A Dual-Circular-Polarized Endoscopic Antenna With Wideband Characteristics and Wireless Biotelemetric Link Characterization

Abstract

In this article, the first-ever dual-circular-polarized wideband conformal endoscopic antenna is designed at the medical implant communication service band (402 MHz) and industrial, scientific, and medical bands (915 MHz and 2.4 GHz). The proposed antenna with a small footprint of 8 mm3 (32 mm $\times 10$ mm $\times0.025$ mm) is printed on flexible polyamide and wrapped onto the inner wall of the capsule to spare the space for the capsule integrated components. For evaluation of the antenna’s performance within a full-package endoscopic device, a homogeneous muscle box and realistic Duke human phantoms were used. For measurement, the fabricated antenna is enclosed inside a 3-D-printed capsule along with the endoscopic system, and the enclosed system is waterproofed. The S-parameters and radiation patterns are measured in a saline-filled American Society for Testing and Materials (ASTM) model and a minced-pork phantom. The measured impedance bandwidths and gains at 402 MHz, 915 MHz, and 2.4 GHz are 236.2%, 104%, and 55.4% and −29.71, −28.7, and −20.8 dBi, respectively. The measured axial-ratio bandwidths are 45.9% and 21.3% at 915 MHz and 2.4 GHz, respectively. Furthermore, the link budget is numerically analyzed and measured via real-time telemetry using software-defined radios. The proposed antenna complies well with the human safety standards and satisfies the range and high data-rate requirements.