Kokusai Denshin Denwa Kabushiki Kaisha

Hideki Saito

Tatsuo Watanabe

Akira Ogawa

Masahisa Yamaguchi, Deceased

A space diversity system in a TDMA communication system employing a communication satellite, in which in order to equalize the path lengths of respective sending paths at the start of communication, a pre-burst is sent out to one of the paths making up the diversity system in a time slot of one frame assigned to an instant station. A sub-burst is sent out to the other of the paths in the assigned time slot. A relative time difference between the pre-burst and the sub-burst is detected from signals sent back to the instant station from the communication satellite or signals received by a distant terrestral station via the communication satellite. On the basis of the result of a comparison operation of relative time difference between the pre-burst and the sub-burst at the time of their sending-out from the instant station with a relative time difference between the pre-burst and the sub-burst received via the communication satellite, variable delay means inserted in one of the paths is controlled so that the two relative time differences become equal to each other.

Space diversity system in TDMA communication system

A space diversity PCM-TDMA telecommunication system using a stationary communication satellite, in which fixed delay circuits are respectively inserted in the sending side and the receiving side of one route at a control equipment, while variable delay circuits are inserted in the sending side and the receiving side of the other route at the control equipment, so that electrical length of one route from the satellite to the control equipment may be the same as that of the other route from the satellite to the control equipment through the route including connection links between the two sites. Diversity switching can be performed with no duplication and lack of signals in accordance with the above construction.

Space diversity system in PCM-TDMA telecommunication system using

A frequency synchronizing system for satellite communication, in which a reference frequency coming from a communications satellite is received by a receiving circuit. A first frequency variable oscillator is provided for generating a transmission signal. A second receiving circuit is provided for receiving through the communications satellite the transmission signal which is the output from the first frequency variable oscillator, A first frequency control circuit is provided for controlling the first frequency variable oscillator for making the frequencies of the outputs from the first and second receiving circuits equal to each other. A second frequency variable oscillator is provided for generating a signal of a frequency twice as high as the reference frequency. A frequency converter is provided for mixing the output from the first or second receiving circuit with the output from the second frequency variable oscillator to produce a signal of a difference frequency substantially equal to that of the transmission signal. A phase detector detects the phase difference between the transmission signal and the output from the frequency converter. A frequency control circuit is provided for controlling the second frequency variable oscillator with the output of the phase detector so that the output frequency of the second frequency variable oscillator is twice as high as the frequency of the reference signal on the communications satellite. The first frequency variable oscillator is replaced by a reference oscillator of constant frequency in a reference station.

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Tachikawa, Japan

Hideki Saito