Showing papers by "Kumar Vaibhav Srivastava published in 2014"

A Compact Microstrip-Fed Triple Band-Notched UWB Monopole Antenna

Abstract: In this letter, a novel low-profile microstrip-fed compact triple band-notched ultrawideband (UWB) antenna is proposed. Notch bands around the 3.3-3.8-GHz WiMAX and 5.15-5.85-GHz WLAN frequencies are obtained by etching out two elliptic single complementary split-ring resonators (ESCSRRs) of different dimensions from the radiating patch of the antenna. Furthermore, by placing two rectangular split-ring resonators near the feedline-patch junction of the antenna, rejection for the 7.9-8.4-GHz X-band frequencies is achieved. Design guidelines for implementing the notch-bands at the desired frequency regions are provided. The match between the simulated and experimental results suggests that the proposed antenna can be a good candidate for application in UWB communication systems.

Triple band polarization-independent ultra-thin metamaterial absorber using electric field-driven LC resonator

Abstract: In this paper, a triple band polarization-independent metamaterial absorber using electric field-driven LC resonators is proposed over wide angle of incidence. The unit cell is designed by parametric optimization in such a way that triple band absorption occurs in C-band. The proposed structure exhibits triple band absorption property for any angle of polarization under normal incidence. It also shows high absorption for wide angle of incidence upto 60° for both TE and TM polarizations. The proposed structure is also fabricated and experimental results provide good agreement with the simulated responses. The constitutive electromagnetic parameters viz. effective permittivity and effective permeability are extracted from the simulated response, which support the absorption phenomena at all these three frequencies. The reflection from the structure is numerically computed and verified with simulated response, and it shows good agreement between them.

Broadband Substrate Integrated Waveguide Cavity-Backed Bow-Tie Slot Antenna

Abstract: A novel design technique for broadband substrate integrated waveguide cavity-backed slot antenna is demonstrated in this letter. Instead of using a conventional narrow rectangular slot, a bow-tie-shaped slot is implemented to get broader bandwidth performance. The modification of the slot shape helps to induce strong loading effect in the cavity and generates two closely spaced hybrid modes that help to get a broadband response. The slot antenna incorporates thin cavity backing (height <;0.03λ 0 ) in a single substrate and thus retains low-profile planar configuration while showing unidirectional radiation characteristics with moderate gain. A fabricated prototype is also presented that shows a bandwidth of 1.03 GHz (9.4%), a gain of 3.7 dBi over the bandwidth, 15 dB front-to-back ratio, and cross-polarization level below -18 dB.

Bandwidth-enhanced polarization-insensitive microwave metamaterial absorber and its equivalent circuit model

Abstract: In this paper, a bandwidth-enhanced polarization-insensitive ultra-thin metamaterial absorber has been presented. A simple equivalent circuit model has been proposed describing the absorption phenomenon to estimate the frequency of absorption of the proposed microwave absorber. The basic structure consists of concentric rings embedded one inside another to enhance bandwidth by incorporating the scalability property of the metamaterials. Simulation results show that the structure has enhanced bandwidth response with full width at half maxima (FWHM) of 1.15 GHz (9.40–10.55 GHz) with two absorption peaks at 9.66 and 10.26 GHz (96% and 92.5% absorptivity, respectively). The structure is symmetric in design giving rise to polarization-insensitivity and can achieve high absorption for oblique incidence up to 40°. The proposed absorber has been fabricated and measured in anechoic chamber, showing that experimental results agree well with the simulated responses.

Multi-band microstrip-fed slot antenna loaded with split-ring resonator

Abstract: A microstrip-fed compact multi-band slot antenna using a single split-ring resonator (SRR) is proposed. The SRR acting as a loading element introduces multiple lower-order resonances in the antenna, which can be controlled by varying the SRR's dimensions as well as its position with respect to the arm of the slot, without altering the geometry of the radiating slot. The concept is validated by a full-wave simulation study and by measurement on a fabricated prototype. The proposed antenna has satisfactory gain and monopolar radiation patterns in all the operating bands.

Bandwidth-enhancement of an ultrathin polarization insensitive metamaterial absorber

Abstract: An ultrathin polarization insensitive microwave metamaterial absorber is discussed, which consists of a periodic array of swastika-like structure printed on FR4 dielectric substrate backed by copper ground. The structure is simulated to give rise to nearly unity (99.64%) absorption at 10.10 GHz (X-band). The proposed structure is symmetric in nature and provides high absorption for any angle of polarization under normal incidence. It also shows high absorption (∼81%) for incident angle upto 60o. Further, a 2 × 2 array using two different variants of the same resonating structure has been studied and by optimizing its geometrical dimensions, the absorption peaks are brought closer to provide an enhanced bandwidth having full width at half maximum of 0.68 GHz (10.04–10.72 GHz). Both the single-band and bandwidth-enhanced structures are then fabricated and experimentally studied which shows good agreement with the simulated results. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:350–355, 2014

Equivalent circuit model of an ultra-thin polarization-independent triple band metamaterial absorber

Abstract: 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.

