Design of a Miniaturized Ingestible Antenna With Complex Input Impedance for Biotelemetry Applications

Abstract

In this work, a miniaturized ingestible antenna with differentially-fed configuration is presented. The proposed antenna structure is patterned on a FR4 substrate with a radius of 5 mm. With the use of the inductive circular loop feed and a folded radiating dipole structure, the antenna can be well miniaturized, and maintains a stable complex input impedance which fully covers the 2.45 GHz ISM band. The equivalent circuit model and analysis on the key parameters are also conducted in detail. And the measurement is finally realized by properly assembling the antenna inside the capsule-shaped case for mimicking the practical scenario. The results of both simulation and measurement show smooth changes of the antenna impedance around the ISM band, which indicates a stable impedance matching performance. The proposed antenna geometry can be easily fabricated and tuned for directly matching to the specific transceiver without additional matching circuit, which can be a good candidate for the miniaturized ingestible devices with space constraints.