Complex Permittivity of Water-Based Liquids for Liquid Antennas

Liquid antennas have attracted increasing attention recently. In this letter, a promising candidate for liquid antennas, namely water with propylene glycol (PG), is investigated using both measurement and numerical simulation approaches. The nonlinear least-squares fitting routines are employed to derive new formulas for the approximation of the complex permittivity of the liquid. The permittivity of this liquid at various temperatures and substance concentration levels are investigated. The results are obtained and compared to the measurement. Good agreements are obtained, and new comprehensive knowledge is gained. In particular, the permittivity of water with PG at various conditions is reported for the first time. These results should be very useful for a range of applications such as liquid antenna designs.