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Showing papers in "Aeu-international Journal of Electronics and Communications in 2018"


Journal ArticleDOI
TL;DR: In this article, a triple band-rejection MIMO/Diversity UWB antenna characteristics are described, which discards worldwide interoperability for microwave access WiMAX band from 3.3 to 3.6 GHz, wireless local area network WLAN band from 5 to 6 GHz and X-band satellite downlink communication band from 7.1 to 7.9 GHz.
Abstract: Triple band-rejection MIMO/Diversity UWB antenna characteristics are described in this paper. Proposed antenna discards worldwide interoperability for microwave access WiMAX band from 3.3 to 3.6 GHz, wireless local area network WLAN band from 5 to 6 GHz and X-Band satellite downlink communication band from 7.1 to 7.9 GHz. Mushroom Electromagnetic Band Gap (EBG) structures helps to attain band notches in WiMAX and WLAN bands. Uniplanar plus shaped EBG structure is used for notch in X-band downlink satellite communication band. Decoupling strips and slotted ground plane are employed to develop the isolation among two closely spaced UWB monopoles. The individual monopoles are 90° angularly separated with stepped structure which helps to reduce mutual coupling and also contributes towards impedance matching by increasing current path length. Mutual coupling magnitude of more than 15 dB is found over whole UWB frequency range. The Envelope Correlation Coefficient is less than 0.02 over whole UWB frequency range.The variations in the notched frequency with the variations in mushroom EBG structure parameters are investigated.The antenna has been designed using FR-4 substrate and overall dimensions is (64 × 45 × 1.6) mm3.

103 citations


Journal ArticleDOI
TL;DR: In this article, a novel four band frequency reconfigurable antenna for 1.6, 2.5, 5.8, and 9.8 GHz frequency bands is presented, which has a compact size of 0.18 λ 0 × 0.
Abstract: This research presents a novel four band frequency reconfigurable antenna for 1.6 (Global Navigation Satellite system (GNSS)), 2.5 (Lower Worldwide Interoperability for Microwave Access (WiMAX)), 5.8 (Wireless local area network (WLAN)) and 9.8 GHz (X-band) frequency bands. The antenna has a compact size of 0 . 18 λ 0 × 0.18 λ 0 × 0.0096 λ 0 at lower resonance of 1.8 GHz and is printed on FR4 material with height (h) = 1.6 mm, dielectric constant ( ( e r ) = 4.4 and loss tangent ( δ ) = 0.02. Multiband phenomenon in the antenna is achieved by etching trapezoidal slot in the radiating monopole and rectangular slots in the ground plane. Frequency reconfiguration in the proposed structure is achieved by placing PIN diode switch between rectangular slot placed in the ground plane. During OFF state, the antenna exhibit quad band with S11

83 citations


Journal ArticleDOI
TL;DR: In this article, mutual coupling reduction between elements of UWB MIMO antenna using small size uniplanar EBG is presented, which consists of two circular shaped monopole radiator swith a slot in ground plane for proper impedance matching.
Abstract: In this paper, mutual coupling reduction between elements of UWB MIMO antenna using small size uniplanar EBG is presented. Proposed UWB antenna geometry consists of two circular shaped monopole radiator swith a slot in ground plane for proper impedance matching. A UC-EBG (Uniplanar Electromagnetic Band Gap) cell of size 6.8 mm × 6.8 mm is inserted between the antenna elements in 4 × 1 array configuration to improve the isolation. Bandgap of the UCEBG is determined using dispersion diagram and suspended stripline method. The proposed antenna is fabricated on 1.6 mm thick, low cost FR4 substrate, possessing an overall size of 27.2 mm × 46 mm. The antenna has been fabricated and experimentally verified. The antenna shows simulated and measured −10 dB impedance bandwidths of 14.6 GHz (3–17.6 GHz) and14.8 GHz (3.6–17.9 GHz) respectively. UCEBG structure exhibits multiple stop bands and suppresses E-plane coupling over these bands. Isolation better than −18 dB is achieved over the complete impedance bandwidth. Radiation efficiency and peak gain of the antenna varies from 78% to 96.7% and 1.4 dB to 4 dB respectively. MIMO parameters, i.e. error correlation coefficient (ECC) better than0.018 and Total active reflection coefficient (TARC) better than −26 dB is achieved over the impedance bandwidth.

