Date of Award


Degree Name

MS in Electrical Engineering


Electrical Engineering


Dean Arakaki


Airborne Early Warning (AEW) systems rely on rotary couplers (RC) to interface rotating antenna elements on aircraft exteriors with stationary onboard systems. The demand for additional channels in new generation AEW systems increases the complexity of rotary couplers significantly. On the other hand, if signals in separate frequency bands use the same channel, existing AEW designs could incorporate additional channels with only minor changes. Passive RF diplexers can accomplish this task. Required characteristics include low-loss (<0.5dB), wideband (4.4:1), and high-power (>6kW) handling capability. Two diplexer candidates are synthesized and characterized with the aid of a commercial circuit simulation package that includes a 3D full-wave EM solver. A semi-lumped coaxial and a digital elliptic diplexer are proposed, both of which have theoretically low-loss and acceptable VSWR characteristics. However, only the latter diplexer meets operating requirements without the excessive tuning or analysis required by the former. Further studies of the semi-lumped diplexer characteristics may make it useful in other applications.

This thesis defines diplexer design goals, provides a brief introduction to filter theory, and compares performance characteristics of the semi-lumped and digital elliptic diplexers. Simulation results for both designs demonstrate that the digital elliptic diplexer is an optimum solution.