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In this paper, we present a design method for a highly efficient retrodirective array (RDA)-based microwave power transfer (MPT) system for the mMTC scenario, and evaluate its characteristics through experiments. Long-range wireless power transfer is required to effectively support the mMTC situation. RDA-based MPT controls and tracks the power beam towards the device within a certain range and it enables efficient power transfer. The overall link budget analysis is examined first and the required antenna gain is calculated. The required antenna gain can be secured using multiple-antenna modules. So, it is possible to design an RDA-based MPT system. In this paper, we implement a reduced RDA-based MPT system and evaluate its characteristics to confirm the feasibility of this design method. Through experiments, it has been confirmed that additional gain can be secured by using multiple antenna modules, and the RDA function can be effectively operated to effectively make a power beam in the direction of the power receiver. Conclusively, the gain of about 2.2dB increased whenever the number of antennas is doubled. The experimental results also show that the RDA-based MPT system designed in this paper is capable of adaptive power beamforming from −30 degrees to 30 degrees. [ABSTRACT FROM AUTHOR]

A novel approach for the dielectric characterisation of 3D printed substrates in S-band applications of patch antennas with different infill percentages is presented in this paper. The meta-structure substrate design has been 3D printed with a fused deposition modelling technique using bio-sourced material poly-lactic acid (PLA). Combining different infill patterns changes the dielectric parameters, and hence, the RF(Radio-Frequency) performance of the design. To validate the usefulness of this approach, the Taguchi sampling technique is used, where nine samples of a meta-structure substrate were designed to determine the dielectric properties of the substrate. The ring resonator technique is used for measuring the dielectric constant and loss tangent of the fabricated substrates. All nine meta-structure substrate shows varying dielectric properties, which can be used for tuning of RF characteristics of the patch antenna. The measured permittivity of various substrate structures ranges between 2.39 and 2.71. The concept of propagation delay is chosen as the selective parameter for the fabrication of the antenna. The results of antenna simulation and fabrication were mapped closely. The proposed meta-structure design antenna resonates at 2.43 GHz with an S11 of −26.60 dB. Gain enhancement of 5% is seen in the selected meta-structure design compared with the simple (solid) structure. This meta-structure substrate design approach using different patterns is simple, scalable and can be realised in other 3D printed antenna applications. [ABSTRACT FROM AUTHOR]

This paper presents a highly isolated pattern diversity multiband MIMO antenna using two ring-shaped radiating elements with a rectangular stub placed inside it. The proposed multiband MIMO antenna is resonating at three frequencies centred at 2.45 GHz, 3.5 GHz, and 5.4 GHz. A high-quality factor U-shaped bandstop filter is designed and placed between the two antenna elements to achieve simultaneous high isolation and pattern diversity. The isolation between the antenna elements at 2.45 GHz, 3.5 GHz, and 5.4 GHz is −25 dB, −20 dB and −35 dB, respectively. The diversity gain is 10 dB, while the ECC is less than 0.05. The antenna is fabricated on a low-cost substrate, FR4, and its dimensions are 31 mm × 31 mm × 0.8 mm. Measured results verify the multiband behaviour of the proposed MIMO antenna. The proposed MIMO antenna is useful for WLAN, WiMAX and 5 G sub-6 GHz-based applications. [ABSTRACT FROM AUTHOR]

This paper presents a hepta-band planar monopole antenna which exhibits circular polarization (CP) at two bands and linear polarization at other five bands. Combination of rectangular slots to form a single E-shaped structure has been introduced in half ground to excite hepta-band operations. Asymmetric trapezoidal parasitic element is also placed under the monopole radiator positioned at upper half ground plane of antenna. Due to asymmetric effect attained by the placement of trapezium, CP is achieved at 4.2 GHz and 10 GHz with 3-dB axial ratio bandwidth of 4.21–4.29 GHz and 9.92–10.01 GHz, respectively. The antenna acquires remaining five resonant modes at 2.4 GHz, 5.4 GHz, 7.2 GHz, 8.86 GHz and 11.8 GHz with 10-dB impedance bandwidth of 90 MHz, 160 MHz, 100 MHz, 200 MHz and 410 MHz, respectively. Sensitive study of the E slot and trapezoidal structured geometry is conducted. The proposed antenna is designed on low cost FR4 (εr = 4.4, tanδ = 0.02). To ensure the practicability, the proposed antenna design is fabricated and measured. A good agreement of simulation and measurement validates the proposed designed. The antenna has potential to cover frequency bands of IEEE802.11, Bluetooth, WLAN, WiMAX, Satellite Communication, Short Range RADARs and Radio band applications. [ABSTRACT FROM AUTHOR]

In this paper, a self-multiplexing textile antenna aided by a substrate integrated waveguide (SIW) is designed for wearable applications. The proposed antenna operates at wireless body area network (WBAN) frequencies such as 5, 5.2, 5.5 and 5.8 GHz. Extended unequal half mode substrate integrated waveguide (HMSIW) cavities are utilised for self-multiplexing operations with the open-ended magnetic wall working as the radiator for the proposed textile antenna. All the four unequal HMSIW cavities share the same electric wall which is realised using brass eyelets. The textile antenna is fabricated and the antenna parameters are measured to elucidate the proposed antenna concept. The port isolation has achieved above 33 dB between any ports. The measured gains for the four frequencies are above 5.1 dBi with high efficiency. The proposed multiplexing antenna is designed in 90 × 65 * 0.57 mm3 dimensions and the proposed antenna has exhibited good performance which makes it suitable for integrating with wearable devices and obviating the extra multiplexer circuits. [ABSTRACT FROM AUTHOR]

A compound reconfigurable monopole antenna (CRMA) having ability to change its frequency, polarisation and also pattern is presented in this paper. Only 6 PIN diodes are positioned on the monopole and ground to achieve reconfigurable operations and thus the antenna can operate over 8 different states. The radiation patterns of the proposed antenna can be tilted into two different directions. In each direction, the antenna can shift its operation in between two different frequency bands, and for each band, switching between two orthogonal circularly polarised (CP) radiation can be possible. A prototype is fabricated and measured. Based on various parametric analyses, a simple design guideline is also presented. By considering its overall simple configuration, low profile, and planar geometry, proposed antenna can be a useful candidate for future wireless applications like cognitive radio, 5 G devices, and so on. [ABSTRACT FROM AUTHOR]

