  Wireless capsule endoscopy (WCE) systems are used to capture images of the
human digestive tract for medical applications. The antenna is one of the most
important components in a WCE system. In this paper, we provide novel small
antenna solutions for a WCE system operating at the 433 MHz ISM band. The
in-body capsule transmitter uses an ultrawideband outer-wall conformal loop
antenna, whereas the on-body receiver uses a printed monopole antenna with a
partial ground plane. A colon-equivalent tissue phantom and CST Gustav voxel
human body model were used for the numerical studies of the capsule antenna.
The simulation results in the colon-tissue phantom were validated through
in-vitro measurements using a liquid phantom. According to the phantom
simulations, the capsule antenna has -10 dB impedance matching from 309 to 1104
MHz. The ultrawideband characteristic enables the capsule antenna to tolerate
the detuning effects due to electronic modules in the capsule and due to the
proximity of various different tissues in gastrointestinal tracts. The on-body
antenna was numerically evaluated on the colon-tissue phantom and the CST
Gustav voxel human body model, followed by in-vitro and ex-vivo measurements
for validation. The on-body antenna exceeds -10 dB impedance matching from 390
MHz to 500 MHz both in simulations and measurements. Finally, this paper
reports numerical and experimental studies of the path loss for the radio link
between an in-body capsule transmitter and an on-body receiver using our
antenna solutions. The path loss both in simulations and measurements is less
than 50 dB for any capsule orientation and location.
