New Transparent Bandpass Filter Using Aluminum Thin-Film Micromesh Structure

In this study, we present the new transparent coplanar waveguide (CPW) bandpass filter using aluminum (Al) thin film micromesh structure. The filter is prepared by the semiconductor process of dc sputtering and standard lift-off technology. In order to achieve the high-performance transparent bandpass filter, the new aluminum thin film micromesh structure with low resistivity to 10
^-8
Ω-cm, uniform Al thin film thickness to 3μm, high optical transparent to 78% and simple manufacturing process has been proposed. The transparent bandpass filter is designed at 2.4 GHz with 3-dB fractional bandwidth (FBW) of 5%, the minimum insertion loss (-20 log |S
₂₁
|) of 1.8 dB and the return losses (-20 log |S
₁₁
|) of 25 dB. The simulated and measured results of the transparent bandpass filter are in good agreement. The proposed transparent bandpass filter is showing a simple coplanar waveguide configuration, low thin film resistivity, high thin film transmittance, high filter performance, and small circuit size.