Direct digital synthesizing method and direct digital synthesizer

摘要

A direct digital frequency synthesis method comprises the following steps: calculating, by a phase accumulation module, a first phase according to a frequency synthesis word (S101); finding an amplitude value by a preset sinusoidal lookup table according to the first phase (S102); finding a second phase by a preset phase lookup table according to the amplitude value (S103); if the second phase is less than the first phase, adjusting and outputting the amplitude value (S105); or else, outputting the original amplitude value (S106); and performing, by a digital-to-analog converter, a digital-to-analog conversion according to the output amplitude value to obtain a sinusoidal wave (S107); wherein, for a N-bit phase accumulation module and a D-bit digital-to-analog converter, the preset phase lookup table has 2^D−1-1 phase boundary value records corresponding to 0˜2^D−1-2 amplitudes, each phase boundary value is stored in N-2 bits. A direct digital frequency synthesizer applying the above method is also disclosed.