CRLH Unit-Cell Loaded Multiband Printed Dipole Antenna

Abstract: In this letter, a conventional single-band printed dipole antenna is loaded with via-less composite right/left-handed (CRLH) unit cells to achieve multiband operation Symmetrical loading of the unit cells provides a dual-band operation, while the asymmetrical loading of unit cells provides a triple-band operation The new operational frequencies are lower compared to the resonance frequency of a reference dipole antenna and are controlled by the unit-cell parameters The radiation patterns at all the operating frequencies of the proposed antennas are omnidirectional Both the dual- and triple-band prototypes of CRLH loaded dipoles are fabricated to validate the results obtained in simulation The results of measurements and electromagnetic (EM) simulations are in good agreement

Dual-Polarized Dual-Band Patch Antenna Loaded With Modified Mushroom Unit Cell

Abstract: In this letter, novel designs of a triple-band linearly polarized patch antenna as well as a dual-band dually polarized patch antenna are proposed. A square slot is etched out along the diagonal of a conventional patch antenna, which is further loaded with a modified mushroom unit cell to achieve a triple-band operation. The lower-order modes are combined to achieve a circularly polarized mode, thus leading to the design of a dual-band dually polarized patch antenna. Both the triple- and dual-band prototypes of a modified mushroom loaded patch are fabricated to validate the results obtained in simulation. The results obtained in both the electromagnetic (EM) simulations and measurements are in good agreement.

Design of a two-dimensional metamaterial cloak with minimum scattering using a quadratic transformation function

Abstract: The presence of extreme material properties and undesired scattering make practical implementation of transformation optics based cloaks an extremely challenging issue. To overcome these problems, a simplified quadratic cloak has been proposed which provides finite material properties at the inner radius of the cloak and impedance match with the free space at the outer radius of the cloak simultaneously. The simultaneous occurrence of finite material properties and impedance match with the free space at the respective boundaries reduces the scattering cross section significantly. The material properties of the proposed simplified quadratic cloak can be realized with two dimensional (2D) metamaterials. The performance of the proposed cloak is examined by plotting the normalized total scattering cross section (SCSt,norm), and the scattering patterns in azimuthal plane. The proposed simplified quadratic cloak shows 10 dB reduction of the scattered field in both the forward and backward directions with respec...

A Three-Dimensional Unconditionally Stable Five-Step LOD-FDTD Method

Abstract: A three-dimensional unconditionally stable five-step locally one-dimensional finite-difference time-domain (LOD-FDTD) method is presented. Unlike the two-step LOD-FDTD and three-step LOD-FDTD methods, the proposed method has second order temporal accuracy. Hence, it gives less numerical dispersion than the two-step LOD-FDTD and three-step LOD-FDTD methods. It also gives less numerical dispersion than the alternating direction implicit finite-difference time-domain (ADI-FDTD) method. Moreover, for every propagation angle θ, it provides very small anisotropy error than the above-mentioned FDTD methods. Effects of the time step and the mesh size on the performance of the proposed method are discussed in detail. In this paper, validation of the stability and the accuracy of the proposed method is done with the help of simulation results. To further show the advantage of the proposed method, performance of the proposed method with artificial coefficients (control parameters) is also discussed in this paper.

A broadband wide angle metamaterial absorber for defense applications

Abstract: This paper presents an ultra-thin metamaterial absorber with L-shaped patches placed diagonally at the top surface. The geometrical dimensions of the unit cell have been optimized in such a way that the structure shows broadband response in C-band. Furthermore, an absorption bandwidth of 2.6 GHz is realized with more than 90% absorptivity level ranging from 4.6 to 7.2 GHz. The proposed structure has been studied under oblique incidence, both for TE and TM polarizations where it shows wideband absorption upto 45 incident angles in both the cases. The structure is fabricated and the experimental results are in good agreement with the simulated responses.

Dual layer polarization insensitive dual band metamaterial absorber with enhanced bandwidths

Abstract: In this paper, a dual layer polarization-insensitive metamaterial absorber with enhanced bandwidths at two distinct frequency bands has been presented. The unit cell of the proposed structure consists of various circular loops whose dimensions are parametrically optimized to exhibit dual band absorption response with full width half maximum (FWHM) bandwidth of 800 MHz at both the frequency bands. The structure is also studied with polarization angle variation where bandwidth-enhanced absorption at both the frequencies has been observed. Also, the structure is studied with oblique incidence under both TE and TM polarizations. It is found that upto 60° incident angles under TE polarization, the bandwidth enhanced absorption for both the bands holds good. The structure behaves as enhanced-bandwidth dual band absorber upto 45° incident angles for TM polarization. The structure is fabricated and experimental results validate simulated responses.

