Dual-tone calibration of six-port junction and its application to the six-port direct digital millimetric receiver

This paper describes a novel dual-tone calibration technique of a six-port using two carriers with closely spaced frequencies. The samples for the calibration are extracted from outputs of four power detectors using a self-adaptive algorithm. The calibration procedure is fully automatic and can be implemented in a system capable of capturing the output waveforms of a six-port. Although the proposed method is applicable to general six-port calibrations, it finds itself particularly suitable for the calibration of a new six-port direct digital MM-wave receiver. It is shown that such a calibration of the digital receiver can be fulfilled on site simply by receiving usual incoming signals. Dual-tone calibrations made at 26.5 GHz, 33 GHz, and 40 GHz demonstrate the same order of accuracy as the conventional six-port calibrations. However, the new technique is much simpler and faster as it requires less effort in its implementation.