Reconfigurable flexible inverted-F antenna for wireless capsule endoscopy

Abstract

In this study, a reconfigurable conformal antenna suitable for Wireless Capsule Endoscopy (WCE) is proposed. The proposed antenna achieves reconfigurable omnidirectional radiation regardless of its orientation and position inside the Gastrointestinal (GI) tract. The reconfigurable omnidirectional radiation pattern is obtained using two PIN diodes, which provide four stats, and with the aid of a microcontroller inside the capsule, a decision can be made to decide which state gives the higher gain simultaneously. The capsule antenna is designed as a meandered Inverted-F antenna (IFA) operating at 433 MHz on Rogers 5880 laminate and attains a volume of 30 × 15 × 0.254 mm3 in planar form, and the conformal form fits inside a capsule with a length of 26 mm and a diameter of 12 mm. The proposed capsule antenna is simulated in muscle, stomach, and colon homogenous boxes in different orientations. It achieves a realized gain of −33.64 dBi inside a colon cube of length 100 mm. The proposed antenna is then tested inside a voxel model. Moreover, the robustness of the communication system containing the capsule antenna is satisfied. When the maximum input power (11 mW) is calculated from the Specific Absorption Ratio (SAR) in the colon, the link Carrier-to-Noise ratio (C/No) is higher than the required C/No for 4 Mbps data rate and at distances up to 3 m. The proposed capsule antenna’s performance is validated by fabrication and measuring it inside a muscle phantom.