Measuring method of complex dielectric constant with monostatic horn antenna in W-band using multiple distance measurements and analysis

To extend the application of the free-space method to measuring a complex dielectric constant, a reflection method with a monostatic horn antenna integrated with two processes to reduce errors is developed. One of the processes can reduce the error caused by unnecessary reflections from objects around an experimental setup. The process is performed by averaging complex reflection coefficients of a sample measured at multiple distances between the antenna aperture and the sample surface. The other process can reduce the error caused by the difference between the positions of the reference plane and the sample surface. In this process, the distance between the two positions is derived by analysis and is used to correct the errors. In this paper, an overview of the developed method is presented. Then, the effectiveness of the two processes is validated by measuring the complex dielectric constants of polytetrafluoroethylene (PTFE) and polyoxymethylene (POM). The results prove that the errors can be reduced, and the complex dielectric constant of a lossy material such as POM can be measured accurately using the developed method.