Mitigating Field Enhancement in Metasurfaces and Metamaterials for High Power Microwave Applications
Metasurfaces and metamaterials have been explored extensively in recent years for their ability to enable a variety of innovative microwave devices. However, because their exotic properties often arise from resonant structures, the large field enhancements under high power microwave illumination can lead to dielectric breakdown and damage to the device. In order to develop metasurfaces and metamaterials capable of being utilized in high power microwave applications, this paper investigates techniques for reducing the maximum field enhancement factor (MFEF) in several types of structures from the literature. Starting with a simple Sievenpiper metasurface, this paper evaluates the dependence of MFEF on the structure design parameters. For more complex metasurface geometries, a genetic algorithm is demonstrated that can evolve structures that have minimal MFEF. In addition, negative index and low index metamaterials are evaluated for field enhancement. By optimizing for low loss and by operating in the resonance tails, metamaterials with low MFEF can be realized for high power applications. To illustrate this, a quad beam focusing metamaterial lens is presented with an MFEF less than 5 over the entire operating band.
IEEE Transactions on Antennas and Propagation