Backside-Radiation Suppression of Circularly-Polarized Quadruple Inverted-F Antennas

A circularly-polarized (CP) quadruple inverted-F antenna (QIFA) with backside-radiation suppression is proposed in this paper. Firstly, the results of characteristic mode analysis (CMA) demonstrate that this QIFA actually works in two orthogonal modes, each of which is equivalent as a couple of parallel magneto-electric (ME) dipoles. Secondly, it’s discovered that the bending direction and bending degree of radiators can affect the beam direction and front-to-back ratio (FTBR) of the antenna respectively. Thirdly, by properly adjusting the height of the short-circuit strip introduced in the final antenna design, the QIFA obtains the optimal impedance matching. Ultimately, the size of QIFA designed in this subject is 14.7 × 14.7 × 10.6 mm
³
, and the FTBR can reach 11.44 dB at the zenith of measured realized gain.