The NBTI Impact on RF Front End in Wireless Sensor Networks

The life time of RF front end in wireless sensor networks (WSN) is so important that it decides whether the whole system can work normally for a long time. Under CMOS technology, negative bias temperature instability (NBTI) is one of the most important factors that decide chips´ life time. Especially with the feature size declining, NBTI effect is becoming more and more serious. Previous works mainly focus on NBTI effect at device level, or NBTI effect in large-scale digital circuits. In this paper, for the WSN node, we study the NBTI impact on the front- end circuits, such as voltage-controlled oscillators (VCO), charge pump (CP), low noise amplifier (LNA), and the whole transceiver system. The circuit level NBTI degeneration models are built for the key modules and the entire transceiver. The mathematical models can be summarized into a conclusion that the phase noise of the VCO will deteriorate, the current mismatch of the CP and the noise figure of the LNA will both increase, and then the sensitivity and adjacent channel selectivity (ACS) will be depressed by NBTI. Under HJTC 0.18-mum technology, our conclusions are proved by the simulation results.