80 citations


Journal ArticleDOI
TL;DR: In this article, a compact coplanar waveguide (CPW) fed ultra-wide band (UWB) multi input multi output (MIMO) antenna is proposed, which consists of two antiparallel hexagonal ring monopole elements.
Abstract: In this paper, a compact coplanar waveguide (CPW) fed ultra-wide band (UWB) multi input multi output (MIMO) antenna is proposed. The antenna consists of two antiparallel hexagonal ring monopole elements. Circular arcs shaped grounded stubs are used to enhance the isolation, both the arcs are connected through stub to make common ground. Tapering of the slots of CPW feed line at feed point, and grounded slots are introduced for impedance matching over UWB. The proposed antenna is fabricated and impedance bandwidth, isolation, radiation pattern, and gain are measured. Moreover, envelop correlation coefficient (ECC) results are given. Proposed antenna structure operates in the frequency range 3–12 GHz with a fractional bandwidth of 120% keeping isolation better than 15 dB. The antenna has a compact size of 45 × 25 mm2.

76 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the nonlinear dynamics of a model of a 4D Hopfield neural networks (HNNs) with a nonlinear synaptic weight and showed that the proposed HNNs model possesses three equilibrium points (the origin and two nonzero equilibrium points) which are always unstable for the set of synaptic weights matrix used to analyze the equilibria stability.
Abstract: This contribution investigates the nonlinear dynamics of a model of a 4D Hopfield neural networks (HNNs) with a nonlinear synaptic weight. The investigations show that the proposed HNNs model possesses three equilibrium points (the origin and two nonzero equilibrium points) which are always unstable for the set of synaptic weights matrix used to analyze the equilibria stability. Numerical simulations, carried out in terms of bifurcation diagrams, Lyapunov exponents graph, phase portraits and frequency spectra, are used to highlight the rich and complex phenomena exhibited by the model. These rich nonlinear dynamic behaviors include period doubling bifurcation, chaos, periodic window, antimonotonicity (i.e. concurrent creation and annihilation of periodic orbits) and coexistence of asymmetric self-excited attractors (e.g. coexistence of two and three disconnected periodic and chaotic attractors). Finally, PSpice simulations are used to confirm the results of the theoretical analysis.

76 citations


Journal ArticleDOI
TL;DR: In this article, new analytical solutions for the RL, LC and RLC electric circuits considering conformable and β -derivatives of type Liouville-Caputo were analyzed.
Abstract: In this paper, new analytical solutions for the RL, LC and RLC electric circuits considering conformable and β -derivatives of type Liouville-Caputo were analyzed. These solutions were obtained by iterating conformable and β -integrals. The fractional derivatives considered have properties similar to the classical fractional integrals and derivatives. Due to these operators depend on two parameters, we obtain a better detection of the memory. Novel fractional conformable β -derivatives in the Riemann-Liouville and the Liouville-Caputo sense are obtained. Numerical simulations of alternative models are presented for evaluating the effectiveness of these representations. Different source terms are introduced in the fractional conformable differential equations in Liouville-Caputo sense.

71 citations


Journal ArticleDOI
TL;DR: This paper introduces a new five-dimensional chaotic system with both hidden attractors and extreme multi-stability, which is very rare in literature and shows its feasibility by the help of electronic circuit implementation.
Abstract: The topic of hidden attractors is a very hot topic in nonlinear dynamics. Multi-stability is another important topic in that area. One recent important category of multi-stable systems is “systems with extreme multi-stability”. In this paper we introduce a new five-dimensional chaotic system with both hidden attractors and extreme multi-stability. Such systems are very rare in literature. Also, we show its feasibility by the help of electronic circuit implementation.

71 citations


Journal ArticleDOI
TL;DR: The results of simulation, using Hspice software and Stanford 32 nm CNTFET library with the voltage of 0.9 (v), indicate much lower power dissipation and power delay product (PDP) in comparison with the previous works.
Abstract: In the following paper, a single bit ternary multiplier utilizing carbon nanotube field-effect transistor (CNTFET) has been presented. Almost in the ternary circuit design, only one supply voltage VDD is used and a voltage division circuit is activated to produce VDD/2 for logic ‘1’, So the direct current from VDD to ground increases the static power considerably. In This paper, using two supply voltages, VDD and VDD/2, the circuit is designed so as VDD/2 could be transmitted to output directly for logic ‘1’ to eliminate direct current from source to ground. This is provided by proper division of truth table and using two level output gates. Also for extending to multi bit multiplier in this way, three type of half adders and one full adder are designed using two supply voltages and removing direct current. The implementation for two bits is reported. The results of simulation, using Hspice software and Stanford 32 nm CNTFET library with the voltage of 0.9 (v), as expected, indicate much lower power dissipation and power delay product (PDP) in comparison with the previous works.

