Series-Fed Microstrip Antenna Lattice With Switched Polarization Utilizing Butler Matrix

A novel concept of a series-fed microstrip antenna array with switched polarization has been proposed. The presented antenna array consists of radiating elements connected together with transmission line sections, creating a lattice with series connections between elements. The lattice is also series fed using slots in the common ground plane. Moreover, it is shown that the proposed antenna array is capable of providing linear, dual-linear, circular, and dual-circular polarization when appropriately fed by a Butler matrix. The theoretical analysis and measurement results of a 4 × 4 microstrip antenna array operating within 5.5-GHz frequency range are presented, showing the potential usefulness of such a structure.