Comparison Among Coaxial Microcalorimeter Models

Abstract

The paper describes the realization process of the high frequency power standard based on a twin broadband microcalorimeter designed for effective efficiency measurement of coaxial power sensors with indirect heating thermocouples. The presented procedures involve microcalorimeter measurement and calibration steps, parameters computation and systematic errors correction for both long-term and accelerated algorithms. Also, a new method for determining the key parameters of high frequency power standards is proposed

Comparison Between Thermoelectric and Bolometric Microwave Power Standards

“…This definition reduces to the typical one given in [19] for bolometers, if we identify P M with the power measured by dc-power substitution. On the other side, we demonstrated in [15] that (1) matches perfectly the alternative definition assumed in [11].…”

“…The voltage e 1SC corrects for the microcalorimeter losses determined by means of the short circuit technique [23]. It is halved if the HF power remains the same when measuring in short circuit condition, [15]. Formula (3) holds well up to about 18 GHz, because in this range, thermoelectric power sensors exhibit a very low reflection coefficient T .…”

“…where e is the measure of the equilibrium temperature reached by sensor mounts after a power substitution, α and R are dimensional conversion coefficients, PS is the total power dissipated in the sensor mount, PL is the power loss along the feeding line, KA and KB are coefficient accounting for the power rate that effectively influence the response of the electrical thermometer [15]. Expression (2) contains, however, all the influence variables that enter the determination process of ηe.…”

“…a thermopile) to HF power and to 1 kHz reference power that is substituted on HF-feeding line. Power substitution can be done also in dc, but 1 kHz power is more appropriate for avoiding errors due to contact thermo-voltages [11], [15]. The voltage e1SC corrects for the microcalorimeter losses determined by means of the short circuit technique [23].…”

Improvements on INRIM Coaxial Microcalorimeter and Outcome of a Model Comparison

“…Raw effective efficiency η raw e has been calculated by means of fitting/ averaging processes applied to thermopile outputs e 1 and e 2 , as already described in [16]- [24]. In short, we used a fitting method based on the Levenberg-Marquardt algorithm that requires as data input the thermopile voltage and the time base value together with their uncertainties [26].…”