A Low-Profile Compact Dual-Band L-Shape Monopole Antenna for Microwave Thorax Monitoring

A low-profile compact dual-band L-shape monopole antenna is designed for microwave thorax imaging. The antenna operates at 433 and 915 MHz in Industrial, Scientific, and Medical band with a compact size of 30 mm x 20 mm x 1.5 mm, which is suitable for wearable devices. It radiates toward in-body direction. The monopole is bent to L-shape for miniaturization. A meandering shorted branch and an open branch are adopted to tune suitable resonance frequencies. The antenna is fabricated. Experiments are conducted with a phantom mimicking human model to verify the design. It is also tested with a human subject. With one antenna as transmitter and the other as receiver, the changes of S21 signals during respiration process verify the feasibility of respiration monitoring with this antenna. The antenna may be used in a microwave thorax imaging system in future research.