Identification of Damaged Waterproofing Layer for Patch Antenna Sensor Embedded in Cement Paste

Abstract

A waterproofing layer is necessary to maintain the performance of a patch antenna sensor, especially when embedded in a wet environment. The influence of varying levels of damaged waterproofing layers on the accuracy and sensitivity of sensors has been analyzed in this article. The behavior of a patch antenna sensor with a possible damaged waterproofing layer is described by an equivalent model with a covered dielectric load. Theoretical calculation and simulation in high-frequency structure simulator (HFSS) version 15 have been utilized to confirm the influence of the leakage. The antenna sensor with a damaged waterproofing layer tends to have a smaller initial resonant frequency and poor accuracy. Considering three antenna sensors with undamaged, half-damaged, and fully damaged waterproofing layers, an experiment is conducted to verify the influence of damage on sensor performance. Compared with the undamaged waterproofing layer case, the case with a fully damaged waterproofing layer has an initial resonant frequency that is 50% smaller, and the error increases from 10% to 33%. The identification method for the damaged condition of the waterproofing layer is summarized based on the irregularity of the return loss (S11) and resonant frequency.