The DTMOS based UHF RF to DC Conversion

The RF rectifier is a key component in wireless sensor networks and RFID applications. It converts the input RF signal into DC voltage to power up a system. Low settling time is important for efficiently acquiring DC voltage in an RFID system. The settling time is defined as the time required by the rectifier to reach the maximum stable DC voltage for a given load condition. The main focus of this work is to reduce the settling time required by the rectifier. Settling time is one of the performance limitations of a rectifier due to the threshold voltage of the transistor. In this work, we are proposing the use of DTMOS (Dynamic Threshold MOSFET) architecture in the design of RF to DC rectifier. In DTMOS, gate and body are tied together, which dynamically alters the threshold voltage to suit the operating state of the circuit. We implemented the DTMOS architecture in a self Vth cancellation (SVC) scheme based rectifier. Settling time is considered as the performance parameter. Results demonstrate that settling time of the modified SVC rectifier is less than 50%, as compared to that of the conventional BTMOS(body terminal tied to source terminal) based SVC rectifier structure. The rectifiers have been implemented using the 180nm standard CMOS technology and the simulations were performed using spectre simulator.