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Showing papers in "Aeu-international Journal of Electronics and Communications in 2021"


Journal ArticleDOI
TL;DR: A higher dimensional chaotic map based on the discrete memristor is presented, and numerical simulations show that the discrete Memristor model can not only enlarge the hyperchaotic region of the original system, but also enhance the system complexity.
Abstract: Although memristor has been widely discussed in recent years, the topic of memristor in discrete domain is rarely mentioned. This paper presents a higher dimensional chaotic map based on the discrete memristor, and the dynamic behavior of memristor at different positions is investigated by chaotic attractor phase diagram, bifurcation diagram, system state analysis and complexity algorithm. Numerical simulations show that the discrete memristor model can not only enlarge the hyperchaotic region of the original system, but also enhance the system complexity. Furthermore, the change of memristor position in the system leads to different performance. These deserve further study and lay the foundation for the future applications of the discrete memristor.

85 citations


Journal ArticleDOI
TL;DR: A four-port MIMO antenna array with wideband and high isolation characteristics for imminent wireless systems functioning in 5G New Radio (NR) sub-6 GHz n77/n78/n79 and 5 GHz WLAN bands is proposed.
Abstract: A four-port MIMO antenna array with wideband and high isolation characteristics for imminent wireless systems functioning in 5G New Radio (NR) sub-6 GHz n77/n78/n79 and 5 GHz WLAN bands is proposed. Each array antenna element is a microstrip-line fed monopole type. The novelty of the antenna lies in loading an “EL” slot into the radiating element along with two identical stubs coupled to the partial ground in order to improve the impedance matching and radiation characteristics across the bands of interest. To further attain high port isolation without affecting the compactness and radiation performance of each antenna element, the technique of introducing an innovative un-protruded multi-slot (UPMS) isolating element (of low-profile 2 × 19 mm2) between two closely spaced antenna elements (with an edge-to-edge distance of approx. 0.03λ at 4.6 GHz) is also presented. Besides demonstrating a small footprint of 30 × 40 × 1.6 mm3, the proposed four-port MIMO antenna array has also shown wide 10-dB impedance bandwidth of 58.56% (3.20–5.85 GHz), high isolation of more than 17.5 dB, and good gain and efficiency of around 3.5 dBi and 85%, respectively, across the bands of interest. Finally, the MIMO performance metrics of the proposed antenna are also analyzed.

83 citations


Journal ArticleDOI
TL;DR: The MIMO antenna is characterized by a good envelope correlation coefficient (ECC), low Channel Capacity Loss (CCL), and high diversity gain, which proves that the presented antenna can be seamlessly housed in miniaturized 5G smart devices.
Abstract: This article presents a printed antenna owing the advantages of compact size and simple geometrical configuration for fifth-generation (5G) 28 GHz communication systems. For better performance and miniaturization purposes, both the ground plane and the radiator of the patch antenna are defected with a rectangular slot. The antenna presents a wide operating bandwidth and high radiation efficiency while keeping reasonable gain. Furthermore, two elements Multiple-Input-Multiple-Output (MIMO) configuration of the proposed antenna was designed for MIMO applications. The MIMO antenna is also characterized by a good envelope correlation coefficient (ECC), low Channel Capacity Loss (CCL), and high diversity gain, which proves that the presented antenna can be seamlessly housed in miniaturized 5G smart devices. The proposed work is verified by experiments which are well-matched with predicted results. In comparison with other related works, the presented work is dominant in terms of wide operating bandwidth, high isolation, low ECC, and compact design.

55 citations


Journal ArticleDOI
TL;DR: A learning circuit that can realize Pavlov associative memory with dual-mode switching is designed and verified by the simulation results, and the inhibition relationship between learning modes is considered and reflects the relationship by adjusting the influence of mode switching period on the learning speed of modes.
Abstract: There are many learning modes in associative memory, but most of memristor-based Pavlov associative memory circuits only have a single mode. A learning circuit that can realize Pavlov associative memory with dual-mode switching is designed and verified by the simulation results. The designed circuit consists of the auditory (visual) synapse, auditory (visual) control voltage module and auditory (visual) inhibition module. This paper considers two different learning modes, auditory mode and visual mode. The modes can run not only separately but also alternately. Besides, the paper also considers the inhibition relationship between learning modes and reflects the relationship by adjusting the influence of mode switching period on the learning speed of modes. As a widespread phenomenon in the natural world, mode inhibition of associative memory can be regarded as a psychological process of living things under different external stimulus. Mode inhibition is an interesting subject, which can allow the artificial neural network to mimic more realistic situations of memory. The dual mode switching is an essential part of life, which can provide more references for the practical application of memristor.

