State-of-the-Art VCO with Eight-Shaped Resonator-Type Transmission Line

A closed-loop transmission line (TL) coupled to an LCR resonator is used in this study for a fully-integrated CMOS rotary traveling wave oscillator (RTWO) based on the rotary traveling wave principle. A technique for the suppression of magnetic coupling noise is presented with eight-shaped inductors. The design and measurement of an 8.53 GHz oscillator in the TSMC 0.18 μm CMOS technology are discussed. The fully-integrated chip occupies a die area of 1.2 × 1.2 mm2. The oscillator consists of four sub-oscillators and uses four 1:1 symmetric twisted transformers, with the secondary inductors connected to form a twisted closed-loop transmission line for coupling the sub-oscillators. The transformers are configured as eight-shaped structures to minimize the far-field magnetic field radiation from each transformer and the whole transformer. At a supply voltage of 1.7 V, the power consumption is 5.84 mW. The free-running oscillation frequency of the RTWO is tunable from 8.53 GHz to 10.0 GHz. The measured phase noise at a 1 MHz frequency offset is −122.4 dBc/Hz at an oscillation frequency of 8.53 GHz, and the figure of merit (FOM) of the proposed VCO with a specific inductor layout is −193.4 dBc/Hz, surpassing other similar RTWOs. The FOM with a tuning range (FOMT) is −195.96 dBc/Hz.