Calibration Methods for Free Space Dielectric Microwave Measurements with a 4-Channel-Network-Analyzer

At microwave frequencies the dielectric properties of ceramic and composite materials can be determined on the basis of free space measurements with the help of a vector network analyzer. For the accurate calibration of the measurement setup the newly developed LN1N2-method (Line Network) and the LNN-method are presented in this article. In contrast to the TRL-technique (Through Reflect Line), the calibration standards of the LNN- and LN1N2-method are all of equal length. This is advantageous for free space applications where a variation of the antenna positions might be critical due to changes of the beam propagation. Whereas the calibration standards of the LNN-method consist of three consecutive positions for the placement of obstacle networks, the LN1N2-method is only in need of two positions. Besides the reduced need of space the obstacle networks can thus be placed symmetrically around the focusing area of the free-space antenna-lens system.