This paper presents a metasurface (MS) providing single to dual transmission frequency bands under different thermal excitation conditions. Vanadium dioxide (VO
2
) has been incorporated into a ...metallic MS design to generate a switching feature under temperature variations. The proposed VO
2
-based MS offers dual band transmission responses at 1.4 THz and 2.66 THz at room temperature (300 K). The same structure exhibits single band transmission response at 1.4 THz by rejecting the higher band, when the VO
2
layer is acting as a metal under thermally heated condition (above 340 K). The device is polarization-insensitive due to four-fold symmetry and transmission performance has been found to be angularly stable up to 40° for both insulating as well as metallic phases. The device responses at two distinct states have also been verified by an equivalent circuit model. This device can find potential applications towards upcoming 6G and futuristic communication systems involving terahertz (THz) frequency band as well as shielding purposes.
This paper proposes a tunable graphene-based wideband metasurface for high absorption in the lower mid-infrared frequency region. The unit cell of the proposed structure consists of slot generated ...out of modified fractal-shaped graphene layer deposited on top of amorphous silicon dioxide (SiO 2 ) grown over 0.1-μm-thick gold layer. The structure exhibits distinctive high absorption greater than 90% absorptivity over the range of 3.69-9.77 THz covering a wideband of 6.08 THz. Incorporation of graphene in the metastructure can tune the absorption bandwidth owing to conductivity modulation of graphene by the control of impurity doping and mechanical stretching. Besides, the absorber is polarization independent under normal incidence because of the fourfold symmetry of the deposited graphene pattern. The designed prototype has been studied under oblique incidences for both transverse electric and transverse magnetic polarizations where wideband absorption has been experienced up to 40° incident angles for both cases. The prototype is found to be as thin as ∼ λ /11 with respect to the lowermost frequency of the absorption. The period of the unit cell is ∼ λ /13 supporting the effective homogeneity condition in subwavelength region. The structure can have applications toward sensing, spectroscopy, etc.
This paper presents equivalent circuit modeling of an ultra-thin polarization-independent metamaterial microwave absorber consisting of three concentric closed ring resonators (CRR). The unit cell ...size as well as the other geometrical dimensions like radii and widths of the rings are optimized so that absorptions take place at three distinct frequencies near to the middle of the FCC defined radar spectrum eg., at 5.50 GHz, 9.52 GHz and 13.80 GHz with peak absorptivities of 94.1%, 99.6% and 99.4% respectively. The equivalent circuit model of the triple band absorber has been developed sequentially considering the single band and double band absorber models. The circuit simulation of the final model agrees well with the full-wave simulation, thus validating the modeling technique. The structure is also fabricated and experimental absorption peaks are found close to the simulated values.
In this paper, a novel, compact, high-gain, directive, and superstrate configuration-based metasurface (MS) antenna has been designed, which incorporates a fractal-shaped slotted patch having a ...periodic arrangement of square patches along with a shorting via at its center and a couple of rectangular slots in the ground plane. The MS is designed over the FR4 dielectric by introducing a periodic arrangement of unit cells in which the unit cell is structured by a C-type patterned patch in the center surrounded by a couple of L-type-shaped patches. The MS is separated by a layer of Teflon from the conventional patch antenna designed over the FR4 dielectric, thereby acting as a superstrate. The proposed antenna provides good impedance matching across the frequency region of 10.14-10.94 GHz with a unidirectional radiation pattern. A fractional bandwidth of 7.6% and a maximum return loss of 24 dB have been realized at 10.44 GHz. The measured realized gain of 7.57 dBi was obtained at the same operating frequency. As the proposed antenna is more efficient, it can be promoted for <inline-formula> <tex-math notation="LaTeX">X </tex-math></inline-formula>-band operations, such as satellite communication, defense purpose, and medical supervision.
In this article, the performance of a meander‐line‐based microstrip patch antenna with split‐ring resonator (SRR)‐based slots and defected ground is analyzed at the terahertz frequency range. The ...designed antenna shows a multiband application within a frequency range of 3.77 to 6.60 THz and operates over six different frequencies (viz. 3.83 THz, 4.24 THz, 5.12 THz, 5.50 THz, 5.95 THz, and 6.50 THz). A maximum return loss of 37 is achieved over the band of 5.85 to 6.18 THz, while a maximum realized gain of 7.54 dBi and a total efficiency of 54% is obtained at 4.24 THz. The ground and radiating elements of the antenna are made of gold. Silicon dioxide is used as a substrate material. The antenna simulation is performed and reported in this study. The proposed antenna finds its applications in the detection of colon cancer, skin cancer, brain tumor, drug detection, and communication fields for point‐to‐point communication purposes.
The performance of meander line based microstrip patch antenna with split ring resonator (SRR) based slots and defected ground has been analysed in this paper at terahertz frequency range. The maximum return loss of 37 dB has been achieved over the band 5.85‐6.18 THz while the maximum realized gain of 7.54 dBi has been obtained at 4.24 THz. The proposed antenna finds its applications in detection of colon cancer, skin cancer, brain tumour, drug detection and communication fields like point to point communication purpose.
