A novel dual-loop multi-phase frequency synthesizer

This work describes a novel dual-loop frequency synthesizer for applications in wireless communications. The synthesizer comprises a dual-loop architecture with a multi-phase voltage controlled oscillator (VCO) in one of the loops. The advantage of this architecture is the improvement of the transient response and channel spacing compared with conventional dual-loop frequency synthesizers. The proposed architecture has been implemented on a Xilinx Virtex-5 PFGA board. Measurement results confirm that the new dual-loop multi-phase frequency synthesizer achieves comparable phase noise performance but superior frequency resolution compared with the conventional dual-loop frequency synthesizer. In addition, both the in-band and out-of-band noise of the proposed architecture are improved compared with a delta-sigma modulated fractional-N frequency synthesizer.