Millimeter-Wave Wideband Circularly Polarized Endfire Planar Magneto-Electric Dipole Antenna Based on Substrate Integrated Waveguide

A wideband circularly polarized (CP) endfire planar magneto-electric dipole antenna based on substrate integrated waveguide (SIW) is proposed for millimeter-wave (mm-wave) applications. The antenna mainly consists of an open-ended rectangular SIW radiating like a magnetic dipole, a parallel electric dipole, and a double-sided parallel-strip line which connects the two dipoles and provides 90° phase difference between them to generate CP radiation. To increase the axial ratio (AR) bandwidth, a pair of triangular slots are etched at the end of the upper and lower broad walls of the SIW, and moreover, a specific bowtie-shaped electric dipole is used instead of the traditional linear one. It has been shown that both the slots and the bowtie-shaped electric dipole can regulate or tune the magnitude of the radiation field of the electric dipole, making it tend to balance with radiation field generated by the magnetic dipole, and hence, leading to a good CP performance. The antenna has a single-layer planar structure, and it shows a −10 dB impedance bandwidth of over 50%, a 3 dB AR bandwidth of 36.6%, and a peak gain of 9.3 dBic.