Direct Digital Synthesizers (DDS) are known to be very spurious due to the use of Digital-to-Analog Convertors (DAC). This paper presents the phase behaviour 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. In simulation, an increase in SFDR of 29 dB resulted. In system prototype, an increase in SFDR of 10 dB resulted.

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Keywords cancellation, interference, mixers, phase modulation, Signal synthesis
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Conference 2015 IEEE Radio and Wireless Symposium, RWS 2015 - RWW 2015
Mack, S. (Simon), & Wight, J. S. (2015). Double Quadrature Mixer for adaptive spur cancellation in ultra-wideband radios. In IEEE Radio and Wireless Symposium, RWS (pp. 78–81). doi:10.1109/RWS.2015.7129780