A Compact, High Roll-off Transmit RejectWaveguide Filter

In this paper, design and realization of a compact, high roll-off waveguide based Transmit Reject Filter (TRF) is presented for application in Extended Ku-band Satellite Communication (SATCOM). A sharp roll-off in RF performance has been achieved by introduction of corrugations in the waveguide structure. Further, short input/output matching networks based on stubs of optimized corrugations has been used for impedance matching. The design method is based on step-shaped band stop elements separated by very short waveguide sections. An 18
^th
order waveguide filter has been designed and realized in a compact length of 130mm. In measurement, low insertion loss of < 0.5dB in passband and sharp roll-off (rejection slope) of > 65 dB per 0.25 GHz has been achieved. This makes the TRF highly suitable for use in Ext. Ku band SATCOM.