Dual band polarization-insensitive wide angle metamaterial absorber for radar application

Abstract: In this paper, an ultra-thin dual-band polarization-insensitive metamaterial absorber with wide-angle characteristics has been presented. The unit cell geometry comprises two circular rings with the inner one cross-connected. Simulated results show two discrete absorption peaks at 2.90 GHz (S-band) and 6.13 GHz (C-band) with absorptivities of 99.66% and 99.83% respectively, which can be used for surveillance and air defense radar applications. The proposed structure is polarization-insensitive and shows high absorption (over 80%) for wide incident angles upto 60 degree for both TE and TM polarizations. The proposed structure has been fabricated and measured, showing good agreement with the simulated responses.

A broadband dumbbell-shaped dielectric resonator antenna

Abstract: In this article, a dumbbell-shaped dielectric resonator antenna (DRA) fed by coaxial probe is proposed for wideband applications. The proposed dumbbell-shaped DRA can be achieved by three-layer structure of same material where the radius of middle cylinder is smaller than the top and bottom disc. In dumbbell-shaped DRA, the effective permittivity varies in both axial and radial direction. A complex hybrid mode similar to HE11δ mode is excited through a coaxial probe. The proposed dumbbell-shaped DRA provides the measured impedance bandwidth of 57.59% (at resonance frequency of 4.48 GHz) from 4.11 to 6.69 GHz for input reflection coefficient (S11) less than −10 dB. The simulated and measured radiation patterns are consistent throughout the operational bandwidth. The average measured gain of proposed antenna is 4.88 dB in the frequency range of 4.11–6.69 GHz. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2944–2947, 2014

Dual-band polarization-insensitive metamaterial absorber with bandwidth-enhancement at Ku-band for EMI/EMC application

Abstract: In this paper, a dual-band metamaterial absorber with bandwidth-enhancement at Ku-band is presented in microwave frequency range The unit cell geometry comprises of two split ring resonators in the top surface of a metal-backed dielectric substrate Simulation result shows that the structure has dual-band absorption response with one band lying in C-band and another in Ku-band with an enhanced bandwidth having full width at half maxima (FWHM) bandwidth of 1 GHz The absorber is symmetric in design and shows polarization-insensitive behavior under normal incidence It also shows high absorption (above 80%) for oblique incidence upto 45° under TE polarization The proposed structure has been fabricated and absorption is measured in anechoic chamber, which shows good agreement with the simulated response The designed absorber is ultra-thin and appears to be potentially instructive for various EMI/EMC applications

Realisation of controllable transmission zeros by perturbation technique for designing dual-mode filter using substrate integrated hexagonal cavity

Abstract: Novel designs of dual-mode substrate integrated hexagonal cavity (SIHC) bandpass filters are proposed in this study. Different filters responses in terms of switching transmission zeros are realised using perturbation technique. With the variation of perturbed length, the change of modal resonant characteristics and field patterns of the degenerate modes are also studied. Two pole and four pole filters with transmission zeros are designed and fabricated. All the theoretical analysis with the help of coupling matrix are verified with experimental results, showing good agreement between them.

A via-less planar quad-band monopole antenna employing complementary split ring resonator and interdigital capacitor

Abstract: In this paper, a novel via-less quad-band planar microstrip monopole antenna has been designed by loading a conventional monopole with complementary split ring resonator (CSRR) and inter-digital capacitor (IDC). The sub-wavelength resonances of the CSRR and IDC are responsible for the multi-band characteristics achieved in this antenna. The proposed antenna can operate in UMTS/ WCDMA/ Bluetooth/ Wi-Fi frequencies with satisfactory peak-gain and impedance bandwidth. The radiation pattern of the proposed antenna is monopolar in all the radiating bands.

Substrate integrated waveguide cavity backed slot antenna for dual-frequency application

Abstract: In this paper, a dual-frequency substrate integrated waveguide (SIW) cavity backed slot antenna has been presented. The unique slot structure includes a pair of slot stubs connected at the center of the radiating slot which helps to create an additional hybrid mode resonance at the higher frequency end. As a result, the antenna resonates at two different frequencies 8.96 GHz and 15.84 GHz with a bandwidth of 240 MHz (2.67 %) and 300 MHz (1.89 %) and gain of 4.47 dBi and 5.4 dBi respectively. The proposed design has been fabricated and measured results are also presented. The measured front-to-back ratio (FTBR) of the radiation pattern is 12 dB and 10 dB respectively and cross polarization level is 20 dB below at both frequencies in the broadside direction.

