Patent ID: 6985703

Claim:
Apparatus for direct synthesis of a modulation waveform, the apparatus comprising: a fractional-N phase-locked loop circuit that includes a counter controlled by a ΔΣ modulator, wherein a sequence output produced by the ΔΣ modulator alternates between integer values to resolve a fractional N value; a two-port voltage-controlled oscillator, the first port receives a control voltage for the phase-locked loop and the second port receives a direct modulation signal; a second input to the fractional-N phase-locked loop that operates to remove the modulation applied at the voltage-controlled oscillator; a variable gain amplifier that receives the sequence output of the phase-locked loop and an amplitude-control signal, wherein an envelope characteristic of the phase-modulated signal produced by the phase-locked loop is modulated; a phase data input circuit that receives the phase modulation data, differentiates the data, and routes the differentiated data to the second input of the fractional-N phase-locked loop as well as the second port of the voltage-controlled oscillator; and an amplitude data input circuit that receives amplitude data and produces a signal that is coupled to a variable gain amplifier, wherein the phase data and the amplitude data experience substantially the same signal delay.