Ultra sharp roll-off bandpass filter design for near pass-band RFI mitigation

This paper presents the design of a compact, suspended microstrip line, bandpass filter with precision Radio-Frequency Interference (RFI) mitigation capability. The presence of strong RFI adjacent to the lower-end of the operating band of the recently upgraded Australia Telescope Compact Array (ATCA) 1-3 GHz cryogenic receiver systems necessitated the development of a band defining filter with a very sharp roll-off characteristic. A bandpass filter with a null for RFI mitigation has been developed and deployed in the newly upgraded 1-3 GHz band receivers. We adopt the image parameter method with m-derived filter section for filter design to obtain very sharp roll-off characteristics for near pass-band RFI mitigation.