Testing of Flexible Metamaterial RF Filters Implemented through Micromachining LCP Substrates

Metamaterials have a wide range of potential uses in areas such as optics, transmission lines, and RF design. The simplest metamaterial structures are Split-Ring Resonators (SRR) and Complementary Split-Ring Resonators (CSSR). Through the combination of various forms of these structures, different applications in the areas previously stated can be achieved. Under this investigation, a metamaterials transmission line was realized through micromachining a Liquid Crystal Polymer (LCP) substrate. Not only does LCP possess useful RF properties, it is flexible and micromachinable. This transmission line consisted of several CSSRs in series, which performed as a high-order, high-frequency filter. This structure was unique to most metamaterial structures because LCP is a flexible substrate. Prototype filters were fabricated and evaluated. One test involved flexing the devices over various radii of PVC pipe sections to evaluate the effects of flexing the substrate on the filter's performance. The filter properties were shown to maintain approximately the same frequency and roll-off while being bent over the various radii of curvature. Therefore, arrays of these filters could be fabricated with planar processes and attached to non-planar surfaces, such as airfoils, for uses such as radar cloaking.