Papers by Mohammad Naser-Moghadasi
─ In this paper we present the results of a simple optically transparent enclosure with efficient... more ─ In this paper we present the results of a simple optically transparent enclosure with efficient electromagnetic shielding. Firstly, Indium Tin Oxide (ITO) enclosures are designed for simultaneously providing high transmittance within a visible range and good shielding effectiveness (SE), where weight reduction, small size, and transparency are challenges. In the next step, gold Nano-layer films of various thicknesses are deposited on the patterned ITO glass using the thermal evaporation method. Then, by making a trade-off between optical transparency and SE, an optimized gold film thickness is selected. To assess the proposed approach, the final experimental results of copper, ITO, and gold deposited enclosures are compared. The results showed that a 9nm gold deposited ITO enclosure, provides efficient electromagnetic shielding better than the ITO enclosure (about 15 dB better at the resonance frequency and much closer to the copper enclosure) and at the same time, acceptable opti...
IET Microwaves, Antennas & Propagation, 2021
A method to significantly increase the gain and isolation of a wideband multiple-input multiple-o... more A method to significantly increase the gain and isolation of a wideband multiple-input multiple-output (MIMO) antenna using metamaterial structures is reported. The proposed metamaterial medium includes just one wall and one superstrate, which are fixed in xz and xy planes of the MIMO antenna, respectively. The dimensions of the proposed MIMO antenna are 13�13�3.5 mm 3 at 30 GHz. A comparison between a simulated MIMO antenna and a conventional microstrip antenna demonstrates the good performance of the proposed metamaterial environment. The corresponding return-loss of the antenna is better than 10 dB over 28-32 GHz for 5G applications. The maximum simulated gain of the antenna is 17.1 dB at 30 GHz, generating a maximum gain enhancement of 11.8 dB in comparison with a MIMO antenna without any metamaterial structures. The isolation (insertion-loss) is 36.7 dB at 30 GHz, which has improved by more than 29.4 dB compared to the conventional one. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Journal of Computational Electronics, 2019
Transparent enclosures formed of nanolayer composite panels have been proposed to provide high tr... more Transparent enclosures formed of nanolayer composite panels have been proposed to provide high transmittance in the visible range as well as good shielding effectiveness in applications with challenging requirements in terms of low weight, small size, and transparency. We present herein a practical method to optimize the performance of such enclosures, then based on the Robinson et al. model, an analytical model is introduced to approximately calculate their shielding effectiveness. The results of the proposed model show acceptable agreement with CST simulation and measurement results, while the Robinson et al. cannot be used to analyze composite enclosures due to its inability to take into account the effects of multilayer panels. In the next step, gold nanolayers with various thicknesses were deposited on patterned indium tin oxide (ITO) glass panels using the thermal evaporation technique. Then, considering the tradeoff between the shielding effectiveness and optical transparency, an optimum thickness for the gold nanolayer was selected. To assess the results of the performance optimization, the results for the copper, ITO glass, and gold-deposited enclosures were compared, revealing that the 10-nm gold-deposited ITO glass enclosure provided good shielding effectiveness, similar to that of the copper structure (and about 20 dB better than that of the ITO glass enclosure) as well as acceptable optical transparency, whereas metallic enclosures cannot provide transparency.
Optical and Quantum Electronics, 2018
The nanoantenna with Fano response is important for solar cell and bio-sensing application becaus... more The nanoantenna with Fano response is important for solar cell and bio-sensing application because of the more electric field enhancement. In this paper, we have presented a new structure based on two parallel nano loops and for achieving the Fano response; we have combined this structure with nano-sphere arrays which make a coupling between two nano loops. The Interaction between these nanoparticles is made bright and dark mode and Fano responses. To improve the electric field in this structure, we have implemented a multi-layer graphene under the nanoparticle. We show that by altering the chemical potential from 0.2 to 0.8 eV the maximum electric field has increased more than 20% for 0.6 eV in comparison to the case for 0.2 eV. We have studied the parameters effect on resonances. In addition, the presented antenna is used for biomaterial and we have compared the bare and coated structures which can consider as a figure of merit factor for optical sensing and imaging. Here, we have utilized the graphene layer with the thickness of 2 nm under the nanoparticle as multi-layer graphene. The structure is simulated based on the FIT method by the CST and for the substrate, we are selected SiO 2 with the thickness of 80 nm which is a normal substrate for graphene deposition and the Palik mode is considered for gold parts. As a result of the fact, the graphene can be considered for controlling the electric field and the optical nanoantenna for bio-sensing.
