Filter characteristics and a low-loss filter design for broadcasting satellites

This paper describes the filters which will come into question in designing a multi-channel, high-power transponder for the 12 GHz band broadcasting satellite of the future. The characteristics of the input/output multiplexers, which are required for using eight channels assigned to Japan, are derived on the condition that the signal degradations and spurious emission are suppressed below the allowable levels. Several kinds of filters are examined for the input/output multiplexers to which the attenuation of 40 dB/15 dB, respectively, are assigned at the adjacent channel edges. Based on the above results, a four-order dual TE(113) mode elliptic filter is designed and fabricated with the purpose of realizing a low-loss filter for the output multiplexer. The measured insertion loss of the filter is 0.35 dB for 37 MHz bandwidth which corresponds to an averaged unloaded Q of 12,000.