A 5GHzI/QPhase-tunable CMOS LCQuadrature VCO (PT- QVCO)forAnalog PhaseCalibrated Receiver Architectures

Thispaperpresents a5-GHzphase-tunable I/Q signal generator ina0.18gmRF CMOS process basedonthe parallel cross-coupling oftwo-GMLC VCOs(QVCO).The proposed circuit achieves anultra-wide I/Qphasetuning range without affecting therelative amplitude errororconsuming additional powerorchiparea. Additionally, inrestoring the phasebalance, itisobserved thattheproposed method improvesphase noiseperformance. Time domain measurements showthatthetwoVCOs,prior tophasetuning, arequadrature locked witha0.80 phaseimbalance and1.4% relative amplitude error.In agreement withpreviouslT developed analysis, I/Qsignals withphaseerrorupto- ±30, beyondwhichtheVCO coresareunlocked, canbedriven to perfect quadrature phase. ThePT-QVCOcanbetunedfrom 3.87-4.45 GHzforthenegative mode,and4.4-5.4 GHzforthe positive mode,a total of-1.5GHz.Thefabricated circuit including padstructures occupies anareaof1.1x0.7 mm2and drains 18mW (excluding buffer circuits) froma1.8V supply voltage.