SPPs Structure Touch Sensing Method with Microstrip Transmission Line

This paper proposes a microstrip touch sensing design compatible with radio frequency (RF) signal communication ability. The design is based on surface plasmon polaritons (SPPs) and employs a microstrip touch sensing structure with multiple periodic parallel open circuit branches, which is further connected in parallel with the signal transmission microstrip. The SPP structure is designed in a U-shaped structure and exhibits multiple resonance characteristics for RF signals. Its S-parameter in the low frequency band is affected by finger or medium touch, while the parallel microstrip transmission line correspondingly maintains signal transmission capability in the high frequency band, which remains unaffected. A physics-informed regression framework based on spectral alignment and Gaussian Process Regression (GPR) is introduced for the analysis of both simulation and experimental results. Based on the spectral-position relationship, touch position detection with an accuracy of within 5 mm is achieved by monitoring changes in the S-parameter response below 4.7 GHz. Meanwhile, a communication passband unaffected by tactile sensing is maintained within the 4.7 GHz to 6.0 GHz frequency range. This design demonstrates significant potential for applications requiring integrated sensing and communication (ISAC), including the Internet of Things and smart wearable devices.