Fujitsu Corporation

Naoto Tanabe

Yoshihito Aono

Yukio Takeda

A satellite communication system broadcasts an information signal from a transmitting station to a plurality of receiving stations via a communication satellite. An answer station is provided among a plurality of receiving stations which are located in a predetermined geographical area. The answer station and the plurality of receiving stations in the designated group are connected by a ground data link. The answer station collects status data of each of the receiving stations to transmit an answer signal to the transmitting station on behalf of the group of receiving stations, so that a transmitting function for each of the receiving stations can be eliminated. The answer station can also act as one of the receiving stations in the designated group.

Broadcasting satellite communication system with improved answer signal

A satellite broadcast communication system which makes a communication via a communication satellite comprises N sub stations respectively assigned a time slot having a predetermined time width T.sub.0, where N is an integer greater than one, and a main station including a broadcast part for broadcasting broadcast information to the N sub station via the communication satellite using a reference frame which has a time width N.times.T.sub.0, a part for receiving a reception acknowledge signal from the sub stations, and a part for setting a multi-frame to a predetermined value. The predetermined value is M.times.T.sub.0 when only M sub stations are subject to reception of the broadcast information, N/M is an integer and M.ltoreq.N, and the predetermined value is M.sub.1 .times.T.sub.0 when only M sub stations are subject to reception of the broadcast information, N/M is not an integer and M.sub.1 is an integer greater than M. Each of the N sub stations include a transmitting part for transmitting the reception acknowledge signal to the main station using the multi-frame which is set in the main station in response to the broadcast information which is received from the main station and is intended for the sub station to which the transmitting part belongs.

Satellite broadcast communication system

A coordinate reading apparatus for reading positions on a tablet, having magnetic-field generating coils, with a magnetic-field detector. The magnetic-field detector produces an analog electric signal corresponding to a desired position to be read on the tablet in response to the magnetic fields induced by the magnetic-field generating coils. The analog electric signal generated by the detector is composed of both a fundamental wave component signal and an n-th order harmonic wave component signal (n being an integer equal to or larger than 2). A processing unit for receiving the analog electric signal from the magnetic-field detector and produces coordinate data corresponding to the desired position to beread on the tablet by analyzing a first rotating magnetic-field vector induced by the fundamental wave component signal and a second rotating magnetic-field vector induced by the n-th order harmonic wave component signal. The phase component of the fundamental wave component signal and the phase component of the n-th harmonic wave component signal are processed so that the coordinate data can be read by the processing unit.

Growing community of inventors

Kawasaki, Japan

Naoto Tanabe