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This paper delves into the intricacies of designing, fabricating, and characterizing a metasurface exhibiting epsilon-negative (ENG) and near-zero index (NZI) properties. Specifically, it focuses on an eye-shaped coupled circular split ring resonator (CC-SRR) metasurface, crafted from copper on an epoxy resin fiber (FR-4) dielectric substrate material. The design is further optimized to induce resonance frequencies at approximately 7.5, 8.8, and 13.4 GHz within the C, X, and Ku bands, respectively. Utilizing the COMSOL Multiphysics and CST Microwave Studio simulation tools, the structural design is developed to ascertain its electromagnetic properties across the 1–15 GHz frequency spectrum. Experimental measurements of the transmission characteristics of the fabricated metasurface align closely with the simulated results. The electromagnetic field distributions of the proposed metasurface structure are scrutinized, revealing tunable characteristics contingent upon variations in the thickness ( t s ) of the dielectric substrate material and the copper resonator thickness ( t m ). Additionally, a theoretical model employing an equivalent circuit, featuring various inductor (L) and capacitor (C) components, is presented to compare against simulated results for the targeted resonance frequencies. [ABSTRACT FROM AUTHOR]

In this article, a meander line with parasitic resonator based on ENG metamaterial is introduced, with nonlinear regression of sensitivity for sensing applications. The unit cell is manufactured on a dielectric substrate of FR-4 with a thickness of 1.5 mm. The electrical dimension of the optimized cell is 0.098λ×0.094λ, where λ is the calculated wavelength at 7.2 GHz resonance frequency. A sensor has been designed by the unit cell to measure the thickness of the polypropylene. The offered metamaterial architecture exhibits resonance frequency 7.2 GHz at C-band with the amplitude of −21.72 dB. The NRW approach based MATLAB software shows properties with an ENG behavior and permeability close to zero. For the analysis procedure, a frequency domain solver with the frequency range of 2–12 GHz was used. ADS software verified the scattering parameters (coefficient of transmission) of the equivalent circuit for the corresponding unit cell with the CST result. The result indicates that this design has SNG features at C-band. The EMR (effective medium ratio) of this suggested unit cell is 10.60 at 7.2 GHz resonance frequency. The bandwidth of the optimized cell is 6.75–7.36 GHz, and the negative permittivity region is 7.2–7.8 GHz 1 × 2, 2 × 2, 4 × 4, and 16 × 16 array of unit cell results have been examined. All the array results show the same with the unit cell. Substrate material has also been changed to see the effect of resonance frequency in the parametric study. Finally, the proposed meander line structure performance was further simulated numerically and experimentally investigated for sandwich combination thickness sensing. It shows a narrow bandwidth sensing range between 6.25 and 6.47 GHz with significant sensitivity (S) and accuracy. The design complies with superior effective medium parameters and affords miniaturization factor for the size. Due to its low profile and high EMR, the planned ENG metamaterial can be a suitable C-band aspirant for sensing applications.

This paper discusses a spider net-shaped triple split ring resonator (SNTSRR) based epsilon-negative metamaterial with a high effective medium ratio. The proposed SNTSRR unit cell structure is a modification of the general split ring resonator and consists of three octagonal-shaped split ring resonators (SRR). Two metal strips attach the split ring resonators to increase the electrical length of the proposed SNTSRR unit cell. The optimized size of the proposed SNTSRR unit cell, using Rogers RO4350B substrate material, is 10 × 10 × 1.524 mm3. The frequency ranges of the transmission of microwave applications are: 2.83–2.89 GHz for S-band, 4.24–4.31 GHz and 6.74–7.06 GHz for C-band, 9.17–9.26 GHz and 10.98–11.16 GHz for X-band, and 12.62–13.00 GHz for Ku-band. The unit cell achieves six resonant frequencies of 2.86 GHz, 4.28 GHz, 6.94 GHz, 9.22 GHz, 11.10 GHz, and 12.89 GHz for S-, C-, X-, and Ku-bands, respectively. A comprehensive investigation of effective medium parameters, scattering parameters, mutual coupling effect, and the unit cell properties with electromagnetic propagation were accomplished in this paper. The proposed SNTSRR unit cell revelations epsilon negative (ENG) properties in the frequency ranges of 2.87–3.05 GHz, 4.27–4.45 GHz, 6.94–7.39 GHz, 9.24–9.34 GHz, 11.12–11.26 GHz, and 12.90–13.24 GHz. For experimental validation, we fabricated the proposed SNTSRR unit cell along with its array construction. After that, we measured the scattering parameters, which showed better agreement between the simulated and the measured outcomes. Furthermore, the coupling effects between the 1 × 2 and the 2 × 2 array structures with different distances were analyzed, and they showed better performance with low impact. Additionally, the calculated effective medium ratio (EMR) is 10.48, which infers compactness and efficacy of the unit cell. It should be noted that the compact size, effective medium parameters, S-parameters, and high EMR make the proposed SNTSRR metamaterial appropriate for quad-band microwave applications. Finally, the proposed SNTSRR unit cell has been employed as an application in 3D cross-fed wideband antenna to enhance the bandwidth and gain of the antenna, which is appropriate for microwave head imaging applications.

