Coaxial filters are currently standard technologies for L-, S-band input filters. This technology has found wide application in mobile missions with multi-beam payloads, but also for TT&C and as IF filters, however, in L- and S-band this technology is inherently large and bulky since it is based on TEM air resonators.
The objective of the project is the assessment of new filter design concepts based on dielectric technology for L- and S-band applications to improve performances mainly in terms of mass and volume. Two Filter BBs and two Filter EMs have been manufactured and tested to fully evaluate the developed technology.
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In the realization of L- and S-band input filters coaxial filters are currently used as a standard technology. Their employment allows for a wide range of flexibility as well as a low IL with excellent performances in terms of spurious free ranges. Despite its advantages, this technology in too large and bulky because TEM air resonators are employed. In last decades it has been proved that dielectric resonators can be employed instead of coaxial resonators in such a kind of filters with a footprint reduction up to 50% and maintaining the same in-band RF performances. Of course a good trade-off in terms of spurious performance, temperature stability, unloaded Q-factor and assembly issues must be found.
Potential advantages and disadvantages using dielectric resonators instead of empty metallic cavities have been reported together with a brief history of their employment and evolution in last decades. The main electromagnetic modes of dielectric resonators and their behaviours were analyzed and described in full-wave simulations as well as their use in possible filtering structures. TM010 mode dielectric resonators with high dielectric permittivity (>40) have been employed, they are the best solution for a good trade-off in terms of volume, spurious free range and Q-factor.