Master’s Thesis, Carleton University and D-TA Systems, March 2013 – Current
Direct Digital Synthesizers (DDS) are known to be very spurious due to the use of the Digital-to-Analog Convertors (DAC). This paper presents the phase behavior of spurs of the AD9912 DDS and its SpurKiller cancellation system. A great variation in spur phase and a variation in increased spurious-free dynamic range (SFDR) was observed. As a result, an adaptive system is proposed using a Double Quadrature Mixer and a variable phase LO. The system is tested at the Intermediate Frequency (IF) of 1.2 GHz simulating an Ultra-Wideband (UWB) radio. The ideal case used is where the spurs are 90° offset from the carrier. An increase of 29 dB in SFDR resulted. In system prototype, an increase in SFDR of 10 dB resulted. This simulation is a proof of concept for adaptive systems that will be realized in future research.
Paper Accepted at CMC Texpo 2014 (click to view)
Double Quadrature Mixer Prototype