Comment on "Synthesis of Symmetrical Branch-Guide Directional Couplers" [Correspondence]

This note considers the approximation problem encountered in the synthesis of branch-guide couplers. An alternate solution to that proposed by R. Levy and L. F. Lind is considered and shown to give generally inferior performance. It is inferred then, that an important design criterion is the requirement that the passband of the coupler contains the maximum number of frequencies of perfect match consistent with elements that are a quarter-wave-length long at midband.