A 5-GHz self-calibrated I/Q clock generator using a quadrature LC-VCO

This paper describes a self-calibration technique to generate precise I/Q signals for frequency synthesis. The phase comparator compares the in-phase signal to the quadrature signal in the quadrature LC-VCO and the charge-pump circuit produces the correction voltage. To verify the functionality of the proposed scheme, the 5-GHz LC quadrature VCO utilized in 5-GHz band wireless LAN, especially, IEEE 802.11a, is designed. The phase error resulting from calibration is under 2-degree in various device mismatches. The oscillator with calibration achieves -121.5 dBc/Hz at 1 MHz offset and exhibits 10 % tuning range. A prototype frequency synthesizer using the proposed scheme is also designed using a 0.18-μm 1-poly, 6-metal standard CMOS process and verified with schematic simulation.