Design and selection of LPF in AFGs

Based on the DDFS technology, the AFG can synthesize not only the sinusoid waveform, but also the non-sine periodic waveform. Being similar to the sinusoid, there are many harmonics and spurious noise in the output of AFG when non-sine waveform is synthesized. The LPF has great influence on the quality of synthesizing. Selecting the appropriate LPF according the output waveform style is a key step in whole system designing. A series of simulation showed that: for sinusoid waveform, the elliptic filter can improve the frequency of synthesize furthest; for non-sine waveform, the Bessel filter can keep the delays of harmonics consistent.