Single-Layered Circularly Polarized Substrate-Integrated Waveguide Horn Antenna Array

In this communication, a circularly polarized (CP) substrate-integrated waveguide horn antenna is proposed and studied. The CP horn antenna is implemented on a single-layer substrate with a thickness of 0.12λ
₀
at the center frequency (1.524 mm) for 24 GHz system applications. It comprises of an integrated phase controlling and power dividing structure, two waveguide antennas, and an antipodal linearly tapered slot antenna. With such a phase controlling and power dividing structure fully integrated inside the horn antenna, two orthogonal electric fields of the equal amplitude with 90° phase difference are achieved at the aperture plane of the horn antenna, thus, yielding an even effective circular polarization in a compact single-layered geometry. The measured results of the prototyped horn antenna exhibit a 5% bandwidth (23.7-24.9 GHz) with an axial ratio below 3 dB and a VSWR below 2. The gain of the antenna is around 8.5 dBi.