Optical and Quantum Electronics, 2018
Optical absorber is important for various applications like solar-cell or optical sensing such as... more Optical absorber is important for various applications like solar-cell or optical sensing such as optical imaging. This paper has investigated the various formations of the cylindrical hollow structure such as triangular, rectangular and hexagonal cross-section and shows the benefit of the hexagonal absorber for 150 THz and the parametric studies investigated for the hexagonal structure. For achieving the multiband absorber, we have used another hexagonal particle inside of the first model the same as the co-axial formation and obtained dual-band characteristic. We show that by the asymmetric model we have the ability to obtain Fano response for the prototype absorber which can be noticed for the wideband application. The electric field shows that the prototype absorber has dipole mode. Finally, we have checked the external material effect on frequency shift as a factor for material recognition. We have compared the frequency shift in hexagonal, co-axial and Fano model for various refractive indexes. The studies show that the co-axial model is more suitable for material recognition, in comparison to hexagonal and Fano models.
IET Microwaves, Antennas & Propagation, 2016
This paper presents the empirical results of a low-profile lightweight antenna based on a periodi... more This paper presents the empirical results of a low-profile lightweight antenna based on a periodic array of the complementary artificial magnetic conductor metamaterial structure, which is realized by loading the antenna with E-shaped slits and inductive microstrip lines grounded using metallic via-holes. The finalized prototype antenna operates over a broadband of 0.41-4.1 GHz, which corresponds to a fractional bandwidth of 165.84%, and has dimensions of 40 × 35 × 1.6 mm 3 or 0.054 × 0.047 × 0.0021 , where is free space wavelength at operating frequency of 410 MHz. The finalized antenna has a peak gain and radiation efficiency of 4.45 dBi and 85.8%, respectively, at 2.76 GHz. At the lower operating frequency of 410 MHz the gain and radiation efficiency are 1.05 dBi and 32.5%, respectively, which is normally highly challenging to realize with very small antennas. The planar nature of antenna enables easy integration with wireless transceivers. Keywords-Planar antennas, multiband antennas, periodic array of complementary artificial magnetic conductor (CAMA), metamaterials (MTMs), broadband wireless transceivers. I. INTRODUCTION Rapid development of wireless communication systems is bringing about a wave of new wireless devices and systems to meet the demands of multimedia applications [1]-[2]. Multi-frequency and multimode devices such as cellular phones, wireless local area networks (WLANs) and wireless personal area networks (WPANs) place several demands on the antennas [3]-[4]. Primarily, the antennas need to have high gain, small physical size, broad bandwidth, versatility, embedded installation, etc. In particular, the impedance bandwidth, radiation patterns, gains and efficiencies are the most important factors that affect the application of antennas in contemporary and future wireless communication systems [5]. Research into metamaterials based on periodic unit-cells has grown rapidly with the discovery of lefthanded metamaterials [6]-[7]. The transmission-line metamaterial (TL-MTM) technology has been applied to various types of antennas, i.e. compact antennas [8]-[12], leaky-wave antennas [13], and series-fed antenna arrays [14]. In [7] the bandwidth and radiation characteristics of monopole antennas, which are based on T-and F-shaped radiators, are loaded with split-ring resonators of various sizes. In [9]-[12], the antenna designs are based on composite right/left-handed transmission-line unit-cells implemented by engraving slits on the radiating patch that is loaded with spiral inductors. This technology brings enabling capabilities, in particular: (i) the ability to strongly manipulate the propagation of EM-waves in confined small structure; and (ii) the freedom to precisely and systematically determine a broad set of parameters including the bandwidth, gain, efficiency, and physical size. Therefore, TL-MTMs appear to be a suitable candidate for developing electrically small antennas for multiband applications. In this paper, a new artificial magnetic conductor (AMC) structure has been proposed for a lowprofile antenna that offers enhanced gain performance, reduced back-lobe level radiation, wideband operation, and small physical footprint. The ground-plane of the antenna acts like a reflector for the radiation impinging on its surface; however the phase of radiation impinging on conductor's surface is reversed which can interfere destructively with the radiated waves from the antenna. This can significantly
Optics Communications, 2016
we present a compact cross-shaped nano-aperture for biomedical and spectroscopy applications. Fur... more we present a compact cross-shaped nano-aperture for biomedical and spectroscopy applications. Furthermore, by adding a graphene coat to structure, we achieved a reconfigurable particle with more transmittance. Finally, a cross shape chain of silicon dioxide is added to structure and it is placed on graphene layer and over the aperture slot. The structure is modeled with FDTD simulation by the CST microwave studio and for substrate, we selected SiN with n ¼1.98 and thickness of 80 nm. The palik model is used for gold layer with thickness of 30 nm and the 2 nm graphene layer is selected for coat. The simulations emphasize that adding graphene coat and silicon dioxide chain is applicable in order to improve the transmittance at mid infrared (IR) frequency. In addition, here we show that the chain structure is useful for enhancement of the E-field in both X and Y direction and it is made useful this particle for energy harvesting. Figure of merit (FOM) is studied for different additional material effects on prototype structure and Δ(E) variation. Finally, we revealed that the current device is highly practical for making differential sensor for detecting nano-particle with more accuracy and sensitivity.