69 citations


Journal ArticleDOI
TL;DR: In this paper, a CPW fed metamaterial inspired quadband circularly polarized antenna is presented, which consists of defected ground structure with a radiating stub, which is at opposite side of the feedline.
Abstract: A CPW fed metamaterial inspired Quadband circularly polarized antenna is presented in this article. The proposed antenna consists of defected ground structure with a radiating stub, which is at opposite side of the feedline. A waveguide mode of analysis is carried out for split ring resonator (SRR) and complimentary split ring resonator (CSRR) to enhance the properties of metamaterials. The proposed antenna analysis is taken iteration wise and used FR-4 Material as the substrate material with Ɛr = 4.4 and analysed using ANSYS electromagnetic desktop. The designed antenna projecting the peak gain of 4.8 dB and it is working in the application bands of WLAN/ISM/Bluetooth at 2.4 GHz, 5.8 GHz and 3.35 WiMAX band, X-band downlink satellite communication system (7.25–7.75 GHz) and ITU band (8–8.5 GHz) with fractional bandwidth of about 70%. Proposed antenna exhibits circular polarization at 2.39–2.55 GHz, 3.05–3.1 GHz, 4–5 GHz and 6.3–6.64 GHz respectively. To know the signal integrity of the antenna, time domain analysis is carried out for identical antennas in two conditions (face to face and side by side) with the help of CST microwave studio. The designed antenna showing excellent correlation in measurements with respect to simulation results.

68 citations


Journal ArticleDOI
TL;DR: In this paper, a routing algorithm based on virtual grid infrastructure and mobile sink is proposed and some of the nodes that are selected by virtual infrastructure keep the last position of the sink.
Abstract: In wireless sensor networks, sensor nodes close to sink have more traffic loads, they will quickly deplete their energy and it will finally lead to network partition and isolate the sink. To solve this problem it is possible to use mobile sink in the network. The proper use of mobile sink creates a balance in energy consumption of network. On the other hand, the sensor nodes need to know the latest position of the mobile sink to transfer their data to it. Informing the nodes about the last sink position leads to high energy consumption and increases delay in the network. In this paper, a routing algorithm based on virtual grid infrastructure and mobile sink is proposed. In the proposed algorithm, some of the nodes that are selected by virtual infrastructure keep the last position of the sink. The simulation results show that the proposed algorithm has better performance in terms of energy consumption and delay compared to similar algorithms.

65 citations


Journal ArticleDOI
TL;DR: In this paper, a compact asymmetric coplanar waveguide (CPW) feed with split-ring resonator (SRR) is proposed to resonate at dual-band operations for WLAN and worldwide interoperability for microwave access (WiMAX) applications.
Abstract: In this paper, a compact asymmetric coplanar waveguide (CPW) feed with split-ring resonator (SRR) is proposed to resonate at dual-band operations for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. The asymmetric CPW-fed SRR patch (ACSP) antenna consists of a meander line, square-shaped split ring, and CPW ground plane. The proposed ACSP antenna resonates at two operating frequencies, namely, 2.48 GHz (2.4–2.74 GHz) and 3.49 GHz (3.25–3.64 GHz) with reflection coefficients (S11) of −16.65 dB and −32.67 dB, respectively. The measured results agree closely with the simulation results of the proposed antenna.

Journal ArticleDOI
TL;DR: This paper introduces a hyperchaotic memristor oscillator which shows both stable and unstable fixed points and designs a fuzzy based PID controller for chaos control in such a memristors oscillator.
Abstract: Chaotic and hyperchaotic systems with interesting behaviors have been of interest in the recent years. In this paper we introduce a hyperchaotic memristor oscillator which shows both stable and unstable fixed points. Such systems have been less investigated in the literatures. It should also to be noted that the proposed hyperchaotic system has only one nonlinearity which is a flux controlled memristor. Depending on the control parameter, the system displays different behaviors and coexisting attractors. A linear quadratic regulator based synchronization of the proposed hyperchaotic system is designed and numerically analyzed. We also design such a fuzzy based PID controller for chaos control in such a memristor oscillator.

