A robust six- to four-port reduction algorithm

The six- to four-port reduction (SFPR) technique has been enhanced in a number of ways. A more stable iteration strategy, which shows improved performance in the presence of noise and with nonideal microwave hardware, is presented. The quality of the five SFPR coefficients is also quantified by a novel variance technique, which allows their effect on reflection coefficient measurement accuracy to be predicted. This variance technique can form the basis of an enhanced reduction algorithm which is less susceptible to iteration divergence. Practical results from a 250-MHz-to-26.5-GHz coaxial six-port reflectometer are presented.<>