Full-wave analysis of cavity-backed and probe-fed microstrip patch arrays by a hybrid mode-matching generalized scattering matrix and finite-element method

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Abstract
A full-wave method to analyze probe-fed infinite phased arrays of arbitrarily shaped microstrip patches residing in a cavity is proposed. The method is based on a combination of the mode matching and finite-element methods (MM-FEM) and provides a rigorous characterization of the coaxial feed. The radiated field to the half space is expressed as a Floquet's harmonic expansion reducing the analysis to a single elementary cell of the periodic antenna. The unit cell is analyzed as an open-ended succession of homogeneous waveguides of diverse cross sections. Each transition between waveguides is solved by a hybrid MM-FEM procedure to obtain its generalized scattering matrix (GSM). Finally, the GSM of the structure, which characterizes the array, is obtained from the individual GSMs by a cascading process. The method is also extended to the analysis of conventional probe-fed microstrip arrays by using the waveguide simulator model. Several prototypes, implemented and measured in a waveguide simulator, have been analyzed to prove the validity and efficiency of the proposed method.