Computation of impedance and efficiency of transmission line with high standing-wave ratio

IT IS ordinarily desirable to operate a radio-frequency or other transmission line with standing-wave ratio as close to unity as possible. When the voltage standing-wave ratio (VSWR) is less than 10, means such as the Smith chart are available for making impedance computations with an accuracy sufficiently good for many purposes. However, in some cases it is desirable or unavoidable to operate the line with high standing-wave ratios. When the VSWR is around 100 the Smith chart is quite satisfactory for reactance but affords no degree of accuracy in reading resistance. This is due to the difficulty of reading even one significant figure on that scale near the periphery, and also to eccentricity in locating the movable arm or the dividers on the center point of the chart.