Design of dual-passband filter using dual mode semicircular dielectric resonators

Abstract: This article demonstrates a dual-passband filter based on dual-mode dielectric resonators (DR). In communication systems, dual-band filters find vital applications as to reduce the size of the system which further decreases the cost of the system. The dual-band filters can be designed using dual-mode DR which are realized using semicircular DR. The designed filter introduces a very low level of complexity by reducing the number of coupling to be handled to realize the filter. The dual-mode concept has been incorporated by using the concept of semicircular DR. Also, the control mechanisms have been provided to work independently with each couplings. The designed filter uses the concept of orthogonal modes in the DR which are further utilized to produce the two passbands. This dual-band filter is operating at center frequencies 5.28/5.58 GHz with almost 1% bandwidth in each band. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:542–547, 2014

Study on ultra-thin dual frequency metamaterial absorber with retrieval of electromagnetic parameters

Abstract: This paper describes the construction of ultra-thin dual frequency absorbers using metamaterials in microwave frequency (C-band). The geometrical dimensions of an electric field driven LC (ELC) structure are optimized using parametric analysis to achieve absorptions at two distinct frequencies, both in the C-band. The simulation of the proposed structure using HFSS shows that absorption occurs at two different frequencies, viz., 5.64 GHz and 6.22 GHz with absorptivities of 99.4% and 94.8% respectively. The absorption is explained by using the electric and magnetic excitations. The structure is also studied with different polarization and incidence angles. The structure is thereafter fabricated and experimental absorptivity response has been measured showing good agreement with the simulated one. After this, the backside of the structure is slightly modified by applying small cuts so that the transmission properties are little enhanced, and hence the effective constitutive parameters are retrieved. The retrieved effective permittivity and permeability are nearly equal to validate absorption.

Equivalent circuit modeling of an ultra-thin dual-band microwave metamaterial absorber

Abstract: This paper presents the equivalent circuit modeling of an ultra-thin microwave metamaterial absorber comprising two concentric closed ring resonator (CRR) structures. The dimension of the unit cell as well as the other geometrical parameters like radii and widths of the rings are optimized so that absorptions take place at two distinct frequencies near to the middle of the FCC radar frequency spectrum. The proposed structure shows peak absorptivities of 93.4% and 99.6% at 5.50 GHz and 9.52 GHz respectively. The equivalent circuit of each CRR is proposed and the overall circuit model is developed accordingly. The simulation of the proposed equivalent circuit agrees well with the numerical simulation, thus validating the modeling. The structure is also fabricated whose results match closely.

A metamaterial-inspired miniaturized dual-band printed directive dipole antenna for GSM/Bluetooth/WLAN applications

Abstract: In this paper, a miniaturized design of printed dual-band directive dipole antenna is proposed. Loading with complementary split ring resonators introduces an additional lower-order resonance in the reference directive dipole. This enables the proposed antenna to operate around 1.7 GHz and 2.42 GHz, covering the GSM/Bluetooth/WLAN application bands. Furthermore, defected partial ground structure is employed to improve impedance matching in the lower order CSRR-induced band. Full-wave simulations in Ansys HFSS show that the proposed dual-band antenna has satisfactory far-field gains of 1.83 dBi and 3.76 dBi in the two respective operating bands.

Design of a novel dual band patch antenna loaded with CELC resonator for WLAN/WiMAX applications

Abstract: A Complementary Electric Field Coupled (CELC) resonator, loaded in the ground plane of a conventional patch antenna to achieve dual band operation is presented here. Two antenna designs have been presented. In the first design, one CELC is etched out from the ground plane of patch antenna which leads to generation of a lower order mode in addition to the conventional patch mode. In order to achieve better impedance bandwidth for the lower order resonant mode two CELC resonators with closely spaced resonant frequencies are etched out from the ground plane of patch antenna in the second design. The proposed antennas can be used in WLAN (Wireless Local Area Network) and WiMAX (Worldwide Interoperability for Microwave Access) applications.

A parameter optimized 3-step LOD-FDTD method based on the (2, 4) stencil

Abstract: A parameter optimized 3-step locally one-dimensional finite difference time domain (LOD3-FDTD) method based on the (2, 4) stencil is presented here. Stability analysis shows that the proposed method is unconditionally stable for all the real values of the parameters. To reduce the numerical dispersion error of the LOD3-FDTD method, two optimization schemes are proposed in this paper. Minimization of dispersion error along the axial directions and minimization of overall numerical dispersion error using global phase velocity error (GPVE) are done in the first and second optimization schemes, respectively. Both the optimization schemes significantly reduce the numerical dispersion error of the LOD3-FDTD method.