Narrow band communication system

• US 5,230,086 A
• Filed: 01/29/1990
• Issued: 07/20/1993
• Est. Priority Date: 02/04/1989
• Status: Expired due to Fees

• Current Assignee: Plessey Semiconductors Limited (Plessey Group Holdings Ltd.)
• Original Assignee: Plessey Semiconductors Limited (Plessey Group Holdings Ltd.)
• Inventors: Saul, Peter H.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Faile, Andrew
• Application Number:
  US07/470,611
• Time in Patent Office: 1,268 Days
• Field of Search: 455/47, 455/51, 455/71, 455/86-88, 455/103, 455/105, 455/313, 455/318, 455/180.2, 455/188.2, 455/51.1
• US Class Current: 455/502
• CPC Class Codes: H04B 7/24 for communication between two or more posts wireless communication networks H04W

Abstract

A narrow band modulation UHF/Microwave communication system comprises a transmit/receive base station having a plurality of transmitter for transmitting information at respective UHF/Microwave channel frequencies to a plurality of remote transmit/receive stations, in which the transmitters at the base station are served in common by a single master oscillator and in which a single reference frequency signal is derived from the master oscillator at the base station and transmitted to all of said remote stations where it serves to provide for frequency locking of the oscillators at said stations to produce synchronization between the frequencies at the base station and the remote stations.

Claims

1. A narrow band modulation UHF/Microwave communication system including a transmit/receive base station and a plurality of transmit/receive remote stations, wherein said base station comprises:

master oscillator means;

means for generating, from an output of said master oscillator means, a plurality of carrier signals of different channel frequencies spaced apart over a band of frequencies;

means for generating, from an output of said master oscillator means, a reference carrier signal of a frequency spaced from said band of frequencies;

means for transmitting information, as narrow band modulation of respective ones of said different channel frequencies, to a plurality of said remote stations; and

means for transmitting, unmodulated, said reference carrier signal to all of said remote stations, and

each of said plurality of remote stations comprise;

means for receiving at least one of said modulated channel frequencies;

means for receiving said unmodulated reference carrier signal;

a controllable frequency slave oscillator;

means for controlling the frequency of oscillation of said slave oscillator in dependence upon the frequency of said reference carrier signal;

means for demodulating said at least one modulated channel frequency with reference to an output from slave oscillator; and

means for generating, from an output of said slave oscillator, at least one carrier signal at a respective one of said different channel frequencies.

2. A narrow band modulation UHF/Microwave communication system as claimed in claim 1 in which the unmodulated reference frequency signal is transmitted periodically to the plurality of remote transmit/receive stations.

3. A narrow band modulation UHF/Microwave communication system as claimed in claim 1 in which the slave oscillator at each remote station is arranged to control a further slave oscillator in the associated transmitter part of the same station.

4. A narrow band modulation UHF/Microwave communication system as claimed in claim 1, in which the master oscillator means at the base station controls at least one further oscillator in the receiver part of the base station.