This paper discusses a low-profile, planar, efficient, and directed CPW-fed monopole antenna with a metasurface (MS) for WLAN as well as modern civil and military applications. A stacked 7 × 7 order ...metasurface (MS) and CPW-fed slotted patch antenna are sandwiched together to create the metasurface antenna (MSA). The overall size of the proposed prototype is 0.25λ
0
× 0.25λ
0
× 0.06λ
0
only, where λ
0
is the free-space wavelength at 2.34 GHz. This antenna has fractional bandwidths of 6.8% and 53.8% at two different frequencies of 2.34 and 8.94 GHz, respectively. With a peak gain of 8.7 dBi and radiation efficiency of 91.1% at 11.51 GHz, the antenna offers directional radiation characteristics in both the E- and H-planes. A comparable circuit model for the proposed prototype has also been described in order to analyze the outcomes of the electromagnetic simulation. The intended prototype has been fabricated, and the experimentally measured results closely resemble the simulated ones.
A broadband polarisation-independent circuit analogue absorber comprising multi-layer resistive frequency selective surfaces (FSS) has been presented in this study. The proposed structure consists of ...a periodic arrangement of square loops loaded with lumped resistors and these square loops are printed on dielectric substrates separated by an air spacer. The simulated result shows the reflectivity below −10 dB in the frequency range from 4.96 to 18.22 GHz (fractional bandwidth of 114.40%) under normal incidence, covering C, X, and Ku bands. An equivalent circuit analysis has been introduced to characterise the proposed absorber, which shows good matching with the full-wave analysis. The effects of the individual FSS layers and the air spacer have been studied and several parametric variations have been carried out to examine the sensitivity of the design parameters on the absorption bandwidth. Finally, the designed absorber has been fabricated and measured in anechoic chamber, which shows good agreement between the experimental results and the simulated responses, under different angles of incidence as well as for various polarisation angles.
This study proposes a metasurface (MS) based high performance antenna in which the radiating patch is embedded with split ring resonators in its square slots. The slotted corner cut rectangular patch ...antenna with defected ground plane and the MS are placed together in the same plane. The designed prototype operates over dual frequencies with impedance bandwidths (S11 < −10 dB) of 4.02% and 28.24% at 9.20 and 11.65 GHz respectively. The antenna possesses a maximum return loss of 42 dB at 11.65 GHz over 11.23–14.5 GHz band while the measured realized gain of 10.66 dBi has been obtained at 14.44 GHz. The antenna exhibits unidirectional far‐field radiation characteristics and the radiation efficiency of 67% has been achieved at 14.44 GHz. The antenna prototype has been fabricated on FR4 dielectric substrate, having an electrical size of 1.16λ0 × 1.82λ0 × 0.06λ0, where λ0 is the free‐space wavelength at 11.65 GHz. This makes the proposed antenna single‐layer, broad impedance bandwidth, high gain and ease of fabrication in nature. The measured results are in good agreement with the simulated ones. The designed antenna can be applicable in defense and military, satellite communication, medical analysis for determination of radio waves and numerous communication fields.
Key Points
Dual band characteristics have been achieved
Gain has been enhanced in both the bands
Experimental results are in compliance with the simulated results
This paper reports a detailed study of a graphene-based metasurface to function as tunable broadband linear to circular polarization converter in the terahertz gap. This device provides a wide ...polarization conversion band of 2.25 THz (3.75 THz to 6 THz) with an enhanced fractional 3-dB axial ratio bandwidth (FARBW) of 46.15%. The proposed structure consists of a simple tri-layer configuration where the meta-atom comprises a patterned graphene layer on a gold-backed silicon dioxide substrate. The proposed reflective-type linear to circular polarization converter (RLCPC) exhibits both right-handed and left-handed circular orientations of the reflected wave in two halves of the operating spectrum, further validated in terms of polarization ellipses developed by an inhouse code. The lack of experimental setup at the above said frequencies available to the authors in their country has been paid off by verifying the response using a detailed circuit model. The RLCPC maintains a thickness of λ o /7.69 with a lattice size of λ o /8.33. The structure also promises a stable wideband circular polarization conversion up to 20° and a dual-band circular polarization conversion up to 40° incident angle of the electromagnetic wave. This device can be useful for THz beam scanning antennas, RCS reduction and THz antennas for space and military radar applications.
This paper reports an elaborated study of a graphene-based transmittive-type triple-band linear to circular polarization converter (TTLCPC) within the lower mid infrared (MIR) region, covering the ...terahertz gap. The linearly polarized incident electromagnetic wave undergoes conversion into the circular polarization at three distinct frequencies viz., 5.72 THz, 13.49 THz and 18.90 THz. The axial ratios (AR) at these three THz bands are under 3 dB till 40°incident angles of the electromagnetic wave. The circular polarized nature of the transmitted electromagnetic wave was verified by generating the polarization ellipses at the three distinct frequency bands. The proposed prototype is designed in the sub-wavelength region by maintaining a thickness of λ/26.11 and a periodicity of λ/4.35 with respect to the lowest frequency band; making the proposed device ultra-thin and compact in nature. The proposed TTLCPC can be useful for electromagnetic measurement, THz detection, THz sensing, THz imaging, THz antenna and stealth technology, etc.
Display omitted
•The graphene metasurface design exhibits linear to circular polarization conversion.•The axial ratios are less than 3 dB till 40°incident angles at three distinct THz bands.•Polarization ellipses confirm circular polarized nature of the transmitted wave.•The design evolution has been studied in details in the light of field distribution.
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