Reconfigurable, fast AFC technique using code estimation and binary search algorithm for 0.2–6GHz software-defined radio frequency synthesis

This paper proposes a reconfigurable automatic frequency calibration (AFC) module for software-defined radio (SDR) application which is designed for 200MHz~6GHz communication standards. A 6-bit capacitor array controls VCO output frequency from 3.05-6.12GHz. A fast locking technique featuring code estimation and binary search algorithm is proposed and verified by transistor-level simulation in 0.13μm CMOS. Multi-configurable thresholds are also adopted for GSM/EDGE, LTE, DVB-H, WiMAX and WLAN standards. The code estimation and binary search algorithm can be customized for dual band/dual path VCO to meet the settling time requirements. Reconfigurable counters in the AFC module can further reduce control bit searching time. The proposed AFC implemented with customized logic achieves the settling time less than 80μs with 13MHz reference frequency.