Composite right–left‐handed‐based antenna with wide applications in very‐high frequency–ultra‐high frequency bands for radio transceivers
IET Microwaves, Antennas & Propagation, 2015
This study presents a metamaterial-based antenna using the concept of composite right–left-handed... more This study presents a metamaterial-based antenna using the concept of composite right–left-handed transmission-lines. The radiation-cells layouts are based on L/F-shaped slits, so these slits are engraved on the radiation-patches for establishing a series-capacitor effect. Moreover, the radiation cells including the spirals and via-holes for the shunt-inductors implementation. By cascading the proper number of cells, the desired antennas for very/ultra-high frequency-bands are designed. The first-antenna with four L-shaped cells isconstructed on the Rogers_RO4003 substrate with thickness of 0.8 mm, so that each of cells occupies the size of 2.3 mm × 4.9 mm. This antenna covers the experimental-bandwidth of 0.2–1.8 GHz, which corresponds to 160% feasible-bandwidth. This antenna resonates at frequencies of 600–850–1200–1550 MHz, so highest gain and efficiency, happened at 1550 MHz, are 3.4 dBi and 88%. For improving the antenna performances, the second-antenna is modelled with one-cell more than first-antenna and with changing in the slit configuration to F-shape and increasing in the same substrate thickness to 1.6 mm. F-shaped antenna has size of 14.5 mm × 4.4 mm × 1.6 mm, covering a measured-bandwidth of 0.11–2.1 GHz with five resonance frequencies at 450–725–1150–1670–1900 MHz, which corresponds to 180.1% practical-bandwidth. Maximum of the measured gain and efficiency of antenna are 4.5 dBi and 95%, which occur at 1900 MHz.
Ultra-Wide Mid-Infrared Supercontinuum Generation in As40Se60Chalcogenide Fibers: Solid Core PCF Versus SIF
IEEE Journal of Selected Topics in Quantum Electronics, 2016
Due to the pronounced scientific and technical attention paid to the mid-infrared spectral region... more Due to the pronounced scientific and technical attention paid to the mid-infrared spectral region, we focus on ultra-wide mid-infrared supercontinuum generation in As<sub>40</sub>Se<sub>60</sub> chalcogenide SIF and PCF - step index and photonic crystal fibers - using a symmetrized split step Fourier method (S-SSFM). Simulations reveal, in response to launching 100 fs input pulses of 50 kW peak powers, with near zero dispersion wavelengths centered about λ<sub>0</sub> = 8.5 μm, into 50-mm long As<sub>40</sub>Se<sub>60</sub> SIF and solid core PCF, 8.5 and 11-μm supercontinua can be achieved, respectively. Moreover, numerical results also show, when ultra-short pulses of center wavelengths λ<sub>0</sub> = 12 μm are launched into those SIF and PCF, ripple free spectra as wide as 10 and 13 μm can be attained, respectively. These spectra are useful for safe spectroscopic medical imaging diagnosis such as early cancer diagnostics, and other spectroscopic applications such as gas sensing and food quality control.