In this paper, an 8-bit programmable digital metasurface is designed in the operating frequency range from 4 to 7 GHz. A monopole antenna operating at 5 GHz is characterised by using a metasurface structure as the ground plane. Various combinations of the metasurface structure are examined by altering the state of each unit-cell between 'ON (1)' and 'OFF (0)' in the coding matrix. The purpose of the 8-bit programmable digital metasurface is to control the electromagnetic wave effectively in the frequency range of interest. Dynamically controllable metasurface structure is utilised to change the unit cells' configurations. In addition, the proposed adjustable metasurface is capable to control the monopole antenna directivity, gain and main lobe magnitude, efficiently. According to various via conditions, different metasurface-based antenna parameters such as return loss (S11), radiation pattern, directivity and surface current distribution are investigated by means of the commercial numerical simulation software, CST microwave studio. Employing the simulation results of the metasurface-based antennas, the artificial neural network (ANN) data set is obtained. 128 activation conditions are trained and tested by Levenberg Marquart learning algorithm. During the ANN procedure, MATLAB is used to obtain accurate results by changing the rate of test and training data set. [ABSTRACT FROM AUTHOR]

A novel four-element MIMO antenna with reconfigurable bandwidth characteristics is reported in this paper. The proposed antenna is evolved using a chamfered rectangular monopole operating from 2.2 GHz to 11.3 GHz. The frequency selectivity of the antenna is accomplished by introducing a bandstop filter adjacent to the microstrip feed line of the UWB monopole. The proposed bandstop filter is constructed by introducing a notch in an all-pass filter. The notch band is carefully chosen such that the integration of the filter with the UWB radiator provides resonances centred around 2.4 GHz and 3.6 GHz suitable for WLAN communications. The bandwidth selection is accomplished using feed selection which is enabled using a set of PIN diodes. This makes the antenna work in two distinct operating modes, namely, the UWB mode (2.2 to >12 GHz) and the dual-narrowband mode (D-NB) (2.4 & 3.6 GHz). The research is further extended towards the construction of a MIMO antenna suitable for mobile networks. The prototype of the proposed four-element antenna is fabricated and analysed for S-parameters, radiation, and diversity characteristics. The average gain of the MIMO antenna array is greater than 4.5 dBi in the UWB/D-NB mode. The proposed antenna is suitable for low power UWB communications and high throughput WLAN such as IoT, sub 6 GHz 5 G communications, etc. [ABSTRACT FROM AUTHOR]

Wireless biotelemetry enables the formation of communication link from living body to an external monitoring device. Isolation of near field electromagnetic (EM) waves from body tissue, and wide bandwidth to avoid frequency detuning in different biological environments are the important parameters of on-body antennas. In this paper, a conformal defected ground patch antenna with artificial magnetic conductor (AMC) is introduced for on-body communication. Initially, a quarter wave wide band antenna with a shorting pin is designed to operate at 2.45 GHz. It resonates effectively on body tissue but most of the near field EM radiations are absorbed by tissue. Poor radiation efficiency of 10% and high specific absorption rate (SAR) value of 7.73 W/Kg were obtained. Thus, to reduce the effect of tissue loading on antenna performance an AMC-based structure is added. Better impedance matching, high efficiency (65%) and directivity (7.3 dBi) is achieved with AMC structure. Furthermore, unidirectional radiation pattern with SAR value of 1.43W/Kg is attained. Wide bandwidth of 600 MHz on phantom enables the antenna to withstand frequency detuning effect due to body postures and movements. Antenna robustness is analysed by bending the structure at different radii along X-axis and Y-axis. [ABSTRACT FROM AUTHOR]

In this research paper, a miniaturized vertically polarized dual band antenna with its 2x2 MIMO configuration is proposed for 5G communication. The single antenna consists of an off-centered fed, concave-shaped patch surrounded by two mirror-image C-shaped strips. It works as a millimeter wave radiator for 28/38 GHz bands which provide the transmission at ultra-high speed with a gain of 7.46 dBi and 8.56 dBi and an efficiency of 77% and 91% at both frequency bands respectively. The antenna offers a small-scale size of 10 x 10 x 0.254 mm3 and the close compatibility of simulated and measured results shows the practical feasibility of the fabricated prototype for 5G handheld devices. It can be used for device to device communication at 28 GHz and 38 GHz can be used for 5G cellular communications with higher speed, connectivity and low latency. Apart from that an electrical equivalent circuit of the antenna based on its physical structure is designed using AWR software and its results are included and compared with the CST results. The low specific absorption value of 1.05/0.288W/kg at 28/38GHz and the appropriate results of various parameters for MIMO design confirm its relevance for the 5G MIMO applications. [ABSTRACT FROM AUTHOR]

The paper proposes a wearable multiband antenna applicable for ISM (Industrial, Scientific and Medical) band, bluetooth, WiMAX, upper WLAN, fifth-generation (5G) smartphone applications, INSAT and radio altimeter, X-band, point-to-point hi-speed wireless, satellite TV, and C-band applications. This antenna is designed to function at resonance frequencies of 2.45 GHz, 4.6 GHz, 6.6 GHz and 8.2 GHz. The proposed textile antenna design dimensions are 50x80x0.56mm3.The antenna presented 47% impedance bandwidth covering the ISM band. The simulated value of the gain provided by the proposed wearable textile antenna is 5.59 dBi, 3.67 dBi, 3.99 dBi, 4.42 dBi at 2.45 GHz, 4.6 GHz, 6.6 GHz and 8.2 GHz resonant frequencies respectively.Simulations are therefore carried out using the human tissue model to show the specific absorption rate (SAR) value of the proposed antenna at different resonant frequencies. The antenna is fabricated and the simulated reflection coefficient validation is done with the measured results. The Antenna in off space provides 45% (2.1-3.32 GHz) impedance bandwidth. The antenna measured on the back of the human body provides percentage impedance bandwidth of 145% covering 1.4 to 8.8 GHz frequency band applicable for ISM band and other wireless applications. [ABSTRACT FROM AUTHOR]

