Impact of Reference Clock and Filtering on the Performance of Direct Digital Synthesizer

Currently Direct Digital Synthesizers(DDS) are becoming more popular for the generation of multiple frequency signals. Conventional method for generating multiple signals is to use different standalone frequency synthesizers or signal sources without any external filtering. In DDS multiple signals can be generated synchronously using a single reference signal. However, selection of correct reference signal and the filters are at most important for the performance of DDS and to suppress the Nyquist(aliasing) frequency components. This article presents a practical perspective on the selection of correct reference signal for the design of DDS. In addition, the impact of usage of filtering and design of different RC filters for the generation of RF signal frequencies of 39 MHz and 53 MHz are discussed.