Open Access
Virtual antenna array for reduced energy per bit transmission at Sub-5 GHz mobile wireless communication systems
(Elsevier, 2023) Alibakhshikenari, Mohammad; Virdee, Bal S.; Mariyanayagam, Dion; García Zuazola, Ignacio Julio; Benetatos, Harry; Althuwayb, Ayman Abdulhadi; Alali, Bader; Xu, Kai-Da; Falcone Lanas, Francisco; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
This paper presents an innovative technique to synthesize a virtual antenna array (VAA) that consumes less energy than conventional antenna arrays that are used in mobile communications systems. We have shown that for a specific spectral efficiency a wireless system using the proposed virtual antenna array consumes significantly less energy per bit (∼3 dB) than a wireless system using a conventional multiple-input multiple-output (MIMO) array. This means the adoption of the proposed VAA technology in smartphones, iPad, Tablets and even base-stations should significantly reduce the carbon footprint of wireless systems. The proposed VAA is realized by employing a pair of linear antenna arrays that are placed in an orthogonal configuration relative to each other. This orthogonal arrangement ensures the radiation is circularly polarized. The size of the standard radiating elements constituting the VAA were miniaturized using the topology optimization method. The design of the VAA incorporates substrate integrated waveguide (SIW) and metasurface technologies. The function of SIW in the design was twofold, namely, to reduce energy loss in the substrate on which the VAA is implemented, and secondly to mitigate unwanted electromagnetic interactions between the neighboring radiating elements and thereby enhancing isolation which otherwise would degrade the radiation characteristics of the array. Metasurface technology served to effectively increase the effective aperture of the array with no impact on the footprint of the array. The consequence of SIW and metasurface technologies was improvement in the gain and radiation efficiency of the array. The proposed four orthogonal 4-element VAA covers the entire sub-5 GHz frequency range, and it radiates bidirectional in the azimuth plane and omni-directional in the elevation plane. Moreover, it is relatively easy to design and fabricate. The proposed VAA has dimensions of 0.96λ0 × 0.96λ0 × 0.0016λ0 at mid-band frequency of 3 GHz. VAA has a measured gain of 25 dBi and radiates with 90% efficiency. The average isolation between the linear arrays constituting the virtual array is better than 27 dB.
Open Access
High-isolation antenna array using SIW and realized with a graphene layer for sub-terahertz wireless applications
(Nature Research, 2021) Alibakhshikenari, Mohammad; Virdee, Bal S.; Salekzamankhani, Shahram; Aïssa, Sonia; See, Chan H.; Soin, Navneet; Fishlock, Sam J.; Althuwayb, Ayman Abdulhadi; Abd-Alhameed, Raed; Huynen, Isabelle; McLaughlin, James A.; Falcone Lanas, Francisco; Limiti, Ernesto; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
This paper presents the results of a study on developing an effective technique to increase the performance characteristics of antenna arrays for sub-THz integrated circuit applications. This is essential to compensate the limited power available from sub-THz sources. Although conventional array structures can provide a solution to enhance the radiation-gain performance however in the case of small-sized array structures the radiation properties can be adversely affected by mutual coupling that exists between the radiating elements. It is demonstrated here the effectiveness of using SIW technology to suppress surface wave propagations and near field mutual coupling effects. Prototype of 2x3 antenna arrays were designed and constructed on a polyimide dielectric substrate with thickness of 125 mu m for operation across 0.19-0.20 THz. The dimensions of the array were 20x13.5x0.125 mm(3). Metallization of the antenna was coated with 500 nm layer of Graphene. With the proposed technique the isolation between the radiating elements was improved on average by 22.5 dB compared to a reference array antenna with no SIW isolation. The performance of the array was enhanced by transforming the patch to exhibit metamaterial characteristics. This was achieved by embedding the patch antennas in the array with sub-wavelength slots. Compared to the reference array the metamaterial inspired structure exhibits improvement in isolation, radiation gain and efficiency on average by 28 dB, 6.3 dBi, and 34%, respectively. These results show the viability of proposed approach in developing antenna arrays for application in sub-THz integrated circuits.
