Compact Filters and Filter Miniaturization
Microstrip filters are already small in size compared with other filters, such as wave-guide filters. Nevertheless, for some applications where the size reduction is of primary importance, smaller microstrip filters are desirable, even though reducing the size of a filter generally leads to an increase in dissipation losses in a given material and, consequently, reduced performance. Miniaturization of microstrip filters may be achieved by using high dielectric constant substrates or lumped elements. However, very often, for specified substrates, a change in the geometry of filters is required and, therefore, numerous new filter configurations become possible . This chapter is intended to describe novel concepts, methodologies, and designs for compact filters and filter miniaturization. The new types of filters discussed include: compact open-loop and hairpin resonator filters, slow-wave resonator filters, miniaturized dual-mode filters, lumped-element filters, filters using high dielectric constant substrates, and multilayer filters, including those based on low-temperature co-fired ceramic (LTCC) and liquid crystal polymer (LCP) packaging materials.
10.1 MINIATURE OPEN-LOOP AND HAIRPIN RESONATOR FILTERS
In the last chapter we introduced a class of microstrip open-loop resonator filters. To miniaturize this type of filter, one can use so-called meander open-loop resonators . For demonstrate a compact microstrip filter ...