Bandwidth and radiation specifications enhancement of monopole antennas loaded with split ring resonators
IET Microwaves, Antennas & Propagation, 2015
New broadband antennas loaded with split ring resonators (SRR) are proposed and investigated. The... more New broadband antennas loaded with split ring resonators (SRR) are proposed and investigated. The results illustrate that by loading the conventional monopole antennas with an asymmetrical meander lines SRR, a lower resonance frequency mode can be excited. The dimensions of the SRR have been selected to provide a resonance close the resonance of the monopole antennas. The results illustrate that when both resonance coincide the antennas bandwidths and radiation properties can be enhanced. The length and width of the antennas are 25 × 10 − 2 λ 0 × 11 × 10 − 2 λ 0 and 25 × 10 − 2 λ 0 × 21 × 10 − 2 λ 0 at 4 GHz for monopole antennas, and 29 × 10 − 2 λ 0 × 21 × 10 − 2 λ 0 at 2.9 GHz for both monopole antennas loaded with SRR. For antennas without SRR loading, maximum of measured gains and efficiencies are 3.6 dBi and 78.5% for F-antenna, and 3.9 dBi and 80.2% for T-antenna, hence they appear at 5 GHz. For antennas with SRR loading, these parameters are 4 dBi and 81.2% for F-antenna, and 4.4 dBi and ∼83% for T-antenna, which appeared at 6 GHz. By implementing the meander lines SRR as a matching load on the monopole antennas, the resulted antennas cover the measured frequency bandwidths of 2.9–6.41 GHz and 2.6–6.6 GHz (75.4 and ∼87% fractional bandwidths), which are ∼2.4 and 2.11 times more than monopole antennas with an approximately same in size.
IEEE Antennas and Wireless Propagation Letters, 2015
In this paper, a practical method to enhance the efficiency of a transparent antenna is presented... more In this paper, a practical method to enhance the efficiency of a transparent antenna is presented. The proposed method which involves homogeneous and heterogeneous gold nano layer deposition by DC sputtering does not have common limitations of transparent materials. By homogeneous deposition of the gold nano layer, ohmic loss will decrease and gain will improve. The results confirm the effectiveness of the method and significant antenna gain improvement at different frequencies. In addition, by heterogeneous deposition method we have shown that transparency can improve. In this method, the gold nano layers with various thicknesses are deposited on the locations where the current density is high. In this case, the antenna gain increases while the transparency is sustained. To assess the performance improvement, copper, ITO, homogeneous and heterogeneous deposited antennas have been compared. Final results and a methodology to select the optimum thickness and location for deposition are also presented.
Progress In Electromagnetics Research Letters, 2008
A new method for improving shielding effectiveness (SE) of a rectangular enclosure with multiple ... more A new method for improving shielding effectiveness (SE) of a rectangular enclosure with multiple apertures has been proposed. In this method in order to compensate the effects of the apertures on reduction of (SE) parameter, instead of the one wall, two metallic walls containing apertures has been used. The numerical simulation uses a symmetric condensed node of TLM-TD (Transmission line Modeling Method-Time Domain) and subsequent Fourier Transform. The shielding effectiveness response to an electric field impulsive excitation is obtained. A study of the influence of the place of apertures in the walls and the distance between the two walls is presented.
Introduction of a Novel Technique for the Reduction of Cross Polarization of Rectangular Microstrip Patch Antenna with Elliptical DGS
Journal of Electromagnetic Waves and Applications, 2008
This paper describes a new technique in reducing the cross-polarization (XP) radiation in a recta... more This paper describes a new technique in reducing the cross-polarization (XP) radiation in a rectangular microstrip patch antenna with elliptical defected ground structure (DGS). The use of DGS on the ground plane of the substrate is easy and can simply be applied in many microwave designs. This proposed structure only reduces cross polarization without affecting the characteristic impedance and co-polarization
International Journal of Antennas and Propagation, 2014
This paper presents an efficient analysis of a substrate integrated waveguide (SIW) single-layer ... more This paper presents an efficient analysis of a substrate integrated waveguide (SIW) single-layer hybrid ring coupler (rat-race) for millimeter-wave and microwave applications. The scattered field from each circular cylinder is expanded by cylindrical eigenfunctions with unknown coefficients that have been solved by electric and magnetic tangential boundary on each metallic via. The coupler S-matrix is calculated by using mode matching that uses the cylindrical vector expansion analysis to minimize the computational time and provides more physical insight. To achieve higher bandwidth, the radiuses of the coupler under analysis have been optimized in Matlab code by invasive weed optimization (IWO) method, and the results have been verified by CST package. The return loss and the isolation are less than −15 dB, and −18 dB, respectively. The insertion loss is divided equally-3±0.2 dB, with0±5and180±10degrees in output ports over the operating frequency bandwidth and the agreement of pha...
IEICE Electronics Express, 2011
An approach to reduce side lobe level (SLL) & back lobe level (BLL) of a printed helical antenna ... more An approach to reduce side lobe level (SLL) & back lobe level (BLL) of a printed helical antenna (PHA) is investigated. The strip width is periodically changed by linear and exponential function. Two linear and exponential types of printed antennas is simulated, fabricated and measured.
