Direct digital synthesizer with tunable phase and amplitude error feedback structures
Jouko Vankka, Jonne Lindeberg, Kari A. I. Halonen · 2003
The error feedback (EF) technique is used to suppress phase and amplitude spurs in direct digital synthesizers (DDS). It allows the reduction of word lengths of phase to amplitude converters and D/A converters. The drawback of the conventional phase EF is that it reduces the phase spurs only at DDS output frequencies, which are near DC or half the sampling frequency. New phase EF structures with arbitrary center frequency for cosine and quadrature output DDS are introduced. The cosine and quadrature DDS with tunable phase and amplitude EF were designed and implemented on a programmable logic device (PLD); our experimental results show their desired operation and performance.