Recent Submissions

  • Silicon-based 0.450-0.475 THz series-fed double dielectric resonator on-chip antenna array based on metamaterial properties for integrated-circuits

    Alibakhshikenari, M.; Virdee, B.S.; See, C.H.; Abd-Alhameed, Raed A.; Falcone, F.; Limiti, E. (2019-09)
    The antenna array designed to operate over 0.450-0.475 Terahertz comprises two dielectric resonators (DRs) that are stacked vertically on top of each other and placed on the surface of the slot antenna fabricated on a silicon substrate using standard CMOS technology. The slot created in the silicon substrate is meandering and is surrounded by metallic via-wall to prevent energy dissipation. The antenna has a maximum gain of 4.5dBi and radiation efficiency of 45.7% at 0.4625 THz. The combination of slot and vias transform the antenna to a metamaterial structure that provides a relatively small antenna footprint. The proposed series-fed double DRs on-chip antenna array is useful for applications in THz integrated circuits.
  • Study on isolation improvement between closely-packed patch antenna arrays based on fractal metamaterial electromagnetic bandgap structures

    Alibakhshikenari, M.; Virdee, B.S.; See, C.H.; Abd-Alhameed, Raed A.; Ali, Ammar H.; Falcone, F.; Limiti, E. (2018-11)
    A decoupling metamaterial (MTM) configuration based on fractal electromagnetic-bandgap (EMBG) structure is shown to significantly enhance isolation between transmitting and receiving antenna elements in a closely-packed patch antenna array. The MTM-EMBG structure is cross-shaped assembly with fractal-shaped slots etched in each arm of the cross. The fractals are composed of four interconnected-`Y-shaped' slots that are separated with an inverted-`T-shaped' slot. The MTM-EMBG structure is placed between the individual patch antennas in a 2 × 2 antenna array. Measured results show the average inter-element isolation improvement in the frequency band of interest is 17, 37 and 17 dB between radiation elements #1 & #2, #1 & #3, and #1 & #4, respectively. With the proposed method there is no need for using metallic-via-holes. The proposed array covers the frequency range of 8-9.25 GHz for X-band applications, which corresponds to a fractional-bandwidth of 14.5%. With the proposed method the edge-to-edge gap between adjacent antenna elements can be reduced to 0.5λ 0 with no degradation in the antenna array's radiation gain pattern. Across the array's operating band, the measured gain varies between 4 and 7 dBi, and the radiation efficiency varies from 74.22 and 88.71%. The proposed method is applicable in the implementation of closely-packed patch antenna arrays used in SAR and MIMO systems.
  • High-Performance 50μm Silicon-Based On-Chip Antenna with High Port-To-Port Isolation Implemented by Metamaterial and SIW Concepts for THz Integrated Systems

    Alibakhshikenari, M.; Virdee, B.S.; See, C.H.; Abd-Alhameed, Raed A.; Falcone, F.; Limiti, E. (2019-09-16)
    A novel 50μm Silicon-based on-chip antenna is presented that combines metamaterial (MTM) and substrate integrated waveguide (SIW) technologies for integration in THz circuits operating from 0.28 to 0.30 THz. The antenna structure comprises a square patch antenna implemented on a Silicon substrate with a ground-plane. Embedded diagonally in the patch are two T-shaped slots and the edges of the patch is short-circuited to the ground-plane with metal vias, which convert the structure into a substrate integrated waveguide. This structure reduces loss resulting from surface waves and Silicon dielectric substrate. The modes in the structure can be excited through two coaxial ports connected to the patch from the underside of the Silicon substrate. The proposed antenna structure is essentially transformed to exhibit metamaterial properties by realizing two T-shaped slots, which enlarges the effective aperture area of the miniature antenna and significantly enhances its impedance bandwidth and radiation characteristics between 0.28 THz to 0.3 THz. It has an average gain and efficiency of 4.5dBi and 65%, respectively. In addition, it is a self-isolated structure with high isolation of better than 30dB between the two ports. The on-chip antenna has dimensions of 800×800×60 μm3.
  • A comprehensive survey of "metamaterial transmission-line based antennas: design, challenges, and applications"

