Rigorous Analysis of Thick Microstrip Antennas and Wire Antennas Embedded in aSubstrate

摘要

An efficient and rigorous method for the analysis of electrically thickrectangular microstrip antennas and wire antennas with a dielectric cover is presented. The method of moments is used in combination with the exact spectral domain Green's function in order to find the unknown currents on the antenna. The microstrip antenna is fed by a coaxial cable. A proper model of the feeding coaxial structure is used. In addition, a special attachment mode was applied to ensure continuity of current at the patch-coax transition. The efficiency of the method of moments is improved by using the so called source term extraction technique, where a great part of the infinite integrals involved with the method of moment formulation is calculated analytically. Computation time can be saved by selecting a set of basis functions that describes the current distribution on the patch and probe in an accurate way using only a few terms of this set. Thick microstrip antennas have broadband characteristics. However, a proper match to 50 Ohms is often difficult. This matching problem can be avoided by using a slightly different excitation structure. The patch is now electromagnetically coupled to the feeding probe. A bandwidth of more than 40 can easily be obtained for this type of microstrip antenna. The price to be paid is a degradation of the radiation characteristics.