  We previously reported on the complex permittivity and dc conductivity of
waste-activated sludge. The measurements, spanning a frequency range of 3 MHz
to 40 GHz, were made using an open-ended coaxial transmission line. Although
this technique is well established in the literature, we found that it was
necessary to combine methods from several papers to use the open-ended coaxial
probe to reliably characterize biological samples having a high dc
conductivity. Here, we provide a set of detailed and practical guidelines that
can be used to determine the permittivity and conductivity of biological
samples over a broad frequency range. Due to the electrode polarization effect,
low frequency measurements of conducting samples require corrections to extract
the intrinsic electrical properties. We describe one practical correction
scheme and verify its reliability using a control sample.
