Design of microstrip moisture sensor for determination of moisture content in rice with improved mean relative error

Microstrip patch sensor was designed for resonant frequency (fr) 8.1 GHz, printed on FR4 material thickness of 1.676 mm, and relative permittivity was 4.4. For simulation, CST Microwave Studio was used. The aim was to measure the moisture content (MC) of basmati rice whose various properties were longest average rice length (L) 7.2 mm, average width (W) 1.61 mm, L/W ratio 4.47, and bulk density was varied from 554.3 to 591 kg/m3 (bulk density was increase with increase of MC). For checking the working performance of design sensor, predicted moisture content (PMC) and actual moisture content (AMC) were compared. In the former case, reflection coefficient of overlaid rice was measured from vector network analyzer; PMC obtained was varied from 10.53% to 21.67%. In latter case, AMC was varied from 10.71% to 21.87%. Therefore, the lowest mean relative error (MRE) was 1.86% at 8.1 GHz. Hence, the proposed sensor was found to be more accurate than previous designs.