Folding method for bandwidth and directivity enhancement of meandered loop ultra-high frequency antenna for heart failure detection system

A wideband antenna with unidirectional radiation is designed for lower ultra-high frequency (UHF) band, which is utilised in medical diagnostic systems, in addition to telecommunications, such as UHF television channels, WiMax, cognitive radio, radio frequency identification, mobile digital TV and CDMA/GSM800. In medical imaging, there are additional antenna design requirements, such as compact size, wide operating bandwidth and unidirectional radiation. A combination of dual monopole feeding, meandering and folding techniques is used to realise the required frequency band and directivity for the antenna, while reducing its size. The final design has the compact size of 0.23λ × 0.08λ × 0.08λ (λ is the wavelength of the lowest measured operating frequency of the antenna), a wide measured operating bandwidth of 50% (590-985 MHz), a peak gain of 3.6 dBi and a measured efficiency of more than 89% over the band of operation. The designed antenna is then used with a compact microwave transceiver, and proper data acquisition and processing algorithms to build a system for the early detection of congestive heart failure. The system is tested using a realistic artificial human torso.