Resonance-cone focusing in a compensating bilayer of continuous hyperbolic microstrip grids

We propose a periodic structure synthesized by arranging continuous transmission-line segments in a two-dimensional planar grid over a ground plane. The periodic grid exhibits hyperbolic spatial dispersion characteristics, leading to the formation of highly directive beams called “resonance cones.” Simulations and experiments at 10GHz show negative refraction and frequency-dependent spatial focusing of the resonance cones, when two such grids with compensating phase properties are interfaced to form a bilayer. The proposed structures are deprived of loading elements or vias, thus leading to ease of fabrication and scalability with frequency for applications, such as spatial filters, multiplexers, and demultiplexers.