Planar Endfire Circularly Polarized Antenna for Low Profile Handheld RFID Reader

The radiation behavior of reader antenna is critical for a compact, low-profile handheld RFID reader. Comparing with the conventional technique, this paper gives a basic review of a novel design approach to planar endfire circularly polarized (CP) antenna, which radiates its main beam in parallel with the printed substrate. To this end, a planar magnetic dipole with vertically polarized component is introduced, while the horizontally polarized counterpart can be realized by a loop or an electric dipole antenna printed on the same substrate. Based on this concept, the combinations with different performances are presented and a summary of some recent advances is given. After that, the mathematical analysis based on parallel complementary dipoles is demonstrated, and the conceptual design configuration is provided accordingly. Finally, an experimental example with low profile and endfire CP characteristic is presented. Experimental validation shows that this new class of planar endfire CP antenna can be a promising alternative for a low-profile handheld RFID reader.