An alternative method for verification of common mode absorption devices

Common Mode Absorption Devices CMADs are absorbing clamps required in the set ups for measurement of radiated disturbances. They should be verified with Vector Network Analyzers (VNAs), which unfortunately have coaxial ports. A CMAD can be connected to the VNA only if it is embedded in adapters. In the verification process, the clamp must be deembedded, i.e. the contribution of adapters must be extracted from the measured S-parameters. The Thru-Reflect-Line TRL calibration of the VNA is a suitable tool for that task, provided the necessary hardware and software facilities of the VNAs are available. If not, alternatives are required. In this paper, the alternative calibration is presented. The symmetry of adapters allows omitting the Reflect-step, providing this approach is preceded with the Short-Open-Thru-Match SOTM calibration. The method presented here consists of two steps only: the Thrustep in which adapters are cascaded face to face and the Linestep in which the rod line is inserted between the adapters. These two standards can have unknown S-parameters. Validation of the method consists in verification of the CMAD available on the market. There is entirely satisfactory convergence of the derived parameters with the data published by the manufacturer in the technical specification.