Sensitivity enhancement for moisture content detection using modified microstrip patch antennas

Abstract

A modified slotted microstrip patch sensor antenna has been developed for sensitivity enhancement to measure the moisture content of leaves. The design incorporates a rectangular slot positioned above the feed of a rectangular patch antenna. The antenna achieves resonant frequency at a lower range than the operating frequency of a traditional patch antenna without slot while maintaining a miniaturized form factor. To evaluate the sensitivity of the proposed modified slotted patch antenna, the variation in the resonant frequency and the reflection coefficient (S11) is observed with the sample under test (SUT), i.e., leaf is placed above the patch. A comparative analysis with regard to sensitivity and shift in frequency is performed between the designed antenna structures. The designed antenna is fabricated on a 0.8 mm F4B substrate in order to resonate within the 2.40–2.80 GHz range under unloaded conditions. The antenna’s sensitivity is tested by performing parametric analysis with respect to the permittivity of the leaf ranging from 20 to 30. The experimental results reveal that the sensitivity of the proposed patch antenna is enhanced by a factor of 1.67 as compared to traditional patch antenna for the four levels of SUT, demonstrating an enhanced sensitivity in detecting the moisture content of leaves.