Department of Electrical and Electronics Engineering
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Item Investigation on the aspect ratio of conducting superstrates in deciding its function as a gain enhancer/suppressor for wideband slot antenna(Springer, 2022-07) Kumar, A. V. PraveenThis paper presents an investigation on the effect of the aspect ratio (AR or width-to-length ratio) of a conducting sheet for radiation control i.e., gain enhancement or suppression, leading to useful applications for wireless communication. A wideband slot antenna working in 6–8.5 GHz band is adopted as the basic antenna. It is found that for the sheet AR < 1, the boresight (θ = 0°) gain in the entire band is enhanced, while for AR > 1, boresight gain suppression is achieved. For an optimum AR such that AR(enhancement) = 1/AR(suppression), the same sheet can serve the above dual purposes according to its azimuthal orientation with respect to the slot. For ϕ = 0° orientation with respect to the slot, the sheet acts as a gain enhancer, while for ϕ = 90° orientation, it suppresses the radiation, both in θ = 0°. Practically, the sheet orientation can be easily controlled manually. Antenna measurements demonstrate an impedance band of 6–8.66 GHz with bidirectional radiation pattern, and 1.11 dBi boresight gain at 7.25 GHz. A conducting sheet of size 1.45λ0 × 0.29λ0 where λ0 is the free-space wavelength at 7.25 GHz, is loaded above the slot which improves the boresight gain by 5.77 dB, and when rotated by ϕ = 90°, suppresses the gain by 8.78 dB, both relative to the original slot antenna.Item Analysis of Normally Incident EM Waves Reflected from a Conformal Meta-surface(IEEE, 2022) Rano, DineshThis paper reports the conceptualization, and analysis of a geometrical approach to determine the shift in the in-phase reflection of three conformal meta-surfaces (MS). For the proposed approach, a planar array consisting of MS unit cells (MS-UCs) of a given dimension is drawn on a circle of desired radius (r). The path traveled by the reflected and incident EM wave in terms of an electrical length results in the shift of reflection angle. For the validation purpose, the conformed arrays are simulated under x- and y-polarized EM waves. The sum of the incident and reflected phases resulting in total shift is determined theoretically and compared with the simulated shifts of the three arrays. Furthermore, one of the conformed arrays is experimentally evaluated under the TEM incidence and compared with the theoretical and simulated result. The excellent agreement between the theoretical and measured results demonstrates the effectiveness of the proposed work.Item Probe-fed wideband AMC-integrated hexagonal antenna with uniform gain characteristics for WLAN applications(Springer, 2020) Singhal, RahulDemand of antennas those possess wide radiation bandwidth while operating in S-band for wireless communication systems is increasing day by day. Thick substrates are popular solution to achieve wideband but they lead to frequency shift and suffer from limited gain. A potential technique to overcome the issue is to integrate an artificial magnetic conductor (AMC) between dielectric layers of a probe-fed thick substrate antenna as proposed in the paper. A parallel plate capacitor is incorporated to compensate impedance mismatch due to inductive probe. An operating band of 340 MHz is observed between 2.24 and 2.58 GHz for a gain greater than 0 dB while antenna exhibits a peak gain of 6.7 dBi. The proposed low profile AMC integrated hexagonal antenna is easy and economical to fabricate using multilayer printed circuit boards. The square loop AMC is analyzed with different inner widths to estimate the band stop frequency in both TE and TM modes. The phenomenon observed in presence of AMC during design and simulations of S-band antenna are validated with experimental results.Item Norman window slot antenna with sectoral feed backed by linear phase reflector for ultra wideband applications(Wiley, 2022-09) Singhal, RahulAn ultra wideband (UWB) slot antenna is proposed, developed, and experimentally validated in this article. The Norman window-shaped UWB slot antenna demonstrates stable radiation characteristics in both directions—zenith (θ = 0°) and nadir (θ = 180°) over the entire UWB frequency range (3.1–10.6 GHz) as observed in both simulations and experiments. A linear phase reflecting UWB frequency selective surface (FSS) is proposed by printing two orthogonal layers of pair of double rectangular loops on the same side of dielectric substrate as a merged frequency selective surface (MFSS). The UWB MFSS is then loaded with the slot antenna and the impact of MFSS on the impedance and radiation characteristics in different configurations of antenna and MFSS together is studied. One configuration with optimum solution is developed for experimental validations followed by the analysis of its radiation characteristics. The proposed antenna demonstrates a directional radiation pattern due to suppression of back lobe radiation when integrated with the UWB MFSS. The proposed antenna demonstrates maximum gain of 7.86 dB with a gain enhancement of 3.6 dB in boresight (θ = 0°) direction when MFSS is applied as a reflector to opposite side of the antenna slot.Item A strip loaded dielectric resonator antenna for circular polarisation(Wiley, 2006-04) Kumar, A. V. PraveenThe paper presents an experimental investigation of a cylindrical dielectric resonator antenna (DRA) with a conducting strip loaded on its top surface enabling circular polarisation. A simple 50Ω microstrip transmission line excites the antenna. The reflection, polarisation, and radiation characteristics of the antenna are studied. The antenna exhibits circular polarisation with an axial ratio (AR) < 3 dB over a bandwidth of 3.14% and a beam width of 60°. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1354–1356, 2006; Published online in Wiley InterScienceItem Magnetic quadrupole mode excitation of a cylindrical dielectric resonator antenna using planar feed(Wiley, 2019-10) Kumar, A. V. PraveenIn this article, excitation of the magnetic quadrupole mode of a cylindrical dielectric resonator antenna, designated as the HEM21δ mode, using planar feeding technique is discussed for the first time. Two types of planar feeds—a dual-microstrip feed and a dual-slot feed are numerically investigated. Results show that the dual-slot feed is more suitable for exciting the HEM21δ mode as it gives better symmetry of the radiation pattern and lower cross-polarization level. A DRA prototype (dielectric constant, εr = 24, loss tangent, tanδ = 0.002, diameter, 2a = 19.43 mm and height, h = 7.3 mm) using dual-slot feed is fabricated and characterized. Measurements demonstrate a resonant frequency of ~ 4.96 GHz, bandwidth of ~4.4%, peak gain of ~3.45 dBi and peak cross-polar level of ~ − 11 dB for the HEM21δ mode, which are in decent agreement with numerical predictions.Item Investigation on the aspect ratio of conducting superstrates in deciding its function as a gain enhancer/suppressor for wideband slot antenna(ACM Digital Library, 2022-09) Kumar, A. V. PraveenThis paper presents an investigation on the effect of the aspect ratio (AR or width-to-length ratio) of a conducting sheet for radiation control i.e., gain enhancement or suppression, leading to useful applications for wireless communication. A wideband slot antenna working in 6–8.5 GHz band is adopted as the basic antenna. It is found that for the sheet AR < 1, the boresight (θ = 0°) gain in the entire band is enhanced, while for AR > 1, boresight gain suppression is achieved. For an optimum AR such that AR(enhancement) = 1/AR(suppression), the same sheet can serve the above dual purposes according to its azimuthal orientation with respect to the slot. For ϕ = 0° orientation with respect to the slot, the sheet acts as a gain enhancer, while for ϕ = 90° orientation, it suppresses the radiation, both in θ = 0°. Practically, the sheet orientation can be easily controlled manually. Antenna measurements demonstrate an impedance band of 6–8.66 GHz with bidirectional radiation pattern, and 1.11 dBi boresight gain at 7.25 GHz. A conducting sheet of size 1.45λ0 × 0.29λ0 where λ0 is the free-space wavelength at 7.25 GHz, is loaded above the slot which improves the boresight gain by 5.77 dB, and when rotated by ϕ = 90°, suppresses the gain by 8.78 dB, both relative to the original slot antenna.Item Material selection of RF-MEMS switch used for reconfigurable antenna using Ashby's methodology(JPRR, 2012-01) Gupta, NavneetThis paper reports material selection methodology for radio frequency — micro electro mechanical systems (RF-MEMS) switches used for reconfigurable antennas. As there are variety of materials available to design engineer, a proper technique to select the best possible material is needed. Three primary performance indices, pull-in voltage, RF-loss, and thermal residual stress, are used to obtain the desired performance. The selection chart shows that aluminum is the most suitable material for being used as bridge material in RF-MEMS switches to provide the best performance in reconfigurable antenna.Item Selection of Microstrip Patch Antenna Substrate for WLAN Application Using Multiple Attribute Decision Making Approach(Hindawi Publishing Corporation, 2014) Gupta, NavneetThis paper presents a material selection approach for selecting microstrip patch antenna substrate for WLAN applications using multiple attribute decision making (MADM) approach. In this paper, different microwave dielectric materials for substrate and their properties like relative permittivity, quality factor, and temperature coefficient of the resonant frequency are taken into consideration and MADM approach is applied to select the best material for microstrip patch antenna. It is observed that Pb0.6Ca0.4ZrO3 is the best material for the antenna substrate in MPA for WLAN applications. It was observed that the proposed result is in accordance with the experimental finding thus justifying the validity of the proposed study.Item Design, optimization and analysis of reconfigurable antenna using RF MEMS switch(Springer, 2020-03) Gupta, NavneetThis paper presents the design, optimization and analysis of a novel radio-frequency micro electromechanical system (RF MEMS) switch for reconfigurable antenna. The proposed antenna operates at frequency band from 4.5 to 12.5 GHz. The antenna is created by reconfiguring its size using a rectangular patch and an inverted U shaped patch via RF MEMS switch. A series metal to metal contact RF MEMS switch is designed and optimized for low actuation voltage with adequate switching speed and excellent RF characteristics. The design of RF MEMS switch is simulated using CoventorWare and RF analysis is performed on Ansys HFSS software. Pull in voltage obtained for the switch is 5.7 V with switching time of 38.7 μs. The isolation obtained is better than − 20 dB for DC to 25 GHz. Insertion loss is less than − 0.4 dB for DC to 60 GHz and return loss is also better than − 23 dB for DC to 60 GHz. Further the designed reconfigurable antenna is simulated using Ansys HFSS software. The antenna is reconfigurable at 4.5 GHz, 8.6 GHz, 9 GHz, 12.3 GHz, 12.4 GHz and 12.5 GHz for different switch positions.