a cmos temperature sensor with a voltage - calibrated inaccuracy of < formula formulatype = " inline " > < tex notation = " tex " > $ \ pm $ < / tex > < / formula > 0 . 15 < formula formulatype = " inline " > < tex notation = " tex " > $ ^ { \ circ } $ < / tex > < / formula > c ( 3 < formula formulatype = " inline " > < tex notation = " tex " > $ \ sigma $ < / tex > < / formula > ) .
self - powered wireless temperature sensors exploit rfid technology .