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Private branch radio communication system using optical fibers

  • US 5,159,479 A
  • Filed: 03/05/1992
  • Issued: 10/27/1992
  • Est. Priority Date: 06/17/1988
  • Status: Expired due to Fees
First Claim
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1. A low power private branch radio communication system for realizing communication between a plurality of portable radio transmitters and a plurality of portable radio receivers, said system comprising:

  • a first portable radio transmitter, located in a first area within a given premises, for selecting an unused first radio carrier frequency from among a plurality of radio carrier frequencies, modulating said first radio carrier frequency with a signal to produce a modulated first radio carrier signal, outputting the modulated first radio carrier signal as a radio signal of limited power in the first area;

    a first repeater means, located in the first area, for receiving the modulated first radio carrier signal transmitted from said radio transmitter and for outputting a modulated optical signal corresponding to the modulated first radio carrier signal received, said first repeater means including a first antenna for receiving said modulated first radio carrier signal, and a light-emitting diode for converting said modulated first radio carrier signal received into an optical signal modulated by said modulated first radio carrier signal;

    an optical transmission medium for transmitting the modulated optical signal output from said first repeater means to a second area within said premises;

    a second repeater means, located in the second area, for receiving the modulated optical signal output from said first repeater means and transmitted by said optical transmission medium, and for generating a modulated second radio carrier signal of limited power having a frequency equal to that of said first radio carrier signal and corresponding to the modulated optical signal received in the second area, said second repeater means including a photo diode for converting said modulated optical signal into said modulated second radio carrier signal; and

    a second portable radio receiver, located in the second area, for receiving a modulated radio carrier signal transmitted thereto, from among a plurality of modulated radio carrier signals having different frequencies and generated in the second area,wherein output powers of all the radio carrier signals of the system are limited to below a power level above which malfunction of electronic equipment in the vicinity of the radio transmission is likely to occur; and

    wherein the first area is an area determined in accordance with said output powers, so that the first repeater means can receive signals generated by the first portable radio transmitted, the second area is an area determined in accordance with said output powers, so that the second portable radio receiver can receive radio signals from the second repeater means, and the first and second areas are arranged in one open space and are unshielded.

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