A Switched Inductor Topology Using a Switchable Artificial Grounded Metal Guard Ring for Wide-FTR MMW VCO Applications

In conventional integrated circuit technologies, a grounded metal guard ring (MGR) is widely used to mitigate the coupling effect between any pair of inductors. Full-wave electromagnetic (EM) simulation results indicate that the guard ring size can significantly affect the inductance value of a single-turn planar inductor. This paper proposes a switchable artificial grounded MGR technique that can not only serve as a guard ring but also change the inductance. Accordingly, an inductor, featuring switchable inductance and high quality factor, is developed for a 60-GHz millimeter-wave wide-frequency tuning range (wide-FTR) and low phase-noise voltage-controlled oscillator (VCO) in 90-nm bulk CMOS technology. The VCO testkey achieves a total tuning range of 9.43 GHz (17%). The measured phase noise levels are -92.2 and -119 dBc/Hz at 1- and 10-MHz offsets, respectively. The experimental results demonstrate that the proposed inductor topology offers the VCO an increase of 36% in the FTR and a competitive performance in phase noise, as contrasted with a conventional varactor-tuned VCO. This VCO achieves a record of -188 dBc/Hz for the FOMT.