A high frequency resolution digitally controlled oscillator with differential tapped inductor

A novel architecture of high frequency resolution LC-tank based digitally controlled oscillator (DCO) is presented in this paper. The proposed architecture utilizes a differential tapped inductor and a capacitor array within the taps for fine frequency tuning. A prototype of 1.6 GHz DCO integrated in 0.18-μm CMOS technology exhibits a tuning range of 40.2% and a phase noise of -123.6 dBc/Hz@1MHz. With a minimal capacitance step of 7.5 fF, the frequency resolution is improved to 7.6 kHz/LSB. The DCO dissipates 3.2 mA from a 1.8 V supply and occupies an area of 0.46 mm
²
.