Modified design of sub-reflector with dielectric cylindrical keeper to enhance gain in axially displaced ellipse reflector with dual polarization

Abstract The study introduces a novel dual-reflector antenna featuring a modified sub-reflector design aimed at improving aperture efficiency. A cylindrical-shaped keeper is introduced to enhance the performance of the sub-reflector. The dual-reflector configuration comprises a main parabolic reflector and a modified sub-reflector, with diameters of 16.5 λ and 2.2 λ , respectively, operating at 5.5 GHz. The antenna demonstrates a bandwidth (BW) of approximately 25.4% (4800–6200 MHz). Experimental measurements indicate favorable characteristics, including low cross-polarization levels (<−25 dB), minimal back lobe levels ( F / B > 30 dB), high isolation between ports (>38 dB), and VSWRs less than 1.5:1 for both port1 and port2. The antenna exhibits an efficiency of around 58% and achieves a measured peak gain of approximately 32 dBi within the operating BW.