Design and Experimental Validation of a Polarization-agile Microstrip Antennas with truncated corners for RF Glucose Monitoring Applications

Abstract

Polarization-agile reconfigurable antenna: can dynamically adjust its polarization state to fit application needs. In the proposed research, this concept is applied to a 5.8 GHz microstrip patch antenna intended for non-invasive RF-based blood glucose monitoring. Using carefully positioned copper strip perturbations, the antenna is intended to alternate between linear polarization (vertical and horizontal) and circular polarization (left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP)). This reconfigurability enables improved interaction with human tissue, enhancing sensitivity to dielectric variations caused by changes in blood glucose levels. Existing Polarization-agile antenna structures were analysed, and a prototype microstrip patch antenna capable of quad-polarization states was designed and simulated at 5.8 GHz. The antenna's performance was verified in terms of return loss (S11), polarization agility, and axial ratio. Various design methodologies for achieving polarization reconfigurability including slot perturbation, truncated corners, and switchable strip loading were studied and implemented to optimize impedance matching and polarization purity. Two antenna structures, operating on the same reconfiguration principle as the prototype, were designed to enhance sensing performance. The modifications primarily focused on improving return loss and axial ratio stability within the ISM 5.8 GHz band. Fabricated antennas were experimentally tested with a Vector Network Analyzer (VNA) and the experimental result were in good agreement with the simulated result. Antenna Structure-2 among the tested showed utmost good impedance matching with return loss of −28 dB at 5.8 GHz, which enhanced the sensitivity for biomedical sensing applications.