A CMOS Digitally Controlled Oscillator for Reconfigurable RF Applications

This paper presents a design of a CMOS digitally controlled oscillator (DCO) using a tunable active inductor (TAI) to reduce the area and cost for reconfigurable multi-band RF applications. The compatibility of this circuit to different wireless standards shows its potential to be implemented for the Internet of Things (IoT). The proposed TAI, based on a gyrator-C topology, achieves coarse frequency tuning due to a 4-bit digitally controlled current source. Implemented in 130 nm CMOS technology, the DCO occupies an area of only $(52\ \times 48)\ \mu\mathrm{m}^{2}$. The circuit offers a frequency tuning from 1.65 GHz to 2.5 GHz for a 4-bit digital control word in [1], [15]. The optimal phase noise is about −87 dBc/Hz@1 MHz offset with power consumption varying from 2.6 mW to 5 mW at a supply voltage of 1.1 V when changing the control word digitally from 1 to 15.