Open Access
Review on unmanned aerial vehicle assisted sensor node localization in wireless networks: soft computing approaches
(IEEE, 2022) Annepu, Visalakshi; Sona, Deepika Rani; Ravikumar, Chinthaginjala V.; Bagadi, Kalapraveen; Alibakhshikenari, Mohammad; Althuwayb, Ayman Abdulhadi; Alali, Bader; Virdee, Bal S.; Pau, Giovanni; Dayoub, Iyad; See, Chan H.; Falcone Lanas, Francisco; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
Node positioning or localization is a critical requisite for numerous position-based applications of wireless sensor network (WSN). Localization using the unmanned aerial vehicle (UAV) is preferred over localization using fixed terrestrial anchor node (FTAN) because of low implementation complexity and high accuracy. The conventional multilateration technique estimates the position of the unknown node (UN) based on the distance from the anchor node (AN) to UN that is obtained from the received signal strength (RSS) measurement. However, distortions in the propagation medium may yield incorrect distance measurement and as a result, the accuracy of RSS-multilateration is limited. Though the optimization based localization schemes are considered to be a better alternative, the performance of these schemes is not satisfactory if the distortions are non-linear. In such situations, the neural network (NN) architecture such as extreme learning machine (ELM) can be a better choice as it is a highly non-linear classifier. The ELM is even superior over its counterpart NN classifiers like multilayer perceptron (MLP) and radial basis function (RBF) due to its fast and strong learning ability. Thus, this paper provides a comparative review of various soft computing based localization techniques using both FTAN and aerial ANs for better acceptability.
Open Access
Optimum power transfer in RF front end systems using adaptive impedance matching technique
(Nature Research, 2021) Alibakhshikenari, Mohammad; Virdee, Bal S.; Azpilicueta Fernández de las Heras, Leyre; See, Chan H.; Abd-Alhameed, Raed; Althuwayb, Ayman Abdulhadi; Falcone Lanas, Francisco; Huynen, Isabelle; Denidni, Tayeb A.; Limiti, Ernesto; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
Matching the antenna’s impedance to the RF-front-end of a wireless communications system is challenging as the impedance varies with its surround environment. Autonomously matching the antenna to the RF-front-end is therefore essential to optimize power transfer and thereby maintain the antenna’s radiation efficiency. This paper presents a theoretical technique for automatically tuning an LC impedance matching network that compensates antenna mismatch presented to the RF-front-end. The proposed technique converges to a matching point without the need of complex mathematical modelling of the system comprising of non-linear control elements. Digital circuitry is used to implement the required matching circuit. Reliable convergence is achieved within the tuning range of the LC-network using control-loops that can independently control the LC impedance. An algorithm based on the proposed technique was used to verify its effectiveness with various antenna loads. Mismatch error of the technique is less than 0.2%. The technique enables speedy convergence (< 5 µs) and is highly accurate for autonomous adaptive antenna matching networks.
Open Access
Metamaterial inspired electromagnetic bandgap filter for ultra-wide stopband screening devices of electromagnetic interference
(Springer, 2023) Al-Hasan, Muath; Alibakhshikenari, Mohammad; Virdee, Bal S.; Sharma, Richa; Iqbal, Amjad; Althuwayb, Ayman Abdulhadi; Falcone Lanas, Francisco; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
Presented here is a reactively loaded microstrip transmission line that exhibit an ultra-wide bandgap. The reactive loading is periodically distributed along the transmission line, which is electromagnetically coupled. The reactive load consists of a circular shaped patch which is converted to a metamaterial structure by embedded on it two concentric slit-rings. The patch is connected to the ground plane with a via-hole. The resulting structure exhibits electromagnetic bandgap (EBG) properties. The size and gap between the slit-rings dictate the magnitude of the reactive loading. The structure was frst theoretically modelled to gain insight of the characterizing parameters. The equivalent circuit was verifed using a full-wave 3D electromagnetic (EM) solver. The measured results show the proposed EBG structure has a highly sharp 3-dB skirt and a very wide bandgap, which is substantially larger than any EBG structure reported to date. The bandgap rejection of the single EBG unit-cell is better than − 30 dB, and the fve element EBG unit-cell is better than − 90 dB. The innovation can be used in various applications such as biomedical applications that are requiring sharp roll-of rates and high stopband rejection thus enabling efcient use of the EM spectrum. This can reduce guard band and thereby increase the channel capacity of wireless systems.