    Alibakhshikenari, M.; Virdee, B.S.; Azpilicueta, L.; Naser-Moghadasi, M.; Akinsolu, M.O.; See, C.H.; Liu, B.; Abd-Alhameed, Raed A.; Falcone, F.; Huyen, I.; et al. (2020-08)
    In this review paper, a comprehensive study on the concept, theory, and applications of composite right/left-handed transmission lines (CRLH-TLs) by considering their use in antenna system designs have been provided. It is shown that CRLH-TLs with negative permittivity (ε <; 0) and negative permeability (μ <; 0) have unique properties that do not occur naturally. Therefore, they are referred to as artificial structures called “metamaterials”. These artificial structures include series left-handed (LH) capacitances (C L ), shunt LH inductances (L L ), series right-handed (RH) inductances (LR), and shunt RH capacitances (CR) that are realized by slots or interdigital capacitors, stubs or via-holes, unwanted current flowing on the surface, and gap distance between the surface and ground-plane, respectively. In the most cases, it is also shown that structures based on CRLH metamaterial-TLs are superior than their conventional alternatives, since they have smaller dimensions, lower-profile, wider bandwidth, better radiation patterns, higher gain and efficiency, which make them easier and more cost-effective to manufacture and mass produce. Hence, a broad range of metamaterial-based design possibilities are introduced to highlight the improvement of the performance parameters that are rare and not often discussed in available literature. Therefore, this survey provides a wide overview of key early-stage concepts of metematerial-based designs as a thorough reference for specialist antennas and microwave circuits designers. To analyze the critical features of metamaterial theory and concept, several examples are used. Comparisons on the basis of physical size, bandwidth, materials, gain, efficiency, and radiation patterns are made for all the examples that are based on CRLH metamaterialTLs. As revealed in all the metematerial design examples, foot-print area decrement is an important issue of study that have a strong impact for the enlargement of the next generation wireless communication systems.
  • Mutual-coupling isolation using embedded metamaterial EM bandgap decoupling slab for densely packed array antennas

    Alibakhshikenari, M.; Khalily, M.; Virdee, B.S.; See, C.H.; Abd-Alhameed, Raed A.; Limiti, E. (2019-04)
    This article presents a unique technique to enhance isolation between transmit/receive radiating elements in densely packed array antenna by embedding a metamaterial (MTM) electromagnetic bandgap (EMBG) structure in the space between the radiating elements to suppress surface currents that would otherwise contribute towards mutual coupling between the array elements. The proposed MTM-EMBG structure is a cross-shaped microstrip transmission line on which are imprinted two outward facing E-shaped slits. Unlike other MTM structures there is no short-circuit grounding using via-holes. With this approach, the maximum measured mutual coupling achieved is -60 dB @ 9.18 GHz between the transmit patches (#1 & #2) and receive patches (#3 & #4) in a four-element array antenna. Across the antenna’s measured operating frequency range of 9.12 to 9.96 GHz, the minimum measured isolation between each element of the array is 34.2 dB @ 9.48 GHz, and there is no degradation in radiation patterns. The average measured isolation over this frequency range is 47 dB. The results presented confirm the proposed technique is suitable in applications such as synthetic aperture radar (SAR) and multiple-input multiple-output (MIMO) systems.
  • A crack closure system for cementitious composite materials using knotted shape memory polymer (k-SMP) fibres

    Maddalena, R.; Bonanno, L.; Balzano, B.; Tuinea-Bobe, Cristina-Luminita; Sweeney, John; Mihai, I. (2020-09-06)
    Formation of cracks represents one of the major causes of concrete deterioration, which can lead to durability and safety issues. In this work, a novel crack closure system is developed, using polyethylene terephthalate (PET) polymer fibres embedded in a mortar mix. The PET polymer has shape memory properties and shrinks upon thermal activation, if free to do so, or otherwise exerts shrinkage restraint forces. A single knot was manufactured at each end of the PET fibres to provide mechanical anchorage into the mortar matrix. Mortar samples with embedded knotted fibres were pre-cracked and subsequently placed in an oven to thermally activate the polymers and induce the shrinkage mechanism into the fibres. Crack closure was measured in the range 45–100%, depending on the geometry, dimension and distribution of the fibres, and the size of the initial crack.
  • Surface wave reduction in antenna arrays using metasurface inclusion for MIMO and SAR systems

