Double patch sensor for identification of stress level and direction

In this article microstrip sensor for evaluation of stress direction and value was proposed. Developed sensor consists of two patches (resonators) of various sizes. Both patches have different operating frequencies and different angles between resonator axis and the direction of mechanical excitation-resonators are arranged along orthogonal axes. Proposed transducer enables determination of the direction and value of stress in the range from 0 to 90 degrees. Patches are fed by T-junction power divider, so they use one excitation port. The resonators were developed for operating frequencies of 2.65 and 2.75 GHz, so a small difference (100 MHz) compared to the sensor with one resonator was obtained between the two resonant frequencies. It enables better use of measuring hardware capabilities, which leads to faster and more accurate measurements. The proposed sensors were evaluated using numerical analysis and measurements. Moreover, the algorithm for identification of direction and stress level was proposed. It uses artificial neural network approximator. The algorithm was positively verified.