Non-destructive testing by using transmission line based microwave sensors

In this research, various types of antennas have been designed and manufactured for the purpose of determining and defining ionized chlorine of sea sand in concrete. Four structures are designed with different models. For the first structure, a Loop-like resonator, for the second structure, a bow-tie shaped resonator, and for the third structure, double-ring resonators are used on both sides of the concrete sample. The fourth structure has a central circular copper resonator with the sample using the transmission line. All of them have concrete samples and non-destructive methods are used in all structures. Different samples of concrete are produced with different amounts and portions of ionized sea sand. Electrical properties of concrete samples for all structures are accomplished in the frequency range of 1-9 GHz. The structures are designed in the Microwave Studio program. The simulation research and analyze of the designed structures shows that the most important resonance frequency shifts, considering the dielectric constant of concrete samples, occur for the Loop-like structure in the range of 1-8 GHz, Bowtie-shaped structure in the range of 1-4 GHz and double Loop structure in 1-9 GHz of frequency band. The important point in designed structures, is the changes of the wave at the resonance frequency (the peak points). The shape of output wave (reflection coefficient S11/ transmission coefficient S12) should change linearly by considering the Dielectric constant and Loss tangent factor (in complex permittivity formula). We have used copper for the resonators of the Bowtie and Loop like structures. We have used FR-4 material for the substrate of forth structure to obtain transmission values. We have simulated four types of designed structures with CST Microwave Software and then obtained the results and evaluated them. Both numerical and experimental tests have given approximately similar results and are in good agreement with each other. These proposed structures can be used in many applications where it is necessary to determine the proportion and degree of ionization of sea sand in cement-based composites such as concrete. Key Words: Metamaterial, Sensor, Sea sand, Concrete