having an interdigital sending part in the forward direction and an interdigital reflecting part in the reverse direction. An electrical phase difference of .phi. (radian) is applied between the sending and reflecting parts, while the distance between the sending and reflecting parts providing a geometrical phase difference therebetween is established to be ##EQU1## where n is a positive integer and .lambda..sub.o is the wavelength of surface acoustic wave. A third, common electrode meanders between the sending and reflecting electrodes.

Unidirectional surface acoustic wave device with meandering electrode

A surface acoustic wave device is provided with plural sets of input and output transducers arranged on a piezoelectric substrate with the input transducers and the output transducers being connected electrically in parallel, respectively. In order to minimize a loss which occurs due to the parallel connections of the input and output transducers, aperture dimensions of either the input transducers or the output transducers are selected such that static capacitances of the respective transducers are equal.

Surface acoustic wave device

In a preferred embodiment, a surface acoustic wave device comprises a piezoelectric substrate, a first electrode formed on the substrate and acting to convert an electrical signal into a surface acoustic wave, and second and third electrodes formed on the substrate and acting to convert the surface acoustic wave into an electrical signal. The second and third electrodes are disposed at different distances from the first electrode and connected electrically with each other. Electrode fingers of the second electrode are arranged in a relationship of the opposite polarity with respect to those of the third electrode so as to cause peaks in the constant frequency interval multi-peak frequency characteristics of the device acting as a filter to take place at frequencies which are (integer+1/2) times the constant frequency interval .DELTA.f. In another preferred embodiment, a plurality of surface acoustic wave device units are formed on a common piezoelectric substrate. Respective units include a set of first, second and third electrodes and operate at different frequency bands which partly overlap. The distance between the first electrode and the second electrode or the third electrode is determined in the respective units such that the delay time due to the propagation of the surface acoustic wave between the input and output electrodes is equal in the respective units and the output voltage of the output electrode is in phase in the respective units, thereby providing accurate peak frequencies over the whole frequency band at which the surface acoustic wave device operates.

A surface-acoustic-wave filter for a channel selection tuning system of a television receiver includes at least two comb filter elements, each of which comprises an input transducer provided on a piezoelectric substrate and adapted to convert an input electrical signal into an elastic surface wave, and first and second output transducers disposed on the substrate for receiving the elastic surface wave propagating in the same direction from the input transducer. The first and second output transducers are positioned from the input transducer with different distances. The transducers of the two comb filter elements are so designed that the respective comb filter elements respond to frequencies of different program channel bands over for example VHF and UHF bands. The distances of the first and the second output transducers from the input transducer in the wave propagating direction are so predetermined that reciprocal of the difference in delay time between the electrical signals derived from the first and second output transducers is equal to a divisor of an interchannel frequency difference in the corresponding channel band.

Surface-acoustic-wave filter for channel selection system of television

An elastic surface wave filter for use as an intermediate frequency filter in a color television receiver, comprising an input electrode provided on a piezoelectric substrate plate for converting an electric signal into elastic surface waves propagating through the surface layer of the piezoelectric substrate plate, a propagation path for the elastic surface waves in the piezoelectric substrate plate and an output electrode for converting the propagated elastic surface wave into an electric signal, wherein the fingers of the input electrode are so arranged that the position at which the overlap of the interleaved fingers is maximum is farther with respect to the output electrode than the middle point along the lengthwise direction of the input electrode and wherein the pitch between the adjacent interleaved fingers is non-uniform on both the sides of the position of the maximum overlap, whereby desired group delay and amplitude characteristics for predetermined frequencies are easily and simultaneously obtained.

Elastic surface wave filter

It has been known that a sound trap or band pass amplifier makes the group delay characteristic of a chromaticity signal component non-uniform. The present invention provides an elastic surface wave filter whose amplitude characteristic is so determined as to be adapted for a video intermediate frequency amplifier and whose group delay characteristic is so determined that the chromaticity signal component in a color composite video signal from a tuner advances further in delay time on the high frequency side than on the low frequency side in order to compensate that non-uniformity of the group delay characteristic from which the chromaticity signal component suffers.

Elastic surface wave filter for color television receiver

A surface acoustic wave device has an electrode finger structure in which the width of finger portions external of envelopes indicating a weighted overlap length and the length of the spaces existing between adjacent finger portions measured widthwise thereof are substantially equal to one half of the wavelength of the acoustic surface wave, the envelopes are symmetric about the center line of a propagation path for the surface acoustic wave, and the finger portions and the spaces between the finger portions are in opposite positional relation to each other about the center line of the propagation path. With this electrode finger structure, occurrence of disturbing reflected signal at the weighted interdigital electrode, which is used as an input/output electrode of the surface acoustic wave device and occurrence of wavefront distortion are prevented and production yield of the device is improved.

Piezoelectric surface acoustic wave device with suppression of reflected

To eliminate disturbance signals caused by the reflection from the unitary stem areas of comb-like electrodes of an interdigital transducer in an elastic surface wave device, the edges of the unitary stem areas perpendicular to the surface wave propagating direction includes at least one pair of partial edges, the positions of the partial edges in each of the at least one pair of partial edges differ by (2n+1).multidot..lambda./4 from each other in the surface wave propagating direction, and the lengths of the partial edges in the each pair are equal to each other, where n represents zero or a positive integer and .lambda. represents the wavelength of the elastic surface.

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Zushi, Japan

Katashi Hazama