Journal ArticleDOI
TL;DR: In this article, a dual band-notched ultra wideband (UWB) multiple-input multiple-output (MIMO) antenna of size 22.26 × 26.0 × 0.8mm 3 is proposed for portable devices.
Abstract: In this paper, a novel compact dual band-notched ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna of size 22 × 26 × 0.8 mm 3 is proposed for portable devices. The antenna comprises of two stepped slot UWB antennas fed by 50 ohms microstrip line, T-shape slot and narrow slot. Dual band-notches from 5.4 to 5.86 GHz and 7.6–8.4 GHz are achieved by loading trident-shape strips on microstrip line. A T-shape slot is used on the ground plane to enhance impedance matching characteristics and to minimize mutual coupling above 4 GHz. To improve isolation further at 3–4 GHz, a narrow slot is used on ground. The proposed antenna is giving a good bandwidth ranging from 3.1 to 11.8 GHz with |S 11 | > 10 dB and mutual coupling larger than 20 dB in the entire operating band except at two rejected bands. The simulation and measurement results demonstrate that the antenna is more suitable for portable device applications.

Journal ArticleDOI
TL;DR: In this article, a quad-port multi-polarized ultra-wideband (UWB) multiple input multiple output (MIMO) antenna system with a new isolation technique is designed for wireless devices.
Abstract: In this study, a quad-port multi-polarized ultra-wideband (UWB) multiple input multiple output (MIMO) antenna system with a new isolation technique is designed for wireless devices. The antenna structure consists of four triangular monopole elements and neutralization ring (NR) structures. The monopoles are back-to-back positioned in symmetrical and orthogonal arrangement. Therefore, they radiate towards four directions without interference, and thus the diversity performance is improved. A novel NR is formed by combining a rectangular ring and a straight line to reduce the mutual coupling due to interoperation of the elements. Each triangular monopole is fed by 50 Ohm microstrip transmission line (MTL) with a thin strip line for ensuring impedance matching. Antenna performance in terms of impedance bandwidth, current distribution, radiation pattern, peak gain and envelope correlation coefficient (ECC) is also investigated. The MIMO antenna system has 3.1–17.3 GHz impedance bandwidth, 1–5 dBi peak gain variation, less than 0.1 ECC. The results indicate that the proposed antenna has the characteristics of larger UWB bandwidth, high isolation by the NR structure, multi-polarization, uniform gain and quasi-omnidirectional pattern.

Journal ArticleDOI
Quan Xu, Zhe Song, Han Bao, Mo Chen, Bocheng Bao 
TL;DR: In this paper, a two-neuron-based non-autonomous memristive Hopfield neural network (mHNN) is explored through numerical analyses and hardware experiments, and the locus and stability of the AC equilibrium point for the mHNN change with the time evolution.
Abstract: This paper explores a two-neuron-based non-autonomous memristive Hopfield neural network (mHNN) through numerical analyses and hardware experiments. It is interested that the locus and stability of the AC equilibrium point for the mHNN change with the time evolution. Dynamical behaviors associated with the self-coupling strength of the memristive synapse are numerically investigated by bifurcation diagrams, Lyapunov exponents and phase portraits. Particularly, bursting behaviors are revealed when the order gap exists between the natural frequency and external stimulus frequency. The interesting phenomena are illustrated through phase portraits, transmitted phase portraits, and time-domain waveforms of two cases. Moreover, breadboard experimental investigations are carried out, which effectively verify the numerical simulations.

Journal ArticleDOI
TL;DR: A new routing protocol that provides QoS in terms of delay and energy consumption is proposed that incurs less delay and is energy efficient and an evaluation of the approach is performed through simulations.
Abstract: Wireless sensor and actuator networks are composed of sensor and actuator nodes interconnected via wireless links. The actuators are responsible for taking prompt decisions and react accordingly to the data gathered by sensor nodes. In order to ensure efficient actions in such networks, we propose a new routing protocol that provides QoS in terms of delay and energy consumption. The network is organized in clusters supervised by CHs (Cluster-Heads), elected according to important metrics, namely the energy capability, the riches of connectivity, which is used to select the CH with high node density, and the accessibility degree regarding all the actuators. The latter metric is the distance in number of hops of sensor nodes relative to the actuator nodes. This metric enhances more the network reliability by reducing the communication delay when alerting the actuator nodes, and hence, reducing the energy consumption. To reach efficiently the actuator nodes, we design a delay and energy sensitive routing protocol based on-demand routing approach. Our protocol incurs less delay and is energy efficient. We perform an evaluation of our approach through simulations. The obtained results show out performance of our approach while providing effective gain in terms of communication delay and energy consumption.