Open Access
Study on on-chip antenna design based on metamaterial-inspired and substrate-integrated waveguide properties for millimetre-wave and THz integrated-circuit applications
(Springer, 2021) Alibakhshikenari, Mohammad; Virdee, Bal S.; Althuwayb, Ayman Abdulhadi; Aïssa, Sonia; See, Chan H.; Abd-Alhameed, Raed; Falcone Lanas, Francisco; Limiti, Ernesto; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
This paper presents the results of a study on improving the performance parameters such as the impedance bandwidth, radiation gain and efficiency, as well as suppressing substrate loss of an innovative antenna for on-chip implementation for millimetre-wave and terahertz integrated-circuits. This was achieved by using the metamaterial and the substrate-integrated waveguide (SIW) technologies. The on-chip antenna structure comprises five alternating layers of metallization and silicon. An array of circular radiation patches with metamaterial-inspired crossed-shaped slots are etched on the top metallization layer below which is a silicon layer whose bottom surface is metalized to create a ground plane. Implemented in the silicon layer below is a cavity above which is no ground plane. Underneath this silicon layer is where an open-ended microstrip feedline is located which is used to excite the antenna. The feed mechanism is based on the coupling of the electromagnetic energy from the bottom silicon layer to the top circular patches through the cavity. To suppress surface waves and reduce substrate loss, the SIW concept is applied at the top silicon layer by implementing the metallic via holes at the periphery of the structure that connect the top layer to the ground plane. The proposed on-chip antenna has an average measured radiation gain and efficiency of 6.9 dBi and 53%, respectively, over its operational frequency range from 0.285–0.325 THz. The proposed on-chip antenna has dimensions of 1.35 × 1 × 0.06 mm3. The antenna is shown to be viable for applications in millimetre-waves and terahertz integrated-circuits. © 2020, The Author(s).
Open Access
Antenna on chip (AoC) design using metasurface and SIW technologies for THz wireless applications
(MDPI, 2021) Althuwayb, Ayman Abdulhadi; Alibakhshikenari, Mohammad; Virdee, Bal S.; Benetatos, Harry; Falcone Lanas, Francisco; Limiti, Ernesto; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
This paper presents the design of a high-performance 0.45-0.50 THz antenna on chip (AoC) for fabrication on a 100-micron GaAs substrate. The antenna is based on metasurface and substrate-integrated waveguide (SIW) technologies. It is constituted from seven stacked layers consisting of copper patch-silicon oxide-feedline-silicon oxide-aluminium-GaAs-copper ground. The top layer consists of a 2 x 4 array of rectangular metallic patches with a row of subwavelength circular slots to transform the array into a metasurface. This essentially enlarges the effective aperture area of the antenna. The antenna is excited using a coplanar waveguide feedline that is sandwiched between the two silicon oxide layers below the patch layer. The proposed antenna structure reduces substrate loss and surface waves. The AoC has dimensions of 0.8 x 0.8 x 0.13 mm(3). The results show that the proposed structure greatly enhances the antenna's gain and radiation efficiency, and this is achieved without compromising its physical size. The antenna exhibits an average gain and efficiency of 6.5 dBi and 65%, respectively, which makes it a promising candidate for emerging terahertz applications.
Open Access
Novel concentric hexagonal-shaped RFID tag antenna with T-shaped stub matching
(IEEE, 2021) Alibakhshikenari, Mohammad; Virdee, Bal S.; Althuwayb, Ayman Abdulhadi; Xu, Kai-Da; See, Chan H.; Khan, Salahuddin; Park, Ikmo; Falcone Lanas, Francisco; Limiti, Ernesto; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
This paper presents a unique concentric hexagonal-shaped ring antenna for radio frequency identification (RFID) tags. The rings are excited with a common microstrip feedline. The radiation characteristics of the antenna is improved by locating a horizontal a parasitic element in the vicinity of the hexagonal-shaped rings. The proposed antenna was used in the implementation of a 3×1 antenna array. The impedance match of the 3×1 RFID tag was enhanced by incorporating a T-shaped stub. The antenna is designed to operate at the UHF band from 800 MHz to 960 MHz. It was implemented on FR-4 substrate with dielectric constant and thickness of 4.3 and 1.6 mm, respectively. The size of the RFID tag antenna is 36×10 mm2. Its impedance was matched to Alien Higgs RFIC chip of impedance 10 – j 82.5 Ω at 895 MHz. Measured results show the proposed RFID tag antenna provides an impedance bandwidth, maximum gain and radiation efficiency of 160 MHz, 2 dBi, and 66.5%, respectively. With effective isotropic radiated power (EIRP) limited to 36 dBm to comply with FCC regulations for UHF band RFIDs it radiates in the broadside direction over a range of 9 m making it desirable for various applications including supply chain management, logistic control, and vehicle identification.
