Integrated Microstrip Antennas and Phased Arrays with Mode-Free Electromagnetic Bandgap Materials for Scan Blindness Elimination

This article discusses the investigation of the use of mode-free electromagnetic bandgap materials, a novel bandgap-antenna structure, to eliminate scan blindness from two-dimensional infinite microstrip phased arrays. This electromagnetic bandgap material is multi-functional; in addition to suppressing both surface and leaky waves, it also radiates to broadside direction as an antenna element within the mode-free bandgap region. A strip line impedance matching network is used to match the bandgap-antenna element's input impedance to 50 , so that the actual bandgap behavior of the structure on the array can be obtained since the strip line does not allow couplings within the matching network. In addition, internal couplings within the unit element of the bandgap-antenna structure, which is composed of four metallic layers, are analyzed in detail; these internal couplings vary with array element's excitation phase or scan angles, therefore, an optimum structure must consider scan behavior as well.