Journal ArticleDOI
TL;DR: In this article, a dual band-notched ultra-wideband (UWB) circular monopole antenna that has two parasitic resonators in the ground plane is presented, which achieves the band rejection characteristics from 5 to 5.4GHz for WLAN and 7.8 to 8.4 GHz for ITU band.
Abstract: A compact dual band-notched Ultra-wideband (UWB) circular monopole antenna that has two parasitic resonators in the ground plane is presented in this paper. The Inverted–U and Iron shaped parasitic resonators are located on the back side of the radiating patch to achieve the band rejection characteristics from 5 to 5.4 GHz for WLAN and 7.8 to 8.4 GHz for ITU band respectively. By cutting a rectangular slot on the ground plane, additional resonance is excited at the higher frequency band, and hence much wider impedance bandwidth can be attained. Applications of the proposed dual band-notched ultra-wideband (UWB) antenna structure with 5.2 GHz and 8.2 GHz center frequencies are demonstrated experimentally. Measured and simulated results of the magnitude of S11, radiation patterns and realized gains show good agreement.

Journal ArticleDOI
TL;DR: In this paper, a memristor emulator circuit consisting of only seven MOS transistors and one grounded capacitor is presented, which is laid by using Cadence Environment with TSMC 0.18
Abstract: In this paper, memristor emulator circuit consisting of only seven MOS transistors and one grounded capacitor is presented. Memristors exhibit nonlinear voltage-current relationship and many previous emulator circuits have multiplier circuit to provide the nonlinear characteristic of the memristor. But there is no any multiplier circuit block in the proposed circuit so the proposed memristor circuit occupies low chip area. The memristor circuit is laid by using Cadence Environment with TSMC 0.18 µm process parameters and its layout dimensions are only 12 µm × 38 µm excluding the area of the capacitor. The post-layout simulation results for memristor are given to demonstrate the performance of the presented memristor emulator in different operating frequencies, process corner, and radical temperature changes. All post-layout simulations agree well with theoretical analyses. Besides the VLSI implementation of the memristor, the proposed circuit is built on the breadboard using discrete circuit elements.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the dynamical behavior of the Tamasevicius et al. (1997) oscillator considering memristor as the nonlinear element by replacing the single diode in the original circuit.
Abstract: This paper investigates the dynamical behavior of the Tamasevicius et al. (1997) oscillator (named TCMNL hereafter) considering memristor as the nonlinear element by replacing the single diode in the original circuit. Various methods for detecting chaos/hyperchaos including bifurcation diagrams, spectrum of Lyapunov exponent, two parameter Lyapunov exponent, Poincare sections and phase portraits are exploited to establish the connection between the system parameters and various complicated dynamics. By tuning the system parameters, some striking phenomena such as quasi-periodic oscillations and asymmetric pair of stable/unstable attractors are depicted. It is also found that the considered memristor induces the phenomenon of coexistence of attractors in wide ranges of bifurcation parameter. Finally, the hardware circuit is implemented and experimental observations are found to be in good agreement with the numerical investigations.

Journal ArticleDOI
TL;DR: The proposed circuit and its application claim that the circuit is much simpler in design and can be utilized in both topologies and the performance of all the proposed circuits has been verified with Cadence Virtuoso Spectre.
Abstract: In this paper, a new design has been proposed for the realization of grounded and floating memristor emulators built with two OTAs and one grounded capacitor. The proposed emulators can be configured in both incremental and decremental topology. This paper also proposes the application of memristor as Amplitude Modulator (AM). The proposed circuit and its application claim that the circuit is much simpler in design and can be utilized in both topologies. The performance of all the proposed circuits has been verified with Cadence Virtuoso Spectre. Furthermore, post-layout simulations and its comparison have been carried out. Moreover, experimentation of the circuits has also been performed and found satisfactory results.

