Simultaneous reduction of amplitude and group-delay variation of input demultiplexer for Ku band satellite transponder

In this paper, design and realization of input demultiplexer(IMUX) for Ku band satellite transponder is described. Circulator chain structure has been used for demultiplexing each channel. Each channel consists of channel filter and external equalizer. External equalizers are designed to reduce the group delay variation and amplitude variation of channel filters simultaneously. Dual-mode technique is adopted for reducing the mass and volume of both the channel filters and external equalizers. Channel filters are designed to have 8-pole elliptic response and equalizers to be of 2-pole reflection-type. For good temperature stability characteristics, INVAR material is used for cavities, irises, and tuning srews of channel filters and external equalizers. The frequency drift has been taken into consideration in design procedure and measured by thermal test. Input demultiplexer is shown to be suitable for Ku band satellite transponder.