Evaluation of uncertainty due to excess heating by an adiabatic line in calorimetric measurement of RF power

We are developing two broadband RF power standards. One is based on 7 mm coaxial line with APC 7 connector for 10 MHz-18 GHz and the other is based on 2.9 mm coaxial line with K connector for 10 MHz-40 GHz. The power measurement principle is calorimetric isothermal control. In these measurements, the effect of excess heating by the adiabatic line becomes important. In the present work, its evaluation method is presented and experimental results are described.