A quadrature LO generator using bidirectionally-coupled oscillators for 60-GHz applications

A technique for generating multiphase reference signals at mm-wave frequencies using coupled oscillators is proposed. Bidirectional coupling is introduced to solve two major issues in conventional multiphase coupled LC oscillators, namely phase noise degradation due to off-resonance operation and ambiguity in the output frequency. A quadrature frequency doubling topology using bidirectionally-coupled oscillators is also presented. An experimental prototype integrated in 90-nm CMOS provides output phases in increments of 45° and achieves a phase noise of -101 dBc/Hz at 1-MHz offset from a 19.6-GHz carrier. The quadrature 40-GHz signal generated on chip drives a single-sideband transmitter that achieves a sideband suppression of better than 45 dB.