Hitachi Denshi Kabushiki Kaisha

Hitachi, Ltd.

Mobile Communications Tokyo Inc.

Yukinari Fujiwara

Hideya Suzuki

Arata Nakagoshi

Makoto Ohnishi

Yoichi Kaneko

Masaru Adachi

Yasuaki Kinoshita

Masayuki Kanazawa

Yoshitaka Shinomiya

Nobuo Sekiguchi

Michiaki Kurosawa

Mitsuo Toya

Yoshio Taneichi

Takehiko Kobayashi

Hideo Nakasawa

A high-frequency power amplifying apparatus includes a plurality of series-connected amplifiers, a power controller for selectively supplying an output terminal with an output from a desired one amplifier in accordance with a demanded output power and for causing one or more amplifiers downstream of the desired one amplifier to be in a cutoff state, and an output delay line connected between the output terminal and the final-stage amplifier and having a line length thereof providing the final-stage amplifier with a high impedance as viewed from the output terminal when the final-stage amplifier is in a cutoff state.

High-frequency power amplifying apparatus

An apparatus comprising an unnecessary frequency component removal unit for removing unnecessary frequency components from a signal supplied from a detector, a unit for obtaining a measured value of delay spread of the signal supplied from the unnecessary frequency component removal unit, an adaptive equalizer for performing adaptive equalization on the signal supplied from the unnecessary frequency component removal unit, and a decoding unit for decoding an input signal, wherein the signal from the unnecessary frequency component removal unit is supplied to the decoding unit through the adaptive equalizer when the measured value of delay spread is larger than a predetermined value, whereas the signal from the unnecessary frequency component removal unit is supplied to the decoding unit without being passed through the adaptive equalizer when the measured value of delay spread is not larger than the predetermined value.

Demodulator including adaptive equalizer and demodulating method in digital communications

An FDMA (Frequency-Division Multiple Access) transmitter-receiver for use in an FDMA communication system which is capable of changing a bandwidth of a channel as required. The FDMA transmitter-receiver includes: a plurality of trans-demultiplexers which are different in the number of channel multiplexings from each other and each of which serves to convert the received FDMA signal into a TDMA signal; a communication signal demultiplexing/multiplexing circuit for subjecting the output communication channel signals from the trans-demultiplexers to demultiplex and channel-reassignable multiplex them; a plurality of trans-multiplexers which are provided in correspondence to the plurality of trans-demultiplexers and each of which serves to convert the output channel signal after demultiplexing and remultiplexing from the associated communication signal demultiplexing/multiplexing circuit into an FDMA signal; an adder for adding the FDMA signals outputted from the trans-multiplexers; and a transmission circuit connected to an output of the adder for transmitting therefrom the signal which has been obtained by adding the FDMA signals. The bandwidth per channel of each of the trans-demultiplexers and the trans-multiplexers is different in correspondence to the number of channel multiplexing.

Transmission/reception method based on frequency division multiple

In a radio communication device which includes at least a modulator, a power amplifier, a demodulator, and a carrier oscillator wherein an input signal to the radio communication device is corrected with a feedback demodulated signal to compensate for possible non-linear distortions in the power amplifier, a phase shift quantity for correction of the phase of the carrier which demodulates the feedback modulated signal in the demodulator is separated into a fixed phase quantity and a variable phase quantity smaller than the fixed phase quantity. The carrier is phase-corrected such that a phase shifter shifts the phase of the carrier by the fixed phase quantity and a second phase shifter shifts the phase of the carrier by the variable phase quantity smaller than the fixed phase quantity.

