Effects of twisting and bending on the performance of a miniaturized truncated sinusoidal printed circuit antenna for wearable biomedical telemetry devices

In this paper, we present a miniaturized Truncated Sinusoidal Printed Circuit Antenna (TSPCA) consisting of a thin conductive film of copper mounted on a flexible substrate for wearable biomedical telemetry and smart clothes applications on the premises of health care and sport medicine facilities. The fundamental resonant mode of the proposed TSPCA is 611 MHz. The flat antenna operates over the frequency range from 608 to 614 MHz (−10 dB return-loss bandwidth of 1.7%) with a bore-sight gain of −29 dBi when operating in a free-space environment. The antenna size has been miniaturized to a 10 mm × 10 mm × 0.5 mm using a shorting plate on a substrate with a relative permittivity of 6.15 and loss tangent of 0.00134. The effects of twisting and bending on the performance of the TSPCA are investigated. It has been found that the maximum change in bore-sight gain, resonant frequency, and S11, with respect to the flat case, is −8.5 dBi, 0.2%, and −4 dB, respectively, with respect to the flat case for bend angles ranging from −45° to 45°. Twisting of the antenna, on the other hand, in the range from −45° to 45° showed a maximum change of −16 dBi, 1%, and −17 dB in the bore-sight gain, resonant frequency, and S11, respectively. The bandwidth remains virtually unaffected for both cases. The performance of the TSPCA is investigated when the antenna is mounted parallel to and at a distance of 0.5 mm from the arm, leg, thigh, and head. It has been found that maximum change in bore-sight gain, resonant frequency, and S11 is −3.5 dBi, 2.5%, and −6.5 dB, respectively with respect to the isolated antenna.