A 3.16 – 12.8GHz low phase noise N-Push/M-push cyclic coupled ring oscillator

Abstract

A topology for realizing wideband ring oscillators is introduced. Five three-stage ring oscillators operating over a frequency range of 1-2.56GHz are coupled using uni-lateral cyclic coupling. This provides phase shifted outputs which are combined twice in an N-Push or M-Push operation (N=3 and M=5) resulting in an output signal of 3.16-12.8GHz. This coupled structure improves phase noise by 10log10M=7dB producing -103.4 and -101.6 dBc/Hz at 1MHz offset for 3.16GHz and 12.8GHz, respectively. A prototype fabricated in 90nm CMOS consumes 13-200mW across the tuning range.