On the Tunability of Apollonian-Loaded Split Ring Resonator Topologies

The demand for more flexible RF systems is being driven by the opening up of additional spectrum to commercial interest and the ability to operate in contested, congested, and constrained environments. These demand signals drive interest in antenna technology advancements, as they are one of the most notable limiting factors in the RF chain. This is even more true in the era of software defined radios. At the forefront of many of these antenna technology advancements are metamaterials and metasurfaces, which are patterned structures that exhibit unusual electromagnetic properties in a bulk context near the point of resonance, such as negative permeability and permittivity. The traditional loading mechanism for these structures consists of the addition of concentric split rings. This approach has some limitations, however. A uniquely flexible circle-packing fractal based loading structure based on the Apollonian gasket is discussed alongside the instantiating methodology. Multiple prototypes based on the structure and compared to the traditional unloaded Split Ring-Resonator (SRR) case to examine a subset of the tradespace of the loading mechanisms. This paper examines 6 different instantiations of the Apollonian-Loaded Split Ring Resonator (ALSRR) to demonstrate a portion of the potential frequency tradespaces offered by the flexible technology and provides a comparison against the unloaded split ring resonator.