Feasibility of Microstrip Components on Paper Substrate

Feasibility of using “paper” as low cost organic substrate of filter and antenna is studied here. Cutoff frequency for the realized 3-pole low pass filter fabricated on paper substrate (dielectric constant=2.24) is around 2.77GHz having insertion loss less than 0.8dB and minimum attenuation less than -23dB at 7.61GHz (pole frequency). The realized filter has a rejection band from 5.5GHz to 9 GHz with value less than -15dB and achieves at same time acceptable pass band with sharpness factor of 4dB/GHz. A 7-pole low pass filter is also fabricated on same paper substrate. Here rejection band below -20 dB has been found from 2.355 GHz to 15GHz. So rejection bandwidth has been widened from 3.5 GHz to 12.645GHz in comparison with the 3-pole even at -20dB. This filter has sharpness factor of 21.14 dB/GHz which is improved by 17dB compared to 3-pole filter. These sharp low pass filters fabricated on paper substrate have major application in RF receivers.Next a simple circular-polarized antenna is proposed having a square metallic patch with two notches, a ground plane, a probe feed and `paper' as substrate. Experimental result shows that the operating frequency is 2.5GHz with an impedance bandwidth (2:1 VSWR) of 90 MHz and axial ratio less than 0.5db. The simulated cross-polarization isolation obtained is greater than 15dB. The proposed circular-polarized antenna of 2.5 GHz has extensive applications in wireless communication, cellular & satellite communications.