Orthomode Transducers With Folded Double-Symmetry Junctions for Broadband and Compact Antenna Feeds

Orthomode transducers (OMTs) using folded six-port waveguide junctions are presented for obtaining the maximum compactness in antenna feeds with very wide performance. The proposed junctions are based on the well-known turnstile and Bøifot configurations, having two symmetry planes for keeping the isolation between orthogonal polarizations and the control of higher order modes. The folded arms provide a combined effect: good matching with very significant size reduction, especially in the transversal plane, reducing mass in satellite systems and allowing feeding eventual dense horn antenna arrays. Two Ku-band OMTs are presented in order to illustrate the advantages of the introduced junctions. The first design covers the band 10.4-18.8 GHz (57.5%) with 24 dB return loss. The second OMT, for the 12.60-18.25 GHz band, has measured return loss better than 29 dB in the design band and insertion loss smaller than 0.11 dB for both polarizations.