A radio frequency identification system comprises a radio-frequency identification substrate and an interrogator. In one embodiment, the radio-frequency identification substrate comprises a plurality of radio-frequency identification devices. In one embodiment, a controller on the substrate controls a first one of the plurality of radio-frequency identification devices based on a state of a second one of the plurality of radio-frequency identification devices. In one embodiment, an antenna system includes an S-shaped portion electrically coupled to an integrated circuit along a central portion of the S-shaped portion. Adjusting the parameters of the segments making up the S-shaped portion controls performance characteristics of a radio-frequency identification device.