Design and Simulation of a Quadrifilar Helical Antenna for Wireless Capsule Endoscopy

This paper proposes a miniaturized quadrifilar helical antenna for wireless capsule endoscopy (WCE). The helix arms of the antenna are made with copper material. The helix height, radius, width and pitch angle is 8.85 mm, 3.3 mm, 0.4 mm and 13.7° respectively. The number of helix's turn is 0.5. A polyimide material is selected for modeling the capsule of WCE. The gastrointestinal tract (GI) with muscle phantom is also modeled using CST Microwave Studio (CST) software package. The performance of the antenna is analyzed in free space, capsule and muscle phantom. Resonant frequency of the antenna inside the body phantom is 3.36 GHz with S11 parameter of -10 dB and bandwidth 1 GHz ranging from 2.8 to 3.8 GHz. The antenna shows an omnidirectional radiation pattern and linear polarization when simulated inside the body phantom. The maximum radiation efficiency is -44.26 dB. Moreover, the gains of the antenna in free space, capsule, and the body model are obtained as 4.317 dB, 4.019 dB and -38.57 dB respectively.