Investigation of coupling structures for coplanar bandpass filters

Single side metallization is one of the big advantages of coplanar waveguide (CPW) circuits. On the other hand, coupling in one plane only may lead to difficulties designing end or side coupled bandpass filters due to rather weak or multi-mode coupling of the filter resonators. A possible alternative is the introduction of two metallization layers separated by an additional dielectric sheet. In this paper, a number of possible coupling structures for bandpass filters based on standard CPW as well as on multilayer structures are investigated and compared, including some novel coupling arrangements.<>