Compact On-board L-band Dielectric-loaded Diplexer for High-power Applications

This paper presents the first experimental results of a very compact L-band diplexer based on TM 010 mode dielectric resonators for high-power on-board satellite applications. A dielectric resonator (relative permittivity >40) operating with the TM 010 mode represents the best trade-off in terms of volume occupation and unloaded Q-factor (above 2000) among several dielectric resonator types considered for the proposed application. The type of input coupling and the geometry of the external resonators have been carefully chosen to improve performance in terms of power-handling, multipactor and PIM. The diplexer T-junction has been designed so as to minimize risk of a high level of PIM and any multipactor discharge up to 100W of input power. The first diplexer prototypes based on 3rd order filters have been manufactured and tested. The measured unloaded Q of the resonators is above 2000 and a stable RF response between -40°C and +90°C has been demonstrated by implementing a proprietary technique ensuring the thermal stability of the filter. A 5th order PIM level of - 118dBm has been measured in the case of two carriers of 50W CW at TX port. 100W of RF power handling has been demonstrated by RF test. Spark 3D simulations show no multipactor discharge up to 900W. The achieved volume saving is above 50% with respect to the reference standard technology (i.e. coaxial cavity filters).