A comparative study of different microstrip planar bandpass filters topologies in an industrial context

One of the most stringent specification in modern microwave equipment is the control of spurious levels. This is a daily concern for microwave engineers designing telecommunication or observation space-borne equipment. AAS- F has studied and developed planar bandpass filters in microstrip mode because they can be easily inserted into hybrids. The investigated filters topologies are coupled lines, interdigitated, hairpin, pseudo-elliptic response and dual behaviour resonator. each of them has advantages and drawbacks, first in term of electrical response but also in term of industrial effective use. For each topology, a list of main characteristics has been identified to allow comparison and easier choice, depending of the targeted application. This includes the reachable bandwidth, the insertion losses or the synthesis easiness. Also, the filters sensitivity to mechanical environment or manufacturing process have been summarized in a handful way. Such a study can give precious inputs for designers in other microwave domains as well.