Frequency and Bandwidth Tunable mm-Wave Hairpin Bandpass Filters Using Microfluidic Reconfiguration With Integrated Actuation

Microfluidically reconfigurable radio-frequency (RF) devices in general have been found attractive for low-loss, wide-frequency tunability and high-power-handling capabilities. Recently, integrated actuation of the microfluidically reconfigurable devices has been proposed for compact mm-wave device applications. This article for the first time introduces microfluidically reconfigurable frequency- and/or bandwidth-tunable bandpass filters (BPFs) operated at the mm-wave band with integrated actuation. The BPFs consist of coupled hairpin resonators. Frequency tuning is achieved by capacitively loading the resonators. Bandwidth tuning is achieved by creating varying capacitive loading among the resonators to control the interresonator couplings. The capacitive loading mechanisms are realized using the selectively metallized plates (SMPs) that can be repositioned within the microfluidic channels. The microfluidic channels are located directly above the stationary metallizations of the filter. Piezoelectric bending actuators placed under the filter's ground plane provide the SMP motion capability. The BPFs perform with the worst-case insertion loss of 3.1 dB. Frequency-tuning capable filters operate within 28-38-GHz band. Fractional bandwidth tunability varies from 7.8% to 16.7% at 38 GHz and 7.6% to 12.5% at 28 GHz for the filter that is capable of both tuning mechanisms. The filters are characterized to handle 5 W of the continuous RF power without needing thick ground planes or heat sinks. In addition, the frequency-tuning speed is characterized to be 285 MHz/ms.