Theoretical Study And Numerical Design Of A Microwave Resonating Sensor For Weigh-in-motion Application

With the overload problem increasingly prominent, the requirement of international traffic management department on the transportation vehicles load management is becoming higher and higher. It requires not only accurate measurement but also simplified and efficient operation process. Currently there are several common used weighing sensors include: bending plate, load cell, piezoelectric sensor, etc. All of them get the vehicle load by measuring the dynamic pressure from vehicle tire. They usually treat stress and strain as indirect measurement parameters. These weighing sensors usually have low measurement precision, high cost and limited application.Considering the disadvantages and limitation of existing Weigh-in-motion(WIM) sensors, a novel WIM sensor based on microwave cavity perturbation theory is proposed in the paper. Theoretical calculation and numerical simulation are carried out to validate the design. The excitation part of the sensor is mainly composed of a cylindrical cavity tube and incentive probe. Firstly, the cylindrical cavity perturbation theory is thoroughly studied, and the resonator parameters including cavity dimension, propagation mode and working frequency are theoretically calculated; Secondly, sufficient numerical simulation by electromagnetic software(HFSS and CST) are carried out to verify the calculation, and the simulation results agree well with the theoretical results; Finally, an optimized microwave WIM sensor system is realized and the measurements in laboratory validate the linearity and uniformity. The design of the novel microwave WIM sensor can hopefully resolve the weighing accuracy problem and utilizing limitation of existing WIM sensors.