Spatial-Filtering Microwave Devices Using Metallic Anisotropic Grids Over Ground

In this review article the authors examine interesting resonance phenomena that result due to peculiar dispersion characteristics of continuous (unloaded) anisotropic grids along with corresponding applications. The phase space (k-space) of these metallic grids at resonant frequencies is characterized by isofrequency dispersion contours that have rectangular and hyperbolic shapes. As a result, energy propagation takes place in specified directions within the periodic structures, an effect called 'self-collimation'. Novel spatial-filtering and wave-guiding devices could be implemented using these properties. Two such spatial-filtering devices using different configurations of anisotropic metallic grids will be reviewed: a microstrip harmonic splitter that separates 3 GHz from its 6 GHz harmonic and a highly selective 5.8/6.2 GHz microstrip diplexer