Application of the Array Scanning Method in Periodic Structures with Large Periods

Abstract

The problem of aperiodic excitation of periodic structures with periods larger than a half-wavelength is revisited. A large number of antennas and other electromagnetic wave propagation problems fall within this category. Because of overlapping branch cuts, the conventional path deformation techniques employed in application of the array scanning method for this type of problem fail when the period is larger than a half-wavelength. A new method based on the subdivision of the integration path and using the double exponential quadrature formula is introduced to alleviate this problem and apply the array scanning method to structures with an arbitrary spatial period. To demonstrate the application of the new method and to validate the results, reflection and transmission coefficients of a frequency selective surface excited by a single electric dipole are calculated. Near fields of the frequency selective surface with aperiodic excitation are obtained and compared with those of a commercial electromagnetic simulator. The proposed method, similar to the path deformation technique, which is applicable to small periods, shows considerable advantage in terms of computational time and memory requirement.