Self-calibrated quadrature generator for WLAN multistandard frequency synthesizer

A self-calibrated quadrature generator capable of generating local oscillator (LO) outputs for IEEE 802.11a-b is presented. The quadrature generator is embedded in a frequency synthesizer that generates reference frequencies at 2.4 and 5GHz. A new sequential calibration scheme maintains the quadrature at the 5-GHz output within a maximum phase error of 2°, while a divide-by-two flip-flop generates the quadrature output at 2.4 GHz. The circuit is fabricated in a 0.25-μm SiGe BiCMOS technology and occupies a silicon area of 2 mm²; the quadrature generator consumes a current of 5 mA from a 2.5-V supply.