Multi-combline warped-mode directional couplers

A first report of multi-combline warped-mode directional couplers using three lines is presented. The technique outlined can be extended to many different designs and additional lines. The specific example given has been designed as a 3-way equal power splitter with a phase difference of 180° and 0° between the two outer lines and the central line. The coupler is fed from the central line at the input. The device exhibits significant coupling over the range 0.7 to 9 GHz, but with ripples at the lower frequencies and loss at the higher frequencies the most useful range is about 3 to 8 GHz.