Minimum Sensitivity Calibration for Reflectometers

Abstract

Sensitivities of the error-corrected reflection coefficient (rc) with respect to the rc's of the calibrating elements are minimized. A minimum can be found if the rc's of the calibrating elements form a regular triangle whose center is the rc to be measured. Based on this result, a method for selecting minimum sensitivity calibrating elements for narrowband measurements of rc's of passive devices is presented. Advantages of the method are demonstrated by numerical and measured examples. Calibration inaccuracies were experimentally reduced by a factor of two in the case of rc's of medium absolute value and rnore significantly in the case of small rc's. This method is especially useful when high-precision calibrating elements are not available and high accuracy is needed. A theoretical possibility for calibrating with only two calibrating elements is also described.