Radio Frequency Energy Harvesting is found to be the best alternative to conventional batteries for providing endless power to the sensor networks connected to perform various applications in the smart city. The electromagnetic energy density in the ambient environment is very low and not uniform, which demands a high gain multi-band rectenna system operating at mostly available energy bands and a suitable rectifier circuit that offers large PCE performance. This paper introduces a triple-band monopole rectenna with enhanced performance for smart city applications. A defective ground structure (DGS) has been investigated for a significant increase in gain with an increasing number of resonant frequencies. The proposed antenna operates over a band of frequencies that lies within 1.25–3 GHz, which covers 1.8/2.1/2.45 GHz frequencies. The antenna offers the gain values of 4.16/6.54/10.2 dB at 1.8/2.1/2.45 GHz frequencies, respectively. A single diode series-connected rectifier has been opted to efficiently operate over a wide range of input power levels from −10 dBm to 5 dBm and offers a minimum conversion efficiency of 60% within the operating bands at 0 dBm input power. The rectenna system is experimentally measured and the measured output voltage at 2.45 GHz frequency is 1.123 V. [ABSTRACT FROM AUTHOR]

There is a strong demand for compact and multiband antennas as wireless technologies become more integrated into automobiles. These antennas must be able to serve multiple services without compromising the size and installation space. In addition, the antenna incorporated should not affect the aesthetic appearance of the vehicle. This paper presents a compact multiple-input-multiple-output (MIMO) antenna working at 2.45 GHz (Wi-Fi/Bluetooth/RFID) and ultra-wideband (UWB) frequencies. A basic rectangular monopole with a self-complementary structure is used to design the antenna element. The size of the antenna element is 20 × 22 mm2. The proposed MIMO cube is developed with four antenna elements in cubical orientation to achieve compactness and better isolation. The overall dimension of the MIMO antenna is 35 × 22 mm2. The diversity antenna shows impedance bandwidth of 2.4–11.5 GHz and isolation of more than 20 dB. The envelope correlation coefficient (ECC) of the MIMO antenna is less than 0.2, diversity gain (DG) is greater than 9 dB, and total active reflection coefficient (TARC) and channel capacity loss (CCL) are less than −10 dB and 0.4 bits/s/Hz, respectively. The gain and efficiency are found to be greater than 1 dBi and 72%, respectively. [ABSTRACT FROM AUTHOR]

This paper presents the design and analysis of a multi-band, dual-polarised monopole antenna consisting of a simple equilateral triangular monopole patch configured with a modified ground structure (MGS). In the presented antenna design, quad-band dual-polarised operation has been obtained by creating the three unequal rectangular slots on the ground structure. The proposed monopole antenna produces four individual frequency bandwidths with the dual sense of polarisation, namely linear polarisation (LP) and circular polarisation (CP). The antenna produces quad-band behaviour with linear wave polarisation in Band1, whereas right-hand circular polarisation (RHCP) in rest frequency bands viz. Band2, Band3, and Band4. The measured impedance bandwidths spread from 2.50 to 4.42 GHz in band2; 5.22 to 6.28 GHz in band3; and 8.40 to 10.30 GHz in band4; whereas the impedance bandwidth extends from 1.35 to 2.14 GHz in linearly polarised band 1. The measured axial ratio bandwidth (ARBW) extends from 2.82 to 3.20 GHz in band2; 5.17 to 5.94 GHz in band3; and 9.30 to 9.70 GHz in band4, respectively. The constant gain profile has been observed in all frequency bands. The proposed antenna can be applied for WLAN/ WiMAX and Wi-Fi applications. [ABSTRACT FROM AUTHOR]

One of the capable technologies in networking systems is the Multiple-Input Multiple-Output (MIMO) technology as it provides better system capacity and a high Bit Error Rate (BER). Still, the transmit antenna selection remains as the greatest issue. More transmit antennas are necessary to achieve maximum capacity, which leads to increased power consumption. Therefore, for solving these issues in the M-MIMO system, this paper introduces a novel Wolf Adapted Herding algorithm (WA-HA) for selecting the optimal transmit antennas using multi-objective constraints that raise the capacity and Energy Efficiency (EE). The proposed algorithm combines the concept of Elephant Herding Optimization (EHO) and Grey Wolf Optimization (GWO) algorithm and it is referred to as the Wolf Adapted Herding Algorithm (WA-HA). This WA-HA algorithm optimises the number of transmit antennas and hence decides which antenna has to be chosen. Finally, the performance of the adopted method is evaluated over other traditional methods like MV-GSA, SLnO, I-SLnO, EHO and GWO in terms of various metrics like EE and capacity. In particular, the capacity of the proposed WA-HA method for ZF under set-up 1 is 51.02%, 30.61%, 22.44%, 8.163% and 55.10% better than the existing models. Furthermore, the computational time of our model is 10.96%, 26.13%, 14.08%, 13.48% and 10.26% superior to that of the existing models, respectively. [ABSTRACT FROM AUTHOR]

Proposed in this paper is a new configuration for a quad-band antenna based on using a metamaterial-inspired defected ground structure. The presented structure is introduced as a new modified metamaterial Complementary Split Ring Resonator (CSRR) with a compact electrical size. The new modified CSRR has been employed in Composite Right/Left-Handed (CRLH) transmission line configuration for ultra-size reduction. Validation for the particle small size is introduced and the detailed analysis for the NRI characteristics has been discussed by extracting the cell constitutive parameters. Hence, a multi-band antenna is designed based on using only one cell of the proposed NRI-TL. Subsequently, a small multi-band antenna is presented for different multi-band functionalities and different radiation properties. The antenna displays quad-resonances at 1.78 GHz, with the typical omnidirectional radiation pattern, 3.28 GHz, 4 GHz, and 4.3 GHz, with the directive broadside radiation properties. The proposed antenna footprint is 10 × 10 cm2, which exhibits a size reduction of up to 80% in comparison with a rectangular patch antenna operating at the lowest frequency band. [ABSTRACT FROM AUTHOR]

Software-defined radio (SDR) deals with the opportunistic detection and allocation of the radio frequency (RF) signals in the cognitive radio network (CRN). The opportunistic spectrum use between primary licenced and secondary unlicensed user depends upon the adequate detection of the spectrum hole. This paper presents a design of a smart compact wideband patch antenna for SDR in cognitive radios. The fractal slot antenna with electromagnetic bandgap structure is designed on 12 × 18 mm2 FR4 substrate as a primary perception module in the cognitive radio sensor network. The wide operating range of antenna 0.68–12.1 GHz is highly compatible with adaptive learning of SDR to deal with dynamic spectrum variation over a large bandwidth. The antenna exhibits high radiation efficiency with consideration of tangential losses of FR4 and sustainable gain 2.5 dBi over the complete impedance bandwidth. The proposed five-layered ANN-ML supervised SDR comprises multispectral resolution via coefficient estimation for primary and secondary user and elicits high throughput of proposed antenna during white space spectrum sensing. The data analytics for ANN-ML has modelled on Python 3.0 IDE and the results are validated to justify the candidature of the antenna for wideband sensing as per the Federal Communications Commission standards for CRN. [ABSTRACT FROM AUTHOR]

