The features of both the tag and reader in a Radio Frequency Identification (RFID) system are preferred collectively for special vehicle applications such as defense systems and traffic enforcement. This work presents a novel multifunctional antenna performing both tag and reader operations in a single unit by altering the switching status. An asymmetrical coplanar waveguide (CPW) with a meander-shaped dipole antenna is designed for a circular polarization (CP) radiation. The reader antenna is fed by a 50 ohm microstrip line, while a rectangular loop is used as a matching network for tag excitation. PIN diodes are incorporated at both feeding lines for switching between the two operations. The antenna exhibits an axial ratio bandwidth (ARBW) of (0.83–0.98) GHz for the reader function and from (0.854–0.984) GHz for the tag function. The 3 dB beamwidth and axial ratio beamwidth (ARbw) attain 135° and 80°, respectively, while performing as a reader, and correspondingly 135° and 55°, respectively, while performing as a tag. The maximum measured reading range is 6.2 m in the H-plane. The CP characteristics of the proposed design are analyzed using field component transformation and found to be in close agreement with the simulation response. A prototype of the proposed structure is fabricated, and the experimental results align with the simulated results.
Mazumder et al. (Sun,) studied this question.