Measurement of complex permittivity of lossy liquids using open-ended waveguide technique

Accurate measurement of complex permittivity of liquid materials at microwave frequencies has various applications such as in assessing the biological and medical effects of microwaves. Techniques for the measurement of complex permittivity include in-waveguide measurement and the open-ended waveguide technique. The latter technique is based on reflection or admittance measurements from which the dielectric (or magnetic) properties of materials can be determined. The technique is nondestructive and accurate. However, the open-ended waveguide structure is difficult for the measurement of liquid materials. We have designed a stepped flange to hold liquids. The effect of the stepped flange on the input admittance is measured. The complex permittivity of a number of liquid samples is measured using the designed flange and the results are compared with those measured using the in-waveguide technique.