Phase Coherent FSK Modulator Using AD9959 Direct Digital Synthesizer

Phase Coherent FSK Modulator Using AD9959 Direct Digital Synthesizer. The standard single channel direct digital synthesizer (DDS) does not switch between frequencies in a phase coherent manner. By design, DDS frequency transitions are phase continuous. However, the circuit demonstrates how to configure the AD9959 multi-channel DDS for a robust phase coherent FSK (frequency shift keying) modulator by summing the outputs of the multi-channel DDS together