High speed and wide tuning range voltage-controlled ring oscillator in 0.18µm CMOS

A differential delay cell with complementary current control to extend the control voltage range as well as the operation frequency is proposed for high speed and wide tuning range voltage-controlled ring oscillator (VCRO). The complementary current control mitigates the restriction that control voltage can not operate at full range in a conventional VCRO. A three-stage VCRO is constructed for verifying the proposed differential delay cell. The VCRO is implemented using 0.18-µm 1P6M CMOS process and 1.8V supply voltage. Measured results show that a wide operation frequency range from 8.36GHz to 1.29GHz is achieved for the full range control voltage from 0V to 1.8V. The measured phase noise is −105.59dBc/Hz at 1MHz offset from the 8.35GHz centre frequency and a figure of merit (FOM) is −165.3 dBc/Hz. The core area is 106µm×76.2µm.