Impact and Modeling of Möbius Connection in the Rotary Traveling Wave Oscillator Performance

Abstract

The new interest in high frequency applications such as 5G and mmWaves have increased the design requirement for the integrated circuits, specifically for the signal generation and base-band processing stages. The Rotary Traveling Wave Oscillator (RTWO) has been proposed not only as clock distribution network when is used in arrays (ROAs), but also for high data rate applications and communication systems. The RTWO has two ring-shaped differential transmission lines as resonator and this resonator ring cannot be built with a constant characteristic impedance due to the characteristics of the CMOS manufacturing processes. The most complex discontinuity of the RTWO resonator is the Mobius connection; this discontinuity is generally manufactured using angles of 90° or 45°, different metal levels and stacks of intermetallic connections (vias). In this work we analyze and model the 45° Mobius connection for different geometrical configurations and technologies. The results show that the Mobius connection commonly implemented using the last two top metal levels is not the optimal and by using a lower metal layer is possible to select the optimal cross-connection in this type of oscillators.