Low-Noise Distributed RC Oscillator

This article proposes a circuit architecture and design strategy of a low-noise oscillator based on the distributed
RC
network. The distributed
RC
network receives a differential step input and propagates the true phase through the resistive path while the complementary phase through the capacitive path. It effectively suppresses the effect of noise by increasing the signal transition slope at the time of interest. It is achieved by embedding a bandpass characteristic with a phase delay of
$\pi $
. A 358-kHz quadrature oscillator with a fourth-stage
RC
network is implemented using the 0.18-
$\mu \text{m}$
CMOS process. It achieves an figure of merit (FoM) of −161.2 dBc/Hz at a 100-Hz offset with a stable 20-dB roll-off in the phase noise and an Allan deviation floor of less than 0.7 ppm.