This paper describes the multiband behaviour of several circular-shaped hybrid fractal antennas. Initially, a circular-shaped fractal antenna (antenna-A) is designed and its performance is scrutinised. Afterwards, hybrid fractal approach is utilised in the design process to enhance the operational performance and the resultant structure is named as circular-shaped hybrid fractal antenna (antenna-B). The volumetric dimensions exhibited by the antennas are 38 × 38 × 1.6 mm3. The ground plane dimension 'LPG' has been optimised specifically with a recently developed teaching-learning-based optimisation algorithm. Fabrication and testing of antenna-B is done in order to justify the proposed strategy. Measured results depict that the fabricated antenna operates at six fundamental resonances with acceptable gain values. A bandwidth of 1.97%, 7.47%, 5.46%, 4.04%, 4.37% and 4.53% is evaluated at the respective bands. Radiation patterns provided by antenna-B are arbitrary bidirectional/ omnidirectional. In addition, the influence of specific design patterns on the performance of antenna-B is studied. Experimental measurements are presented and compared with the simulated ones. From practical outcomes, it is suggested that the proposed antenna-B can be useful for several wireless communication applications such as Satellite communication for downlink, Fixed satellite communication, Radiolocation, Direct broadcast satellite communication and Radars. [ABSTRACT FROM AUTHOR]

In this paper, the construction of a miniaturised hexagonal microstrip antenna (MSA) loaded with Defected Ground Structure (DGS) and Metamaterial (MTM) superstrate proposed for 5.2 GHz WLAN application is presented. Initially, the fundamental resonant frequency of the hexagonal MSA was reduced from 14.8 GHz to 5.2 GHz using a rectangle DGS. For the suggested antenna model a miniaturisation of about 64.86% is achieved, which makes the antenna to approach electrically small antenna. Finally, the characteristics of MSA loaded with DGS and an MTM superstrate, which enhances the peak gain, directivity, and efficiency. The suggested miniaturised antenna with substrate dimensions of 0.25λ0 × 0.243λ0 mm2 (or) 14.4 × 14 mm2 of thickness h1 = 1.6 mm fabricated on an FR4 epoxy of dielectric constant 4.4. By employing an MTM superstrate, of RT Duriod substrate of thickness h2 = 1.575 mm above the proposed miniaturised hexagonal MSA at a height of h3 = 14.4 mm, a gain increased from 3.32 dBi to 6.38 dBi is attained at 5.2 GHz. The simulated outcomes of the suggested model are in association with experimental results of the prototype model. [ABSTRACT FROM AUTHOR]

This paper presents the design of Meander and Koch Curves based Wearable Hybrid Fractal Antenna (MKWHFA) using Particle Swarm Optimisation (PSO) and Iterative Function System (IFS). The proposed antenna design combines two fractal geometries i.e. Meander and Koch curve to enhance its performance characteristics. It uses the Jean material as a substrate having a dielectric constant of 1.7 and height 1 mm. The patch and the ground plane made using the copper tape. ANSYS/Ansoft HFSS V13 software is used for simulating and designing for the proposed MKWHFA. Parametric analysis on this antenna's ground plane is done to achieve the desired resonant frequency, gain, and bandwidth. A mathematical model is derived using the IFS to generate the fractal geometry in MATLAB software. The feed position of MKWHFA optimised using PSO technique. The MKWHFA with Meander-Koch slot resonates at 2.4508 GHz, 5.4005 GHz, 6.6503 GHz, and 8.0002 GHz with corresponding gains 5.61 dB, 8.55 dB, 5.07 dB and 3.24 dB, bandwidths 291 MHz, 94 MHz, 222 MHz and 310 MHz respectively. The proposed MKWHFA fabricated and tested in the laboratory. There is a good agreement between the simulated and experimentally measured results. [ABSTRACT FROM AUTHOR]

In this paper, a novel half T-square strip fractal antenna has been proposed. The antenna has been designed on FR4 (ɛr = 4.4) substrate with a size of 26 × 20 × 1 mm. The reported antenna resonates at 0.91 (0.89–0.95 GHz), 2.16 GHz (2.1–2.23 GHz), 4.19 GHz (3.9–4.4 GHz), 5.22 GHz (5.1–5.3 GHz), 7.69 GHz (7.3–8 GHz), and at 9.16 GHz (9.1–9.3 GHz) having a gain of 5.6 dB, 0.2 dB, 1.4 dB, 2.1 dB, 2.4 dB, and 2.5 dB, respectively. The antenna size has been miniaturised by 93% in terms of the lowest resonating frequency in comparison to a conventional patch antenna by using fractal geometry. The proposed antenna covers the frequency bands for applications such as Radiolocation, deep space research, Aeronautical Radio Navigation services (ARNS), Maritime Radio Navigation services (MRNS), and Fixed Satellite Services (FSS). The prototype of the proposed half T-square strip fractal antenna has been fabricated. The measured and simulated results are in good agreement. [ABSTRACT FROM AUTHOR]

Cooperative relaying is an effective technique to combat multi-path fading, improves system capacity and enhances the coverage. In this paper, three different types of operations of infrastructure-based multi-antenna cooperative relay network have been investigated. Closed form expressions of outage probability and average error rate for each type of operation have been derived, when the relay and destination perform maximum ratio combining (MRC) of signals. The effect of antennas installed on relay and its placement has also been studied in this work. [ABSTRACT FROM AUTHOR]

