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

• Current Assignee: Small Power Communication Systems Research Laboratories Co., Ltd.
• Original Assignee: Small Power Communication Systems Research Laboratories Co., Ltd.
• Inventors: Takagi, Tasuku
• Primary Examiner(s): Coles, Sr., Edward L.
• Assistant Examiner(s): NEGASH, KINFE MICHAEL
• Application Number:
  US07/845,356
• Time in Patent Office: 236 Days
• Field of Search: 359/113, 359/115, 359/124, 359/145-146, 359/152, 359/154, 359/173-174, 359/176, 359/179, 370/35, 370/75, 375/3
• US Class Current: 398/116
• CPC Class Codes: H04B 10/25753 Distribution optical network, e.g. between a base station and a plurality of remote units
• CPC Class Codes: H04B 7/00 Radio transmission systems, i.e. using radiation field H04B10/00, H04B15/00 take precedence

Abstract

A private branch radio communication system includes a portable radio transmitter and a portable radio receiver. The system further includes first and second repeaters respectively located in first and second areas within a given premises and coupled to each other through an optical fiber cable. A radio signal output from the portable radio transmitter is converted into an optical signal by the first repeater, and is then supplied to the second repeater through the optical fiber cable, and converted into a radio signal which is received by the portable radio receiver.

Claims

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.

2. A lower power private branch radio communication system for realizing simultaneous two-way communication between a plurality of portable transceivers, said system comprising:

a first portable radio transceiver, used in a first area within a given premises, for selecting an unused first radio carrier signal from among a plurality of radio carrier signals having different frequencies, modulating the selected first radio carrier signal, and generating the modulated first radio carrier signal as a low power radio signal in the first area, and for receiving a modulated radio carrier signal transmitted thereto, from among a plurality of low power modulated radio carrier signals generated in the first area and having different frequencies, and demodulating the radio carrier signal received;

a second portable transceiver, used in a second area within said premises, for selecting an unused second radio carrier signal from among a plurality of radio carrier signals having different frequencies, modulating the selected second radio carrier signal, and generating the modulated second radio carrier signal as a low power radio signal in the second area within said premises, and for receiving a modulated radio carrier signal transmitted thereto, from among a plurality of radio carrier signals generated in the second area and having output powers of different frequencies, and demodulating the modulated radio carrier signal received;

a pair of fist and second optical transmission media, arranged within said premises, each for coupling the first and second areas to each other;

a first two-way repeater means, arranged in the first area within the premises, for receiving the modulated first radio carrier signal output from said first portable radio transceiver and supplying a modulated optical signal corresponding to the modulated first radio carrier signal received to said first optical transmission medium, and for receiving a modulated optical signal transmitted through said second optical transmission medium and generating a low power modulated radio carrier signal corresponding to the modulated optical signal received in the first area; and

a second two-way repeater means, arranged in the second area within the premises, for receiving the modulated optical signal output from said first repeater means and transmitted through said first optical transmission medium, and generating a low power modulated radio carrier signal corresponding to the modulated optical signal received in the second area, and for receiving the low power modulated second radio carrier signal output from said second portable radio transceiver and supplying a modulated optical signal corresponding to the modulated second radio carrier signal received to said optical transmission medium,

wherein output power of all the radio carrier signals generated by the system are limited to be below a power above which malfunction of electronic equipment in the vicinity of the radio transmission is likely to occur; and

wherein the first and second areas are areas determined in accordance with said output power, so that the first and second transceivers can transceive signals with the first and second two-way repeater means, respectively, and the first and second areas are arranged in one open space and are unshielded.

3. A system according to claim 2, wherein said first two-way repeater means includes a transmitting/receiving antenna, electrical/optical signal converting means for converting a radio signal received by said transmitting/receiving antenna into an optical signal, and optical/electrical signal converging means for converting, into an electrical signal, an optical signal transmitted through said optical transmission medium and supplying the electrical signal to said transmitting/receiving antenna.

