A Novel Scheme of Self-Tuning for Phase Locked Loop

A novel self-tuning scheme is proposed,in which a wide tuning range is realized by digital and analog tuning circuit to reduce VCO gain.The digital tuning scheme divides a wide tuning range into many smaller bands,and self-tuning circuit is used to assign proper subband for a given channel frequency,so that PLL can be locked to proper frequency when combined with analog tuning circuit.A self-tuning PLL with a tuning range from 1.7 GHz to 2.1 GHz and 5-bit control word was implemented based on the proposed scheme.SpectreVerilog simulation shows that the circuit can operate effectively and quickly self-tune to the proper frequency range in 20 μs,and then switch to analog tuning process.Operating at reset self-tuning or channel switching self-tuning mode,the circuit is also applicable for PLL with a fully integrated wide-range VCO.