# Measurement of Dielectric Properties of Thin Materials for Radomes Using Waveguide Cavities
###### Abstract
As such, they may not be available within most labs that have not previously conducted research into resonance and characteristic measurements of materials. Therefore, a much more accessible method is needed. Waveguide cavities are also a popular method for measuring microwave frequencies. This method requires a waveguide cavity for the chosen operation band of frequency, a network analyzer, the sample material cut to the size of the cavity, and foam to hold the sample in place within the cavity. The same method used with the resonator method is then followed to obtain the S21 parameter of the cavity with and without the sample present. This difference is then used to calculate the permittivity and loss tangent. This method, used in [18, 19], is easily accessible for most microwave and RF labs that may be interested in determining these material characteristics themselves. The biggest downfall of this method is that it is destructive, in that samples must be made to fit within the cavity. For example, flexible fabrics need to be cut to size to fit within the waveguide for testing. Therefore, some wastage is present for this method. However, the waveguide method is accurate at lower loss values, making it appealing for many applications [20]. Due to the accessibility of the equipment required, it is also considered more economically viable, especially compared with the capacitance method, which can require specific microwave and network analyzer probes. Overall, there are various techniques available in the literature for measuring thin films at multiple frequencies. However, our goal with this paper was to provide detailed steps for an accurate measurement method that can be performed with simple equipment available in most RF labs. This method also utilizes a new setup, where the material sample is never fully placed within a null of the electric field, which means that multiple modes are available for useful measurement. This then allows for dielectric property measurements to be more accessible while also acknowledging how simple and cost-effective this process can be. Unlike other works on dielectric measurement, this paper provides comprehensive information, including a review of all dielectric measurement methods for different types of materials, factors for choosing the best method, theoretical details of the current measurement method, details of simulations, and all measurement factors and setup configuration for a vector network analyzer (VNA). This thorough approach was designed to help readers replicate the experimental process for their materials and understand the considerations for their own measurement setups. In addition, to the best of our knowledge, this is the only paper that covers the results from the measurement of several materials after proposing and explaining the method and simulation in detail, including pictures of the measurement setups. This is different from other papers that only cover the mathematical background of the model and theoretical materials. The following Section 2 outlines the methods followed for this measurement process, while Section 3 outlines the simulated and measured results obtained using this method and discusses what these findings mean. Finally, the conclusions drawn from this research are summarized in Section 4.