An Inductor‐Less Quadrature Digitally Controlled Oscillator (QDCO) Based on Active Transformer Coupling in Standard CMOS Technology

ABSTRACT A wide tuning range 6‐bit digitally programmable quadrature DCO using two coupled active transformers is proposed. The proposed inductor‐less QDCO is constructed by two tail‐less cross‐coupled LC oscillators, loaded by two coupled active transformers, with antiphase coupling. Active transformers are designed based on cascode‐grounded active inductors with digital programmability and analog tunability. The coarse tuning of the active transformer‐coupled quadrature DCO (ATC‐QDCO) is obtained by controlling a programmable current steering structure, and for fine tuning, an analog voltage is applied to the varactors. A 6‐bit digital code controls all four active inductors used in the proposed structure. By programming these 6 digital control bits, the output frequency of QDCO is controlled from 320 MHz to 3 GHz, with frequency tuning range of 162%, and the phase noise varies from 78/7 to 86/5 dBc at a 1‐MHz offset. The proposed structure is designed and simulated in a 0.13‐m standard CMOS technology. The performance of the proposed structure is verified in different process corners, and variations of temperature and voltage. With a 1‐V power supply, the power consumption of the structure is from 11.1 to 15.3 mW. A silicon area of 0.002 mm is consumed by the proposed ATC‐QDCO.