Ultra-thin tunable microwave absorber using liquid crystals

Fusco, Vincent; Cahill, R.; Hu, Wencheng; Simms, S.

doi:10.1049/el:20082191

Cited by 25 publications

(14 citation statements)

References 5 publications

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“…Recently the anisotropic property of nematic state liquid crystals (LC) [6] has been exploited to create an ultra thin microwave absorber with a resonant frequency which is tunable over a 2% band centred at 10.1 GHz [7]. This structure gives a reflection coefficient which is below -10 dB in the frequency range 9.93 -10.3 GHz (4%).…”

Section: Introductionmentioning

confidence: 99%

“…This structure gives a reflection coefficient which is below -10 dB in the frequency range 9.93 -10.3 GHz (4%). The absorber which is identical in construction to a HIS consists of a periodic array of microstrip patches which was placed on the surface of a cavity containing a 500 μm thick layer of lossy LC material [7]. A small bias voltage was used to vary the permittivity of the LC between two extreme values ε ⊥ and ε // corresponding to the states where the molecules are orientated perpendicular and parallel to the flux lines in the region between the patch and ground plane.…”

Section: Introductionmentioning

confidence: 99%

“…A small bias voltage was used to vary the permittivity of the LC between two extreme values ε ⊥ and ε // corresponding to the states where the molecules are orientated perpendicular and parallel to the flux lines in the region between the patch and ground plane. In this paper we describe the design and performance of a thin Salisbury screen absorber which gives a very much larger -10 dB reflectivity bandwidth than the absorber reported in [7]. The arrangement employs a tunable LC based HIS to modulate the reflection component (φ HIS ) of the total signal phase.…”

Section: Introductionmentioning

confidence: 99%

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Electronically tunable liquid crystal based Salisbury screen microwave absorber

Seman

Cahill

Fusco

2009

2009 Loughborough Antennas &Amp; Propagation Conference

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In this paper we describe the design, manufacture and performance of an electrically thin (0.15λ) dynamically adaptive Salisbury screen absorber. The structure is backed by a high impedance surface which is constructed on a 250 μm thick liquid crystal substrate. The shift in the resonant frequency of the radar absorber is obtained by exploiting the voltage dependent anisotropic property of nematic state liquid crystals. Simulated results show that the reflection minimum is tunable over a 2.3 % bandwidth and the reflectivity is below -10 dB in the frequency range 8.8 -10.05 GHz (13%). Numerical predictions for normal incidence operation are shown to be in close agreement with experimental results when bias voltages are applied in the range 0 V to 20 V.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Electronically tunable liquid crystal based Salisbury screen microwave absorber

Seman

Cahill

Fusco

2009

2009 Loughborough Antennas &Amp; Propagation Conference

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“…target) is able to control the echo characteristic after sensing and feedback. In recent two decades, to achieve such active absorption modulation, several composite structures have been proposed [3][4][5][6][7][8][9][10][11][12][13][14][15] by resorting to mechanical or electrical methods. In Ref.…”

mentioning

confidence: 99%

“…In Ref. 4, approximate 200MHz tuning range in frequency is also demonstrated by varying the DC bias-voltage applied upon a liquid crystals material that locates between a metal backplane and a periodic array of micro-strip patches. In the latest ten years, introducing lumped circuit elements (i.e.…”

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confidence: 99%

Active microwave absorber with the dual-ability of dividable modulation in absorbing intensity and frequency

Wu¹,

Hu²,

Wang³

et al. 2013

AIP Advances

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We present the design, fabrication and experimental demonstration of an electrically active absorber at microwave frequency. Unlike those proposed before, simulation and experiment data present that its working frequency and absorbing intensity can be both but separately controlled. The electromagnetic coupling analysis reveals that the feature arises from the dividable frequency and amplitude modulation on an active magnetic resonator controlled by varactor and pin diodes. Such separable modulating behaviors are further confirmed by the equivalent LC circuit model. It is believed that this will be an important step towards smart application of active absorber.

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Liquid‐Metal‐Enabled Flexible Metasurface with Self‐Healing Characteristics

Mitra

Babu

et al. 2022

Adv Materials Inter

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an emerging material, liquid metal when used in combination with polydimethylsiloxane (PDMS) finds applications in soft/ flexible and wearable electronics. [2] Due to its flexibility and deformability, liquid metal encapsulated in PDMS has recently shown self-healing characteristics after damage on the device. [7][8][9] Gallium-based liquid metal has been explored in various applications ranging from electrocardiogram, [10] microcooling, [11] thermometers, [12] flexible electrodes, [13,14] flexible interconnection, [15] strain sensors, [16] pressure sensors, [17] inkjet printing, [18] energy harvesting, [19,20] and magneto-hydrodynamic pumps. [21] Metasurface-based frequency selective surface (FSS) exists in 1D or 2D as periodic arrays of sub-wavelength metallic elements on dielectric surfaces. [22,23] Based on material, physical construction, [24] and geometry, [25] the FSSs are classified into high-pass, low-pass, band-pass, and bandstop filter. [25,26] The performance and behavior of the FSS is dependent on the geometry, periodicity, array size, and choice of materials (conductivity and permittivity). [24] The FSSs have been extensively studied [27] since 1960s, however its fundamental origin can go back to Marconi and Franklin's patent of reflectors in 1919. [28] The ability to tailor FSSs to curtail certain frequency band makes it a vital component in communication applications including radar, [23,29,30] microwave absorber, [29] satellite, [23,31] electromagnetic interference shielding, [32] dichroic sub reflectors, [33] reflect array lenses, [34] lens antenna, [35] polarizers, [36] stealth blankets, [37] and wireless networks. [23,38] Traditional metasurfaces have been realized on rigid substrates using materials such as glass, [23] quartz, [39] polytetrafluoroethylene (PTFE) reinforced with glass, [40] commercially available FR-4-based printed circuit boards, [41][42][43] Rogers 5880 PTFE composites supported with glass microfibers. [44] The varactor diodes like BB 837 or BB 857-02 V, [41,45] liquid crystal, [40,46] and silver paint were either soldered, [41] filled/deposited, [40,46] or painted into these mechanically rigid substrates. [23,47] Recently, liquid metal injection in all connected microfluidic channels in PDMS has been used to realize physically flexible metasurfaces with or without incorporation of soldered chip resistors. [48,49] While the metasurface is flexible, serial injection/withdrawal of liquid metal in all connected microfluidic channels may limit its application (e.g., metasurface that needs unconnected patterns). Injection filling is also known for leaving airgaps and may cause device delamination. [50] A flexible self-healing metasurface using gallium-based liquid metal encapsulated in polydimethylsiloxane (PDMS) operating in the X-band (8-12 GHz) is reported. A band-stop metasurface with center frequency at 9.82 GHz is designed using floating patches surrounding the respective end cap of a Jerusalem cross. A large-scale (up to 10 × 10 array) metasurface is patterned in PDMS and ...

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Ultra-thin tunable microwave absorber using liquid crystals

Cited by 25 publications

References 5 publications

Electronically tunable liquid crystal based Salisbury screen microwave absorber

Electronically tunable liquid crystal based Salisbury screen microwave absorber

Active microwave absorber with the dual-ability of dividable modulation in absorbing intensity and frequency

Liquid‐Metal‐Enabled Flexible Metasurface with Self‐Healing Characteristics

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