Extending the Frequency Range of the Power Sensor Calibration Factor Determination

Power sensors (PSs) are used in many RF power measurements, so a determination of their accuracy in the full frequency range of interest is very important. The calibration factor (CF) of a PS, or more precisely, the uncertainty of its measurement, represents the parameter that has a significant impact on the absolute power measurement uncertainty. An improved method for the CF determination of PS using a thermal converter (TC) as a reference standard and a resistive power splitter for frequencies below 10 MHz is proposed. The improvement of the proposed method is based on the experimental determination of the power splitter symmetry as the most influential parameter, which reduces the overall measurement uncertainty more than six times. The symmetry characterization of the power splitter is performed by an alternative method with the TC. As a result, traceability of the RF power below 10 MHz and extended frequency range of CF measurement to dc with competitive measurement uncertainty using the existing equipment is established. The majority of the broadband RF power standards and network analyzers operate at high frequencies. The proposed method overcomes the lack of their availability at frequencies below 10 MHz and can be applied to all types of average PSs. Uncertainty sources analysis and measurement uncertainty budget for the normalized CF of a diode PS are presented as an example.