Influence of selected parameters of the substrate of a microstrip textile antenna on changes in its resonance frequency under the influence of humidity

Abstract

Textile antennas are one of the more essential parts of an electronic system incorporated in modern smart garments, used, for instance, for monitoring physiological signals. The article presents the study of the influence of selected parameters of the substrate of a textile microstrip antenna on the changes in its resonant frequency under the influence of changes in humidity. The impact of moisture was investigated for antennas with two different substrates: polyester and cotton. These materials differ significantly in their ability to absorb and release water. The article shows the construction of a measuring stand, measurement results for short and long-term exposure to moisture, and its statistical analysis. The obtained results indicate that textile antennas with a polyester substrate show more stability of the resonance frequency of the antenna compared to the antenna with a cotton substrate, regardless of changes in humidity. It has also been demonstrated that antennas exposed to prolonged, multi-day humidity variations exhibit higher changes in their resonant frequency than antennas subjected to short-term, 1-day variations.