Direct-digital synthesis using delta-sigma modulated signals

A new technique that uses a DSM signal in a common technique for digitally synthesizing an arbitrary waveform, which is generally known as direct-digital synthesis (DDS), is described in this paper. In this way, the DDS frequency resolution is not restricted to the phase resolution in DDS and requires no phase truncation technique. As a simulation result, a low-pass filtered output waveform is smooth at a lower frequency with respect to the clock frequency. At lower frequencies, this technique leads to a higher spurious-free-dynamic-range than that of an ideal linear interpolator output with the same phase resolution. Therefore, the proposed combination of DSM signal and basic DDS is able to realize high frequency resolution and high spectral-purity at a lower frequency band using a small circuit.