A Differentially Fed Antenna With Complex Impedance for Ingestible Wireless Capsules

A differentially fed capsule antenna with a complex input impedance is proposed in this letter. The antenna maintains a circular flat shape with a diameter of 10 mm and operates at the desired band of the RF chip (2.4–2.525 GHz). With the utilization of an inductively coupled fed structure and dual meandered radiators, a –10 dB impedance bandwidth of 10.2% is achieved. In the meantime, the high impedance tunability can be realized by adjusting corresponding structural parameters. The operating mechanisms and parametric studies are explored in detail to investigate the characteristic of the proposed structure. The capsule antenna prototype is fabricated, assembled, and measured according to the practical scenario. The measured results highly agree with the simulation ones, which indicate that the proposed antenna could be a good candidate for wireless capsule endoscopy applications.