Compact Rx/Tx Channel Duplexer with Tuning Capability for Integration in a 26GHz High Capacity Short Haul Radio Equipment

A novel Ka-band Rx/Tx channel duplexer1 design with tuning capability is established for the 26GHz band. Thus, only a single hardware is necessary to serve all duplex channel combinations of the overall radio frequency band - a prerequisite for large scale low cost unit production. The applied filters consider optimal tailored transfer functions with transmission zeros, realized with compact planar overmoded TE103 cavity structures to accommodate the extreme rejection demands while maintaining low insertion loss. A further design aspect has been easy integration and interfacing into the waveguide subsystem of the radio equipment. The complete duplexer structure has been designed using a mode matching based CAD. To satisfy the stability of the responses for the given outdoor environmental conditions it has been realized from silverplated INVAR sheets - a technique supporting the low cost issue. Good agreement of computed and measured results and the successful testing of the tuning capability verifies the design.