Alps Electric Co., Ltd.

Shoichi Asano

Kazuharu Aoki

Takeo Suzuki

A gain control circuit capable of keeping a constant gain without being affected by ambient temperature includes a variable resistor element connected to a power supply terminal, a control unit for controlling the resistance value of the variable resistor element on the basis of a gain control voltage, an amplifying transistor that is supplied with a power supply voltage through the variable resistor element, a current detecting resistor that is interposed between the variable resistor element and a collector of the amplifying transistor, and a voltage detecting unit that detects a drop dropped by the current detecting resistor. The dropped voltage detected by the voltage detecting unit is fed back to the control unit to control the resistance value of the variable resistor element such that a current flowing through the current detecting resistor does not vary.

Gain control circuit capable of reducing change in gain due to variation of ambient temperature

A dual-band frequency converter unit, for selectively performing frequency conversion between a 2.4-GHz high-frequency-band signal or a 5-GHz high-frequency-band signal and a baseband signal by frequency mixing, includes a local oscillator for generating a local oscillation signal; a first frequency divider for generating a half-frequency signal of the local oscillation signal; and a second frequency divider for generating a quarter-frequency signal of the local oscillation signal. Frequency conversion between the 2.4-GHz high-frequency-band signal and the baseband signal is performed by frequency mixing using the half-frequency signal of the local oscillation signal. Frequency conversion between the 5-GHz high-frequency-band signal and the baseband signal is performed by frequency mixing using the local oscillation signal and the quarter-frequency signal of the local oscillation signal.

Dual-band frequency converter unit with high operability

A feedback circuit is connected between the input electrode of amplifying element of an amplifying circuit of the initial stage and the output electrode of amplifying element of an amplifying circuit of the final stage. The feedback circuit is structured by a serial circuit of a voltage dropping means resulting in almost constant voltage drop regardless of an increase or decrease of current and a feedback resistor, and a bias voltage is supplied, via the feedback circuit, to an input electrode of the amplifying element in the amplifying circuit of the initial stage from an output electrode of the amplifying element in the amplifying circuit of the final stage. Thereby, current dissipation is reduced and signal loss is lowered.

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Fukushima-ken, Japan

Shoichi Asano