Tunable microwave coupler buried in low-temperature co-fired ceramic

This paper outlines a method of tuning a microwave broadside coupler buried in low-temperature co-fired ceramic. Etching a slot in the exposed ground plane tunes the characteristic impedance Z/sub 0/ of a stripline coupler. An iterative method computes the correct dimensions of the slot. Applying the method salvages microwave circuits detuned due to manufacturing tolerances.