MEMS tunable filters based on DGS and waveguide structures: a literature review

In the last two decades, filters based on defected ground structure (DGS) have been employed in various radio frequency systems, and there has been a significant growth in using these structures. In non-tunable filters, a separate unit is used for each telecommunication channel, while the use of tunable filters can reduce the size of multichannel filters. In this paper, tunable filters based on DGS, microstrip and coplanar waveguide (CPW) structures are reviewed. The filters that are designed in this area include either new DGSs or improvements in the previous structures. This paper focuses on tunable filters that have been based on CPW with DGS in the literature since these filters can be easily implemented using CPW lines with coplanar elements realization, no via hole is needed in these filters and radiation loss is less in CPW lines compared to other types of lines. To the best of the author's knowledge, there is currently no review article on the tunable filters based on microstrip and CPW in MEMS technology. This paper can be very useful for starting to work on tunable filters that include DGS.