Area-Efficient and Wideband Tunable Quadrature Colpitts Oscillator with Active Inductors

Abstract

This study presents a new wide-tunable, area-efficient and low-phase noise quadrature voltage-controlled oscillator(QVCO). Initially, a modified Colpitts voltage-controlled oscillator (VCO) is proposed in which all transistors are cross-connected in a self-biased scheme to increase negative resistance and facilitate the startup condition. Besides, instead of a passive inductor, a modified tunable active inducer (AI) is used in the proposed Colpitts VCO. Then a new AI-based QVCO is presented by the in-phase anti-phase coupling of two identical Colpitts VCOs. The core VCOs are coupled by the current source transistors of the AI and in this way, no extra coupling devices are used. The proposed AI-based QVCO is designed and simulated in TSMC [Formula: see text] CMOS technology by Cadence. Post-layout simulation results show that the proposed QVCO occupies only [Formula: see text] of chip area, and has a phase noise of −106.6[Formula: see text]dBc/Hz at 1[Formula: see text]MHz offset from the 0.7[Formula: see text]GHz oscillation frequency. A wide frequency tuning range (FTR) of 68% (i.e., 0.68–1.4[Formula: see text]GHz) is achieved by adjusting the tuning voltage of the active inductor (AI), and the total power consumption is 7.2[Formula: see text]mW. Coarse and fine frequency tuning of the QVCO is available by changing the emulated inductors and varactors, respectively, that gives [Formula: see text] of 1100 and 34[Formula: see text]MHz/V, respectively.