A 5GHz Transformer-Coupled CMOS VCO Using Bias-Level Shifting Technique

la this paper we report a low phase noise transformeccoupled CMOS VCO using bias-level shining technique. Two fully integrated voltagecoatrolled oscillators (VCOs) are presented as a proof of concept. A conventional LC VCO with a current source achieves a phase noise of - 116.67 dBe/Hz at 1 MHz offset from 5.6 GHz center frequency, taking 3.9 mA from 1.5 V power supply. The proposed transformer-coupled VCO achieves a phase noise of -124.17 dBe/Hz at 1 MHz olfset from a 5.8 GHz carrier frequency with 5.1 mA bias current fmm 1.5 V power supply. The VCO performances are compand with the previously reported CMOS VCOs in the range of 4-6 GHz oscillation frequencies.