This paper presents the design and fabrication of a proximity coupled feed disk resonator coated with multi walled carbon nanotubes (MWCNTs) and polypyrrole chitosan
(PPy-CHI)layers as a napropamide sensor. Computer Simulation Technology (CST)microwave studio was used to obtain the best design of the disk resonator and feed line
position in a 5 GHz resonant frequency. Also, MWCNTs-PPy-CHI layers were coated on the disk resonator using electric field deposition, and the chemical interaction between the sensing layer and napropamide was investigated via a Fourier transform infrared spectroscopy (FTIR). The evaluation of the system was performed using different concentrations of commercial napropamide and pure napropamide at room temperature (25 ⁰C). The experimental results proved that the proximity coupled feed disk resonator that was coated with MWCNTs-PPy-CHI layers was simple, fast (Measurement- time=5 seconds), accurate (as low as 0.1 ppm), and low cost; it also has the potential to be produced as a portable instrumentation system for detecting napropamide in water and soil.