Journal ArticleDOI
TL;DR: In this paper, two types of fractal antennas are designed, one by superimposing Hilbert curve on Minkowski curve known as Hilbert Minkowsky Antenna (HMA) and other by superposing Minkowy curve on Hilbert curve, known as MinkOWy Hilbert Antenna(MHA), and compared in terms of performance parameters like gain, S11dB, radiation pattern, current distribution and VSWR at all resonant frequencies.
Abstract: In this paper two types of fractal antennas are designed, one by superimposing Hilbert curve on Minkowski curve known as Hilbert Minkowski Antenna (HMA) and other by superimposing Minkowski curve on Hilbert curve known as Minkowski Hilbert Antenna (MHA). Both antennas are compared in terms of performance parameters like gain, S11(dB), radiation pattern, current distribution and VSWR at all resonant frequencies. Both antennas are designed using HFSS software. FR4 material is used as a substrate material. Prototype of both antennas are designed, fabricated and tested at Vector Network Analyzer (VNA). It is found that Hilbert Minkowski Antenna has better performance in terms of Gain while Minkowski Hilbert Antenna is better in terms of number of frequency bands. A comparison between the characteristics of individual Hilbert and Minkowski curve based antennas is done with the characteristics of hybridized (MHA and HMA) antennas. It comes out that MHA and HMA have more number of frequency bands than individual Hilbert and Minkowski curve based antennas. A comparison has also been done between simulated and measured results of both antennas. Simulated and measured results for both the antennas are in agreement with each other.

Journal ArticleDOI
TL;DR: In this article, a compact antenna based on fractal and metamaterial loads techniques was proposed for wireless applications and the proposed antenna is suitable for reconfigurable antenna is shown in this paper.
Abstract: ‬ We have described a compact antenna based on fractal and metamaterial loads techniques. The microstrip patch antenna is assumed as a basic antenna and then the effect of fractal structures is implemented. The fractal patch is considered as a right-handed element and then by adding a left-handed element, the antenna miniaturization is achieved by using the metamaterial loads technique. The equivalent circuit is also used to describe the element effect on miniaturization and parametric models clarify them. The proposed antenna is modified for wireless applications and experimental results confirm our simulation results. In addition, we show that the proposed antenna is suitable for reconfigurable. By joining the unit cells together with various arrangements and changing the effective length, the various inductances can be obtained. Finally, by adding reconfigurable characteristic to the proposed antenna, the gain and radiation pattern can be controlled as shows in this paper. The patch antenna has low bandwidth and gain and so we have developed the patch antenna with defected ground to improve the bandwidth and the Frequency Selective Surface (FSS) is used to achieve higher gain and bandwidth. The final antenna is covering 2.4, 3.5 and 5.5 GHz with higher gain than the patch antenna.

Journal ArticleDOI
TL;DR: An audio encryption scheme based on the novel digital programmable multi-scroll chaotic system, which is programmable and can be changed real-time, is introduced.
Abstract: In recent years, information security is an increasingly vital problem. In this paper, we introduce an audio encryption scheme based on the novel digital programmable multi-scroll chaotic system. The chaotic system is described by three differential equations with piecewise nonlinear functions. More interesting, the number of scrolls of the proposed chaotic system is programmable and can be changed real-time. The system is discretized by Euler method and the digital implementation is provided. Based on this, a chaos-based audio secure communication system is developed by using feedback drive-response synchronization. The number of scrolls changes randomly by extracting control signals from the encrypted data. A series of security analyses are applied, showing good performance of the method. The system is verified through experiment on an Altera Cyclone IV FPGA platform, which effectively confirms the theoretical analysis.

Journal ArticleDOI
TL;DR: In this paper, a tunable terahertz (THz) absorber based on a graphene sheet and ribbons has been proposed and compared with the results obtained using full-wave simulations.
Abstract: Terahertz (THz) absorbers due to the high potential of providing reliable applications in modern devices and technology are increasingly being investigated. Recently, a dual-band THz absorber based on a graphene sheet and ribbons has been proposed in which the results were obtained using Full-wave simulations and its authors have not provided any specific design method. In this work, we have proposed and investigated that tunable THz absorber by its circuit model. A developed transmission line method beside the analytical circuit model of graphene continues sheet and periodic arrays of graphene ribbons are used to obtain analytical expressions for the circuit model. Here, first of all, we have compared the results of the proposed method with the results of that paper and secondly, using impedance matching concept we have proposed multi-band tunable THz absorber with near-unity absorption by the same structure. Then, we have compared the results of our circuit method with the Full-wave simulations. In either case, our proposed method in addition to excellent performance in terms of runtime and memory sources, has an acceptable agreement with the results of the Full-wave simulations. The proposed method is general and can be applied to design and simulate the other sub-wavelength structures.

