A Low-Profile Wideband CP End-Fire Magnetoelectric Antenna Using Dual-Mode Resonances

A low-profile wideband circularly polarized (CP) magnetoelectric (ME) antenna with high-gain and an end-fire radiation beam is proposed in this paper. It consists of a magnetic dipole (M-dipole) and two pairs of printed crossed strips to produce vertically and horizontally polarized E-field components, respectively. With the appropriate combination, the proposed ME antenna exhibits an inherent 90 degrees-phase difference at endfire for these two field components. CP end-fire radiation, therefore, can be achieved. Two techniques using the L-probe coupled feeding structure to excite the M-dipole operating at both the basic (0.5 lambda-) and higher (1.5 lambda-) modes for the dual-mode resonances and using two pairs of printed strips with different dimensions for the dual-frequency resonances are introduced to realize the wideband operation. The measurement results show that the wide impedance bandwidth (IMBW) of 2.40-4.24 GHz (1.84 GHz, 55.4%) and 3 dB axial-ratio bandwidth (ARBW) of 2.36-3.86 GHz (1.5 GHz, 48.2%) are achieved. In addition, the stable end-fire radiation patterns with a peak gain of 7.57 dBi are observed over the operating band. The bandwidth for 3 dB gain variation is 2.34-3.97 GHz. Hence, the proposed antenna with its main beam in parallel with the substrate shows the potential for some point-to-point communications such as the radio-frequency identification (RFID) system.