Abstract
The orientation of a capsule changes randomly when it traverses in the gastrointestinal tract, which might result in communication failures between the capsule and the external equipment. This is partially because the antenna in capsule is directive or has nulls on its radiation pattern, which are difficult to avoid, especially for the electrically small capsule type of antennas. In this paper, a conformal capsule antenna with reconfigurable radiation pattern is proposed as a proof of concept to overcome this dilemma. By employing two MOSFETs, the proposed capsule antenna can operate under four states. The desired frequency range around 2.45 GHz is covered by all the four states, while the radiation pattern changes with the operating state; hence, an omnidirectional radiation pattern with no nulls can be synthesized. Besides, an additional impedance bandwidth in low gigahertz range occurs under two operating states. Given the various functions, the antenna maintains simple and compact and is conformal to the inner wall of the capsule shell. Operating mechanism of the proposed capsule antenna is discussed in detail, and prototypes are fabricated to validate the design.