Analysis of device mismatches effect on the performance of UWB-Ring VCO

This paper presents analysis of device mismatches effects on fully differential UWB ring VCO dedicated to Wireless Body Area Network sensor node. Mismatches are the most critical imperfection in high precision differential UWB ring VCO circuit. In reality MOS devices exhibit threshold voltage (Vth) mismatch. Simulated in a .18μm CMOS process, the results show that the voltage threshold mismatch affects relative accuracy for the frequency by 3.43%, for the output magnitude by 9.9% and for the phase noise by 6.9% as a worse case. This mismatch can increase the startup time considerably which leads to performance degradation. In order to produce precise and stable frequency from the UWB-Ring VCO designers need to minimize transistors dimensions' mismatch, gate-source voltage and threshold voltage variation.