A Free Space Microwave Characterization of CNT-Epoxy based Nanocomposites using Two Patch Antennas

The influence of nanofillers percentage on a patch antenna return loss (RL) was investigated through experimental and numerical analysis. Free space measurements were carried out on six samples reinforced with carbon nanotubes (CNTs) containing 0, 0.5, 1, 2, 4 and 5 wt%. The experimental measurements were obtained using a Vector Network Analyser (VNA) and a patch antenna with a resonance frequency of 5 GHz and a fractional bandwidth of 3%. The antenna field regions were calculated and the samples were tested at the reactive, radiating near-field, and far-field. The findings indicate distinctive behaviours. At the reactive near-field region, the CNTs, as expected, seem to diminish the RL values around resonance frequencies. On the contrary, at radiating near-field and far-field, the CNTs provoke the variation of RL in the antenna bandwidth accordingly their percentage. Especially after the electrical percolation threshold (EPT). Moreover, a numerical study was performed. Using the Finite Element Method (FEM) and an idealized model of the RL behaviour values were simulated. At higher CNTs percentages (i.e., EPT), unique behaviours were found. The alteration in the key electromagnetic properties is confirmed in experimental and numerical studies.