Non-linear compensation circuit for a power amplifier

A communication system having a carrier oscillator for generating a carrier of predetermined frequency, a quadrature modulator for orthogonally modulating the carrier by input baseband I and Q signals and outputting a quadrature modulation wave, and a quadrature demodulator for orthogonally demodulating the quadrature modulation wave using the carrier and outputting demodulation baseband I and Q signals. The phase of the carrier input to the quadrature demodulator is shifted by a predetermined amount in accordance with a phase shift signal. The amplitude of the demodulation baseband I and Q signals output from the quadrature demodulator is corrected on the basis of a control signal, and demodulation baseband I and Q signals thus corrected are output. The amplitude of the input baseband I and Q signals is corrected on the basis of the control signal, and the baseband I and Q signals thus corrected are input to the quadrature modulator. An amplitude error is detected between the amplitude-corrected demodulation baseband I and Q signals. The control signal is generated so that amplitude coincides between the baseband I and Q signals of the quadrature modulation wave coincide and between the demodulation baseband I and Q signals output from the quadrature demodulator on the basis of the detected amplitude error.

Communication system control method and communication system using the

With respect to a mobile communication system, intelligence learns a cell boundary where the field strength of adjacent base stations becomes equal, by measuring field strength of communications, and from this data determined and stored over a period of time, the intelligence calculates the position and velocity vector of each mobile unit, from which a priority for hand-off can be determined. Hysteresis of the hand-off is determined with respect to hand-off boundaries located a fixed distance from the measured cell boundary, with hand-off preferably being soft hand-off within the narrow hand-off boundaries. Priority is particularly determined using fuzzy logic and calculation of the time estimated for the mobile unit to reach the cell boundary. Battery consumption of the mobile units is improved by prolonging the interval of checking the position of mobile units, when the mobile units are moving slowly or not moving at all. The determination of the cell boundary is updated continuously, to compensate for environment changes affecting field strength.

Mobile communication switching across cell boundaries

In an amplifier using at least two transistors are amplifying elements, the bases (or gates) and the collectors (or drains) of the transistors are commonly connected. A first impedance element is connected between the bases (or gates) and the collectors (or drains). A second impedance element is connected between an emitter (or source) of each transistor and a ground. A third impedance element is connected between the emitters (or sources).

Amplifier

A synthesizer apparatus includes a reference oscillator for generating a reference signal, a voltage controlled oscillator (VCO) whose oscillation frequency is controlled by a control signal, a frequency divider, which is intermittently operated, for frequency-dividing the output signal from the VCO, and a phase comparator for comparing the phases of the reference signal and the output signal from the frequency divider, and supplying a control signal to the VCO in accordance with the phase difference. The phase comparator outputs an average value signal having an average value corresponding to a difference in pulse rise times of the output signal from the frequency divider during an operation period of the frequency divider.

Frequency synthesizer with low power consumption

A system for detecting an abnormal condition of a high frequency output signal in its power level, comprising: a variable gain power amplifier which receives a high frequency input signal and produces an amplified high frequency output signal; a negative feedback control loop connected to the power amplifier, for automatically setting the power level of the amplified high frequency output signal to a desired one of a plurality of predetermined power levels, the negative feedback control loop being so arranged as to produce a DC signal which is constant in its magnitude so far as the power level of the high frequency output signal is maintained at its set value whichever one is selected from the plurality of predetermined power levels, the gain of the power amplifier being controlled on the basis of the DC signal; and a comparator which compares the DC signal with a reference signal to judge as to whether the high frequency output signal is abnormal or not in its power level.

System for detecting abnormal condition of high frequency output signal

In a radio station system utilizing multi-channel transmission and reception frequencies of the type comprising a transmitter and a receiver wherein the frequency difference between the transmission and reception frequencies is made to be equal to an intermediate frequency, there is provided a source of multi-frequency signal which determines the multi-channel transmission and reception frequencies. The output of the multi-frequency signal source is utilized directly as a local oscillation signal of the receiver and the frequency of the output of the multi-frequency signal source is shifted by a modulated wave having a frequency twice the intermediate frequency and the frequency shifted output is utilized as the transmission frequency.

Growing community of inventors

Musashimurayama, Japan

Yukinari Fujiwara