Open Access
A comprehensive survey on 'circular polarized antennas' for existing and emerging wireless communication technologies
(IOP Publishing, 2022) Nadeem, Iram; Alibakhshikenari, Mohammad; Babaeian, Fatemeh; Althuwayb, Ayman Abdulhadi; Virdee, Bal S.; Azpilicueta Fernández de las Heras, Leyre; Khan, Salahuddin; Huynen, Isabelle; Falcone Lanas, Francisco; Denidni, Tayeb A.; Limiti, Ernesto; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
Circular polarized (CP) antennas are well suited for long-distance transmission attainment. In order to be adaptable for beyond 5G communication, a detailed and systematic investigation of their important conventional features is required for expected enhancements. The existing designs employing millimeter wave, microwave, and ultra-wideband (UWB) frequencies form the elementary platform for future studies. The 3.4-3.8 GHz frequency band has been identified as a worthy candidate for 5G communications because of spectrum availability. This band comes under UWB frequencies (3.1-10.6 GHz). In this survey, a review of CP antennas in the selected areas to improve the understanding of early-stage researchers specially experienced antenna designers has presented for the first time as best of our knowledge. Design implementations involving size, axial ratio, efficiency, and gain improvements are covered in detail. Besides that, various design approaches to realize CP antennas including (a) printed CP antennas based on parasitic or slotted elements, (b) dielectric resonator CP antennas, (c) reconfigurable CP antennas, (d) substrate integrated waveguide CP antennas, (e) fractal CP antennas, (f) hybrid techniques CP antennas, and (g) 3D printing CP antennas with single and multiple feeding structures have investigated and analyzed. The aim of this work is to provide necessary guidance for the selection of CP antenna geometries in terms of the required dimensions, available bandwidth, gain, and useful materials for the integration and realization in future communication systems.
Open Access
Metasurface-inspired flexible wearable MIMO antenna array for wireless body area network applications and biomedical telemetry devices
(IEEE, 2023) Althuwayb, Ayman Abdulhadi; Alibakhshikenari, Mohammad; Virdee, Bal S.; Rashid, Nasr; Kaaniche, Khaled; Atitallah, Ahmed Ben; Armghan, Ammar; Elhamrawy, Osama I.; See, Chan H.; Falcone Lanas, Francisco; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
This article presents a sub-6GHz ISM-band flexible wearable MIMO antenna array for wireless body area networks (WBANs) and biomedical telemetry devices. The array is based on metasurface inspired technology. The antenna array consists of 2× 2 matrix of triangular-shaped radiation elements that were realized on 0.8 mm thick Rogers RT/duroid 5880 substrate. Radiation characteristics of the array are enhanced by isolating the surface current interaction between the individual radiators in the array. This is achieved by inserting an electromagnetic bandgap (EBG) decoupling structure between the radiating elements. The radiating elements were transformed into a metasurface by etching sub-wavelength slots inside them. The periodic arrangement of slots acts like resonant scatterers that manipulate the electromagnetic response of the surface. Results confirm that by employing the decoupling structure and sub-wavelength slots the isolation between the radiators is significantly improved (>34.8 dB). Moreover, there is an improvement in the array's fractional bandwidth, gain and the radiation efficiency. The optimized array design for operation over 5.0-6.6 GHz has an average gain and efficiency of 10 dBi and 83%, respectively. Results show that the array's performance is not greatly affected by a certain amount of bending. In fact, the antenna maintains a gain between 8.65-10.5 dBi and the efficiency between 77-83%. The proposed MIMO antenna array is relatively compact, can be easily fabricated on one side of a dielectric material, allows easy integration with RF circuitry, is robust, and maintains its characteristics with some bending. These features make it suitable for various wearable applications and biomedical telemetry devices.