Abstract
In this paper, we propose a switchable band-pass/band-stop filter using liquid metal alloy as a fluidic switch. The filter is designed based on the Chebyshev response and implemented using a three-stage quarter-wavelength resonant structure. The fluidic switch is realized by injecting eutectic gallium–indium (EGaIn) in the microfluidic stubs, engraved in the polydimethylsiloxane (PDMS) material. When the fluidic switch selects the short stub using a micro-pump and microprocessor for switching, the filter acts as a bandpass filter (BPF) with the short stubs. When the fluidic switch selects the open stub, the filter acts as the bandstop filter (BSF) with the open stubs. At the BPF mode, the center frequency is 2.5 GHz and the 1-dB bandwidth is 1.75–3.07 GHz. The insertion loss is 0.5-dB ± 0.4-dB. At the BSF mode, the 15-dB bandstop bandwidth is 2.4–2.65 GHz with 2.5 GHz center frequency.
Highlights
A switchable bandpass/bandstop filter has received particular attention as it enables radio systems to be operated in an interference-congested environment [1], reduces the size [2], solves the complexity problem [3], and reduces the cost [4,5,6,7]
For a dynamic interference situation, the bandpass/bandstop filters (BPF/BSF) are used in the bandstop mode to reduce the high-power interference close to the desired signal, while the bandpass filter is selected for a lower interference environment [8]
When the fluidic switch selects the open stub, the proposed filter is working as a BPF
Summary
A switchable bandpass/bandstop filter has received particular attention as it enables radio systems to be operated in an interference-congested environment [1], reduces the size [2], solves the complexity problem [3], and reduces the cost [4,5,6,7]. Tunable filters with bandpass/bandstop using new structures such as electromagnetic bandgap (EBG), closed-ring resonator, and two- and four-pole resonators [2,10] have been investigated. In these filters, active devices such as a varactor diode, pin diode, radio frequency micro-electro-mechanical system (RF MEMS), or some other actuation mechanisms have been employed to facilitate the switching. When the fluidic switch selects the open stub, the proposed filter is working as a BPF. When the fluidic switch selects the open stub, the proposed filter is working as is working as a BSF.
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