Power sensing RF termination apparatus including temperature compensation means

摘要

A power sensing RF termination comprising a calibration means allows the user to correct for part-to-part variation, miss match loss and output offset. The power sensing RF termination comprises a first and second temperature sensitive resistors connected at a first common junction, a switching means for connecting either an RF input or a DC power reference to the first common junction, a first switch for connecting either a DC voltage source or a first current detecting resistor to the first temperature sensitive resistor, and a second current detecting resistor connected to the second temperature sensitive resistor. A first output terminal is connected to the junction between the first switch and the first temperature sensitive resistor. A second output terminal is connected to the first common junction. A third output terminal is connected to the junction between the second temperature sensitive resistor and the second current detecting resistor. The first and second temperature sensitive resistors have substantially the same temperature coefficient of resistance; but the first temperature sensitive resistor has a positive temperature coefficient of resistance while the second temperature sensitive resistor has a negative temperature coefficient of resistance. Using the measurements of the voltages at the first, second and third output terminals, a calibration table is formed correlating the power absorbed in the first and second temperature sensitive resistors to the ratio between the voltage drop across either the first or second temperature sensitive resistor and the voltage drop across both the first and second temperature resistive resistors.