3D frequency selective surfaces for structural health monitoring systems

The research work in this dissertation mainly highlighted to the study of capability 3D Frequency Selective Surfaces to act as a sensor in structure monitoring. A new type of three-dimensional (3D) Frequency Selective Surfaces (FSS) applied for passive sensing in Structural Health Monitoring (SHM) is presented. Square shape FSS are chosen in this research which it able to govern the sensitivity of frequency response. Moreover, these FSSs are modified in a 3D form to feature enhanced performance compared to conventional FSSs and sensors. More specifically, the proposed 3D FSS is able to control its sensitivity |S21| in either TE or TM incident waves. In this research, incident angle characteristics are evaluated for SHM application to obtain angular responses of up to 80 degrees. The resonant behavior of the TE-incident wave is shown to be sensitive towards the incident angle and is suitable to be used for monitoring any building tilting and damages. This is due to the significant 3D length hanges of the conductor elements. Meanwhile, the TM-incident wave is found to be insensitive (frequency operation not shifting) towards the incident angle. There have some novelty have been introduced in this work such 3D FSS give an extra advantage to perform as a passive sensor and equation for relation between frequency response and incident angle are derived.