Reduction of Electromagnetic Field Distortion in Microwave Sensors in Contact With Skin Tissues

The electrically resistive epidermis, the outermost layer of skin tissues, can substantially distort the electromagnetic (EM) field of microwave sensors, limiting the depth of penetration into the body. To address this issue, a geometrically modified microstrip transmission line ( $\mu $ TL) is structured, designed to minimize EM field distortion upon contact with skin tissues. This novel structured $\mu $ TL (S $\mu $ TL) enhances the performance of conventional $\mu $ TLs (C $\mu $ TLs) and microwave C $\mu $ TL resonators. The S $\mu $ TL’s design involves inverting the ratio of the C $\mu $ TL length and the ground region underneath it, creating a vertical inversion that introduces a consistent phase shift positively correlated with the inversion ratio. This added phase shift alters the reflected phase of the C $\mu $ TL. Furthermore, the polarization direction of the EM field in the S $\mu $ TL changes. This research study explores the application of the S $\mu $ TL within a C $\mu $ TL resonator sensor, demonstrating that the structured design allows for greater control over the intensity of EM field interactions with the surrounding medium. By facilitating stronger EM field interactions, the S $\mu $ TL sensor exhibits improved shape factor (SF) and sensitivity. Experimentation confirms that the EM field of the S $\mu $ TL-based sensor penetrates deeper into turkey skin tissue compared to that of the conventional C $\mu $ TL sensors, highlighting its potential for more effective EM field penetration and performance in sensor applications.