Analysis of the Effects of Elements Parasite on Cross-Coupled Oscillator in Millimeter Wave Band

In this paper, a cross coupled LC oscillator is analyzed in millimeter wave band. By using the negative resistance method and two port model for the elements, more accurate formula is obtained for calculation of the oscillation frequency and the oscillation startup condition. The new developed equations demonstrate the effects of parasitic elements, especially RG and CGD, on the oscillator behavior in millimeter wave band, which leads to dependency of the oscillation condition to the oscillation frequency. The presented equation shows that the RG prevents the oscillation at high frequencies. Furthermore, minimum value of the inductor used in the oscillator is determined for maximum oscillation frequency. The presented equations are verified by simulations using Advanced Design System (ADS) and the foundry design kit for TSMC 0.18 um RF-CMOS technology.