Dielectric receiving multi band filtering filter for cellular base stations

A novel dielectric receiving multiband fitting filter (MBFF) for cellular base stations is presented. This filter is composed of a dielectric bandpass filter and some dielectric bandstop filters. Dielectric resonators that compose the bandstop filter are AFRs (active feedback resonators). Because an AFR is small and has high unloaded Q, the bandstop filter becomes compact and has sharp rejection characteristics. Physical size of the MBFF is 88×480×400 mm. Insertion loss is 2.0 dB, and attenuation is 20 dB. The construction and performance of the AFT, the active bandstop filter in which AFRs are used, and the MBFF in which active bandstop filter is used are described