Design of ultra wide-band low-band implant antennas for capsule endoscope application

This paper investigated two kinds of design of implant antennas in ultra wide-band (UWB) low-band (3.4-4.8 GHz) for capsule endoscopes. First, two kinds of hemispherical antennas, one has a helical structure and the other has a loop structure, were designed. The hemispherical antennas match for the shape of capsule endoscopes. The reflection coefficient S₁₁ and the directivity of the hemispherical antennas in UWB low-band were investigated in detail. Next, a simplified planar design of the hemispherical loop antenna was proposed for being easy to fabricate. The characteristic of the planar loop antenna in UWB low-band was investigated by both numerical simulation and experiment. In addition to the S₁₁, the path loss of the fabricated planar loop antenna was also measured in a fluid phantom simulating a human body tissue, with a planar unbalance dipole antenna as the receiving antenna. The measured path loss was compared with the simulated result, and good agreement was confirmed between them.