Calibration of a Dual-Polarized Probe Using the 16-Term Calibration Model

A calibration method for square or circular waveguide-based dual-polarized probes is proposed based on the 16-term network analyzer calibration model, allowing systematic errors, such as polarization impurity and mismatches to be corrected. The unique issues associated with such a dual-polarized probe are discussed, namely, the difficulty in creating thru or delay calibration standards and known asymmetric reflect standards. A novel calibration procedure solving the 16-term calibration model is developed and proposed, which overcomes these issues by utilizing three known symmetric reflect standards, one unknown asymmetric reflect standard, and an optional unknown but reciprocal standard. Subsequently, two Ka-band (26.5-40 GHz), square-waveguide-based dual-circularly polarized probes are fabricated along with the required calibration standards, and the proposed calibration method is then applied and its efficacy verified. In addition, the ability of the calibration algorithm to correct for polarization impurity is demonstrated through synthetic aperture radar (SAR) measurements in conjunction with a sample containing a plurality of identical targets with different relative orientations.