Hitachi, Ltd.

Other

Hiroshi Usami

Satoshi Takahashi

Hideo Nishijima

Ken Takei

Toshiro Suzuki

Kaneyuki Okamoto

Akihiro Shibuya

Yuuji Ishida

Tadashi Matsumoto

Katsuhiko Goto

Eimatsu Moriyama

Tetsuo Onodera

Kiyoshi Hamaguchi

Yoichi Saito

Mitsuhiko Mizuno

In a time-division multiplexing wireless communication system, an antenna module has plural antenna elements. Receiver high-frequency circuit synthesizes signals from the antenna elements according to an antenna directivity having a desired beam pattern. Demodulator selects one of the received signals from wireless terminals according to the synthesized received signals, and determines transmission beam direction information for use in directing the beam in the selected direction. Weighting circuit generates weight coefficients for setting of the beam patterns and transmission beam directions according to the transmission beam direction information, and produces transmission time slots according to a table listing the relations of the transmission beam directions and the time slots for use in the beam radiation in those directions. Down-link fixed beam-forming circuit and modulator control the antenna module using the generated beam pattern, beam direction and transmission time slots to transmit the down-link signal.

Wireless communication method and system using beam direction-variable antenna

The present invention is directed to a TDMA communication system which is adapted to different communication environments or prepares different communication environments and allows each mobile station to be set for working in any one of the different communication environments. The communication system commonly uses a TDMA format that has a fixed frame-length and a constant number of bits for each of the slots composing the frame. The communication environments have prepared respective sets of communication conditions, each set including a transmission power, a modulating method, the number of multiplexed signals, error-correction, an antenna gain, a frequency hopping value and a diversity value. At each mobile station and each base station, one of plural sets of communication conditions for respective environments is selected to establish communication with each other under the selected environment.

Time-division multiple-access communication system

In an automatic tracking system for a magnetic recording and reproducing apparatus wherein tracking is controlled so as to increase an amplitude of a reproduced signal which is delivered from a rotary head for reproducing a track recorded by a helical scan system, the amplitudes of the reproduced signal are detected at a plurality of points of time within one rotational cycle of the rotary head, and the tracking is controlled so as to increase a minimum value among the detected values at the plurality of points of time.

Tracking correction for a rotary head by detection of the minimum signal

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Yokohama, Japan

Hiroshi Usami