This paper presents the design of a compact arc shape slot antenna and its application in multiple inputs and multiple-output (MIMO) communications. The unit cell antenna has a footprint of 15 × 15 mm2. The antenna with arc shape stub loaded feedline provides broadband impedance matching extending from 3 GHz– 9.5 GHz. The antenna is made dual-polarised using orthogonal feed structure. A four-port, two-element MIMO antenna is constructed by replicating the unit cell design in a parallel fashion. Broadband isolation enhancement is achieved by using a modulated microstrip line embedded with circular patches of varying diameters. The four-port MIMO antenna provides 10 dB additional enhancement in comparison with the unmodulated microstrip line decoupling unit cell. The prototype antenna is fabricated and the simulation results are verified using experimental measurements. The antenna offers an average peak gain of 5.2 dBi and efficiency greater than 75%. The MIMO parameters such as envelope correlation coefficient, diversity gain, mean effective gain are evaluated and presented. The proposed antenna is one of the most compact 4 port solution reported in the literature. [ABSTRACT FROM AUTHOR]

In this paper, a multiband oval ring patch antenna is presented. The proposed antenna consists of a quarter wavelength folded meander line attached inside the ring and a pair of quarter wavelength 'L' shaped stubs are attached outside the ring which helps antenna in radiating at multiple resonant frequencies with proper impedance matching performance. Antenna with the dimensions of 10 × 12 × 1.524 mm3 has been designed, fabricated and tested. The proposed antenna exhibits −10 dB impedance at the centre frequency of 6.21 GHz(315 MHz), 9.4 GHz(671 MHz), 16.78 GHz(441 MHz), and 25 GHz(3.21 GHz) from the experimental results. It covers a wide variety of wireless applications namely C-band communications (4 GHz-8 GHz), X-band communications (8 GHz-10 GHz), Ku-band communications (16 GHz-17 GHz), and K-band communications (24 GHz-27.3 GHz). The proposed antenna exhibits gains of 1.01 dBi, 1.2 dBi, 5.6dBic and 8.1 dBi along with the efficiencies of 60.14%, 74.3%, 78.6% and 83.64% at 6.21 GHz, 9.42 GHz, 16.78 GHz, and 25.4 GHz respectively. The patch exhibits Right Hand Circular Polarisation (RHCP) at 16.78 GHz and linear polarisation at remaining resonant frequencies. The measured and simulated results are in good agreement. [ABSTRACT FROM AUTHOR]

This paper presents a highly compact dual-band elliptical wide-slot (EWS) antenna with high bandwidth dimension ratio (BDR) having one inverted L-slot for WLAN and WiMAX applications. Initially, the broadband characteristic of 4.4–9.3 GHz is obtained by using an EWS in the ground plane. To include 3.5 GHz WiMAX wireless standard, a parasitic elliptical patch is embedded in the centre of the elliptical wide-slot. With an increase in semi-major axis length of the parasitic patch, the overlapping capacitance between the microstrip-line and the parasitic patch increases, thereby showing a broadband characteristic ranging from 3.59 to 7.08 GHz and BDR of 1423. An inverted L-shaped slot is etched in the ground plane to generate a frequency band around 2.4 GHz, integrating the 2.4 GHz WLAN and 2.5 GHz WiMAX wireless standards. The measured 10 dB return loss bandwidth due to mirrored L-shaped slot is 440 MHz (2.34–2.78 GHz) with BDR of 923. As a result, the EWS with parasitic patch and mirrored L-shaped slot together gives an overall size of 0.132 λ L × 0.14 λ L where λ L is the lowest free-space wavelength corresponding to the operating frequency of 2.34 GHz. The measured peak gain of lower and upper-frequency bands is 6.95 and 6.82 dB. [ABSTRACT FROM AUTHOR]

In this paper, a dual-band circular polarised (CP), Multiple Input Multiple Output (MIMO) antenna with bi-directional polarisation is presented. Designed antenna is operating at two frequency bands i.e. 5.4 GHz–6.2 GHz and 7.0 GHz–7.4 GHz. A rectangular dielectric resonator (DR) is excited by two ports for designing an MIMO antenna system. To generate the Circular polarisation, ground plane is modified by etching an inverted Z-shaped slot. The fundamental mode T E 111 X , T E 111 Y and higher order mode T E 121 X , T E 121 Y are generated in the antenna structure due to the specified geometry which excites the circular polarisation. 3-dB axial ratio (AR) bandwidth of 300 MHz (5.7 GHz–6.0 GHz) and 200 MHz (7.0 GHz–7.2 GHz) is obtained for the lower and upper bands, respectively. Maximum isolation is 19 dB, and 15 dB for the targeted bands have been achieved. S-parameters, gain and radiation pattern are measured to authenticate the simulated results. Envelope correlation, diversity gain, mean effective gain and channel capacity loss are calculated from the measured parameters; their values lie within the optimum range. Results show that antenna is suitable for WLAN 5.5/5.8 GHz and X-band downlink communication at 7.0 GHz. [ABSTRACT FROM AUTHOR]

In this paper, a reduced mutual coupling dual-band multiple-input-multiple-output (MIMO) antenna is reported. A thin rectangular slot is incorporated into an unlicensed 5.2 GHz band rectangular patch antenna (RPA) to excite another industrial, scientific and medical (ISM) 2.4 GHz band. In the 1 × 2 MIMO configuration, antennas are closely placed at a distance of λ m a x / 8 and the mutual coupling between antenna elements is suppressed by incorporating a dual-band electronics-bandgap (EBG) structure. A mushroom kind of EBG arrangement with two different square-shaped plates on the top and the bottom of the EBG is done to exhibit dual-band rejection characteristics. MIMO communication parameters, envelope correlation coefficient (ECC), diversity gain (DG), and multiplexing efficiency ( η M U X ) are calculated exhibiting excellent performance of the proposed antenna. Prototype of the antenna is fabricated and good agreement is found amongst simulation and measured results. [ABSTRACT FROM AUTHOR]

In this paper, firstly, a common mistake in the formulation of the array factor of concentric elliptical antenna array (CEAA) is pointed out and corrected. Secondly, several CEAAs are optimally designed to have the smallest sidelobe level (SLL). This is accomplished using four optimisation algorithms; Antlion Optimisation algorithm (ALO), Grasshopper Optimisation Algorithm (GOA), Symbiotic Organisms Search (SOS) and a newly proposed hybrid algorithm based on ALO and GOA. Two cases for CEAA synthesis are presented. The goal in the first case is to find the optimal values for the current amplitudes ( I n 's) to minimise the sidelobe level, assuming that the antennas' positions are fixed along the ellipses. In the second case, the current amplitudes ( I n 's) are assumed to be unity, and the optimisation problem is to find the optimal values for the elements positions along the ellipses. The results of the proposed optimisation algorithms are compared to uniform antenna array results. [ABSTRACT FROM AUTHOR]

