A CMOS high-performance inductorless ring VCO with extended monotonic tuning voltage range

A high-performance inductorless ring VCO with wide tuning range and extended monotonic tuning voltage range (MTVR) is proposed and fabricated in standard 0.18 µm CMOS technology. By combining the crossing-strength-tuning and load-resistance-tuning techniques with opposite tuning characteristics, the MTVR for the proposed VCO can be widened significantly. The dual-delay path technique is employed to improve the oscillating frequency. The cross-coupled pair is added to reduce phase noise and guarantee reliable differential-mode oscillation over the wide tuning voltage range. With an occupied area of 475 µm × 275 µm and a single supply voltage of 1.8 V, measurement results show the proposed VCO can oscillate with a frequency range from 1.57 to 2.76 GHz, phase noise of −91.12 dBc/Hz @ 1 MHz and FOM_T of 164.5 dBc/Hz @ 1 MHz and extended MTVR.