Variation of resonant frequency of a rectangular microstrip patch antenna due to accumulation of water over its surface

In the work presented here, the effect on the resonant frequency of a rectangular microstrip patch antenna-due to accumulation of water over its microstrip patch surface-during rainy seasons is studied. A probe-fed rectangular microstrip patch antenna having dimensions 84 mm × 70 mm (W × L), fabricated on the Duroid^® substrate (ε_r = 2.4) of thickness 1.524 mm (60 mill) and resonant frequency equal to 1.34 GHz, is used for the experiment. The antenna is assumed to be in outdoor condition such that the microstrip patch surface lies horizontal so that water may be accumulated over its surface during rainy conditions. This effect is emulated by pouring distilled water over the antenna patch surface to form a water layer of uniform thickness successively of 1 to 5 mm-and its effect on the resonant frequency of the antenna is observed. An empirical relation between percentage change in resonant frequency and the height of water layer over the rectangular microstrip patch antenna surface is presented.