    Alibakhshikenari, M.; Virdee, B.S.; See, C.H.; Abd-Alhameed, Raed A.; Falcone, F.; Limiti, E. (2019-11)
    An effective method is presented for suppressing mutual coupling between adjacent radiating elements which is based on metasurface isolation for MIMO and synthetic aperture radar (SAR) systems. This is achieved by choking surface current waves induced over the patch antenna by inserting a cross-shaped metasurface structure between the radiating elements. Each arm of the cross-shaped structure constituting the metasurface is etched with meander-line slot (MLS). Effectiveness of the metasurface is demonstrated for a2×2antenna array that operates over six frequency sub-bands in X, Ku and K-bands. With the proposed technique, the maximum improvement achieved in attenuating mutual coupling between neighbouring antennas is: 8.5 dB (8-8.4 GHz), 28 dB (9.6-10.8 GHz), 27 dB (11.7-12.6 GHz), 7.5 dB (13.4-14.2 GHz), 13 dB (16.5-16.8 GHz) and 22.5 dB (18.5-20.3 GHz). Furthermore, with the proposed technique (i) minimum center-to-center separation between the radiating elements can be reduced to 0.26λ0, where λ0 is 8.0 GHz; (ii) use of ground-plane or defected ground structures are unnecessary; (iii) use of short-circuited via-holes are avoided; (iv) it eliminates the issue with poor front-to-back ratio; and (v) it can be applied to existing arrays retrospectively.
  • Study on antenna mutual coupling suppression using integrated metasurface isolator for SAR and MIMO applications

    Alibakhshikenari, M.; Virdee, B.S.; See, C.H.; Abd-Alhameed, Raed A.; Falcone, F.; Andujar, A.; Anguera, J.; Limiti, E. (2018-09-27)
    A metasurface based decoupling structure that is composed of a square-wave slot pattern with exaggerated corners that is implemented on a rectangular microstrip provides high-isolation between adjacent patch antennas for Synthetic Aperture Radar (SAR) and Multi-Input-Multi-Output (MIMO) systems. The proposed 1×2 symmetric array antenna integrated with the proposed decoupling isolation structure is designed to operate at ISM bands of X, Ku, K, and Ka. With the proposed mutual coupling suppression technique (i) the average isolation in the respective ISM bands listed above is 7 dB, 10 dB, 5 dB, and 10 dB; and (ii) edge-to-edge gap between adjacent radiation elements is reduced to 10 mm (0.28λ). The average antenna gain improvement with the metasurface isolator is 2 dBi.
  • High performance on-chip array antenna based on metasurface feeding structure for terahertz integrated circuits

    Alibakhshikenari, M.; Virdee, B.S.; See, C.H.; Abd-Alhameed, Raed A.; Limiti, E. (2019-09-01)
    In this letter a novel on-chip array antenna is investigated which is based on CMOS 20μm Silicon technology for operation over 0.6-0.65 THz. The proposed array structure is constructed on three layers composed of Silicon-Ground-Silicon layers. Two antennas are implemented on the top layer, where each antenna is constituted from three sub-antennas. The sub-antennas are constructed from interconnected dual-rings. Also, the sub-antennas are interconnected to each other. This approach enhances the aperture of the array. Surface waves and substrate losses in the structure are suppressed with metallic via-holes implemented between the radiation elements. To excite the structure, a novel feeding mechanism is used comprising open-circuited microstrip lines that couple electromagnetic energy from the bottom layer to the antennas on the top-layer through metasurface slot-lines in the middle ground-plane layer. The results show the proposed on-chip antenna array has an average radiation gain, efficiency, and isolation of 7.62 dBi, 32.67%, and -30 dB, respectively.
  • Overcome the Limitations of Performance Parameters of On-Chip Antennas Based on Metasurface and Coupled Feeding Approaches for Applications in System-on-Chip for THz Integrated-Circuits

    Alibakhshikenari, M.; Virdee, B.S.; See, C.H.; Abd-Alhameed, Raed A.; Falcone, F.; Limiti, E. (2019-12-10)
    This paper proposes a new solution to improve the performance parameters of on-chip antenna designs on standard CMOS silicon (Si.) technology. The proposed method is based on applying the metasurface technique and exciting the radiating elements through coupled feed mechanism. The on-chip antenna is constructed from three layers comprising Si.-GND-Si. layers, so that the ground (GND) plane is sandwiched between two Si. layers. The silicon and ground-plane layers have thicknesses of 20μm and 5μm, respectively. The 3×3 array consisting of the asterisk-shaped radiating elements has implemented on the top silicon layer by applying the metasurface approach. Three slot lines in the ground-plane are modelled and located directly under the radiating elements. The radiating elements are excited through the slot-lines using an open-circuited microstrip-line constructed on the bottom silicon layer. The proposed method to excite the structure is based on the coupled feeding mechanism. In addition, by the proposed feeding method the on-chip antenna configuration suppresses the substrate losses and surface-waves. The antenna exhibits a large impedance bandwidth of 60GHz from 0.5THz to 0.56THz with an average radiation gain and efficiency of 4.58dBi and 25.37%, respectively. The proposed structure has compact dimensions of 200×200×45μm3. The results shows that, the proposed technique is therefore suitable for on-chip antennas for applications in system-on-chip for terahertz (THz) integrated circuits.
  • Automated reconfigurable antenna impedance for optimum power transfer

