A 0.855-9.342 GHz octa-phase LC VCO for multimode direct conversion receiver in 0.18-mu m CMOS

Abstract

New fully integrated, multiband octa-phase LC VCOs are presented. The VCO is composed of four identical differential VCOs and implemented at a 0.18-mu m TSMC CMOS process. Four individual VCOs are connected by a series-coupling transistor to obtain the octa-phase signal and low phase noise characteristic. For multiband operation, a band-tuning circuit is designed. The circuit is composed of a switching capacitor circuit and MOS varactors, and allows the VCO to operate at a frequency range of three standards (CDMA 2000 1x, WCDMA, WiBro) and to be tuned to select a channel in each frequency range. The measured phase noises of the VCO are -105 dBc at 100 kHz., -115 dBc at 1 MHz, and -130 dBc at 10 MHz for CDMA 2000 1x, WCDMA and WiBro, respectively, while the VCO drains 12 mA and consumes 21.6 mW with output buffers at the frequency band from a 1.8 V supply.