This invention relates to a novel architecture of a passive RFID (Radio-Frequency Identification) tag which is highly miniature in size, capable of metal mounting and suitable for global operation in the entire UHF band (860 MHz to 960 MHz) without necessity of territory specific optimization of the antenna design layout.This invention envisages a novel antenna design that consists of a circular or rectangular microstrip antenna of ultra-small size (−λ/50), which is suitably loaded in shunt by lumped components resistor (R), inductor (L) and capacitor (C). The feed point, feed layout and the loading values are so optimized that a single tag will display optimum performance in all the territories.This invention relates to a method of encapsulating the passive tag with radio transparent materials like Radel® R, as well as a metal backplane so that the encapsulated tag can withstand autoclaving while maintaining the required performance.