    Alibakhshikenari, M.; Virdee, B.S.; See, C.H.; Abd-Alhameed, Raed A.; Falcone, F.; Limiti, E. (2019-12)
    This paper presents an approach to implement an automatically tuning antenna for optimising power transfer suitable for software defined radio (SDR). Automatic tuning is accomplished using a closed loop impedance tuning network comprising of an impedance sensor and control unit. The sensor provides the control unit with data on the transmit or receive power, and the algorithm is used to impedance of a T-network of LC components to optimize the antenna impedance to maximise power transmission or reception. The effectiveness of the proposed tuning algorithm in relation to impedance matching and convergence on the optimum matching network goal is shown to be superior compared with the conventional tuning algorithm.
  • An Evaluation of a Linguistically Motivated Conversational Software Agent Framework

    Panesar, Kulvinder (UNIVERSITAT POLITÈCNICA DE VALÈNCIA, 2019-07)
    This paper presents a critical evaluation framework for a linguistically motivated conversational software agent (CSA). The CSA prototype investigates the integration, intersection and interface of the language, knowledge, and speech act constructions (SAC) based on a grammatical object, and the sub-model of belief, desires and intention (BDI) and dialogue management (DM) for natural language processing (NLP). A long-standing issue within NLP CSA systems is refining the accuracy of interpretation to provide realistic dialogue to support human-to-computer communication. This prototype constitutes three phase models: (1) a linguistic model based on a functional linguistic theory – Role and Reference Grammar (RRG), (2) an Agent Cognitive Model with two inner models: (a) a knowledge representation model, (b) a planning model underpinned by BDI concepts, intentionality and rational interaction, and (3) a dialogue model. The evaluation strategy for this Java-based prototype is multi-approach driven by grammatical testing (English language utterances), software engineering and agent practice. A set of evaluation criteria are grouped per phase model, and the testing framework aims to test the interface, intersection and integration of all phase models. The empirical evaluations demonstrate that the CSA is a proof-of-concept, demonstrating RRG’s fitness for purpose for describing, and explaining phenomena, language processing and knowledge, and computational adequacy. Contrastingly, evaluations identify the complexity of lower level computational mappings of NL – agent to ontology with semantic gaps, and further addressed by a lexical bridging solution.
  • Conversational artificial intelligence - demystifying statistical vs linguistic NLP solutions

    Panesar, Kulvinder (Universitat Politécnica de Valéncia, 2020-05)
    This paper aims to demystify the hype and attention on chatbots and its association with conversational artificial intelligence. Both are slowly emerging as a real presence in our lives from the impressive technological developments in machine learning, deep learning and natural language understanding solutions. However, what is under the hood, and how far and to what extent can chatbots/conversational artificial intelligence solutions work – is our question. Natural language is the most easily understood knowledge representation for people, but certainly not the best for computers because of its inherent ambiguous, complex and dynamic nature. We will critique the knowledge representation of heavy statistical chatbot solutions against linguistics alternatives. In order to react intelligently to the user, natural language solutions must critically consider other factors such as context, memory, intelligent understanding, previous experience, and personalized knowledge of the user. We will delve into the spectrum of conversational interfaces and focus on a strong artificial intelligence concept. This is explored via a text based conversational software agents with a deep strategic role to hold a conversation and enable the mechanisms need to plan, and to decide what to do next, and manage the dialogue to achieve a goal. To demonstrate this, a deep linguistically aware and knowledge aware text based conversational agent (LING-CSA) presents a proof-of-concept of a non-statistical conversational AI solution.
  • A Design of Crossed Exponentially Tapered Slot Antenna with Multi-Resonance Function for 3G/4G/5G Applications

    Ojaroudi Parchin, Naser; Basherlou, H.J.; Abd-Alhameed, Raed A. (2020-06-08)
    In this research work, a planar crossed exponentially tapered slot antenna with a multi-resonance function is introduced. The presented antenna design is ascertained on a low-cost Rogers 5870 dielectric with a circular schematic. The antenna is designed to support several frequency spectrums of the current and future wireless communications. The configuration of the design contains a pair of crossed exponentially tapered slots intersected by a star-shaped slot in the back layer and a bowtie-shaped radiation stub with a discrete feeding point extended among the stub parts. The crossed exponential slots exhibit a wide impedance, and the star slot generates an extra resonance at the upper frequencies. For S11 ≤ -6, the antenna provides a wide operation band of 1.7 to 5.9 GHz supporting several frequency bands of 3G, 4G, and 5G communication. The fundamental characteristics of the proposed slot radiator are studied, and good performances have been achieved.
  • Dielectric-Insensitive Phased Array with Improved Characteristics for 5G Mobile Handsets

