Frequency Domain Phase Shift Measurement Technique Applied to a Multiphase Rotary Travelling-Wave VCO

In this letter, the design of a multiphase 18.5 GHz Rotary Travelling-Wave Oscillator (RTWO) is presented. Lack of symmetry in such a structure can result in oscillation in a standing wave rather than the travelling wave mode. In order to determine the mode of the signal, before going through the time consuming steps of time domain phase shift measurement, we have proposed a preliminary phase shift measurement technique in the frequency domain for a high frequency RTWO. This new technique was verified against direct phase measurements for a multiphase RTWO fabricated in a 0.25 μm BiCMOS process with good agreement. In other measurements, the VCO achieved a tuning range of 1.1 GHz and output power of -5.3 dBm.