Results of attenuation and power measurements in the high frequency and microwave ranges with standard instruments based on coaxial and waveguide technology

A description is given of the present state of the standard devices established at the Physikalisch-Technische Bundesanstalt for attenuation and power calibrations in the MHz and lower GHz frequency range. An international intercomparison of precise coaxial attenuators at 30 MHz is discussed; the results and their uncertainties are presented. Reference is made to the results of an international intercomparison of waveguide attenuators for low attenuation values at 10 GHz. In all cases the total uncertainties of the PTB measuring devices are below 0.001 dB. Concerning power measurements, the different microcalorimeter systems developed at PTB in the mentioned frequency range are demonstrated. It is shown that thermal disturbance according to RF heating of the isolation section within the microcalorimeter may cause errors in the determination of the effective efficiency of the order of 0.005. A correction method is given. The random and systematic uncertainties under optimum conditions are tabulated. The results of an international intercomparison of power transfer standards are presented.