Apparatus and method for synchronizing a plurality of remote transmission and receiving stations and providing automatic gain control of the synchronizing signal

• US 5,278,690 A
• Filed: 06/19/1992
• Issued: 01/11/1994
• Est. Priority Date: 05/16/1991
• Status: Expired due to Term

• Current Assignee: George P. Vella-Coleiro
• Original Assignee: George P. Vella-Coleiro
• Inventors: Vella-Coleiro, George P.
• Primary Examiner(s): Chilcot, Jr., Richard E.
• Assistant Examiner(s): BACARES, RAFAEL D
• Application Number:
  US07/900,766
• Time in Patent Office: 571 Days
• Field of Search: 359/125, 359/143, 359/144, 359/167, 359/172, 359/173, 359/145, 359/152, 359/113, 359/114, 359/153, 455/51, 455/70, 455/71, 455/69, 455/88, 455/33.1, 455/53.1, 455/54.1, 455/67.4, 379/379, 379/56, 379/58, 379/59
• US Class Current: 398/139
• CPC Class Codes: H04B 7/2675 Frequency synchronisation
• CPC Class Codes: H04J 1/065 Synchronisation of carrier sources at the receiving station with the carrier source at the transmitting station
• CPC Class Codes: H04J 14/0298 with sub-carrier multiplexing [SCM]
• CPC Class Codes: H04W 56/0035 detecting errors in frequency or phase
• CPC Class Codes: H04W 88/08 Access point devices
• CPC Class Codes: H04W 88/085 Access point devices with remote components

Abstract

System synchronization is achieved in a system of remote stations serving a particular cell site or base station by combining rf signals transmitted to the base station from the cell site with a reference signal to form a composite signal. This composite signal is used to modulate the output of a base station laser transmitter. The composite signal is transmitted to the remote station where the reference frequency is extracted and used to synchronize the rf circuits of the remote station. Special diagnostic features are built into the remote station transceivers so that equipment functioning may be monitored at the base station.

Claims

1. In a cellular radiotelephone system, apparatus for synchronizing a plurality of remote transceiver stations and a base station connected to the remote stations to a common reference signal having a reference frequency;

comprising;

the base station including;

a first input for receiving an RF radio signal,

a second input for receiving a reference signal,

a base station splitter connected to the second input for splitting the reference signals into first and second base paths,

a base signal combiner circuit connected to the first input and the first base path and operative for combining the RF radio signal and the reference signal into a first RF composite signal,

a laser device connected to the base signal combiner circuit and operative for converting the first RF composite signal into an AM composite light signal,

a transmitting light fiber link having a first end connected to the laser device,

a remote transceiver station connected to a second end of the light fiber link to receive the AM composite light signal of the laser device and including;

an optical signal received connected to the light fiber link and operative for separating the reference signal from the AM composite light signal for synchronizing operations in the remote station;

a remote station splitter connected to the optical signal receiver and operative for splitting the reference signal into first, second and third remote paths,

RF signal transmission apparatus connected to the optical signal receiver and operative for providing radio signal transmission of RF signal outputs of the optical signal receiver,

a first frequency synthesizer connected to the first remote path to accept the reference signal separated from the AM composite light signal and generate a RF carrier signal at a cellular frequency to be modulated by a maintenance signal returned to the base station to indicate status of the remote station,

RF signal reception apparatus in the remote transceiver station for receiving cellular telephone radio signals and including a mixer,

a second frequency synthesizer connected to the second remote path to accept the reference signal separated from the AM composite light signal and generate a local oscillator signal applied to the mixer for down converting received RF radio signals;

an RF maintenance receiver connected to the third remote path to accept the reference signal separated from the AM composite light signal and generate a signal frequency to tune the RF maintenance receiver to a control signal frequency generated by the base station for maintaining the remote station;

a remote signal combiner circuit coupled to the RF signal reception apparatus and the first and second remote paths whereby the remote signal combiner circuit generates a return RF composite signal.

a remote optical transmitter connected to the remote signal combiner circuit and operative for converting an output of the remote signal combiner to an AM return optical signal,

a second transmitting light fiber interconnecting the remote optical transmitter to the base station,

a base optical receiver at the base station connected to the second transmitting light fiber and connected to receiver circuitry at the base station for separating the RF signals from the AM return optical signal, the receiver connected to receive the reference signal from the second base path, and including

an AGC amplifier responsive to an amplitude of the reference signal to adjust an amplitude of the RF signal to compensate for optical losses in the second transmitting light fiber.

2. In a cellular radiotelephone system, apparatus for synchronizing a plurality of remote transceiver stations and a base station connected to the remote stations to a common reference signal having a reference frequency;

as claimed in claim 1;

comprising;

maintenance monitoring circuitry at the remote station connected to receive intelligence signals and to the second remote path to receive the second reference signal.

3. In a cellular telephone system, a method for synchronizing a plurality of remote transceiver stations and a base station connected to the remote stations to a common reference signal having a reference frequency;

comprising the steps of;

at the base station, receiving a RF radio signal, and receiving a reference signal, and splitting the reference signal into first and second base signal paths;

combining the RF radio signal and the reference signal from the first base signal path into a first RF composite signal, and converting it into an AM composite light signal;

transmitting the AM composite light signal to the remote transceiver station via a light fiber link;

receiving the AM composite light signal transmitted on the light fiber link at the remote transceiver station and separating the received reference signal from the AM composite light signal into first, second and third remote paths,

receiving RF signals at the remote transceiver station;

utilizing the received reference signal in the first remote path to generate a RF carrier signal at a cellular frequency and modulating the RF carrier signal with maintenance alarm signals at a first frequency synthesizer to generate a return RF composite signal returned to the base station to indicate status of the remote station;

converting the return RF composite signal into an AM return composite light signal, and transmitting the AM return composite light signal via a second light fiber link to the base station;

at the base station receiving the AM return composite light signal and separating the RF signals and adding a reference signal from the second base signal path;

utilizing the received reference signal in the second remote path to generate a local oscillatory signal applied to a mixer for down converting received RF radio signals;

utilizing the received reference signal in the third remote path for use by an RF maintenance receiver to tune to a signal frequency generated by the base station for monitoring the remote station; and

controlling a gain of the received RF signal in response to an amplitude of the reference signal to compensate for amplitude variations in the second light fiber link.