Design of a three-stage ring-type voltage-controlled oscillator with a wide tuning range by controlling the current level in an embedded delay cell

This paper presents a new design for a three-stage voltage-controlled differential ring oscillator embedded with a delay cell for a wide tuning range from 59 MHz to 2.96 GHz by adjusting the current level in the delay cell. The ring oscillator consists of a voltage-to-current converter, coder circuit, three-stage ring with delay cells, and current monitoring circuit to extend the tuning range of the proposed voltage-controlled oscillator. Each functional block has been designed for a minimum power consumption using the TSMC 0.18 mu m CMOS technology. We simulate the performances of the proposed voltage-controlled oscillator in terms of phase noise, power consumption, tuning range, and gain. Our simulation results show that the proposed oscillator has the linear frequency-voltage characteristics over a wide tuning range. At each tuning range (mode), the calculated phase noise of the proposed ring oscillator at each tuning range (mode) was -87, -85, -81, and -79 dBc/Hz at a 1 MHz offset from the center frequency. The DC power of the proposed voltage-controlled oscillator consumed 0.86-3 mW under a 1.8 V supply voltage. (C) 2013 Elsevier Ltd. All rights reserved.