49 citations


Journal ArticleDOI
TL;DR: In this article, a concentric circle compound reconfigurable (frequency, polarization, and pattern) microstrip antenna for lower-S band (2.0-3.0 GHz) applications is presented.
Abstract: The article presents a concentric circle compound reconfigurable (frequency, polarization, and pattern) microstrip antenna for lower-S band (2.0 GHz-3.0 GHz) applications. Varying the capacitance of four varactor diodes from 4.15pF (0 V) to 0.94pF (6 V), the resonant frequency of the antenna can be tuned from 2.10 GHz to 2.90 GHz (34.52% tunable bandwidth). These diodes are incorporated to bridge the gap between the circle and ring of concentric geometry. The arc slots and C-shape wings are used for polarization and pattern reconfiguration, respectively. The arc slots are etched from the edge of circle geometry and loaded with RF PIN diodes to provide the different polarization states: linear polarization, left-hand circular polarization (LHCP), and right-hand circular polarization (RHCP). Simultaneously, the pattern reconfigurability can be attained with C-shape wings, placed around the concentric circle geometry; hence, patterns are tilt at 0 ° and ± 50 ° . The pattern reconfigurability also controlled through the RF PIN diodes. The designed antenna is experimentally verified and shows the maximum gain of 4.31 dBic and 4.04 dBi in polarization and pattern reconfigurable mode, respectively. Besides, it provides an excellent axial ratio ( 3 dB) and stable radiation patterns. Therefore, the proposed compound reconfigurable antenna can be served for a future communication system and improves the signal quality without any destruction.

35 citations


Journal ArticleDOI
TL;DR: In this article, a frequency reconfigurable MIMO antenna for 4G and early 5G applications is presented, which consists an array of two radiating/receiving elements positioned diagonally opposite to each other for better isolation (>12dB) and pattern diversity.
Abstract: In this work, a frequency reconfigurable MIMO antenna for 4G and early 5G applications is presented. The MIMO antenna design consists an array of two radiating/receiving elements positioned diagonally opposite to each other for better isolation (>12 dB) and pattern diversity. Each antenna element in MIMO array has a single module consisting two meandered radiating arms which could be connected or disconnected to the 50 Ω feedline electronically using two PIN diodes to operate in two switchable frequency bands/modes, 2.4 GHz or 3.5 GHz assigned for 4G/LTE and early 5G/Sub-6 GHz wireless communication technologies, respectively. The length of each radiating arm is around half-wavelength at operating frequency of interest (2.4 GHz or 3.5 GHz). The overall size of the MIMO antenna system is 120 mm × 60 mm × 1.52 mm. The proposed MIMO antenna configuration provides a 28.81% FBW (2.0 GHz to 2.7 GHz) and 49.7% FBW (2.57 GHz to 4.27 GHz) in both the resonance modes, respectively. The measured antenna gain values in two switchable frequency modes are 3.7 dBi and 4.2 dBi, respectively with overall efficiency > 60%. A low envelope correlation coefficient (0.0056 at 2.4 GHz and 0.0009 at 3.5 GHz) is achieved. Furthermore, the SAR and hand mode analysis is carried out to verify the performance of the MIMO antenna for mobile handset. The measured ergodic channel capacity of the MIMO antenna has been achieved more than 10b/s/Hz for both the mode.

33 citations


Journal ArticleDOI
TL;DR: In this article, a triple-nigh band dual-port ultra-wideband (UWB) MIMO antenna is designed from a single port UWB antenna, which consists of an arrow-head shaped radiator loaded with two open-ended inverted L-shaped slots (slot #1 and Slot #2) and one U-shaped slot (Slot #3) followed by a pair of mushroom type EBG structures.
Abstract: Quadruple notch band dual-port ultra-wideband (UWB) MIMO antenna is reported in this article. The proposed MIMO antenna is designed from a single port UWB antenna, which consists of an arrow-head shaped radiator loaded with two open-ended inverted L-shaped slots (Slot #1 and Slot #2) and one U-shaped slot (Slot #3) followed by a pair of mushroom type EBG structures. The inverted L-and U-shaped slots are liable for generating triple notch band behavior at 3.3 GHz, 4.03 GHz, and 5.4 GHz, respectively. Besides this, the antenna produces an extra notch band function at 6.0 GHz using a pair of mushroom type EBG structures. In addition to this, the antenna covers wideband ranging from 3.0 to 10.7 GHz which suitably meets the requirement of ultra-wideband (UWB) applications. The design is modeled over FR4 Epoxy material and having an overall size of 43 × 34.9 × 1.6 mm3. However, a rectangular decoupling strip is introduced below the substrate layer for reducing mutual coupling between them. Therefore the suggested antenna is having efficient notch controlling capabilities and its performance characteristics are evaluated and analyzed in terms of rejecting frequencies, Current concentrations, ECC, Diversity Gain, and radiation patterns.

