Three-Dimensional Open-Ended Slot Antenna for Heart Failure Detection System Employing Differential Technique

The design of a folded open-ended slot antenna for an early-stage congestive heart failure (CHF) detection system operating at ultra-high frequency (UHF) is presented. The antenna is formed using a three-dimensional open-ended slot with a compact size of 0.24 λ₀ × 0.09λ₀ × 0.04 λ₀ (λ₀ is the lowest operating frequency of the antenna), and a slotted microstrip feeder used to achieve wide operating bandwidth of 58% (550-1000 MHz). A CHF detection system is then built using the proposed antenna, a compact microwave sensor, and a differential detection technique. The main objective of such a system is to map the torso area searching for any fluid accumulation in the lungs as the main symptom of CHF. To that end, a pair of the proposed antenna is attached to an adjustable platform to vertically scan the torso. A differential detection technique is applied on the backscattered signals to map the scattering profile of the torso and detect any changes in the electrical properties of the lungs caused by fluid accumulation. A detection threshold is applied to differentiate between healthy and unhealthy cases. The obtained images have a pixel resolution of 0.1 cm in depth and 1 cm in height. The experimental results on an artificial torso indicate that the system can detect fluid differences as small as 4 mL, with a measurement error of less than 3%.