Development of the complex permittivity measurement system for high-loss biological samples using the free space method in quasi-millimeter and millimeter wave bands

The free space method using a pair of lens antennas was modified for the complex permittivity measurement of biological samples from 20 to 110 GHz. Two methodologies were used to obtain the complex permittivities by the free space method, which were based on the reflection and transmission coefficients. The measurement results obtained with the two methodologies were compared with each other. The measured complex permittivities of the biological samples from the free space method were then compared with those measured using the coaxial probe method. Finally, the measurement data were also compared with those from measurement methods developed in past literatures. (paper)