Microfluidically Reconfigurable Microstrip Line Combline Filters With Wide Frequency Tuning Capabilities

Microfluidically repositionable selectively metallized plates (SMPs) are utilized for the first time to design and realize microstrip line combline filters with wide frequency tuning and high power-handling capability. A continuous frequency tuning range of 2.7:1 is achieved by utilizing tight coupling between the SMP and open-ended microstrip line resonators in order to change their length for tuning from 2.5 to 4 GHz and capacitively load one of their open ends for tuning from 1.5 to 2.5 GHz. The unloaded quality factor (Q
_u
) of the resonators is maintained relatively constant (210-190) across the entire tuning range allowing for the low insertion loss (IL) and high power-handling capability. Specifically, a ~5% constant fractional bandwidth fourth-order filter design is discussed and experimentally verified. The filter exhibits less than 3-dB IL across the 2.7:1 tuning range. It is shown that the filter's power handling capability can reach up to 15 W under constant average power excitation.