Miniaturized C-Band SIW Filters Using High-Permittivity Ceramic Substrates

International audienceThis paper introduces an effective way to buildefficient miniature C-band filters using high-permittivityceramics. The objective was to evaluate the feasibility ofsuch filters using commercial electromagnetic simulators anda conventional fabrication process. For the demonstration,the substrate integrated waveguide (SIW) technology waschosen. Compared with planar solutions, this configurationoffers good quality factors and good electrical performancesas a consequence. However, its dimensions are large, leadingto unacceptably large footprints for many applications. Thesolution proposed in this paper is based on a ceramic substratewith a permittivity of 90, which allowed us to work with shorterwavelengths. In comparison with a standard alumina substrate(permittivity εr = 9.9), this approach makes it possible to reducethe footprint up to nine times. Two prototypes were realized on aTrans-Tech ceramic substrate (thickness = 635 μm, εr = 90, andtanδ = 9 · 10−4). The first prototype is a folded sixth-order SIWfilter including a cross coupling combining coplanar waveguideprobes and a thin microstrip line on an InterVia substrate. Thesecond one is a folded eighth-order SIW filter without crosscouplings. Here, we compare the sixth-order prototype with anidentical one built on alumina. The eighth-order filter, which hadno alumina counterpart, is a potentially useful alternative forsituations where complex technological steps must be avoided