An Accurate and Low Cost Complex Permittivity Measurement System Using a Planar Resonant Sensor

A microwave planar resonant sensor for the measurement of the complex permittivity in compact areas of the material under test (MUT) is presented. Both thin and thick samples can be considered. Compared to transmission or reflection sensors, the adoption of a scalar 2-port measurement procedure reduces the system and improves its robustness. The measuring system requires only the calculation of two parameters, namely the resonant frequency and the 3dB bandwidth, thus achieving a substantial reduction of cost and computation time. The low cost of the sensor is such as to allow its use even in a disposable manner.