32 citations


Journal ArticleDOI
TL;DR: In this paper, a rectangular dielectric resonator based connected ground quad-elements MIMO antenna fed using substrate integrated waveguide (SIW) is proposed for millimeter-wave 5G application.
Abstract: A rectangular dielectric resonator based connected ground quad-elements MIMO antenna fed using substrate integrated waveguide (SIW) is proposed for millimeter-wave 5G application. SIW in TM10 mode was used to excite multiple modes in the dielectric resonator to achieve multiple resonance. An individual element of the proposed MIMO antenna is arranged in a cross shaped structure to achieve polarization and spatial diversity. The proposed MIMO system operates at dual operating frequency bands having impedance bandwidth of 24% (24.50–27.50 GHz) and 12% (33–37 GHz). The isolation better than 22 dB and 17 dB is achieved throughout the proposed bands without using any additional isolation techniques. The proposed MIMO antenna has a peak gain of 9.9 dB and minimum radiation efficiency of 96%. It radiates in a broadside direction with acceptable MIMO diversity results where envelope correlation coefficient is below 0.15, channel capacity loss is below 0.6 bits/sec/Hz, diversity gain of 9.98 dB, and total active reflection coefficient below −10 dB over the desired band of operation. The prototype of the quad-elements SIW fed DRA MIMO was manufactured after which the antenna and diversity performance parameters were measured and satisfactory correlation is observed.

31 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the DC and analog/RF performance metrics of 3-nm gate length (LG) silicon-on-insulator (SOI) FinFET using HfxTi1−xO2 high-k material in gate stack to improve sub-threshold characteristics.
Abstract: In this paper, for the first time, we have investigated the DC and analog/RF performance metrics of 3 nm gate length (LG) silicon-on-insulator (SOI) FinFET using HfxTi1−xO2 high-k material in gate stack to improve subthreshold characteristics. The 3-D device performance of single-k, dual-k, and hybrid spacer is compared without spacer dielectric, and DC characteristics are presented. In this move, it is noticed that the device attains the highest ION/IOFF ratio of ~109 compared to ~105 due to an increase of effective gate length by fringing fields with spacer dielectric. Moreover, to evaluate and understand the nanostructure performance comparison is made between Junctionless (JL), Accumulation (ACC), and Inversion (INV) modes. The device exhibits excellent DC characteristics with ION/IOFF ratio of ~109, subthreshold swing (SS) of ~61.8 mV/dec, drain induced barrier lowering of (DIBL

30 citations


Journal ArticleDOI
TL;DR: The proposed miniaturized UWB MIMO antenna is a potential candidate for the compact and portable devices and is compared with the state of the art antennas to demonstrate the valuability of the proposed antenna for the UWBMIMO applications.
Abstract: A simple but effective four port miniaturized Multiple Input Multiple Output (MIMO) antenna operating at wide-Ultra-wideband (UWB) region (3–13.5 GHz) including UWB (3.1–10.6 GHz), 11 GHz (10.7 to 11.7 GHz) and 13 GHz (12.75 to 13.25 GHz) frequency bands is proposed here. The phenomenon of the polarization diversity by deploying four orthogonal antenna elements is used to enhance the isolation between the MIMO antenna elements. The overall size (40 × 40 × 1.524 mm3) of the antenna is reduced by mitigating the unwanted interaction between the antenna elements by modifying patch shape and placing them in closed proximity to each other. The simulated results are verified by the measurements of the prototpe MIMO antenna. The results are compared with the state of the art antennas to demonstrate the valuability of the proposed antenna for the UWB MIMO applications. The proposed miniaturized UWB MIMO antenna is a potential candidate for the compact and portable devices.

29 citations


Journal ArticleDOI
TL;DR: An efficient curve fitting method is used which approximates the frequency-domain behavior of the filter and transposes the fractional-order transfer function into the integer-order domain, resulting in a rational integer- order transfer function and its implementation is possible using conventionalinteger-order realization techniques.
Abstract: A new category of fractional-order filters, realized without employing a fractional-order Laplacian operator is introduced in this work. This can be achieved through the utilization of an efficient curve fitting method which approximates the frequency-domain behavior of the filter and transposes the fractional-order transfer function into the integer-order domain. Thus, the procedure results in a rational integer-order transfer function and its implementation is possible using conventional integer-order realization techniques. Therefore, there is no need for fractional-order elements to realize this class of filters. Design examples of this new kind of filters are presented with the derived simulation and experimental results confirming their correct performance.

