Plant Moisture Content Measurement System Based on Microwave Pseudo Waveguide

Moisture content (MC) is an important parameter of plant and matters in agriculture and forestry. In this article, microwave technology is used for the measurement of leaf MC. A moisture measurement system based on microwave pseudo waveguide is proposed. The system includes transmission antenna, pseudo waveguide structure, and receiver antenna. Scattering parameters with sweeping frequency are utilized to characterize the interaction between the microwave electromagnetic field and the leaves under test. The acquired microwave signals are then optimized with frequency band selection method. The data derived from the microwave method are compared with the standard gravitic method. The long short-term memory (LSTM) neural network algorithm is used to establish the MC prediction model and displays good predictive capability with the coefficient of determination (R-2 = 0.9178), root mean square error (RMSE = 0.0343), and mean absolute error (MAE = 0.0271). The data measured by the microwave method agree well with those by the standard gravitic method. The microwave pseudo waveguide sensing together with the data processing method is nondestructive and fast, which is promising for the measurement of the MC of plant leaves in agriculture, forestry, and food industry.