In this paper, we introduce a novel approach for an efficient solution of matrix equations arising in the method of moments (MoM) formulation of electromagnetic scattering problems. This approach is based on the characteristic basis functions (CBFs), which are used to substantially reduce the matrix size because these bases are not bound by the conventional λ/20 domain discretization. As a result, it is possible to electrically solve large problems with much fewer unknowns than those needed when using conventional RWG basis functions. The accuracy and efficiency of the CBFs are demonstrated in a variety of scattering problems to illustrate the versatility of the approach. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 95–100, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10685

A novel fractal DGS has been presented. The DGS lattice is a fractal Sierpinski-carpet type, instead of the rectangular holes used previously so that DGS can be adjusted by the filling factor. Simulation has shown that the proposed fractal DGS can provide more efficient size-reduction of the microstrip structure and better bandgap characteristics than the dumbbell-shaped DGS. A lowpass filter with the fractal DGS is designed and fabricated. Simulation and measurement confirms the validity of the proposed fractal DGS and the LPF configuration and design procedure. The LPF is simple. Additionally, the power-handling capability of low-pass filters can be improved by using the microstrip line with DGS. EFFICIENT ANALYSIS OF A CLASS OF MICROSTRIP ANTENNAS USING THE CHARACTERISTIC BASIS FUNCTION METHOD (CBFM)

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A mixed coupling structure has been proposed for the cross coupling of a comb-line filter. The mixed coupling is a result of the superposition of the electric coupling by an electric probe and the magnetic coupling by a coupling window between nonadjacent comb-line resonators. It is shown that the desired electric coupling can be achieved easily with a tuning screw in the magnetic coupling window region. Moreover, the fabrication errors and the errors due to the adjacent coupling structures can be compensated for easily, and tuning the positions of the transmission zeros is easy with the proposed structure.The validity of the mixed coupling structure was verified by applying it to the cross coupling of a four-pole comb-line bandpass filter. The theoretical and measured responses of the examined filter show good agreement with each other. AN EFFICIENT TECHNIQUE FOR ANALYZING MULTIPLE FREQUENCY-SELECTIVE-SURFACE SCREENS WITH DISSIMILAR PERIODS V. V. S. Prakash and Raj Mittra

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