Asymmetric RF tags for ingestible medication compliance capsules

In the paper we present an RF tagging device that can be attached to the outer surface of a standard sized capsule as a cost-effective method of validating medication compliance via electronic detection of an ingested pill inside the digestive tract. We propose two asymmetric RF tagging architectures that circumvent problems associated with signal attenuation inside the human body and poor radiation efficiency of electrically small antennas. The proposed devices are powered by low frequency AC signals to create externally detectable RF bursts in the 915MHz ISM band. Prototype test RFICs were fabricated in 130nm CMOS technology and experimentally validated inside phantom solution to mimic signal propagation inside the human torso.