Method and system for reducing direct digital synthesizer (DDS) and mixer spurios

Abstract

A waveform generator circuit provides low spurious output signal and includes a primary DDS for generating a RF signal at a first frequency. A DAC receives an output signal from the primary DDS and converts the digital DDS output to an analog output. A spectrum analyzer identifies spurious signals in the DAC output determining the amplitude and frequency characteristics of the spurious signals. The waveform generator includes at least one cancellation DDS configured to generate a pre-distortion signal corresponding to frequencies where spurious signals are expected due to non-linearities in the DAC circuitry. The pre-distortion signals are phase offset from the determined spurious signals to cancel the spurious signals. The pre-distortion signals are combined with the output of the primary DDS. The combined signal contains the primary DDS output signal and pre-distortion signals to produce an analog output signal which cancels out the expected spurious signals.

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