Hitachi, Ltd.

Chuichi Sodeyama

Keiro Shinkawa

Masaki Noda

Hiroji Shoyama

Shigeo Matsuura

Mitsuhisa Shinagawa

Hirozi Shoyama

Masakazu Kondo

Noboru Usami

A matching circuit for a pre-amplifier of an SHF band television signal receiver is disclosed. The matching circuit comprises a stub line arranged near a gate terminal of an FET, and a pair of stub lines connected to a transmission line, one being a stub line exhibiting a short circuit impedance at a lower frequency than operating frequencies of the matching circuit and the other being a stub line arranged oppositely to the stub line and exhibiting a short circuit at a higher frequency than the operating frequencies. A distance between the stub line and the pair of stub lines is selected to be approximately equal to 1/4 wavelength of a center frequency of the desired signal band.

Matching circuit for a pre-amplifier of SHF band television signal

A microwave oscillator circuit with an FET, a dielectric resonator and a micro-strip line has a capacitive reactance element connected between the source terminal of the FET and ground or between the source and drain terminals of the FET, so that the oscillation frequency fluctuations due to the power supply voltage fluctuations or the ambient temperature variations can be suppressed.

FET Microwave oscillator being frequency stabilized by capacitive

A receiving circuit for a television receiver for receiving an FM-modulated television signal is disclosed, in which the oscillation frequency of a local oscillator circuit is fine adjusted by a voltage of a sync signal of the FM-modulated television signal thereby to receive the television signal properly.

FM Television signal receiving circuit

A microwave oscillator circuit comprises a micro-strip line having a substrate of a dielectric material, a semiconductor such as a Gunn diode or an FET, and a dielectric resonator connected to the micro-strip line as a resonator circuit. A hole is formed in the substrate beside the micro-strip line, or the substrate is cut off to provide a recess. Through this hole or recess, as the case may be, the dielectric resonator is directly secured to the metal casing supporting the micro-strip line on the opposite side thereof or to the grounding conductor of the micro-strip line.

Micro-strip oscillator with dielectric resonator

A mixer circuit formed of a micro strip line for converting an input signal in SHF band into an intermediate frequency signal in UHF band is disclosed which includes an arch-shaped half-wavelength line having a length equal to one half of the wavelength of the input signal and a series circuit of two diodes connected between both ends of the half-wavelength line, and in which the input signal and a local oscillation signal are applied respectively to the junction point of the diodes and one end of the half-wavelength line, and the intermediate frequency signal is delivered from a given point on the half-wavelength line.

Mixer circuit

A self-oscillating mixer circuit to operate mainly at SHF band comprises a single-gate FET and a micro strip line. The gate or source terminal of the FET is connected to a radio frequency signal input line. A feedback path is provided between the drain terminal and the gate or source terminal. An intermediate frequency output line is connected to the drain electrode of the FET. A dielectric resonator is coupled to the radio frequency signal input line to improve the stability of an oscillator frequency and to suppress leakage of a local oscillator signal.

Self-oscillating mixer circuit

A mixer circuit employing a distributed constant circuit using a strip line includes a strip line for applying a high frequency signal and a local oscillation signal to a diode. The strip line is provided with a filter for exclusively blocking the local oscillation signal and a filter for exclusively blocking the high frequency signal. The strip line further includes a line which acts as a shortcircuit for an intermediate frequency signal and as an open impedance for the high frequency signal and the local oscillation signal.

Mixer circuit arrangement

An SHF band oscillation circuit using a field effect transistor (FET) having a feedback path between gate and drain or source and a resonator connected to the gate. Impedances connected to the respective terminals of the FET comprise microstrip lines. A gate bias circuit includes a temperature-sensitive semiconductor device so that a gate bias is changed with the change in ambient temperature. In this manner, the change of oscillation frequency which would otherwise occur by the change of the ambient temperature is compensated. The resonator connected to the gate comprises a dielectric resonator to further stabilize the oscillation frequency.

SHF band oscillator circuit using FET

A device for frequency-converting multi-channel broadcast signals consists of a local oscillator for generating at a time a single oscillation frequency, a mixer and a frequency discriminator for automatically controlling the oscillation frequency of the local oscillator. The frequency discriminator delivers a dc zero voltage when the frequencies of plural signals applied to the discriminator coincide with those of the carrier waves of the frequency-converted multi-channel broadcast signals. If the frequencies of the plural signals applied to the discriminator differ from those of the carrier waves, the discriminator delivers a dc output voltage whose amplitude depends upon the difference.

Growing community of inventors

Yokohama, Japan

Chuichi Sodeyama