Multi-antenna systems for wireless capsule endoscopy

Abstract

With the advent of new medical diagnostic techniques, the wireless capsule endoscopy has been emerged as more convenient than traditional endoscopy for the digestive tract monitoring. The typical use of wireless capsule endoscopy is to diagnose intricate areas of the small intestine. However, the current wireless capsule endoscopy systems suffer from low data rate which cannot meet the requirement for transmitting high resolution images. The poor quality of received images can bring ambiguities during the diagnosis.

In this master thesis, the MIMO antennas employing polarization diversity is proposed for a wireless capsule endoscopy system at 433 MHz ISM band. The polarization diversity between in-body capsule and on-body receiver is considered to be main responsible for increasing the data rate. Two conformal dual polarized loop antennas are designed for the in-body capsule transmitter, while two planar dual polarized printed monopole antennas are designed for the on-body receiver. The on-body receiving antennas are designed using the flat and flexible substrates to study their impacts on the size, bandwidth and efficiency.

The simulated refection coefficients of proposed in-body MIMO antennas are less than -10 dB over the required bandwidth (400-500 MHz). The mutual coupling between them is found to be less than -20 dB over a wide range of frequencies. The on-body MIMO antennas are measured on the liquid phantom to validate the simulated results. The simulated and measured results showed good agreement of matching in terms of reflection coefficients and mutual coupling. Moreover, the size of on-body antennas found to be compact by using the high permittivity substrate. The on-body MIMO antennas are also measured on the human body. It is observed that the lossy properties of skin significantly reduce the mutual coupling between the MIMO antennas.