A Multi-Band Cylindrical Conformal Antenna with Low Specific Absorption Rate for Wireless Medical Capsule Endoscopy
A multi-band cylindrical conformal endoscopy antenna with low specific absorption rate (SAR) is designed for endoscope applications, which covers the Industrial, Scientific and Medical bands (ISM 902-928 MHz, 2.4-2.4835 GHz), Medical Device Radio Communications Service band (MedRadio 401-406 MHz) and Wireless Medical Telemetry Service (WMTS 608-614 MHz). The proposed antenna radiates as a symmetrical meanderline structure with a center loaded parasitic opened-loop element, which is bent into the cylindrical conformal shape and wrapped onto the inner wall of the capsule shell. The parasitic opened-loop element excites low frequency resonance at 403 MHz and reduces the SAR values of the antenna. The measured relative bandwidth (|S11| < -10 dB) of the antenna implements 133% ultra-wideband, ranging from 0.35 GHz to 1.76 GHz, and 39% wideband, ranging from 2.01 GHz to 3 GHz. The peak gains and the peak 1 g SAR values at 403 MHz, 611 MHz, 915 MHz, 2.4 GHz are -26.6 dBi, -18.9 dBi, -11.8 dBi, -11.3 dBi, and 83, 82, 94, 153 W/kg, respectively. The results indicate that the proposed antenna complies well with the human safety standards.