Complex permittivity determination based on a radio frequency device

We describe the design, fabrication, and evaluation of a new on-wafer four port device for measurement the complex permittivity of materials over the continuous frequency range from 1.5 GHz to 2.75 GHz. The proposed device consists of two 3dB directional coupler connected through two U-shaped slot line sections with the same length. This method can afford high accurate measurement results by only two measurements of scattering parameters. One measurement is for the empty device and the other for the material under test loaded on U-shape slot-line of the device. Additionally, we compute the complex permittivity of the materials under test from the measured scattering parameters. Our measurements show excellent agreement with transmission methods.