Patent ID: 7714623

Claim:
A waveform generator comprising: a first direct digital synthesis (DDS) circuit comprising a first phase accumulator and a first waveform look-up table that generates a frequency-tunable first DDS output based on a first phase output from said first phase accumulator; a second direct digital synthesis circuit comprising a second phase accumulator and a second waveform look-up table that generates a frequency-tunable second DDS output signal based on a second phase output from said second phase accumulator, wherein said frequency-tunable second DDS output signal has the same frequency as said frequency-tunable first DDS output signal, wherein said first waveform look-up table and said second waveform look-up table have same data contents, wherein said first phase output has a first phase in modulo counting based on a modulus and said second phase has a second phase in modulo counting based on said modulus, and wherein said first phase is ahead of said second phase by positive integer times a frequency tuning word that is commonly employed by said first phase accumulator and said second phase accumulator; a first state machine providing a frequency tuning word input and a first phase offset word input to said first phase accumulator at a frequency transition of said frequency-tunable first DDS output signal; a second state machine providing said frequency tuning word input and a second phase offset word input to said second phase accumulator at a frequency transition of said frequency-tunable second DDS output signal; and a reference clock providing a reference clock signal to said first phase accumulator, said second phase accumulator, said first state machine, and said second state machine.