Data encoder/decoder for data transceiver

DETAILED DESCRIPTION A data transceiver in accordance with the present invention uses separate transmit and receiver antennas for transmitting and receiving data-modulated signals, respectively.
A single local oscillator provides both the RF carrier for the transmit signal and the local oscillator ("LO") signal for the down-conversion of the receive signal in the receiver section.
The LO signal is conveyed from the transmitter section to the receiver section in the form of the radiated transmit signal from the transmit antenna to the receive antenna.
Full duplex operation is achieved by cancelling out the transmit data from the down-converted receive signal which has been introduced by the modulated transmit signal used as the LO signal, and by setting the carrier of the local oscillator at a frequency which is offset from that of the incoming data-modulated carrier signal by an amount equal to the desired intermediate frequency.
In further accordance with the present invention, a frequency modulator is provided in which a phase-lock-loop is used for generating a frequency-modulated signal.
The phase-lock-loop receives a reference signal and generates an output signal which is synchronized to the reference signal in accordance with an internally generated frequency control signal.
A modulator receives a binary data signal and in accordance therewith modulates the frequency control signal, which in turn causes the output signal frequency to be modulated.
In still further accordance with the present invention, a binary-to-trinary data encoder is provided for encoding binary data to trinary data.
The first of the three trinary data values corresponds to an absence of binary data transitions, the second of the three trinary data values corresponds to positive binary data transitions, and the third of the three trinary data values corresponds to a negative binary data transitions.
In a preferred embodiment of the present invention, the trinary data values are represented by a frequency-modulated signal in which one of three frequencies each represents one of the trinary data values