Perturbation formulation for nearly-degenerate microstrip dipole eigenmodes

System eigenmodes of N-coupled, nearly degenerate microstrip dipoles are investigated through a singularity-expansion-based perturbation formulation. This method is based on integral-operator techniques employing rigorous dyadic Green´s functions for the layered microstrip environment. Mutual coupling between microstrip antennas has been previously accounted for by full-wave formulations, and similar full-wave methods provide a comparison to this approximate formulation. System eigenmodes are found to form symmetry states about the isolated dipole eigenmode. The special case of N=2 coupled dipoles results in symmetric/antisymmetric coupling, which can be separated analytically.<>