IMPROVING THE PERFORMANCE OF LC VCO USING THRESHOLD VOLTAGE CONTROL TECHNIQUES

Abstract

As the electronics industry is evolving towards low power applications, along with extensive research in the concept of Internet of Things (JoT), the demand for low power and high data rate wireless modules is increasing radically. Due to the technology limitations on integration of passive components and their quality, it has been a challenging issue to design a single chip radio. Among several blocks in a transceiver, voltage controlled oscillator's (VCO) performance is very important to meet strict requirement of wireless standards. The prospect of integrating monolithic with multi-standards and multi-bands transceivers has been increased with the advancement in MOS fabrication technology. To implement and design low-cost integrated transceiver systems, CMOS technology turn out to be a pretty attractive process choice. Hence, it is undeniably a great area that can be explored to improve the standards of wireless communication. CMOS based LC oscillators at high frequencies need to be explored so as to achieve single chip transceivers at low cost with high reliability. In this report, I present a broad review of CMOS based LC oscillators followed by various performance parameters like phase noise, tuning range etc. Then various optimization techniques, focusing mostly on cross coupled configuration, are discussed followed by the several earlier publications (work) done in this area. A novel-circuit technique to enhance threshold voltage using substrate is presented by shorting drain and substrate unlike shorting source and substrate as in all previous works. Also, by using positive voltage at substrate contact, the performance of oscillator is analyzed. Various topologies of LC oscillators were compared presenting their respective merits and demerits. A detailed analysis on this Vh-enhanced MOSFET is presented followed by its effect on complementary cross coupled oscillator. Tuning range of about 34% is achieved in enhanced cases in contrast to just 10% is traditional case. An optimised oscillator with tuning range of 38% with FOMt of 199.8 is designed and compared with earlier publications.