A Negative Feedback Looped Voltage-Controlled Ring Oscillator With Frequency Voltage Converter

This paper proposes a negative feedback looped voltage-controlled ring oscillator (VCRO) with a frequency voltage converter (FVC) to suppress the phase noise. Measurement results of the negative feedback looped VCRO fabricated in a one-poly six-metal 1.8-V 0.18- μm CMOS process show that the phase noises are -90, -90, -94, -102, and -110 dBc/Hz at 1-kHz, 10-kHz 100-kHz, 1-MHz, and 10-MHz offset from 922.9-MHz output frequency, respectively. The proposed negative feedback looped VCRO reduces the phase noise of a conventional VCRO by 35 ~ 8 dB from 1 kHz to 1 MHz. Measurement results show that the FVC can be combined with various VCRO and LC voltage-controlled oscillator architectures in a negative feedback loop to improve their phase-noise characteristic further.