A Circularly Polarized Cylindrical Cavity backed Substrate Integrated Waveguide Antenna for Millimeter wave Applications

In this paper, a circularly polarized cylindrical cavity backed substrate integrated waveguide resonator for millimeter wave application is proposed. A feeding structure is designed and integrated on the same layer of circular cavity backed antenna. The feeding structure comprises of orthogonal feed, using substrate integrated waveguide technology. A circular ring slot is etched on the top plane of the cavity to radiate antenna in broadside direction. Two symmetrical rectangular slots are placed diagonally on the top metal plane of cavity and position of feed is optimized which improves the impedance matching. The dimensions of the proposed antenna with feeding structure is 3.55 lambda x 3.56 lambda x 0.19 lambda, where lambda is the guided wavelength. The antenna achieves a peak gain of 5.85dBi, peak directivity of 6.23dBi, radiation efficiency of 94.1% and an axial ratio of 120MHz bandwidth below 3dB.The proposed antenna maintains a low profile and is compatible with planar structures. A comparative study of microstrip feeding and substrate integrated waveguide feeding is done and results are plotted in Ansys high frequency structure simulator. The performance of antenna is measured in terms of reflection coefficient, radiation pattern, front to back ratio, gain and directivity. The proposed antenna provides high gain, circular polarization and high frontto-back ratio at the high frequency thus, it is suitable for various millimeter wave applications.