A Stacked Dual-Frequency Microstrip Patch Antenna for Simultaneous Shear and Pressure Displacement Sensing

This paper presents a simultaneous shear and pressure displacement sensor based on the microstrip patch antenna technology. The antenna sensor consists of a dual-frequency patch antenna, a superstrate, and a rectangular director. The two fundamental resonant frequencies of the patch antenna are influenced by the lateral and vertical positions of the director with respect to its radiation patch. Therefore, the shear and pressure displacements of the director can be determined simultaneously from two fundamental antenna resonant frequencies. The antenna sensor was designed, fabricated, and tested to characterize its sensing performance. An algorithm was developed to inversely determine the shear and pressure displacements from the measured antenna frequencies. We validated that the typical measurement uncertainties of the antenna sensor is +/- 0.3 mm for the shear displacement and +/- 0.15 mm for the pressure displacement. The presented shear/pressure displacement sensor is intended for monitoring the interaction between the human body and assistive medical devices (e.g., prosthetic liners, diabetic shoes, seat cushions, and so on).