Quarterwave transformers (line length = l /4 having characteristic impedance Z0)
are used to transform the edge input impedance of the square MSA to 100V.
The feed point is located on the 100-V line in such a way that one side
length is longer than the other by l /4 to provide a 90° phase difference at
the two edges of the square MSA.
This also ensures a match with the 50-V coaxial feed as two 100-V lines on each side of the feed point are in parallel.