In this article, a square enclosed circle split ring resonator (SEC-SRR) based metamaterial is described that shows negative permittivity (ENG) with near-zero-index (NZI) of refraction. The unit cell of this metamaterial is formed with two SRR rings, one with square in shape and another circular shaped. The inner circular SRR has related to the outer square SRR by the metal strip. The analyzed design is very simple, but the outcome of this recommended unit cell is high i.e., it covers the multiband S-, C-, and X- bands. Rogers is used as a substrate to design the proposed SEC-SRR that has a thickness of 1.524 mm. The unit cell has a dimension (electrical) of 0.070λ × 0.070λ. The simulation software CST microwave studio-2019 is used to identify transmission (S21) and reflection (S11) coefficient and from this knowledge relative permittivity, permeability and refractive index is obtained by using MATLAB code based on Nicolson-Ross-Wier (NRW) method. The simulated resonance frequencies are 2.61, 6.32 and 9.29 GHz with well-matched to the measured ones. The negative permittivity regions are obtained in 2.63–2.87 GHz, 6.39–7.45 GHz, and 9.37–9.52 GHz covering S-, C-and X-bands, respectively. The equivalent circuit is modeled in Advanced Design Software (ADS) and verified by comparing obtained S21 with CST output. The designed unit cell also exhibits NZI property, and high effective medium ratio (EMR) of 14.37 at lower resonance frequency. The applicability of NZI property of this ENG metamaterial has been investigated by applying for gain enhancement of LPDA antenna. Due to its near zero refractive index, negative permittivity, high EMR and simpler design, the proposed metamaterial can be utilized for S-, C-, and X-bands applications, especially for improving the gain of satellite and radar antennas with special features.

In this paper, coupled ring split-ring resonator (CR-SRR) based epsilon negative (ENG) metamaterial with high effective medium ratio (EMR) is designed and investigated for microwave applications. The metamaterial unit cell is a modification of the conventional split-ring resonator, which consists of three major outer split rings with two face to face horizontal E segments placed at the center. All the rings are intercoupled with each other to increase the electrical length. The coupling effect is clearly observable as it provides multi-frequency resonances and a higher value of the effective medium ratio. The electrical length of the proposed unit cell is 0.064λ × 0.064λ, where λ is the wavelength calculated at the lowest resonance frequency (2.24 GHz). The designed unit cell is fabricated on a FR-4 substrate, having a thickness of 1.5 mm. Negative permittivity is observed at frequencies ranging from 2.15 to 2.3 GHz, 4.4–4.95 GHz, 5.7–6.1 GHz, 8.46–9.2 GHz, and 10.6–10.98 GHz. It also exhibits near-zero refractive indexes in the vicinity of these frequency ranges. The equivalent circuit is also designed for the proposed unit cell. The values of the lumped components are optimized by using Advanced Design Software (ADS). This circuit also demonstrates similar multi-band resonances. A high effective medium ratio (EMR) of 16.74 at 2.24 GHz indicates the compactness of the proposed unit cell. Array performance is also investigated by using 1 × 2, 2 × 2, and 16 × 16 array of unit cells. Multiband resonances of the transmission coefficient, |S21| are also noticed from these arrays. For high EMR and small size, the proposed metamaterial is suitable for S, C, and X-bands applications in wireless communications.

