Hitachi, Ltd.

Isao Akitake

Isao Fukushima

Yoshimi Iso

Hitoshi Watanabe

Norio Minami

Shigeki Inoue

Makoto Katagishi

Tsutomu Noda

Norio Hosaka

Hideo Ohnuki

Hiroshi Shirai

Kazuhiko Yamazaki

A high-frequency apparatus usable as a branching filter, branching filter module and/or a radio communication apparatus. The high-frequency apparatus includes a conductor substrate, a first dielectric layer provided on the conductor substrate, a strip conductor provided on the first dielectric layer, and a second dielectric layer provided on the strip conductor and having through holes provided therein. At least one elastic surface-wave element is provided over the second dielectric layer in a position above the strip conductor and is connected to the strip conductor by the through holes.

Branching filter, branching filter module and radio commnication

An AM stereophonic demodulator circuit for an amplitude/angle modulation system, comprising an AM detector circuit for producing a stereophonic sum signal (L+R), an FM or PM detector circuit for producing a stereophonic difference signal (L-R), and control means for extracting a DC voltage proportional to an antenna input level from the AM detector circuit so as to use the DC voltage to control the gain and amplitude of an FM or PM detector stage including the FM or PM detector circuit.

AM Stereophonic demodulator circuit for amplitude/angle modulation system

In an FM receiver having an amplifier for amplifying an FM signal of intermediate frequency applied to an input terminal, and a phase multiplier type FM demodulator for demodulating the FM signal of intermediate frequency amplified by the amplifier, a noise muting circuit is disposed between the demodulator and the amplifier for muting noise transmitted from the amplifier to the demodulator when no FM signal input appears at the input terminal. This noise muting circuit comprises a pair of diodes connected in inverse-parallel with each other.

Noise muting circuit in FM receiver

An equalizer amplifier of a negative feedback type comprises a common-emitter amplifier, an emitter follower amplifier cascade-connected thereto, and a negative feedback network connected between the output terminal of the emitter follower amplifier and the input terminal of the common-emitter amplifier with its negative feedback level increased as the frequency increases, wherein an inductance element is connected in series with the negative feedback circuit to attenuate harmful signals whose frequencies are higher than those of audio signals, thereby making large the ratio of signal to noise in the equalizer amplifier.

Audio frequency amplifier

A phase-shifting multiplication type FM demodulation circuits comprises a gate circuit including a first and a second switching circuit adapted to be switched for an FM intermediate frequency signal, a resonance circuit and a phase-shifting element. The FM intermediate frequency signal is phase-shifted for about .pi./2 (or 90.degree.) and the phase-shifted signal (frequency) is fed to the second switching circuit of the gate circuit after the phase-conversion of the phase-shifted FM signal by means of a phase-shifter device. The demodulation circuit further includes a bias resistor for the second switching circuit which resistor serves also as a resonance resistor of the resonance circuit, a substraction circuit for detecting output signal from the gate circuit, an output resistor for determining magnitude of the output signal from the subtraction circuit, and a lowpass filter for eliminating higher harmonics from the output signal appearing across the output resistor thereby producing a demodulated output.

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Toyokawa, Japan

Isao Akitake