| Microstrip and slot antennas with novel feeds suitable for monolithic microwave integrated circuit (MMIC) applications are investigated both experimentally and theoretically, using the cavity model as well as a full-wave analysis. The input impedance of a microstrip antenna fed by an arbitrarily oriented slot in the ground plane is computed using the cavity model theory. This study is extended to the calculation of the feed locus for circular polarization operation. Simple design formulas are obtained for CP electromagnetically excited microstrip antennas.The coplanar waveguide-fed microstrip antenna is then analyzed using the full-wave analysis. Boundary conditions are enforced on a portion of the coplanar waveguide as well as on the patch antenna. The integral equations are solved by applying the Galerkin method of moments in the spectral domain. The reflection coefficient on the coplanar waveguide is calculated for several frequencies and compared with the experimental results.The reflection coefficient of a slot element fed by a semi-infinite microstrip line is calculated by the method of moments in conjunction with multiple scattering analysis. The reflection coefficient of the open microstrip line, and the transmission and reflection coefficients of the slot, fed by the infinite microstrip line, are first calculated. Then, the input impedance of the microstrip line-fed slot is obtained for an arbitrary stub length. |
