A hybrid physical optics-moment method for large nose radome antennas

This paper presents a hybrid physical optics-moment method (PO-MM) for an efficient but accurate analysis of the radiation from antennas through a large nose-type radome. In this work, the radome is assumed to be a body of revolution (BOR). However, such an assumption is not necessary for the hybrid PO-MM technique. For a BOR structure, the overall problem is reduced to a two dimensional one where the near-zone antenna fields are decomposed into cylindrical modes each of which can then be analyzed separately. For analysis, the radome surface is divided into two sections: a MM-section and a PO-section. The MM-section is near the tip of the radome where it is necessary to treat the fields via the rigorous moment method for BOR. A ray optics or PO approximation is employed to calculate the surface currents on the remaining flatter sections of the radome where tip diffraction effects are not pronounced. The PO equivalent currents on the large PO-section of the radome surface are then incorporated into the MM matrix equations as sources for the final analysis. This hybrid process results in a much smaller size of the matrix equations as compared to using the moment method solution everywhere. Numerical examples are presented to demonstrate that radomes up to 100 wavelengths long can be efficiently handled with no appreciable compromise in accuracy.