A Small UHF Label Antenna for Embedding in Metallic Objects

Abstract

The drill strings used in oil drilling have a limited life in that a section may be used 400 times or until the diameter reduces 20 mm from wear against the surrounding rock. RFID labelling the pieces of the drill string allows the recording of usage and location data at a particular depth of the drill head, aiding in the planning of a rotation scheme, so that any one particular section is not constantly at a position of high stress. Such RFID tags embedded in metal may be used for other metal asset tracking applications. Previous work [1,2] has been performed at HF frequencies but there is increasing interest in UHF frequencies as the frequency of choice for object tracking [2]. In this paper it is shown that suitable antennas can be made from capacitor structures sensitive to electric fields perpendicular to the metal surface. An HFSS simulation environment for antenna applications was used to relate simulated results to known empirical results from both publications and their own experiments. Both the simulations and the measurements indicated that the antenna concept is suited to the application.