Journal ArticleDOI
TL;DR: This work surveys the development of various energy harvesting methodologies utilized to drive wearable devices, and the addressed harvesters are piezoelectric, glucose biofuel cell, triboelectic generators, thermoelectedric generators, solar cells, and radio frequency (RF) harvester.
Abstract: For the specifications of Wireless Body Area Networks (WBANs), eHealth systems, and wearable devices, batteries are not desirable. They maximize the sensor nodes’ size and need to be replaced every few years through human interference. Energy harvesting is now being studied as the primary source of electricity for wearable devices. Several initiatives have succeeded in using energy harvesting to operate the wearable devices’ electronic components. However, to rely primarily on energy harvesting in wearable devices, some obstacles need to be addressed. This work surveys the development of various energy harvesting methodologies utilized to drive wearable devices. The addressed harvesters are piezoelectric, glucose biofuel cell, triboelectric generators, thermoelectric generators, solar cells, and radio frequency (RF) harvesters. The advantages, disadvantages, and challenges of the addressed harvesters are mentioned. The application of the harvesters in invivo experiments is also discussed.

Journal ArticleDOI
TL;DR: In this article, an innovative frequency reconfigurable metamaterial-based microstrip patch antenna was proposed for multiple bands by using a PIN diode as a switch, which achieved frequency tunability for a range of 3 GHz to 9 GHz.
Abstract: The manuscript represents an innovative frequency reconfigurable metamaterial-based microstrip patch antenna. The proposed structure provides frequency tunability for multiple bands by using a PIN diode as a switch. The performance of the proposed antenna structure is simulated, fabricate, and compared for copper and liquid (water-sea) based split-ring resonator (SRR). The tooth is added to the outer of the split-ring resonator for gain enhancement and better frequency tunability. Frequency tunability is achieved by connecting the patch antenna with a PIN diode that reduces the size of the antenna. Five switching modes (all switch off, one switch on, two switches on, three switch on and all switch off) of the proposed antenna structure is presented and their reflectance response (s11), the number of bands, bandwidth, directivity, and total gain is compared for copper and liquid (water-sea) structure with and without a tooth. Results of Fabricated structure and simulated also compared. Frequency tunability is observed for a range of 3 GHz to 9 GHz. The proposed antenna is useful for a weather forecast, satellite communication, and raw satellite feed and many more.

Journal ArticleDOI
TL;DR: A new VCII based implementation of grounded capacitance multiplier is proposed employing two VCIIs, two resistors and one grounded capacitor, with main features are wide frequency range, high resolution, low series resistance, simple structure, low power consumption and maximum percentage error.
Abstract: Capacitive multipliers have found wide applications in capacitive interfaces and other analog circuits requiring large value capacitors. Recently a new active building block (ABB) called second generation voltage conveyor (VCII) has been proved to be useful in many analog signal processing applications. Due to the interesting features offered by VCII, in this paper a new VCII based implementation of grounded capacitance multiplier is proposed employing two VCIIs, two resistors and one grounded capacitor. The circuit can produce both positive and negative multiplication factors in a range of −50 to +50. Its main features are wide frequency range, high resolution, low series resistance, simple structure, low power consumption and maximum percentage error of 7.8%. The circuit enjoys high frequency range up to 10 MHz, even if it employs a floating capacitor in its structure. The behavior of the proposed circuit is analysed by taking into account also the effects of VCII parasitic elements and non-ideal gains. SPICE simulation results using a 0.35 µm CMOS technology parameters are reported. The proposed circuit has been also experimentally tested by using AD844 as VCII. Measurement results on the standalone capacitance multiplier have shown a mean percentage error of 9% across the entire gain range. Finally, the application of the proposed circuit in realizing a low pass filter is also presented to demonstrate the proposed circuit feasibility.

Journal ArticleDOI
TL;DR: In this paper, a high gain and wideband circular polarization (CP) patch antenna using reflective focusing metasurface was proposed and demonstrated and the initial design of patch antenna is made of a slot planar patch radiation part fed by coplanar waveguide (CPW).
Abstract: In this paper, a high-gain and wideband circular polarization (CP) patch antenna using reflective focusing metasurface was proposed and demonstrated. The initial design of patch antenna is made of a slot planar patch radiation part fed by coplanar waveguide (CPW). The simulated return loss below −10 dB of the initial design is from 6.2 to 13.8 GHz with the relative bandwidth of 76%, and the average gain is only about 4.5 dBi. In addition, the simulated 3-dB axial ratio bandwidth (ARBW) of the initial design is 78.7% from 6 to 13.8 GHz. The antenna structure was modified to enhance the gain and radiation performance by adding the reflective focusing geometric metasurface. The metasurface with wideband high efficiency cross-polarization reflection, is arranged to construct the phase gradient paraboloid for energy gathering. Simulation results indicated that the antenna combined with reflective focusing metasurface achieves an effective wideband impedance bandwidth (return loss

