Coupling phenomena in conductor-back slotline structures

Leakage phenomena possible in conductor-backed slotlines are investigated through an analysis of coupled slotlines for possible application to a nonproximity directional coupler. Two coupled slotlines with finite width of the conductor backing are analyzed using the spectral domain method. The propagation constants and experimental results obtained confirm that coupling is caused by leakage through the conductor backing. It is shown that the slotlines couple with each other even if they are physically separated by a large distance. The coupling phenomena were confirmed through an experiment on forward-coupling directional couplers. It was found possible to prevent the leakage by adding an additional top layer.<>