Metal-based epsilon negative metamaterials (MTMs) have been investigated for use as a waveguide liner to allow for an electromagnetic passband below the cutoff frequency of the empty waveguide. In this paper, we investigate both the theory and a practical implementation of an MTM lined waveguide. Specifically, we have investigated the use of inductive meander lines as the elements of a vacuum-electronics-compatible MTM structure to line one side of a rectangular waveguide. The MTM implementation creates an effective medium with a Drude–Lorentz dispersion response. The transmission of the waveguide and dispersion were both simulated and measured experimentally and demonstrate good agreement. [ABSTRACT FROM PUBLISHER]

• The MTM is developed on the FR-4 substrate where the electrical dimension of the substrate is 0.20λ × 0.20λ × 0.02λ. The CST software is used to design the proposed TCC MTM unit cell. • The epsilon negative (ENG) properties are exhibited over the frequency range of 2.61–5.15 GHz, 6.43–8.23 GHz, and 9.28–10.45 GHz, where the near-zero index (NZI) is observed over the frequency range of 3.40–4.66 GHz, 7.41–7.75 GHz, and 10.17–10.31 GHz respectively. • The tunability is investigated within the frequency range of 3.38–3.44 GHz, 7.53–8.10 GHz, and 10.24–10.79 GHz by varying the cross-coupled adjacent metallic element length. • The tenability, ENG, and NZI properties with a high EMR value enable the proposed TCC MTM unit cell for significant microwave applications, including S, C, and X frequency bands. • The proposed unit cell may be a strong contender for improving frequency stability and efficiency for multiband wireless communications as well as gain and bandwidth of the antenna and filter designs and operations. This study examines epsilon-negative (ENG) and near-zero index (NZI) tunable cross-coupled (TCC) metamaterial (MTM) unit cells for multi-band wireless communications. The square split ring resonator (SSRR), a cross-coupled metallic element, and a star-like shape are added at the center of the resonator. The EMR value is 10.24, representing the proposed structure's compactness. The tunability characteristics are investigated by varying the cross-coupled nearby metallic element length within the frequencies of 3.38–3.44 GHz, 7.53–8.0 GHz, and 10.24–10.79 GHz. The NZI characteristics are observed within the frequencies of 3.40–4.66 GHz, 7.41–7.75 GHz, and 10.17–10.31 GHz, respectively, while the ENG characteristics are observed at 2.61–5.15 GHz, 6.43–8.23 GHz, and 9.28–10.45 GHz, respectively. The bandwidth of the designed TCC MTM unit cell is 2.49–4.00 GHz, 6.89–7.83 GHz, and 9.75–10.64 GHz, respectively. The tunability, ENG, and NZI characteristics with a high EMR value enable it for critical microwave applications, including S, C, and X frequency bands. The anticipated structure may be a good candidate for enhancing the gain and bandwidth of the antenna and filter designs and operations, as well as frequency stability and efficiency for multi-band wireless communications. [ABSTRACT FROM AUTHOR]

This Letter presents a metamaterial-based compact one-unit-cell epsilon negative zeroth-order resonant antenna designed on a microstrip line. The size of the proposed antenna is only 7.85 mm × 18 mm (or 0.05λ0 × 0.12λ0) at 1.79 GHz owing to zeroth-order resonance. Closed-form design equations for the proposed antenna are provided based on the equivalent circuit employing transmission line theory considering radiation loss. The return losses based on circuit/EM simulations and measurement are in excellent agreement. The measured antenna bandwidth is 17 MHz (about 1%) and total gain is 2.6 dBi. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2991–2994, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24751 [ABSTRACT FROM AUTHOR]

• A novel SNTSSR based ENG metamaterial has been designed for microwave applications. • It provides multiband resonances at S-, C-, X-, and Ku-bands with six resonances. • Metamaterial exhibits negative permittivity and near zero refractive index. • Performance of 1 × 2 and 2 × 2 array is investigated that shows similar quad band features. • It has been used to enhance the bandwidth and gain of a 3D cross-fed wideband antenna. This paper discusses a spider net-shaped triple split ring resonator (SNTSRR) based epsilon-negative metamaterial with a high effective medium ratio. The proposed SNTSRR unit cell structure is a modification of the general split ring resonator and consists of three octagonal-shaped split ring resonators (SRR). Two metal strips attach the split ring resonators to increase the electrical length of the proposed SNTSRR unit cell. The optimized size of the proposed SNTSRR unit cell, using Rogers RO4350B substrate material, is 10 × 10 × 1.524 mm3. The frequency ranges of the transmission of microwave applications are: 2.83–2.89 GHz for S-band, 4.24–4.31 GHz and 6.74–7.06 GHz for C-band, 9.17–9.26 GHz and 10.98–11.16 GHz for X-band, and 12.62–13.00 GHz for Ku-band. The unit cell achieves six resonant frequencies of 2.86 GHz, 4.28 GHz, 6.94 GHz, 9.22 GHz, 11.10 GHz, and 12.89 GHz for S-, C-, X-, and Ku-bands, respectively. A comprehensive investigation of effective medium parameters, scattering parameters, mutual coupling effect, and the unit cell properties with electromagnetic propagation were accomplished in this paper. The proposed SNTSRR unit cell revelations epsilon negative (ENG) properties in the frequency ranges of 2.87–3.05 GHz, 4.27–4.45 GHz, 6.94–7.39 GHz, 9.24–9.34 GHz, 11.12–11.26 GHz, and 12.90–13.24 GHz. For experimental validation, we fabricated the proposed SNTSRR unit cell along with its array construction. After that, we measured the scattering parameters, which showed better agreement between the simulated and the measured outcomes. Furthermore, the coupling effects between the 1 × 2 and the 2 × 2 array structures with different distances were analyzed, and they showed better performance with low impact. Additionally, the calculated effective medium ratio (EMR) is 10.48, which infers compactness and efficacy of the unit cell. It should be noted that the compact size, effective medium parameters, S-parameters, and high EMR make the proposed SNTSRR metamaterial appropriate for quad-band microwave applications. Finally, the proposed SNTSRR unit cell has been employed as an application in 3D cross-fed wideband antenna to enhance the bandwidth and gain of the antenna, which is appropriate for microwave head imaging applications. [ABSTRACT FROM AUTHOR]

