Miniaturized S-band Diplexers for Space Applications with high far out-of-band Rejection

The paper presents the results of theoretical considerations, supported by the results of simulations, concerning the implementation of a miniaturized S-band diplexer based on SIR (Stepped-Impedance Resonators). The project is the next stage in the development of S-band diplexers, manufactured by WiRan. This time, the focus was on minimizing the dimensions and weight of the device and achieving high far-out-of-band-rejection (FOOBR) of 2nd-5th order harmonics. At the same time, efforts were made to keep the remaining electrical parameters attractive, thus meeting the project requirements set by European Space Agency. The choice of the diplexer technique (SIR with Teflon disc-PTFE) was dictated by the excellent FOOBR results obtained in this type of solutions. According to the assumptions, the project is to be implemented at least at the Technology Readiness Level 6. Nevertheless, efforts will be made to ensure that the project finally ends at TRL 9. In this article a band pass filter is presented being a demonstrator of technology to be applied in final diplexer with extraordinary spurious-free performance of up to 5 times the edge frequency of TX filter and very good multipactor performance, which is critical aspect in space applications. Although high quality factor is maintained, the resulting geometry allows for compact realization of diplexer.