Direction control of wave propagation in Rotary Traveling Wave Oscillator (RTWO) using phase offset technique

RTWO is a transmission line based technology for generation of near square or sine wave signals with multiple phases. Without a startup circuit for control of propagation, the direction of traveling wave is mostly nondeterministic. The direction is defined by the least resistance path of the transmission line. Startup circuits have been demonstrated to work for low frequencies of operation. The drawback of such circuits includes an increase in the power budget. Startup circuits are also not ideal for high frequency applications because of the parasitic capacitance they introduce. Presented in this paper is an offset technique for direction control. This technique involves connecting at least one of the gain stages through a segment of transmission line. The transmission line introduces a phase shift between the input and output of the gain stage and creates two signal amplification paths at the start of oscillation. Conventionally, the current injected by the gain stages will follow the path of higher amplification, thus defining the direction of propagation.