Variation of Dielectric and Attenuation Properties for Tree Leaves with Moisture Contents at Microwave Frequency

Present studies report the experimental results on the dielectric and attenuation parameters for leaves of two different tree species at X-Band microwave frequency, 10.5 GHz. Leaves of two different tree species viz., Azadirachta indica (Neem) and Acacia indica (Babool) have been used in these measurements. Complex dielectric constants of these tree leaves have been measured by using waveguide cell method with the help of an automated X-band microwave set-up, whereas attenuation of microwave signal is measured by free space method. Initially, dielectric and attenuation properties of newly plucked leaves are measured. Then the gravimetric moisture content (wet basis) of the leaf sample was gradually reduced by drying it in a hot air oven at 45 to 50 o . Our results show dependence of dielectric and attenuation properties of tree leaves mainly on their Moisture Content (MC %) and also to some extent on the shape and size of tree leaves. The complex dielectric constant is found directly proportional to the insertion loss and reflection coefficient, whereas it is inversely proportional to the return loss and transmission coefficient. Possible applications of such studies in remote sensing of forests and mobile communications are discussed.