A New Class of Microstrip Directional Couplers

By using Cohn's slotline in combination with a microstrip, simple 90/spl deg/ as well as 180/spl deg/ directional couplers of any coupling value can be made. As examples an ultra flat 10 db coupler for 1 - 12 GHz, an octave wide (2 - 4 GHz) magic tee and an almost lumped proximity coupler for 2 - 8 GHz (all on alumina substrate) have been made.