Journal ArticleDOI
TL;DR: In this paper, a linear circularly polarized (CP) antenna array using non-identical CP elements, where the Chinese character-shaped patches are employed to form a linear array, is presented.
Abstract: Here we present a novel linear circularly polarized (CP) antenna array using non-identical CP elements, where the Chinese character-shaped patches are employed to form a linear array. Namely, the single-feed CP Zhong-, Guo-, and Meng-shaped patch antennas have collected to form a three-element antenna array. A one-to-three power splitter with equal amplitudes but unequal phase-shifts at its output ports was deliberated as the feed network for the linear array. The challenge of this antenna array design is the appropriate phase excitation to the non-identical radiating elements so that the CP gain and operating bandwidth can meet the requirements of the application(s), in which we undertook an in-depth investigation. A proof-of-concept design example for 2.4 GHz wireless local area network (WLAN, IEEE 802.11b/g/n) has demonstrated the effectiveness of the combination technique on the non-identical CP antenna elements. The simulation, in combination with experimental validation, obtained an on-axis 3-dB axial-ratio bandwidth from 2.28 to 2.59 GHz (12.7%), whereas a broadside gain of 9 dBic at 2.5 GHz and an overall efficiency of 82% were recorded within the bandwidth.

Journal ArticleDOI
TL;DR: In this paper, a very compact dual band-notched two-port multiple-input multiple-output (MIMO) antenna with low mutual coupling is presented for portable ultra-wideband systems.
Abstract: In this paper a very compact dual band-notched two-port multiple-input multiple-output antenna with low mutual coupling is presented for portable ultra-wideband systems. This antenna with overall size 18 × 35 × 1.6 mm3, consist of two identical monopole elements which fed by two 50 Ω coplanar waveguide lines and fabricated adjacent to each other on the top side of a FR-4 substrate with shared ground plane. To reduce the mutual coupling between elements, a rectangular stub was introduced between them and then it modified to a T-shaped stub. For further reduction, a rectangular slot etched out of the connected ground plane. Due to the results, proposed antenna achieves wide impedance bandwidth at each port, from 2.3 to 12 GHz covering the whole UWB spectrum except at two eliminating bands. Although this antenna has small size and simple structure, the mutual coupling between elements is lower than −20 dB. By etching out two rectangular single complementary split-ring resonators from the radiating patch, dual band-notched characteristics are obtained in WiMAX and WLAN bands. Envelope correlation coefficient of less than 0.035, nearly omnidirectional pattern, 90% radiation efficiency despite lossy substrate, high multiplexing efficiency (>−1 dB) except at two notches and peak gain near 6dBi are some other characteristics of this design.

Journal ArticleDOI
TL;DR: In this article, a high gain and wideband multiple-input multiple-output (MIMO) for 5G new radio (NR) networks is introduced, where an artificial magnetic conductor (AMC) is located underneath the MIMO antenna to improve the gain by about 55% over the entire achieved frequency band (26-31.5 GHz).
Abstract: A high gain and wideband multiple-input multiple-output (MIMO) for 5G new radio (NR) networks is introduced in this paper. The single unit is a monopole antenna with partial ground plane and two small triangles are cut out from the patch to produce the proposed frequency band. The two elements are located orthogonal to each other in order to reduce the mutual coupling without using isolation structure at the desired frequency 28 GHz. An artificial magnetic conductor (AMC) is located underneath the MIMO antenna to improve the gain by about 55% over the entire achieved frequency band (26-31.5 GHz). The Suggested antenna model with the AMC structure is fabricated to verify the simulation results in terms of S-parameters, radiation patterns, gain, and diversity parameters. It is worth noting that the experimental results have the same trend of the simulation ones which makes the suggested AMC-based MIMO antenna applicable for 5G NR networks.

Journal ArticleDOI
TL;DR: In this paper, a fractal shape based MIMO antenna with microstrip feeding for sub 6 GHz applications is proposed, which is a flower-shaped construct with added rectangular strips patch and circular, rectangular slots are introduced into the ground plane to reduce the isolation between the patches.
Abstract: This article presents fractal shape based MIMO antenna with microstrip feeding for sub 6-GHz applications. The proposed fractal based structure is a flower-shaped construct with added rectangular strips patch and circular, rectangular slots are introduced into the ground plane to reduce the isolation between the patches. The main purpose in designing 2 × 1 MIMO system antenna is to enhance the scattering signals and optimize the performance. The proposed structure uses FR-4 material with a dimension of 25 mm × 38 mm. The 2 × 1 MIMO structure resonate at 3.5 GHz for the sub 6 GHz 5 G communications with directional radiation pattern. The performance characteristics of the antenna such as surface current distributions, radiation patterns and S-parameters are investigated. In addition the performance of diversity system of MIMO structure including the total active reflection coefficient (TARC), multiplexing efficiency, envelope correlation coefficient (ECC) and diversity gain (DG) are studied. For this proposed MIMO structure all antenna parameters are found that within an acceptable range.

