Compact Directive On-body UWB Antenna for Wireless Capsule Endoscopy Systems

摘要

Wireless Capsule Endoscopy (WCE) application is a challenging topic inciting a good designed receiving antenna, in order to improve the wireless communication with the capsule endoscope. In this context, the paper introduces a compact antenna operating at the low Ultra-Wide band (UWB) 3.75-4.25 GHz, defined in IEEE 802.15.6 standard for BAN (Body Area Networks) applications. The proposed UWB antenna is targeted to on-body use, to serve of receiving antenna, and has a total size of $30 imes 25 imes 1.6$ mm3. In free space, the antenna has a directional radiation pattern with 9 dB measured gain at 4 GHz center frequency, and it covers the - 10 dB impedance bandwidth of 3.75-4.45 GHz range. Then, the antenna was placed at different distances next to a voxel model, to consider the human body effect on the antenna characteristics. Besides, measurements were carried out on a male person by taking into account two antenna positions, named “Parallel” and “perpendicular”, on the human body surface. The proposed antenna does not present any risk on the person safety. The maximum SAR value is estimated of 0.095 W/kg for the different positions, in compliance with IEEE C95.3 standard on 10 g average tissue. The on-body matching studies were followed by in-body investigations, by analyzing the power consumption by means of power-field probes, from skin to the Small Intestine (SI) layers in voxel model. All the conducted studies conclude that the antenna, in both positions, is a good receiving antenna suitable for Wireless Capsule Endoscopy communications.