RF and Six-Port Microwave Sensing Techniques for Nondestructive Testing and Evaluation

The physical and mechanical properties of urban structures can be inspected and monitored using nondestructive testing and evaluation (NDT&E) techniques. In particular, microwave methods have recently attracted the research community as a viable method to address NDT&E applications in a wide range of applications [1] . In its essence, the measuring instrument is build up with a microwave detection system connected to a sensor, i.e. antenna or probe. The measured reflected or transmitted wave through the material under investigation is a function of moisture content, density, type and properties of constituents, presence and type of contaminants, presence of fatigue cracks. In contrast with conventional NDT&E techniques, RF and microwave tools operate at relatively low power in a non-contact manner. Lateral and depth resolutions can be improved by appropriate design of the sensor.