Journal ArticleDOI
TL;DR: In this article, the authors introduced characteristics mode analysis (CMA) to study the dual-polarization behavior of simple monopole antenna, which consists of monopole feed with symmetric arms (SA), resonating at 2.45 GHz and right-handed stub (RHS) connected to resonate at 5.8 GHz.
Abstract: In this paper, Characteristics mode analysis (CMA) is introduced to study the dual-polarization behavior of simple monopole antenna. The antenna consists of monopole feed with symmetric arms (SA), resonating at 2.45 GHz and right-handed stub (RHS) is connected to resonate at 5.8 GHz. The SA has linear polarization and RHS has circular polarization. CMA is introduced to explore dual-polarized properties and validated on modal metrics. The intuition of antenna design is further extended to 4-port MIMO antenna configuration. Due to rotationally symmetrical connected ground topology, another induced resonance at 1.54 GHz is observed. A L-shaped stub is further connected to one-end of the monopole arm of each antenna element, that function as 2.5 GHz resonator and an effective isolator. The overall antenna dimension is 0.3 λ × 0.3 λ × 0.018 λ (where λ is the lowest operating wavelength) and the elements are spatially separated with edge-to-edge spacing of 0.018 λ with port isolations > 15 dB. The MIMO antenna operates at 1.54 GHz, 2.5 GHz with linear polarization and at 5.63 GHz as circular polarization. The antenna gains with radiation efficiencies are 0.62 dBi ( > 60%), 4 dBi ( > 70%) and 4.25–6 dBc ( > 80%). The computed ECCfar−fields is 0.3, showing its potential for pattern and polarization diversity MIMO environments. A prototype antenna is fabricated and measured with good agreements and found compatible for L-band, lower WLAN and upper WLAN applications.

Journal ArticleDOI
TL;DR: This work proposes a quadratic system with only two stable node-foci, which can generate double-wing chaotic hidden attractor, and designs multi-wing 3D chaotic systems with hidden attractors that coexist with stable point attractors.
Abstract: Some dissipative dynamical systems only have stable equilibria or have no equilibrium point but are able to generate chaos of non-Sil’nikov type. This category of chaotic attractors belong to hidden attractor, which is difficult to be located in the phase space. In this work, we aim at designing multi-wing 3D chaotic systems with hidden attractors. We first proposes a quadratic system with only two stable node-foci, which can generate double-wing chaotic hidden attractor. Using rotation symmetry, we construct multi-fold cover of the quadratic system and obtain multiple symmetric stable equilibria. Two examples of 2-fold and 3-fold covers of the chaotic system are presented. Furthermore, the rotation symmetry is applied to no-equilibrium system to generate multi-wing chaotic hidden attractors. By means of bifurcation diagram, finite-time Lyapunov exponents, phase portraits, and attraction basins, it is shown that the multi-wing chaotic attractors always coexist with stable point attractors. The local initial condition areas and complex boundaries for different coexisting attractors are addressed. Finally, the designed systems are implemented by analog circuit and microcontroller to verify the multi-wing hidden attractors.

Journal ArticleDOI
TL;DR: The differential pairs of the proposed OTA combine, for the first time, the multiple-input MOS technique along with the dynamic threshold voltage MOS to achieve a very simple and power-efficient CMOS structure with increased total transconductance.
Abstract: A new solution for a low-voltage multiple-input dynamic threshold operational transconductance amplifier (MIDT OTA) for low-frequency signal processing applications is presented. The differential pairs of the proposed OTA combine, for the first time, the multiple-input MOS technique along with the dynamic threshold voltage MOS to achieve a very simple and power-efficient CMOS structure with increased total transconductance. Further, the proposed MIDT OTA has been used to realize a fifth-order low-pass filter (LP) and a sixth-order band-pass filter (BP) using coupled-biquads. The proposed OTA and the filter applications are supplied with 0.5 V and consume 5 nW and 25 nW, respectively. The input band pass filter noise is 82.76 µV, while the dynamic range is 59.5 dB for the third intermodulation distortion (IMD) of 2%. The proposed circuits were designed in a 0.18 µm TSMC technology, and validated by simulations using Cadence platform.

