Patent ID: 6975687

Claim:
A modulator comprising: an offset QPSK modulator, said offset QPSK modulator operative for receiving input data and generating a first output signal representing the modulation to be imposed on a carrier signal to effect offset QPSK modulation of said input signal and a second output signal representing an amplitude of said input data; a frequency modulator comprising a sigma-delta modulator, said frequency modulator operative for receiving said first output signal generated by said offset QPSK modulator, and generating a control signal representing the desired frequency of said carrier signal such that said carrier signal represents said input signal offset QPSK modulated; a phase-lock loop circuit comprising a voltage controlled oscillator for generating said carrier signal and a programmable frequency divider, said programmable frequency divider receiving said control signal as an input signal, said programmable frequency divider operative for changing the frequency of the carrier signal in accordance with said control signal, and an amplifier having variable gain for receiving and amplifying said carrier signal output by said phase-lock loop circuit, said second output signal controlling the amount of gain of said amplifier; and wherein said offset QPSK modulator comprises: a demultiplexer for receiving said input data and generating I and Q quadrature signals corresponding to said input data; a delay circuit operative for receiving said Q quadrature signal from said demultiplexer and for delaying the Q quadrature signal relative to the I quadrature signal; a digital waveform generator operative for receiving said I quadrature signal output by said demultiplexer and said delayed Q quadrature signal output by said delay circuit, and for generating a digital signal indicating the modulation to be imposed on said carrier signal.