In this research paper, the development of an artificial neural network (ANN) model for the designing of a compact dual-band hybrid fractal antenna (CDHFA) that covers Wireless Medical Telemetry Service and industrial, scientific and medical (ISM) bands are described. The projected CDHFA is designed by using 1.6mm thick, FR4 substrate whose permittivity is 4.4 and obtained by the combination of different fractal geometries. The dimensions of the projected CDHFA are interlinked with each other. A set of 80 CDHFAs with different dimensions is designed to obtain a data dictionary for the implementation of ANN. From the experimental results, it is depicted that the resonant frequencies are 1.4290 and 2.4380 GHz with S(1,1) values −12.4 and −15.72 dB, respectively. A comparison between feed forward back propagation network, generalised regression neural network and desired outputs in terms of average absolute error is also done. The simulation, experimental and ANN results are well matched that indicates the effectiveness and accuracy of the developed ANN model for biomedical applications. [ABSTRACT FROM AUTHOR]

User-relay assisted OFDMA-based cellular networks have gained great importance recently since these networks are indicated as one of the powerful technologies that will contribute the 5G standard. These networks can be used with novel three-phase frame structure unlike classical two-phase frame structure and can be enhanced with multiple antennas to utilise the advantages of them. The main advantage of the three-phase frame structure is taking care of the limitations of the current transceiver design in practical systems and not allowing users to be relay and user simultaneously. Diversity and capacity gains are also the advantages of extending the network with multiple antennas. In this paper, we will use the novel three-phase frame structure for downlink MISO-OFDMA cellular networks and develop resource management algorithms as relay selection and resource allocation to observe the benefits of this system. [ABSTRACT FROM AUTHOR]

A highly miniaturized miniaturised meander-shaped implantable antenna is proposed for biomedical applications. The antenna has a volume of 12.29 mm3 and is designed with slots only. Using only slots on patch and ground surface, the fabrication of proposed implantable antenna is quite effortless unlike using techniques of sorting pin, metamaterial, and multiple patch stacking. The analysis shows that the proposed antenna has excellent impedance bandwidth of 140 MHz (2.39 GHz to 2.53 GHz) with resonating frequency of 2.41 GHz, circular polarisation with an axial ratio bandwidth of 80 MHz (2.45 GHz to 2.53 GHz), gain of −23.45 dB, acceptable SAR 901 W/KG in industrial, science and medical band (ISM). The detail parametric study of the designed antenna with substrate/superstrate materials, different human body tissues, different depth of penetration in human tissues, and thickness of substrate/superstrate have been analysed successfully. For the authenticity purpose, the results are correlated with the prepared skin mimicking gel (saline solution) in vitro model. The fabricated antenna indicates similar performance as provided by the proposed simulated antenna design. [ABSTRACT FROM AUTHOR]

In existing grouped multilevel space-time trellis codes (GMLSTTCs), the groups of transmit antennas are predefined, and the transmit power is equally distributed across all transmit antennas. When the channel parameters are perfectly known at the transmitter, adaptive antenna grouping and beamforming scheme can achieve the better performance by optimum grouping of transmit antennas and properly weighting transmitted signals based on the available channel information. In this paper, we present a new code designed by combining GMLSTTCs, adaptive antenna grouping and beamforming using the channel state information at transmitter (CSIT), henceforth referred to as weighted adaptively grouped multilevel space time trellis codes (WAGMLSTTCs). The CSIT is used to adaptively group the transmitting antennas and provide a beamforming scheme by allocating the different powers to the transmit antennas. Simulation results show that WAGMLSTTCs provide improvement in error performance of 2.6 dB over GMLSTTCs. [ABSTRACT FROM AUTHOR]

In this paper, a new and blind algorithm for active user enumeration in asynchronous direct sequence code division multiple access (DS-CDMA) in multipath channel scenario is proposed. The proposed method is based on information theory criteria. There are two main categories of information criteria which are widely used in active user enumeration, Akaike Information Criterion (AIC) and Minimum Description Length (MDL) information theory criteria. The main difference between these two criteria is their penalty functions. Due to this difference, MDL is a consistent enumerator which has better performance in higher signal-to-noise ratios (SNR) but AIC is preferred in lower SNRs. In sequel, we propose a SNR compliance method based on subspace and training genetic algorithm to have the performance of both of them. Moreover, our method uses only a single antenna, in difference to the previous methods which decrease hardware complexity. Simulation results show that the proposed method is capable of estimating the number of active users without any prior knowledge and the efficiency of the method. [ABSTRACT FROM AUTHOR]

This work presents a parasitic wide band compact planar antenna for 5 G mm-wave applications. Besides having high bandwidth (5.22 GHz), the prospective antenna provides an enhanced gain of 5.23dBi which is achieved due to the reflector elements used in the design. The radiating element has a small planar rectangular geometry, with optimised dimensions of 0.342 λ0 × 0.199 λ0 × 0.005 λ0 at 28 GHz frequency of interest and has been designed and fabricated on a substrate of Rogers-RT/Duroid 5800 having a thickness of 0.147λ0 with loss-tangent of 9 × 10−4 and permittivity of 2.2. The proposed antenna operates in the frequency range of 24.71 to 29.93 GHz which falls under the n257 and n258 NR operating band of the FR2 band as defined by ITU for the millimetre wave 5 G spectrum. It is also affirmed in the study that the impedance bandwidth can be tuned by controlling the coupling gap between the radiating and parasitic patches. The measured results of the fabricated prototype of the patch are compared with the simulated results and the two results are in good agreement with each other. The pursuance of the proposed design in terms of gain, efficiency, radiation pattern, and wide bandwidth, qualifies the prototype as a viable option for mm-wave communication. [ABSTRACT FROM AUTHOR]

This paper deals with a microwave sensor for classifying tangerines by flavour using coupled-patch antennas. The operating frequency of the antennas is 2.45 GHz. The sensor determines the flavour of each tangerine by measuring the magnitudes of coupled signals of the antennas with the tangerine fruit at the centre. The sorting is carried out using an artificial neural network implemented on a field programmable gate array. The classification performance of the sensor is 95% accurate, so it has potential for use in sorting tangerines by flavour. In addition, the system uncertainty is analysed to determine optimal operating conditions. [ABSTRACT FROM AUTHOR]

