An analysis of mutual coupling on doubly curved convex surfaces

We first discuss the problem of finding geodesics on doubly curved surfaces. When the geodesics are found, a hybrid method of UTD and MoM is used to calculate the mutual coupling between circular apertures arbitrarily positioned on a doubly curved surface. Thus, a full 3D analysis has been performed. To represent the aperture fields, a single mode approximation is used. In order to verify the theoretical results, a general paraboloid of revolution (GPOR), with circular waveguide fed apertures, was built at Ericsson Microwave Systems AB, Molndal, Sweden. This has given the possibility of experimentally verifying the theoretical model for a general doubly curved surface. To the authors´ knowledge, no such verification is available in the literature. It was found that measured and theoretical results in terms of mutual coupling agree very well. As expected, the mutual coupling results are very dependent on polarisation. In fact, the defining of polarisation directions and the need for polarisation control are important issues for doubly curved conformal array antennas.