Coated Conical Antenna for Automotive Application

In this paper, the use of a cavity-backed Hilbert surface as an efficient slot-like narrowband radiating aperture is suggested, to exploit its own unique electromagnetic characteristics in the context of radio frequency identification (RFID) applications. The proposed meta-slot antenna (MSA) consists of a Hilbert surface window (HSW) made of a cascade of space-filling slot inclusions of order three and backed by a very shallow cavity that contributes to its surface impedance and radiation characteristics. A straight longitudinal microstrip line printed on a thin, low permittivity substrate, whose ground plane includes the HSW, feeds the aperture through distributed electromagnetic coupling. As illustrated by simulation results and measurements, the antenna behaves as a magnetic current sheet over a ground plane, with a highly frequency-selective impedance response and unidirectional radiation pattern.