In this article, a square enclosed circle split ring resonator (SEC-SRR) based metamaterial is described that shows negative permittivity (ENG) with near-zero-index (NZI) of refraction. The unit cell of this metamaterial is formed with two SRR rings, one with square in shape and another circular shaped. The inner circular SRR has related to the outer square SRR by the metal strip. The analyzed design is very simple, but the outcome of this recommended unit cell is high i.e., it covers the multiband S-, C-, and X- bands. Rogers is used as a substrate to design the proposed SEC-SRR that has a thickness of 1.524 mm. The unit cell has a dimension (electrical) of 0.070λ × 0.070λ. The simulation software CST microwave studio-2019 is used to identify transmission (S 21) and reflection (S 11) coefficient and from this knowledge relative permittivity, permeability and refractive index is obtained by using MATLAB code based on Nicolson-Ross-Wier (NRW) method. The simulated resonance frequencies are 2.61, 6.32 and 9.29 GHz with well-matched to the measured ones. The negative permittivity regions are obtained in 2.63–2.87 GHz, 6.39–7.45 GHz, and 9.37–9.52 GHz covering S-, C-and X-bands, respectively. The equivalent circuit is modeled in Advanced Design Software (ADS) and verified by comparing obtained S 21 with CST output. The designed unit cell also exhibits NZI property, and high effective medium ratio (EMR) of 14.37 at lower resonance frequency. The applicability of NZI property of this ENG metamaterial has been investigated by applying for gain enhancement of LPDA antenna. Due to its near zero refractive index, negative permittivity, high EMR and simpler design, the proposed metamaterial can be utilized for S-, C-, and X-bands applications, especially for improving the gain of satellite and radar antennas with special features. [ABSTRACT FROM AUTHOR]

In this paper, coupled ring split-ring resonator (CR-SRR) based epsilon negative (ENG) metamaterial with high effective medium ratio (EMR) is designed and investigated for microwave applications. The metamaterial unit cell is a modification of the conventional split-ring resonator, which consists of three major outer split rings with two face to face horizontal E segments placed at the center. All the rings are intercoupled with each other to increase the electrical length. The coupling effect is clearly observable as it provides multi-frequency resonances and a higher value of the effective medium ratio. The electrical length of the proposed unit cell is 0.064λ × 0.064λ, where λ is the wavelength calculated at the lowest resonance frequency (2.24 GHz). The designed unit cell is fabricated on a FR-4 substrate, having a thickness of 1.5 mm. Negative permittivity is observed at frequencies ranging from 2.15 to 2.3 GHz, 4.4–4.95 GHz, 5.7–6.1 GHz, 8.46–9.2 GHz, and 10.6–10.98 GHz. It also exhibits near-zero refractive indexes in the vicinity of these frequency ranges. The equivalent circuit is also designed for the proposed unit cell. The values of the lumped components are optimized by using Advanced Design Software (ADS). This circuit also demonstrates similar multi-band resonances. A high effective medium ratio (EMR) of 16.74 at 2.24 GHz indicates the compactness of the proposed unit cell. Array performance is also investigated by using 1 × 2, 2 × 2, and 16 × 16 array of unit cells. Multiband resonances of the transmission coefficient, |S 21 | are also noticed from these arrays. For high EMR and small size, the proposed metamaterial is suitable for S, C, and X-bands applications in wireless communications. [ABSTRACT FROM AUTHOR]