The reference spur reduction technique for frequency synthesizers

Different topologies of charge pumps proposed for reference spur reduction at the output of the phased-locked loops. Usually they are based on differential topology or employ additional circuits such as operational amplifiers. The proposed solution is based on charge injection compensation technique. The modelling shows spur reduction up to 10 dB comparing to traditional approaches. Finally, the 2.4 GHz transmitter was fabricated in a 180nm UMC CMOS process. It achieves in worst case -74.4dBc at the both ends of frequency band and -79.1dBc in the center.