A low-cost method with high yield and good performance is presented by pHEMTs (pseudomorphic high electron mobility transistors) to be used in phase shifter switches. In this method, the capacitor in “off” mode (Coff) of transistor is reduced, without variation of the transistor structure. The transistor structure in switch mode can be optimised. This method increases the transistor isolation in turn “off” mode, while there is no change in resistance of the transistor in “on” mode (Ron). Transistor dimension is determined in turn “off” mode (Vg =−4.5 V) and standard form of 4 × 75 μm. So, in this method, insertion loss will be reduced without a perceptible change in transistor dimension. Thus, design and fabrication capability of some circuits such as phase shifters, antenna switches, SPDT (single port double throw) – without any change in technology – are increasing. In this paper, post layout and measurement result for a sample block of phase shifter are shown. [ABSTRACT FROM AUTHOR]

Cognitive Radio (CR) is a regulated technique for opportunistic access of idle resources and it is expected that the golden service of spectrum sensing is to be achieved via the robust sensing technique to sense the unused spectrum in an opportunistic manner. In this paper, we propose multiple energy detectors (MED) utilising adaptive double-threshold (ADT) for spectrum sensing. In the present framework of CR networks, each CR node is equipped with MED and each energy detector with single antenna. Numerical results show that it improves detection performance at very low signal-to-noise ratio (SNR), and overcomes sensing failure problem. Further, the scheme was analysed in conjunction with cooperative spectrum sensing (CSS), where each CR users employ selection combining (SC) scheme to take global decision by MED with adaptive double-threshold (MED_ADT). It is further found that this arrangement improves detection performance around 6.3% as compared to hierarchical with quantisation method at –10 dB SNR, under the case when a small number of sensing nodes are used in spectrum sensing. [ABSTRACT FROM AUTHOR]

A dual-band 2 × 1 multiple-input-multiple-output (MIMO) antenna based on substrate integrated waveguide (SIW) cavity for both satellite (in K-band) and 5 G applications is proposed. Initially, the SIW cavity consisting of metallic vias on all four sides is implemented. For MIMO configuration, this cavity is divided into two smaller SIW cavities using a row of metallic vias and excited using the coaxial feed. By etching an asymmetric cross-slot (AXS) with tuned dimensions on top of the SIW cavity, a dualsense of circular polarisation (CP) in both frequency bands is obtained. The fabricated prototype of the proposed SIW antenna shows impedance bandwidth (IBW) of 15.36% (22.60–26.36 GHz; BandI) and 4.64% (29.04–30.42 GHz; BandII). The completely overlapping axial-ratio bandwidth (ARBW) with IBW of 15.16% (22.62–26.33 GHz) and 3.10% (29.20–30.12 GHz) with a peak gain of 12.47 and 7.71 dBi is obtained in BandI and Band II, respectively. The proposed antenna shows front-to-back ratio (FBR) of more than 20 dB in both resonating frequency bands. The measured results of the proposed MIMO antenna agree well with the simulation. [ABSTRACT FROM AUTHOR]

The proposed work contains a quasi-self-complementary (QSC) half-cut flower-shaped ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna with dual-band-notch characteristics. The overall size of the antenna is 27 × 39 mm2, which offers impedance bandwidth from 2.67 GHz to 11.7 GHz. The inter-port isolation is more than 15 dB over the FCC defined UWB range of frequencies. A reverse 2-shaped slit is etched off from a flower-shaped patch to reject the interfering WiMAX/C-band (3.28–4.19 GHz), whereas an inverse P-shaped stub is placed near the feed arm a notch at the WLAN band (5.1–6.15 GHz). Further, the performance of the proposed antenna is analysed by comparing the simulated results with the fabricated ones. Moreover, diversity parameters such as envelope correlation coefficient (ECC), channel capacity loss (CLL), mean effective gain (MEG), effective diversity gain (EDG) and total active reflection coefficient (TARC) are computed, which makes the proposed QSC UWB-MIMO antenna a suitable candidate for high-speed wireless applications. [ABSTRACT FROM AUTHOR]

In this work, a circularly polarised (CP) slot antenna based on linear polarisation conversion metasurface (PCM) is proposed for broadband radar cross-section (RCS) reduction and gain improvement. The proposed metasurface is designed using the chequerboard alignment of PCM unit cells and its mirrored ones to meet the phase cancellation principle required for RCS reduction. An improved loading technique of the PCM consisting of rearrangement of the PCM unit cells across the radiating slot is employed to enhance the gain of the proposed antenna. The measured results show that the operating bandwidth of the proposed antenna is in the range of 9.8–10.8 GHz. The maximum gain achieved is 2.4 dB more than the reference antenna while the 3-dB axial ratio bandwidth (ARBW) obtained is 9.8–10.6 GHz. The proposed antenna achieves an average RCS reduction of 11 dB in the frequency region of 6–18 GHz in comparison to the reference antenna. [ABSTRACT FROM AUTHOR]

In this article, a 2 × 2 microstrip array antenna integrated with FIN defected ground structure (DGS) is investigated, which is designed for 3.24 GHz band operation. The FIN-DGS has been etched from the ground plane in the H-plane direction between two contiguous elements in a symmetric manner. Therefore, it suppresses the cross-polarisation (XP) radiation in the antenna without affecting its co-polarisation (CP) radiation characteristics. A proposed antenna has been designed and experimentally verified and shows <35 dB XP (±50º) radiation around boresight of the radiating elements in the H-plane with 10.7 dBi gain. The variation of XP fields has been investigated using the modal field distribution. The designed antenna provides a wide range of applications in adaptive arrays and space antennas, where 3D coverage with decreased XP values is the primary constraint. [ABSTRACT FROM AUTHOR]

A single-layer, four-element multiple-input-multiple-output (MIMO) antenna for 5 GHz (5150–5850 MHz) band WLAN application is proposed. Each unit element consists of three sections and this behaves as a travelling wave antenna, which enables frequency scanning feature. The combination of orthogonal feeds and placement of elements introduce dual-polarisation, and pattern diversity respectively. Thus, the proposed MIMO antenna offers a higher degree of freedom (pattern diversity, frequency scanning and dual polarisation), which makes it exceptional. The proposed MIMO antenna has a maximum impedance bandwidth of 17% (4.93–5.87 GHz) corresponding to port 4 and isolation of 17.5 dB, which is achieved without additional decoupling/isolation enhancement circuits. The envelope correlation coefficient of 0.25, capacity loss less than 0.4 bits/sec/Hz, and the mean effective gain (MEG) ratio of 0 dB in the desired frequency band quantifies the diversity performance for WLAN applications. The proposed MIMO has gain from 2 to 5.5 dB and occupies a compact volume of 1.3 λ × 1.3 λ × 0.02 λ mm3, which may be one of the most miniaturised electrical configurations. [ABSTRACT FROM AUTHOR]

