Sugar and Salt Concentration Detection in Water Employing ENZ Metamaterial Microwave Sensor

Abstract

A design of high sensitivity Vivaldi antenna is introduced for detecting the low sugar and salt concentrations in water. The reason for selecting the Vivaldi antenna configuration is to provide two desired features; ultra-wideband and a high directivity so the surrounding clutter effect can be minimized. The prospective antenna embraces the ultra-wideband (UWB) from 4 GHz to 11 GHz. Two techniques are exploited to improve the antenna detectability; epsilon-near-zero (ENZ) metamaterial and antenna aperture amending. The ENZ metamaterial is very sensitive to the permittivity of the substrate, so any loading effect can easily alter the electric field distribution and hence affect the antenna phase properties. The high sensitivity can be increased by operating at a higher frequency. The aperture amending is used to improve substrate-air matching. An equivalent circuit model is scrutinized for further emphasis of the ENZ metamaterial operation, showing good agreement with EM simulation results. In terms of phase variation, the designed antenna is employed to sense sugar and salt in water. The amount of sugar and salt affects the material characteristics of the solution and, as a result, the reflected phases. Practical observations reveal that when the sugar and salt contents in the liquid increase, the phase falls. The simulation and measurement results of a fabricated prototype have good agreement. The time-domain analysis is discussed, revealing low distortion of received pulses.