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Abstract

A frequency shift keyed (FSK) data transmission system utilizes existing power lines to transmit data by superimposing a high frequency FSK signal on the power line carrier. A transmitter includes a phase locked loop which is locked on the power line carrier frequency and which synthesizes the FSK signal and a timing signal which defines the data rate of the transmitter. As each bit is transmitted, an oscillator control signal either speeds up or slows down the loop oscillator temporarily to produce the FSK signal. A receiver demodulates the data transmission from the power line by separating a power line carrier frequency component and a FSK signal component. The receiver includes a phase locked loop which locks onto the power line carrier frequency and which synthesizes a reference frequency and a timing signal which defines the data rate of the receiver. The receiver also includes a frequency discriminator circuit which compares the FSK signal with the synthesized reference signal and produces a digital data output signal at the data rate synthesized by the phase locked loop.

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First Claim