The metamaterial inspired low-cost diamond-shaped fractal antenna (DSFA) based on edge-coupled (EC) parasitic split ring resonator (SRR) for multiband wireless application is presented and investigated in this manuscript. Initially, three iterations of DSFA are designed and found that second iteration reveals the more number of frequency bands as compared to the other iterations. For proper impedance matching characteristics, partial ground plane has been introduced in the designing of antenna and low-cost FR4 glass epoxy substrate with thickness of 1.6 mm is used with an overall size of 32 × 36 mm2. Further, the EC parasitic SRR is loaded in the geometry of the proposed antenna and compared with the unloaded antenna and noted that the loaded antenna reports the better results in terms of bandwidth and reflection coefficient. The loaded antenna exhibits the maximum bandwidth of 5.68 GHz (1.67–7.34 GHz) and a maximum gain of 8.63 dB at 2.3 GHz and 9.90 dB at 19.9 GHz. The prototype of the proposed DSFA has been fabricated and tested for the authentication of measured results with the simulated results and found both are in agreement with each other. Proposed DSFA with EC parasitic SRR is best suitable for different wireless applications because of its multiband behaviour. [ABSTRACT FROM AUTHOR]

This communication presents the design of an asymmetrical hexagonal-shaped wideband antenna based on Characteristic Mode Analysis (CMA). An L-shaped slot is used to change the distribution of mode surface currents. Current modes and characteristic fields of the desired modes are studied to improve bandwidth. A simple 50 Ω microstrip line is used to excite the selected modes and obtain wideband impedance matching. The antenna is printed on a low-cost FR4 substrate with a size of 30 mm × 29 mm × 1.6 mm. The design approach is experimentally validated through fabricated prototype antenna. It exhibits impedance bandwidth of 110.22% from 2.7 to 9.33 GHz, and thus covers most wireless systems, such as WPAN, WiMax, WLAN, RFID and C-band. [ABSTRACT FROM AUTHOR]

A new type of metasurface (MTS) structure consisting of two diagonally connected rings is proposed. Proposed MTS with 16-unit cells are arranged in 4 × 4 cells, which converts linearly polarised (LP) to circularly polarised (CP) wave with axial ratio bandwidth (ARBW) of 50 MHz. Four different LP antennas, microstrip fed, coaxial fed, slot antenna, and aperture antenna have been used to test the utility of the MTS for conversion LP to CP. LP to CP has been achieved by merely placing MTS as a superstrate above these antennas. Microstrip antenna has impedance matching bandwidth (IMBW)170 MHz (2.51–2.68 GHz) while ARBW is 20 MHz(2.52–2.56 GHz). The coax fed has IMBW 100 MHz (2.5–2.6 GHz), and ARBW is 50 MHz(2.53–2.58 GHz). Slot antenna has IMBW 830 MHz(2.16–2.99 GHz); however, ARBW is 80 MHz (2.40–2.48 GHz). Aperture antenna has IMBW 710 MHz(2.16–2.87 GHz), and ARBW is 80 MHz(2.56–2.64 GHz). Coaxial fed and aperture antenna have fabricated with the MTS, and their measured results agreed well with simulated, which validate the effectiveness of the proposed metasurface. The proposed MTS could be useful as a polarisation converter in S-band for any antenna. [ABSTRACT FROM AUTHOR]

Mechanical distortion errors in active phased-array antennas (APAA) include both random error and mechanical distortion. Random error is generated during the manufacturing and assembly process, and mechanical distortion is caused by external loads such as high thermal difference, vibration and impact loads. The combination of random error and mechanical distortion results in unexpected and significant degradation of the antenna electromagnetic performance, which has become an obstacle to development of high-performance APAA. After introducing the mechanical distortion errors into the antenna electric field as an additional phase factor, a coupled structural-electromagnetic model of the planar rectangular APAA was developed to describe the coupling relationship between mechanical distortion error and electromagnetic performance. The combined influences of the radiated element numbers, mechanical distortion and element position random error on the antenna electromagnetic performances are analysed, and valuable results for engineering application are discussed. [ABSTRACT FROM PUBLISHER]

The outage probability (OP) performance of transmit antenna selection (TAS) in a decode-and-forward relaying mobile-to-mobile system with relay selection overN-Nakagami fading channels is investigated. Exact closed-form expressions for the OP of two TAS schemes are derived, and the optimal power allocation optimisation problem is formulated. The OP performance is evaluated via Monte Carlo simulation to verify the analysis. The results obtained show that the optimal TAS scheme has better performance than the suboptimal TAS scheme, but the performance gap between these techniques decreases as the number of source antennas increases. [ABSTRACT FROM AUTHOR]

Quality and properties of microwave circuits depend on all the circuit components. One of these components is the substrate. The process of substrate material selection is a decision-making problem that involves multicriteria with objectives that are diverse and conflicting. The aim of this work was to select the most suitable substrate material type to be used in antennas in the microwave frequency range that gives best performance and reliability of the substrate. For this purpose, a model was built to ease the decision-making that includes hierarchical alternatives and criteria. The substrate material type options considered were limited to fiberglass-reinforced epoxy laminates (FR4εr = 4.8), aluminium (III) oxide (aluminaεr = 9.6), gallium arsenide III–V compound (GaAsεr = 12.8) and PTFE composites reinforced with glass microfibers (Duroidεr = 2.2–2.3). To assist in building the model and making decisions, the analytical hierarchy process (AHP) was used. The decision-making process revealed that alumina substrate material type was the most suitable choice for the antennas in the microwave frequency range that yields best performance and reliability. In addition, both the size of the circuit and the loss tangent of the substrates were found to be the most contributing subfactors in the antenna circuit specifications criterion. Experimental assessments were conducted utilising The Expert Choice™ software. The judgments were tested and found to be precise, consistent and justifiable, and the marginal inconsistency values were found to be very narrow. A sensitivity analysis was also presented to demonstrate the confidence in the drawn conclusions. [ABSTRACT FROM AUTHOR]