Theory and Tables of Optimum Symmetrical TEM-Mode Coupled-Transmission-Line Directional Couplers

New equal-ripple polynomials were determined and applied to the synthesis of symmetrical TEM-mode coupled-transmission-line directional couplers (using exact methods). Tables of designs for symmetrical couplers of three, five, seven, and nine sections having mean couplings of -3.01, -6, -8.34, -10, and -20 dB, and having several equal-ripple tolerances in the coupling band are presented. Symmetrical maximally-flat directional-coupler designs having three, five, seven, and nine sections are also presented to complete the tables.