Equivalent lumped circuit model and S-parameter of indirect-heating thermoelectric power sensor

In this paper, an equivalent lumped circuit model used to obtain the S-parameter of indirect-heating thermoelectric power sensor is proposed. The working principle of indirect-heating thermoelectric power sensor includes electric-thermal conversion by terminal resistors based on Joule effect and thermal-electric conversion by thermopile based on Seebeck effect. The lumped circuit model takes into account the parasitic parameters of terminal resistors and the electromagnetic coupling between resistors and thermopile. In order to validate the model, S11 of the thermoelectric power sensors with different lengths of thermopile and distances between resistors and thermopile are measured from 1 GHz to 20 GHz. The calculated S-parameters, based on the lumped circuit model, agree reasonably well with the measured results. The results of equivalent lumped circuit model indicate that the S11 is influenced by the distance between resistors and thermopile, and does not change obviously with the length of thermopile and incident power. The present lumped circuit model is useful to reasonably determine the S-parameter of indirect-heating thermoelectric power sensor.