A 3-D Printed Lightweight Miniaturized Dual-Band Dual-Polarized Feed Module for Advanced Millimeter-Wave and Microwave Shared-Aperture Wireless Backhaul System Applications

A 3-D-printed lightweight miniaturized dual-band dual-polarized feed module of wireless backhaul systems consisting of a dual-band air-filled waveguide orthomode transducer (OMT) and a shared-aperture conical horn radiator is investigated. The OMT operating in both Ku- and E-bands with a large frequency ratio is realized by combining the turnstile-junction-type and Bøifot-junction-type OMTs sharing a common-mode-composite coaxial port. A design method of the dual-band OMT considering the requirement for a self-supporting geometry in metallic 3-D printing is presented, so that its compact configuration that is difficult to fabricate by traditional milling technology can be fulfilled conveniently in a whole piece with the use of commercial 3-D printing facilities. A millimeter-wave horn with a small radiation aperture is embedded into a larger aperture of a microwave horn. A proper longitudinal offset between them is introduced to guarantee promising radiation characteristics of the shared-aperture scheme in the two bands. By connecting the OMT with the radiator, the proposed dual-band dual-polarized feed module with a weight of only 100 g is manufactured and measured. Excellent performance, involving the wide bandwidths of 46.7% and 31.2% at microwave and millimeter-wave frequencies, a high isolation of almost larger than 40 dB, a high radiation efficiency of about 90%, and stable dual-polarized radiation patterns with low cross polarizations, is confirmed experimentally. Benefitted from the geometric and operating merits, the feed module would be attractive for applications in advanced millimeter-wave and microwave shared-aperture wireless backhaul systems.