Journal ArticleDOI
Bocheng Bao, Li Xu, Ning Wang, Han Bao, Quan Xu, Mo Chen 
TL;DR: In this article, the memristor element is equivalently implemented by a diode-bridge cascaded with an inductor, and a new third-order RLCM-four-elements-based chaotic circuit is presented.
Abstract: This paper presents a new third-order RLCM-four-elements-based chaotic circuit, in which the memristor element is equivalently implemented by a diode-bridge cascaded with an inductor. Mathematical model is established and its equilibrium stability is analyzed. The dynamical properties of the memristive chaotic circuit are disposed by MATLAB numerical simulations and confirmed by breadboard experimental measurements. In particular, the antimonotonicity phenomena of coexisting periodic and chaotic bubbles are observed under some specified control system parameters and the evolutions of coexisting bubbles are exhibited with the variations of two control system parameters. The presented memristive chaotic circuit is very simple and only third-order but can emerge complex dynamics with chaos, period, coexisting bifurcation modes, and coexisting bubbles.

Journal ArticleDOI
TL;DR: In this paper, a multiband dual-polarized rectenna for RF energy harvesting in C-band application range is presented, where a matching network has been designed and is connected in between receiving antenna and the rectifier circuitry in order to match the antenna and load in different frequency bands.
Abstract: The paper presents a multiband dual polarized rectenna for RF energy harvesting in C-band application range. The receiving antenna of the designed rectenna is consisting of a truncated corner square patch loaded with several circular slots, L-slots and U-slot. A proximity coupled feeding arrangement is used for obtaining a wide impedance bandwidth so that the complete C-band from 4 to 8 GHz can be covered. The proposed antenna has the advantage of compact size and dual polarization since circular polarization is realized at three bands (5.42 GHz, 6.9 GHz and 7.61 GHz) in the −10 dB impedance bandwidth range. For efficient RF to DC conversion a two-stage voltage doubler rectifier is used considering that it provides a higher voltage multiplication with a small threshold voltage at its primary stage. For ensuring maximum RF to DC conversion efficiency; a matching network has been designed and is connected in between receiving antenna and the rectifier circuitry in order to match the antenna and load in different frequency bands. It is observed that a maximum conversion efficiency of 84% is achieved at 5.76 GHz. The proposed rectenna has been fabricated and it is found that measured results are in good match with the simulated results.

Journal ArticleDOI
TL;DR: In this article, a three-channel WDM system with two Laguerre-Gaussian modes (LG00 and LG01) was investigated for mitigation of frequency-selective fading under strong atmospheric turbulence, and the performance of four-level quadrature amplitude modulation for orthogonal frequency division multiplexing (OFDM) of radio subcarriers in the WDM-MDMs system was investigated.
Abstract: Radio-over-free-space-optics (Ro-FSO) technology may pave the way towards a ubiquitous platform for seamless integration of radio and optical networks without expensive optical fiber cabling. In this paper, to increase the capacity of Ro-FSO, mode division multiplexing (MDM) of two modes has been capitalized in a three-channel WDM system spaced by 1 nm over a FSO link of 80 km, resulting in a 120 Gbps six-channel Ro-FSO system. The SNR and received power of MDM of two Laguerre-Gaussian modes LG00 and LG01 is compared with respect to MDM of two transverse donut modes. The performance of four-level quadrature amplitude modulation (QAM) for orthogonal frequency division multiplexing (OFDM) of radio subcarriers in the WDM-MDMs system is investigated for mitigation of frequency-selective fading under strong atmospheric turbulence.