4. A system according to claim 2, wherein said second two-way repeater means includes a transmitting/receiving antenna, electrical/optical signal converting means for converting a radio signal received by said transmitting/receiving antenna into an optical signal, and optical/electrical signal converting means for converting, into an electrical signal, an optical signal transmitted through said optical transmission medium and supplying the electrical signal to said transmitting/receiving antenna.

5. A private branch radio communicating system comprising:

a plurality of portable radio transceivers;

a plurality of first optical transmission media;

a plurality of second optical transmission media;

a plurality of two-way repeater means, each two-way repeater means being connected to one of the plurality of first optical transmission means and one of the plurality of second optical transmission media, and being distributed throughout a plurality of areas within a given premises, for receiving radio signals generated in the respective areas where the repeater means are distributed and for supplying optical signals corresponding to the signals received to the respective ones of the plurality of first optical transmission media, and for receiving optical signals inputted through the respective ones of the plurality of second optical transmission media and for generating radio signals, corresponding to the signals received, in the respective areas; and

optical signal multiplexing means including optical to electrical signal converting means for converting, into electrical signals, optical signals transmitted through said plurality of first optical transmission media, adding means for adding said electrical signals converted by said optical to electrical converting means, electrical to optical converting means for converting said added electrical signal into an optical signal, and supplying means for supplying the optical signal converted by said electrical to optical converting means to each of said plurality of second optical transmission media.

6. A system according to claim 5, wherein said each of portable radio transceivers outputs a radio signal having a field intensity which allows the signal to be received in any part of one of said areas.

7. A system according to claim 5, wherein the radio signal outputted by each of said two-way repeater means has a field intensity allowing the signal to be received in any part of the corresponding area in which the two-way repeater means is located.

8. A system accordingly to claim 5, wherein said each of two-way repeater means includes a transmitting and receiving antenna, electrical to optical signal converting means for converting a radio signal received by said transmitting and receiving antenna into an optical signal, and optical to electrical signal converting means for converting, into an electrical signal, an optical signal transmitted through said second optical transmission medium and for supplying the electrical signal to said transmitting and receiving antenna.

9. A system according to claim 5, wherein said optical signal multiplexing means includes optical to electrical signal converting means for converting, into electrical signals, optical signals transmitted through said plurality of first optical transmission mediums, adding means for adding said electrical signals converted by said optical to electrical converting means, electrical to optical converting means for converting said added electrical signal into an optical signal, and supplying means for supplying the optical signal converted by said electrical to optical converting means to each of said plurality of second optical transmission mediums.

10. A low power private branch radio communication system, comprising:

a first portable radio transmitter, located in a first area within a given premises, for modulating a signal and outputting the modulated signal as a radio signal of limited power in the first area;

a first repeater means, located in the first area, for receiving the radio signal transmitted from said radio transmitter and for outputting an optical signal corresponding to the signal received, said first repeater means including a first antenna for receiving said radio signal, and a light modulator for receiving, as a modulation signal, the signal received by said antenna and for converting said signal received into an optical signal;

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

a second repeater means, located in the second area, for receiving the optical signal output from said first repeater means and transmitted by said optical transmission medium, and for generating a radio signal of limited power corresponding to the signal received in the second area, said second repeater means including a photo detector for detecting said optical signal and a second antenna for outputting the signal detected by said photo detector as a radio signal;

a second portable radio receiver, located in the second area, for receiving the radio signal output from said second repeater in the second area and demodulating the signal received; and

wherein output powers of each of the radio signals emitted from radio transmitters of the system do not exceed an intensity, at a position of 3 meters from the corresponding transmitter, of a few hundred microvolts per meter.

11. A system according to claim 10, wherein:

the output powers of each of the radio signals of the system are limited to below a power level which provides a field intensity of less than 500 microvolts per meter at 3 meters distance from the corresponding radio transmitter source.