Journal ArticleDOI
TL;DR: To prove superiority of the proposed 7T SRAM cell in the various design metrics, it is compared with six state-of-the-art SRAM cells at subthreshold supply of VDD = 0.3 V and is the second/first/third best cell in terms of R SNM/WSNM/write access time (TWA).
Abstract: The internet of things (IoTs)-based systems require battery-enabled energy-efficient memory circuits to operate at low voltage domain, especially below the transistor’s threshold. This study presents a single-ended 7T SRAM cell for IoTs applications. Cell core of the proposed 7T SRAM cell is composed of a novel Schmitt-trigger circuit in which a dynamic body bias technique is applied to a standard CMOS inverter through a feedback mechanism, whereby the threshold voltages of two MOSFETs can be changed, thus changing the switching voltage. The proposed 7T SRAM cell employs only one bitline to perform both read and write operations to reduce active power consumption. Read operation of the proposed 7T SRAM cell is conducted using only a single n-type MOSFET transistor driven by QB node. This transistor isolates bitline from storage nodes during read operation, improving read stability (RSNM) and read delay (TRA). A p-type MOSFET controlled by write wordline is placed inside the cell core to cut its feedback path off during write operation. This mechanism eliminate writing ‘1′ issue in single-ended SRAM cell and facilitate write ‘1′ operation, resulting in write-ability (WSNM) enhancement. To prove superiority of the proposed 7T SRAM cell in the various design metrics, it is compared with six state-of-the-art SRAM cells at subthreshold supply of VDD = 0.3 V. The proposed 7T SRAM cell is the second/first/third best cell in terms of RSNM/WSNM/write access time (TWA). Furthermore, an improvement of at least 2.55X in TRA and 12.58X (2.02X) in read (write) energy consumption is achieved by the proposed 7T SRAM cell. Although, the proposed 7T SRAM cell offers some disadvantages, nevertheless it offers the best proposed figure of merit.

Journal ArticleDOI
TL;DR: In this paper, a miniaturized ultra wide stopband frequency selective surface (FSS) with angular stability and polarization insensitivity is presented, which is composed of four symmetric square loops connected to each other using a small metallic strip.
Abstract: In this paper, a miniaturized ultra-wide stop-band frequency selective surface (FSS) with angular stability and polarization insensitivity is presented. The FSS is composed of four symmetric square loops connected to each other using a small metallic strip. The proposed FSS shows good band rejection over the entire ultra-wideband (UWB), where

Journal ArticleDOI
TL;DR: A Genetic Algorithm (GA) based sink mobility technique for WSN that provides increase in network lifetime than other protocols and a network energy consumption model is proposed that implements the fitness evaluation operator of the GA process.
Abstract: In a sink mobility based Wireless Sensor Network, the sink node moves on a trajectory in the network region and collects the data of the sensor nodes in the vicinity. Sink mobility reduces the distance from average source node to sink and saves network transmission energy. This paper proposes a Genetic Algorithm (GA) based sink mobility technique for WSN. Network region is divided into the optimal number of clusters and a sink movement trajectory is built over there. The GA process determines the optimal sink locations on the trajectory for each cluster. The moving sink stops at the optimal sink locations and gathers data from the nodes of the related clusters. An optimal sink location consumes minimum node energy in data transmission. For determining the optimal sink location for a cluster, the GA initializes a population of chromosomes. Further, a network energy consumption model is proposed that implements the fitness evaluation operator of the GA process. The developed GA model converges into a set of optimal sink locations on the trajectory for each cluster. The results depict that the GA based sink mobility provides increase in network lifetime than other protocols.

Journal ArticleDOI
TL;DR: In this article, a novel metasurface absorber is designed for RCS reduction as well as high isolation in a 4-elements MIMO antenna, where a unit cell of the absorber was amalgamated by concentric circular and elliptical-shaped rings with four 300-ohms lumped resistances.
Abstract: In this article, a novel metasurface absorber is designed for RCS reduction as well as high isolation in a 4-elements MIMO antenna. A unit cell of metasurface absorber is amalgamated by concentric circular and elliptical-shaped rings with four 300 ohms lumped resistances. Absorbance at the intended frequency band (i.e. 8.75 GHz-9.00 GHz) of metasurface absorber is more than 90.0% and its reflectivity is tending to zero. Therefore, the isolation between antennas due to this absorbance is improved by 12 dB, and the total isolation of the antenna is achieved less than 23 dB. Similarly, the Radar cross-section (RCS) of the antenna is also significantly reduced by 10dBm2. This MIMO antenna with an absorbing structure is fabricated on a richly existing FR4 substrate with dimensions of 55 × 40 × 1 mm3. The performance of the designed MIMO antenna is also judged by diversity parameters similar to Envelope correlation coefficient (ECC), Directive gain (DG), Mean effective gain (MEG), Channel capacity loss (CCL), Total Active Reflection Coefficient (TARC), and channel capacity, etc. for the proposed frequency band. The simulated and measured ECC of the proposed MIMO is less than 0.073 which exhibits that this antenna is suitable for military application in radiolocation and navigation.

