Reflection amplitude shape-based approach for low-cost permittivity measurement

The permittivity measurement is important for the characterization of material properties in various applications. Traditional methods, such as the well-known Nicolson–Ross–Weir (NRW) technique, usually require the phase information of measured parameters and need the expensive vector network analyzer, making the measurement system complicated and costly. In this paper, we present a reflection amplitude shape-based approach for determining the permittivity of low-loss block materials. Moreover, the measurement only relies on the shape of the reflection signal amplitude curves, thus not only the phase measurements and absolute calibration can be avoided, but also the strict requirement of the absolute amplitude measurement can be eliminated. A simple and low-cost measurement system consisting of a portable signal generator, a power divider, a detector, and a data acquisition card is used to capture the reflection signals. The measured reflection amplitude curve is normalized and compared with the theoretical ones, which are calculated by the NRW technique with the Debye model. Using the genetic algorithm, parameters of the Debye model are estimated from the optimal theoretical reflection curve, and finally the permittivity can be calculated. Experimental validations of various materials have been carried out, and the experimental results demonstrate the potential of the proposed system for the low-cost phase-free permittivity measurement.