Compact orthomode power divider for high-efficiency dual-polarisation rectangular horn antennas

This paper introduces a new waveguide component that combines the electrical functions of an orthomode transducer and of a power divider. Following investigations on the design of dual-polarisation rectangular horn antennas with an edge ratio of 2 for phased array applications, it was found that the combination of two square horn antennas would lead to higher radiation efficiency and compactness than a single rectangular horn antenna. The drawback of such a configuration is that it brings additional complexity to the beam forming network as an additional power divider layer is required. To overcome this limitation, we have investigated the possibility to implement this additional power division section into the orthomode transducer (OMT) design, resulting in a new component referred to as an orthomode power divider. The main advantage of this new component is that it has almost the same size as a normal OMT, while combining the functions of two power dividers and two OMTs in a standard “separate functions” design approach. This paper describes this new component and illustrates its performances through a specific design in Ku-band. Excellent simulation results, including low return loss and high orthogonal polarisation isolation, were obtained over a bandwidth of about 1 GHz for a design center frequency at 12 GHz.