US 4,380,062 AGranted

Communication system providing simultaneous two-way transmission

AssigneeRixon, Inc.

InventorsRichard L. Stuart, Fred C. Killmeyer

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Abstract

A two-wire, carrier-type communication system is provided which enables simultaneous two-way transmission over two-wire circuits in the same spectrum. Carrier signals in quadrature are used to allow separation of signals within the same frequency spectrum. The carrier recovered at each subscriber station is used to demodulate the received signal and, after being phase shifted 90.degree., is applied as carrier to the transmitter modulator. The transmitters at the subscriber stations are thus the same as that at the central office but are locked to the receiver and 90.degree. out of phase. A bidirectional control phase adjustment network at the central station adjusts the phase of the signal received thereby until the received carrier is 90.degree. out of phase with the transmit carrier.

Claims17

Dependent claims

A communication system which enables signals to be simultaneously transmitted and received on a two-wire line in the same spectrum, the system comprising:

a first station comprising:
transmitter means including means for modulating a transmit carrier with an input signal to produce a transmit signal;
receiver means including means for demodulating a received signal with a signal corresponding to the transmit carrier phase shifted by 90.degree. to produce an output signal;
and
a variable phase network for automatically adjusting the phase of the received signals so that the received carrier signal is 90.degree. out of phase with the transmit carrier signal;
and
a second station connected to the first station by the two-wire transmission line comprising:
means for receiving the first station transmit signal;
a phase locked loop, responsive to the transmit signal of the first station, for generating a first recovered carrier signal corresponding to the first station transmit carrier and a second recovered carrier signal corresponding to the first station transmit carrier phase shifted by 90.degree.;
transmitter means including means for modulating the second recovered carrier signal with an input signal to produce a transmit signal;
and
means, connected to the output of the second station receiving means, for demodulating the first station transmit signal with the first recovered carrier to produce an output signal.

9 more elements

A communication system which allows simultaneous two-way transmission and reception of signals in the same frequency band along a two-wire line, the system comprising:

(A) a central station comprising:
(1) a signal transmitter including:
(a) means for generating first and second carrier signals, the second carrier signal being 90.degree. out of phase with the first carrier signal;
and
(b) means for modulating the first carrier signal with an audio signal to produce a transmit signal;
(2) hybrid means for simultaneously applying the transmit signal to the two-wire line and for receiving a signal applied to the central station over the two-wire line;
and
(3) a signal receiver, including:
(a) means for demodulating the received signal with the second carrier signal to produce an audio output signal;
(b) means, responsive to the second carrier signal and the received signal, for outputting a signal representative of a detected phase difference between the two signals;
and
(c) means, connected between the two-wire line and the hybrid means and responsive to the phase difference signal, for varying the phase of transmitted and received signals applied along the two-wire line whereby these signals are maintained substantially in quadrature;
and
(B) a subscriber station comprising:
(1) a signal receiver, including:
(a) phase locked loop means, responsive to the transmit signal from the central station, for generating a first carrier signal in phase with the received transmit signal and a second carrier signal 90.degree. out of phase with the received transmit signal;
(b) means for demodulating the received signal applied to the subscriber station with the first carrier signal to produce an audio output signal;
(2) a signal transmitter, including means for modulating the second carrier signal with an audio signal to produce a transmit signal;
and
(3) hybrid means for simultaneously applying the subscriber station transmit signal to the two-wire line and for receiving the central station transmit signal.

17 more elements

Dependencies are inferred from the claim text.