Modeling Microstrip Line Fed Slot Antennas with Arbitrary Shape

A hybrid technique from the reciprocity theorem, method of moments, and triangular basis function is developed to investigate the scattering and radiation properties of microstrip line fed arbitrarily shaped aperture antennas. The electric field distribution on the arbitrarily shaped aperture is expanded by a set of triangular basis functions. S parameters and the unknown magnetic current coefficients are obtained by matching the boundary conditions on the aperture and applying the reciprocity theorem simultaneously. The rectangular, exponentially-tapered, and dumbbell slots are investigated using this technique. Inclination and offset of the aperture are introduced to improve the antenna radiation characteristics. Good agreement between experimental and numerical results has been obtained. Lastly, the advantages and limitations of this technique are discussed.