Hitachi-kokusai Electric Inc.

Kokusai Electric Co., Ltd.

Kotaro Takenaga

Kiyoshi Funada

Takeshi Ishigami

Hiroichi Yonenaga

Yoichi Okubo

Masaki Suto

Takashi Uchida

Noriyuki Kagaya

Hiromichi Hayase

Yasuyuki Yufu

The present invention relates to an economical and highly reliable receiving apparatus for receiving radio signals transmitted from a mobile communication terminal within radio zone. The receiving apparatus has antenna sections that receive radio signals transmitted from the mobile communication terminal and are provided in each of a plurality of sectors divided from the radio zone, and receiving units that are provided in each of the antenna sections and that perform a predetermined process to the radio signals received by the antenna section.

Receiving apparatus

An attenuator of the current invention allows the adjustment in attenuation at a constant impedance level. The attenuator includes at least three variable resistors. Two of the three variable resistors have the substantially same linear resistance characteristics and are controlled in a substantially identical manner. One of the three variable resistors has a non-linear resistance characteristic and is controlled concurrently with the above two variable resistors. As a result of the above resistance characteristics and control, the attenuation is adjusted with respect to the resistance while impedance is maintained at a constant level.

Variable attenuator device having substantially constant impedance

A feed forward type distortion compensation amplification apparatus includes a first division unit for dividing an input signal into a first channel signal and a second channel signal, a main amplifier for amplifying the first channel signal, a variable attenuation unit for processing the second channel signal to provide an amplitude adjusted second channel signal, a delay unit for delaying the amplitude adjusted second channel signal, a second division unit for dividing an output signal of the main amplifier into a third channel signal and a fourth channel signal and subtracting one of the third channel signal and the delayed second channel signal from the other to extract a distortion component introduced by the main amplifier, and a distortion compensation unit for removing a distortion component introduced into the fourth channel signal by the main amplifier, by using the distortion component extracted by the second division unit.

Feed forward amplification apparatus for compensating non-linear distortion

A distortion compensation amplifier has a distortion detection loop that divides an input signal, amplifies one divided signal with an amplifier and uses the amplified signal and another divided signal to detect a distortion component generated and introduced into the amplified signal in the amplifier. The amplifier additionally has a distortion removal loop that removes the detected distortion component from the amplified signal produced by the amplifier. The distortion detection loop comprises a filter for reducing the distortion component of the amplified signal output by the amplifier that was generated and introduced into the amplified signal in the amplifier and detects the distortion component reduced by the filter. The distortion removal loop removes from the amplified signal the detected distortion component that was produced by the amplifier and reduced by the filter.

Distortion compensation amplifier

A metal-oxide semiconductor field-effect transistor (MOSFET) amplifier circuit includes a compensation circuit with a low cost MOSFET and a constant current circuit providing a constant drain current of the MOSFET, which maintains an operational point of the amplifier at an optimal state at all times. The MOSFET amplifier circuit includes a first MOSFET, a constant current circuit including a variable resistor, an operational amplifier, a power supply and a resistor, a second MOSFET having a constant current generated by the constant current circuit as a drain current thereof, and a voltage control circuit including operational amplifiers and resistors for applying a gate source voltage of the second MOSFET to the first MOSFET as a gate-source voltage thereof.

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Tokyo, Japan

Kotaro Takenaga