Abstract
In this paper, we have proposed a frequency-switchable complementary split-ring resonator (CSRR)-loaded quarter-mode substrate-integrated-waveguide (QMSIW) band-pass filter. For frequency switching, a microfluidic channel and liquid metal are used. The liquid metal used is eutectic gallium-indium (EGaIn), consisting of 24.5% indium and 75.5% gallium. The microfluidic channels are built using the elastomer polydimethylsiloxane (PDMS) and three-dimensional-printed microfluidic channel frames. The CSRR-loaded QMSIW band-pass filter is designed to have two states. Before the injection of the liquid metal, the measured center frequency and fractional bandwidths are 2.205 GHz and 6.80%, respectively. After injection, the center frequency shifts from 2.205 GHz to 2.56 GHz. Although the coupling coefficient is practically unchanged, the fractional bandwidth changes from 6.8% to 9.38%, as the CSRR shape changes and the external quality factor decreases. After the removal of the liquid metal, the measured values are similar to the values recorded before the liquid metal was injected. The repeatability of the frequency-switchable mechanism is, therefore, verified.
Highlights
Improvements in frequency-switchable devices, such as PIN diodes [1,2,3,4], varactor diodes [5,6,7,8], radio frequency microelectromechanical systems (RF MEMS) [9,10,11,12], and field-effect-transistor (FET)switches [13,14] have enabled the growth of frequency-switchable technology, owing to its reliability and versatility
We introduced a quarter mode substrate-integrated-waveguide (QMSIW) cavity resonator, with approximately 75% reduction in size compared to a full SIW resonator, while maintaining the same resonant frequency [27,28,29]
We propose a frequency-switchable complementary split-ring resonator (CSRR)-loaded quarter-mode substrate-integrated-waveguide (QMSIW) band-pass filter
Summary
Improvements in frequency-switchable devices, such as PIN diodes [1,2,3,4], varactor diodes [5,6,7,8], radio frequency microelectromechanical systems (RF MEMS) [9,10,11,12], and field-effect-transistor (FET). Switches [13,14] have enabled the growth of frequency-switchable technology, owing to its reliability and versatility These switchable mechanisms need additional DC bias networks. In the case of frequency-switchable applications, to fill microchannels with conducting materials, a liquid metal, such as eutectic gallium-indium (EGaIn, indium (In) 24.5% and gallium (Ga) 75.5%) is extensively used, since it is easy to inject and non-toxic in nature [19,20,21]. Injecting the liquid metal inside microfluidic channels constructed over an elastomeric substrate (e.g., polydimethylsiloxane (PDMS)). Injecting liquid metal into microfluidic channels offers a simple method for shaping the metal into useful structures such as switches, to achieve reconfigurability in filters, antennas, and other similar devices. The substrate-integrated-waveguide (SIW) cavity resonator is a well-known technology that provides advantages of compact size, easy fabrication, and low leakage loss [25,26]. The microfluidic channel was fabricated using a three-dimensional (3D) printer which provided simpler and faster fabrication compared to conventional lithography [31,32]
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