Finding initial estimates needed for the Engen method of calibrating single six-port reflectometers

It is shown how the initial estimates of the six-port to four-port reduction parameters needed for the Engen six-port calibration method can be found with a minimum of reflective terminations by using six-port parameters obtained by either of two previously published methods (U. Stumper, ibid., vol.37, p.222-30, 1989, or B. Neumeyer, Doctoral thesis, Technische Universitat Munchen, Munich, West Germany, 1989). With these methods, only five reflection values are needed, which can easily be realized by waveguide offset short-circuit reflection standards of different lengths, in the range of millimeter waves