Journal ArticleDOI
TL;DR: A memristor neural network circuit is designed, which can recognize and sequence four characters simultaneously, which may provide a reference for the development of new brain-like system.
Abstract: Hopfield neural network has been widely used in image recognition because of its associative memory behavior. In this paper, a memristor neural network circuit is designed, which can recognize and sequence four characters simultaneously. It mainly includes three modules, namely a character recognition module, a signal processing module and a sequence module. The character recognition module consists of four individual character recognition units, corresponding to the recognition of four character images (W, H, A, T). The character recognition module includes calculation submodule and iteration submodule. After the operation of the calculation submodule and the iterative submodule, the four-character images distributed by noise can be identified simultaneously. The signal processing module is used to simplify the output signals of the character recognition module by four adder units. The sequence module ensures that stable state is eventually converged to the word (WHAT). The synapse weight circuit given in this paper can obtain different weights, so as to realize the function of associative memory. The iterative process circuit of Hopfield neural network is also designed to further demonstrate the iterative process. The neural network circuit composed of memristors maybe smaller, which may provide a reference for the development of new brain-like system.

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TL;DR: In this article, an autapse implemented with a locally active memristor, is introduced into the Fitzhugh-Nagumo neuron and thus a new neuron model is established, and the local stability of the neuron model with and without time delay is analyzed, respectively.
Abstract: Due to the natural non-volatility and distinctive plasticity, memristors are considered as ideal devices to mimic biological synapses. In this study, an autapse which is implemented with a locally active memristor, is introduced into Fitzhugh–Nagumo neuron and thus a new neuron model is established. The local stability of the neuron model with and without time delay is analyzed, respectively. Four coexisting firing patterns, including chaotic spiking, periodic spiking, periodic bursting and chaotic bursting, dependent on the memristor initial values, are explored. We find that the neuron has four regular attraction basins and its firing pattern can be regulated by choosing appropriate initial values. The time delay has an important effect on firing activities and the neuron model transits from periodic spiking, to chaotic bursting, and then to chaotic spiking with the increase of the time delay. Furthermore, the influence of the autaptic intensity on firing activities of the neuron is also revealed. In order to verify the complex firing activities, a neuron circuit is constructed and circuit simulations are performed.

Journal ArticleDOI
TL;DR: In this paper, a miniaturized quad-band polarization independent metamaterial loaded ultra-thin absorber is presented, which exhibits four distinct absorption bands with peak absorptivity of 9575, 9593, 9769, and 9564% at 32, 532, 1115, and 1673 GHz.
Abstract: In this paper, a miniaturized quad-band polarization independent metamaterial loaded ultra-thin absorber is presented The structure of the proposed absorber designed such that one resonator provides three absorption bands independently albeit another resonator contributes in two absorption bands further combination of mentioned resonators provides four absorption bands As a result of this proposed metamaterial absorber exhibits four distinct absorption bands with peak absorptivity of 9575%, 9593%, 9769%, and 9564% at 32, 532, 1115, and 1673 GHz, respectively The simulated full width at half maximum (FWHM) bandwidths are found as 90 MHz (315–324 GHz), 220 MHz (521–543 GHz), 410 MHz (1094–1135 GHz), and 700 MHz (1638–1708 GHz) correspondingly Moreover, the designed absorber structure is ultra-thin with a thickness of 001 λ0 and unit cell is miniaturized with electrical size of 011 λ0 × 011 λ0 corresponding to free-space wavelength (λ0) calculated at lowest absorption frequency The metamaterial characteristic of proposed unit cell has been validated by discussing complex dielectric permittivity, magnetic permeability and dispersion diagrams Owing to the four-fold symmetry of absorber unit cell structure, it shows polarization insensitive behavior The proposed ultra-thin absorber can be applied in various applications like stealth technology, imaging, electromagnetic interference suppression, sensing, and wireless applications

Journal ArticleDOI
TL;DR: In this article, a modified miniaturized Antipodal Vivaldi Antenna (AVA) array with suppressed mutual coupling is proposed for broadband 5G millimeter wave (mm-wave) application.
Abstract: A modified miniaturized Antipodal Vivaldi Antenna (AVA) array with suppressed mutual coupling is proposed for broadband 5G millimeter wave (mm-wave) application. The configuration is constructed by using eight radiating elements with single 1-to-8 power divider networks. By adding several notch structures, printed on the ground plane, the mutual coupling between the array elements are suppressed. Therefore, the radiating system has maximal additional isolation of 35.6 dB, enhanced gain of 13.36 dB, and extended impedance bandwidth of 26.5–29.5 GHz. In order to validate the design of the radiating system, the AVA array configuration is fabricated and measured with an overall dimension of 21.45 × 52.35 × 0.787 mm3. The experimentally validated gain value of the conventional AVA array antenna and modified array antenna is 4.7–8.35 dB and 8.62–12.67, respectively.