IEICE Electronics Express, 2011
The TE 21 tracking mode coupler is usually used in satellite auto tracking feed antennas. A mode ... more The TE 21 tracking mode coupler is usually used in satellite auto tracking feed antennas. A mode coupler comprises a power dividing section and a mode converting section. The power divider splits the input signal into two parts, which are coupled to an overmoded circular waveguide through longitudinally slots. This paper presents the effects of shape and size of slots on sidewall coupling. A prototype x band mode converter with rounded-end shaped slots is built and tested. A back-to-back transmission measurement shows good agreement with simulation results. The optimum size and shape of side wall slots has 20%, 3 dB transmission bandwidth.
IEICE Electronics Express, 2011
This paper describes the design and realization of a multimode tracking feed antenna system, for ... more This paper describes the design and realization of a multimode tracking feed antenna system, for a circularly polarized wave, which can generate sum and difference patterns suitable for monopulse tracking in remote sensing earth stations. It uses TE 11 and TE 21 modes, in a smooth circular waveguide, to obtain the sum and difference patterns. The higher order mode, TE 21 generated within the feed is separated from the fundamental mode, TE 11 by using a mode coupler. Circular polarization is converted to linear polarization by pin polarizer septum. The design of the multimode corrugated horn and polarizer are described in some details. The prototyped horn designed here operates in the frequency range of 7.2-8.8 GHz. Sum and delta patterns and polarizer axial ratio are presented. The close agreement between measured and simulated data validates the present design.
IEICE Electronics Express, 2010
In this paper a fully differential comparator-based switchedcapacitor (CBSC) pipelined ADC is pre... more In this paper a fully differential comparator-based switchedcapacitor (CBSC) pipelined ADC is presented. For better performance and accuracy, we modified the differential architecture and introduced some practical issues on preset levels designing. For comparison, we used a simple comparator which can compensate offset easily. Finally we designed a 12b 40 MS/s Fully Differential CBSC Pipelined ADC with proposed architecture in a 0.18-μm standard CMOS process. It achieves 75.2-dB spurious-free-dynamic range (SFDR) and 69.78-dB SNDR. In addition it consumes 4.1 mW from a 1.8-V power supply at 40 MS/s, which obtains a figure of merit of 460 fJ/step.
IEICE Electronics Express, 2010
In this paper a new structure for comparator-based switched-capacitor circuits has been presented... more In this paper a new structure for comparator-based switched-capacitor circuits has been presented. In contrast with the conventional architecture the proposed algorithm utilizes an extra comparator to make a variable comparator threshold, in order to attenuating the overshoot at the end of the coarse phase. for better designing we introduced some practical issues on preset levels designing. After that this paper proposes a feed forward offset compensation which can avoid offset accumulation in proposed architectures. Finally we designed a 10b 20 MS/s Fully Differential CBSC Pipelined ADC with proposed architecture in a 0.18-μm standard CMOS process. It achieves 74.4-dB spurious-free-dynamic range (SFDR) and 58.34-dB SNDR. In addition It consumes 2.6 mW from a 1.8-V power supply at 40 MS/s, which obtains a figure of merit of 210 fJ/step.
Proposal for Supercontinuum Generation by Optofluidic Infiltrated Photonic Crystal Fibers
IEEE Journal of Selected Topics in Quantum Electronics, 2014
ABSTRACT We propose a technique based on optofluidic infiltration to design a photonic crystal fi... more ABSTRACT We propose a technique based on optofluidic infiltration to design a photonic crystal fiber (PCF) to control chromatic dispersion for supercontinuum generation. Selectively infiltrating the PCF air-holes with an optical fluid having an appropriate refractive index, we have achieved a PCF with low confinement loss and ultra-flattened near zero dispersion centered about λZD ~ 1325 nm, without a need for nano-scale geometrical tuning. Numerical simulations show that femto-second pulses, with center wavelengths within the range of 1250 nm ≤ λ0 ≤ 1625 nm, can generate relatively flat supercontinuum spectra as wide as 640 to 1180 nm, passing through a 250 mm long PCF whose dispersion profile is engineered via selective optofluidic infiltra-tion. Simulations also show that optical fluid with refractive index of nF=1.32 for input signals having the aforementioned range of wavelengths result in the widest flat supercontinua. This is attributed to the smallest corresponding effective mode area as well as the smallest and flat corresponding dispersion both of which enhance the PCF nonlinearities.
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Papers by Mohammad Naser-Moghadasi