Ultra low power LNA design for wireless sensor networks

Abstract

Wireless Sensor Network (WSN), which was originally proposed for military applications such as battlefield surveillance, has been gaining more and more focus from academic because of its vast potential in civilian applications, such as environment, habitat monitoring, home automation, healthcare application, etc. The fast development in wireless sensor networks during recent years has driven a huge demand for ultra-low power low cost ICs. The ultra-low power restriction results from the fact that each sensor node needs to sustain months or years of time with only one single battery, while the low cost requirement is a reflection of massive number of sensor nodes needed to form one sensor network. As the most power consuming part in a receiver, radio frequency (RF) front-end is essential in low power design and it determines the total power consumption to a large extent. In this thesis, two basic amplification stages, common source (CS) and common gate (CG), are analyzed and compared from the input matching, gain, noise and linearity aspects, all of which are important parameters for Low Noise Amplifier (LNA) design. The comparison is focusing on the ultra-low power domain and a summary is thus yielded. From the summary, common gate topology gives better noise performance than common source topology does in the ultra-low current regime, which is contradictory to conventional knowledge. Finally, the design principles introduced in the summary are kept as guideline in ultra-low power LNA design. Two implementations, one CS based LNA design and one CG based LNA design, demonstrate and verify the different characteristics between common source and common gate in ultra-low current domain.