Structuring research on conformal antennas - an European collaboration

Kurzfassung

A conformal antenna is defined as an antenna that conforms to a surface whose shape is mainly determined by considerations other than electromagnetic, e.g. aerodynamic or hydrodynamic considerations. This definition should be extended to antennas whose shape is not planar and whose shape is determined with specific electromagnetic reasons like coverage requirements. For example, arrays on cylindrical structures offer a possibility either to create directed beams in arbitrary direction in horizontal plane, or to create an omnidirectional pattern. Spherical arrays have the capability of directing single or multiple beams through a complete hemisphere. Such properties make conformal antennas attractive candidates for future antenna systems where a variety of beam-forming and beam-steering capabilities will be needed, and where the antennas will be integrated in the surfaces of different vehicles or platforms. For example, a modern aircraft has many antennas protruding from the structure, for navigation, various communication systems, instrument landing systems, radar altimeter etc. There can be as many as 40 different antennas (or even more), and integrating these antennas into the aircraft skin is highly desirable. The topic of this paper is the work carried out in Work Package 2.4-3 of the EU network Antenna Centre of Excellence (ACE). From the beginning of the ACE network, the basic objective is to structure better the ongoing research on conformal antennas, dispersed in several European universities or industrial Research centres. In more details, the objectives in this workpackage are: - sum up advantages and critical items for various conformal antennas; - structure continued research in direction of the most useful antenna architectures and geometries; - select benchmarking structures, which should apply to conformal antennas, and test the accuracy of software developed for designing conformal antennas; - help students/PhDs exchange between various European academies and companies. The work is split into 3 topics: 1. Full benchmarking of conformal antennas. 2. Development of “new” hybrid programs. The hybrid SD -UTD program is now able to analyse two classes of conformal arrays: waveguide elements embedded in symmetric multilayer structure (circular-cylindrical or spherical) and embedded in multilayer cylindrical structure with general cross-section (till now the program is tested with cylinders that have elliptical cross-section). The development of the hybrid method for analyzing curved frequency selective has started at the end of 2006. In the proposed new method, the FSS (i.e. the large finite array) is divided into N subarrays, and each subarray is separately analyzed with a rigorous full-wave method. The subarrays have to overlap because the same element in a subarray will have different induced physical or equivalent currents depending on whether it is simulated as an inner element or an edge element, since the edge elements “do not see” the rest of the array environment. The scattered field is calculated as a superposition of the EM field radiated by the inner parts of N subarrays. 3. Development of algorithms for optimizing beam synthesis and beam-steering. In particular, the algorithm properties, when they are applied to conformal arrays, are investigated and compared to planar equivalent cases.