High-Q MOS-Varactor Modeling for mm-Wave VCOs

High-Q and scalable MOS varactor for mm-wave VCO has been studied. To realize high-Q varactor in mm-wave region, low varactor capacitance and low series resistance of unit cell are essential. Since low varactor capacitance and low series resistance are impossible to realize simultaneously, optimization and scalable model are necessary. This paper presents strategy of high-Q optimization, a novel scalable model for mm-wave varactor, and confirmation results by VCO measurements. The Q of small-geometry varactor improved 30 times at f = 30 GHz. The novel scalable varactor model improved its accuracy from 21.9% to 1.7%.