US Patent 7599977 Direct digital synthesizer system and related methods

A direct digital synthesizer (DDS) has reduced spurious signals and includes a DDS core that produces a digital representation of a signal to be synthesized. A plurality of DDS circuits are operatively connected to the DDS core, each having a digital-to-analog converter connected to the DDS core for receiving the digital representation and converting it into a signal. A modulator is operatively connected to an oscillator circuit and digital-to-analog converter for receiving signals from the digital-to-analog converter and producing a modulated output signal. The individual frequencies of the respective DDS circuits are randomly and continuously changed from each other. A mixer receives and mixes the modulated output signals from the plurality of DDS circuits to create a mixed output signal at a selected and fixed frequency.