Journal ArticleDOI
TL;DR: In this paper, two Moore Antennas are designed which are different from each other in terms of 50 ¾Ω microstrip transmission line only, and the same size Feed line is applied at right and left side of the substrate and termed as Left Side Feed Line (LFL) and Right Side feed Line (RFL).
Abstract: In this paper, initially two Moore Antennas are designed which are different from each other in terms of 50 Ω microstrip transmission line only. Same size Feed line is applied at right and left side of the substrate and termed as Left Side Feed Line (LFL) and Right Side Feed Line (RFL). To improve the multiband behavior of Moore Antenna, it is being fused with Koch curve and resultant antenna is named as Moore – Koch Hybrid Fractal Antenna (MKHFA) where Koch curves are superimposed on Moore curve. Two distinct MKHFA’s are designed as MKHFA with LFL and MKHFA with RFL. In order to attain the more number of frequency bands, improved gain, better impedance matching and improved bandwidth, both the MKHFA’s are loaded with Split Ring Resonator (SRR). Proposed antennas are designed on FR4 glass epoxy substrate with thickness 1.6 mm, relative permittivity 4.4. Results of Moore Antenna has been compared with MKHFA and found that MKHFA exhibits multiband behavior. A comparison between unloaded MKHFA using LFL/RFL and loaded MKHFA using LFL/RFL has been made and found that later case exhibits better results in terms of increase in number of frequency bands, bandwidth enhancement and improvement in gain. Prototypes of proposed MKHFA using LFL loaded with SRR and MKHFA using RFL loaded with SRR have been fabricated and tested for their results. The comparison between the simulated and measured results have been done and found in good agreement with each other. The overall dimensions of proposed MKHFA using LFL/RFL loaded with SRR is 25 mm × 25 mm and can be useful for different wireless applications such as Bluetooth (2.41–2.49 GHz) for ISM band, IEEE 802.11 g/b (2.40–2.48 GHz), WiMAX (2.5–2.69 GHz), WLAN (5.15–5.35 GHz), X-band satellite communication (7.1–7.76 GHz). Proposed MKHFA using LFL loaded with SRR also reports peak gain 5.76 dB and bandwidth 770 MHz, whereas, MKHFA using RFL loaded with SRR confirms peak gain 8.56 dB and bandwidth 750 MHz.

Journal ArticleDOI
Yanyan Shi1, Jianwei Jing1, Fan Yue1, Lan Yang1, Yan Li1, Meng Wang1 
TL;DR: A novel compact broadband rectifying antenna (rectenna) is presented for ambient radio frequency (RF) energy harvesting and a single stub matching network is investigated for impedance matching and the RF to DC conversion efficiency is improved at low input power.
Abstract: In this paper, a novel compact broadband rectifying antenna (rectenna) is presented for ambient radio frequency (RF) energy harvesting. Slot antennas with excellent bandwidth and matching characteristic are designed by etching fractal geometries with different iteration order on a radiation patch. A rectifier with a single stub matching network is investigated for impedance matching and the RF to DC conversion efficiency is improved at low input power. Simulation and the experiments have been carried out to evaluate the performance of antenna and rectifier respectively. A good match is observed between the simulated and measured results. The experimental results show that antenna features a broad bandwidth from 2.15 GHz to 2.9 GHz and the maximum conversion efficiency of rectifier is up to 64% at 0 dBm. The highest conversion efficiency of rectenna is 62% and the maximum output voltage is 1.5 V at the input power of 0 dBm.

Journal ArticleDOI
TL;DR: The analysis and simulation results indicate that the proposed cell eliminates read disturb and outperforms the earlier 9T TFET bitcell in terms of static and dynamic write performance by using power cut-off and write-0 only technique.
Abstract: Design of ultra-low power SRAM with robust operation for Internet of Thing (IoT) sensor node is a new challenge. In this work, a novel 9T TFET based SRAM bit cell is proposed. The analysis and simulation results demonstrate that the proposed cell eliminates read disturb issue and outperforms the state-of-the-art 9T TFET bit cell in terms of static and dynamic write performance. The presented circuit topology incorporates power cut-off and write ‘0’ only technique to enhance the write performance. The proposed cell exhibits 1.15× higher write margin (WM), 25% lower write delay, consumes 73% (57%) lower write (average) energy, 7% smaller standby leakage power measured at VDD = 0.3 V. The proposed cell also shows significant improvement in the read/write performance as compared with existing 7T and 8T TFET cells. Our proposed cell also eliminates half-select disturb issue to make it suitable for bit-interleaving architecture that is a must for enhanced soft error immunity.