This thesis is about split-ring resonators and their application as biosensors. Split ring resonators are a special resonator type which consists of a metallic loop etched on a dielectric substrate. They provide a resonant frequency which is determined by the electromagnetic parameters of the substrate and the geometry of the metallic loop. For sensor applications, the metallic surface will be bio-functionalized and if molecules are attaching onto the resonator surface the resonant frequency of the resonator is changed proportional to the load of biomolecules. The aim of the thesis is to optimize the design of different split-ring resonators to get a high-quality biosensor. The operating frequency of the investigated split-ring resonators is between 1.5 and 2.5GHz.