Analysis and optimization of ring oscillator using sub-feedback scheme

This work proposes a topology using a ring oscillator with sub-feedback loops to generate multiple phases. It is composed of an N-stage main ring (arbitrary N larger than 3) and k-stage sub-feedback loops, where k is not the common divisor of N, N output phases can be obtained. With a linear model analysis, it comes to a result that oscillating frequency is related to k, and the phase difference between adjacent stages. With smaller k, higher oscillating frequency can be achieved.