Hitachi-Kokusai Electric Inc.

Hitachi Denshi Kabushiki Kaisha

Masayuki Kanazawa

Yukinari Fujiwara

Masaru Adachi

Minoru Sakaihori

Masanori Kudo

Kin'ichi Higure

Yuzo Hiraki

The present invention provides a polling method in a radio digital communication system making it possible to shorten time required for polling without causing increase in an error rate and to efficiently manage and administrate communications. In a digital radio communication system for collecting information from a plurality of terminal stations by polling, a polling response signal to be transmitted from each terminal station to a base station has a frame format constructed of a one-frame in which a cyclic bit pattern is placed at a leading end of the frame format.

Polling method and vehicle search method in digital radio communication system

A radio communication system having a plurality of mobile stations, at least one base station, and a control side apparatus connected to the base station. Each mobile station has a mode switching instruction reception unit for receiving an instruction for switching from a radio communication mode for performing a radio communication operation to a loudspeaker mode or a hot mic mode, a destination identifying information storage unit for storing information for identifying a communication apparatus which serves as a communication partner when the mode switching instruction reception unit receives the instruction for switching to the hot mic mode, and a destination identifying information transmission unit responsive to the received instruction for switching to the hot mic mode by the mode switching instruction reception unit for transmitting the information stored in the destination identifying information storage unit over the air.

Radio communication system

A negative feedback amplifier for a transmitter, in which a vector corrector outputs the corrected signals, an adder adds the feedback signals of the in-phase component and the quadrature component to the in-phase component and the quadrature component of the output of the vector corrector, respectively, a modulator performs a quadrature modulation with respect to the in-phase component and the quadrature component of the outputs from the adder, a power amplifier amplifies the output of the modulator, a demodulator performs a quadrature demodulation to a part of the output of the power amplifier and outputs the feedback signals of the in-phase component and the quadrature component, and the vector corrector performs a correcting operation of canceling an error of at least one of the phases and the amplitudes of the in-phase component and the quadrature component occurring in the demodulator.

Negative feedback amplifier for transmitter, transmitter, and method of correcting error in the negative feedback amplifier

A mobile communication system, and method, having, in an operational area of the base station, a plurality of mobile stations each capable of operating in an arbitrary one of two kinds of communication mode, i.e., a base station dependent mode for conducting communication via a base station and a direct communication mode for conducting direct communication between mobile stations. Information containing an important message to be received by all mobile stations is transmitted from the base station in the base station dependent mode. Upon receiving the information containing the important message, a mobile station placed in the base station dependent mode transmits the information containing the important message in the direct communication mode. As a result, all mobile stations placed in the direct communication mode receive the important message.

Mobile communication system and method having base station dependent mode and a direct mode

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.

Growing community of inventors

Kodaira, Japan

Masayuki Kanazawa