CMOS Differential Ring Oscillators: Review of the Performance of CMOS ROs in Communication Systems

Abstract

The integrated differential ring oscillator (DRO) in complementary metal oxide semiconductor (CMOS) technology has been used in numerous products for a long time. Its presence has been extended to high-speed clock and data recovery (CDR) circuits for optical communication, analog and digitally controlled oscillators, frequency dividers of high-frequency synthesizers, clock generators of digital circuits, analog-to-digital converters (ADCs), and many more applications [1]-[5]. Implementations of these ring oscillators are seen in emerging technologies such as ultrawideband (UWB) and radio frequency identification (RFID) as well as wireless sensor networks (WSNs) and short-range communication devices [6], [7]. The DRO is a good design choice for integrated circuit (IC)designers because of its continued use in different bulk CMOS technologies. This article presents implementation techniques and performance comparisons of the DRO as a CMOS voltage-controlled oscillator (VCO) in low radio frequency (RF) bands, along with presentation and discussion of a number of circuit approaches.