Direct digital frequency synthesis method and synthesizer

A direct digital frequency synthesis method comprises the following steps: determining a key node of a target waveform, and generating a target phase, a target amplitude and a first derivative value according to the key node; constructing a waveform lookup table according to the target phase, the target amplitude and the first derivative value; calculating a reference phase by using the frequency control word and the phase control word; reading a target amplitude and a first derivative value from the waveform lookup table according to a matching relationship between the reference phase and the target phase; performing tertiary Hermite interpolation on the target amplitude by using the target phase and the first derivative value to obtain an actual amplitude; and generating a digital signal according to the actual amplitude, and outputting an analog waveform through digital-to-analog conversion and filtering in sequence. According to the direct digital frequency synthesis method and the synthesizer provided by