Analysis of Device Mismatches Effect on the Performance of UWB Receiver Front-End in Wireless Body Area Network Sensor Nodes

Abstract

Today it is important to manufacture high quality integrated circuits which are insensitive to device mismatches. This paper presents an analysis of MOSFET transistors mismatches effect on the performance of UWB receiver front-end which constitute the most important part of Wireless Body Area Network sensor node. The receiver is based on Balun LNA with 25% fully differential double-balanced passive mixer. A PMOS and NMOS transistors mismatch models were proposed to determine LNA output offset voltage and mixer offset current respectively. The analysis result suggests that, to minimize NMOS current mismatch, and thus reducing second-order inter modulation distortion, the overdrive voltage  must be maximized. A Monte Carlo and harmonic balance simulations were performed using 0.18µm CMOS process to evaluate the impact of mismatch as well as V_th mismatch on the receiver gain and IIP2. Simulation results show that IIP2 of the receiver is less sensitive to mixer NMOS mismatch but receiver gain is more sensitive. The receiver IIP2 confidence interval in case of NMOS  mismatch is [24.674, 24.77]dBm and in case of NMOS V_th mismatch is [24.659, 24.857]dBm. This show the robustness of the proposed UWB receiver front end. Therefore the proposed circuit meets the requirement of UWB system perfectly which make it suitable for WBAN applications.