The present invention provides for a method and apparatus to control
non-adjacent cross-coupling in a micro-strip filter. In instances of weak
cross-coupling, such as a filter circuit on a high dielectric constant
substrate material (e.g., LaAIO.sub.3 with dielectric constant of 24), a
closed loop is used to inductively enhance the cross-coupling. The closed
loop increases the transmission zero levels. For strong cross-coupling
cases, such as a filter circuit on a lower dielectric constant substrate
material (e.g., MgO with dielectric constant of 9.6), a capacitive
cross-coupling cancellation mechanism is introduced to reduce the
cross-coupling. In the latter instance, the transmission zero levels are
moved down.