    Ojaroudi Parchin, Naser; Basherlou, H.J.; Abd-Alhameed, Raed A. (2020-08)
    In this manuscript, a high-performance beam-steerable phased array antenna is introduced for fifth-generation (5G) mobile handsets. The configuration of the design is arranged by employing eight dielectric-insensitive L-ring/slot-loop radiators in a linear form on the top edge of the handset mainboard. The beam-steerable array design exhibits high radiation performances even though it is implemented on a lossy FR-4 material. The proposed design exhibits an impedance bandwidth of 18-20 GHz with the center frequency of 19 GHz. It provides satisfactory characteristics such as wide beam-steering, high gain and efficiency characteristics indicating its promising potential for beam-steerable 5G smartphones. The characteristics of the antenna array are insensitive for different types of dielectrics. Furthermore, the designed antenna array offers quite good radiation behavior in the presence of hand phantom.
  • 60 GHz Multi-Sector Antenna Array with Switchable Radiation-Beams for Small Cell 5G Networks

    Ojaroudi Parchin, Naser; Jahanbakhsh Basherlou, H.; Al-Yasir, Y.; Abd-Alhameed, Raed A.; Excell, Peter S. (2020)
    A compact design of multi-sector patch antenna array for 60 GHz applications is presented and discussed in details. The proposed design combines five 1×8 linear patch antenna arrays, referred to as sectors, in a multi-sector configuration. The coaxial-fed radiation elements of the multi-sector array are designed on 0.2 mm Rogers RT5880 dielectrics. The array operates in the frequency range of 58-62 GHz and provides switchable directional/omnidirectional radiation beams with high gain and high directivity characteristics. The designed multi-sector array exhibits good performances and could be used in the fifth generation (5G) cellular networks.
  • kPWorkbench: A software suit for membrane systems

    Konur, Savas; Mierla, L.; Ipate, F.; Gheorghe, Marian (2020)
    Membrane computing is a new natural computing paradigm inspired by the functioning and structure of biological cells, and has been successfully applied to many different areas, from biology to engineering. In this paper, we present kPWorkbench, a software framework developed to support membrane computing and its applications. kPWorkbench offers unique features, including modelling, simulation, agent-based high performance simulation and verification, which allow modelling and computational analysis of membrane systems. The kPWorkbench formal verification component provides the opportunity to analyse the behaviour of a model and validate that important system requirements are met and certain behaviours are observed. The platform also features a property language based on natural language statements to facilitate property specification.
  • Ultrasonic micromoulding: Process characterisation using extensive in-line monitoring for micro-scaled products

    Gülçür, Mert; Brown, Elaine; Gough, Tim; Romano, J.-M.; Penchev, P.; Dimov, Stefan; Whiteside, Benjamin R. (2020-10)
    Industry-standard quality management systems such as Six Sigma and emerging Industry 4.0 compliant production processes demonstrate the importance of in-line condition monitoring of manufacturing methods for achieving the highest levels of product quality. Measurement data collected as the process is running can inform the operator about unexpected changes in machine operation or raw materials that could negatively impact production; and offer an opportunity for a process control intervention to stabilise production. However, micro-manufacturing production lines can pose a challenging environment for deploying such systems, since processing events can occur extremely rapidly and in harsh environments. Moreover, the small scale of micro-nano featured components can make sensor installation even more problematic. Recently, ultrasonic micromoulding has drawn attention in niche markets due to its unique advantages for processing thermoplastics as a new micro-manufacturing technology. The process differs from conventional moulding significantly by eliminating the need for a plasticising screw and using direct application of ultrasonic energy to melt the polymer. This offers numerous benefits such as decrease in energy usage, moulding at lower pressures, easier cleaning, and reduced material residence times, the latter which could be beneficial for pharma-grade polymers or polymers with active ingredients. However, very little work has been reported attempting to monitor the process using in-line measurements. This work aims to evaluate the characteristics of the ultrasonic micromoulding process for microinjection moulding of a microneedle array using a range of sensor technologies including: data recorded by the machine controller; a high-speed thermal camera and a cavity pressure transducer. The data has captured the highly dynamic process environment with a high degree of accuracy. The relationship between the process data and dimensional quality of the ultrasonically micromoulded products has been quantified and subsequently implemented as a cost-effective in-line quality assurance method.
  • Faster visual reaction times in elite athletes are not linked to better gaze stability

    Barrett, Brendan T.; Cruickshank, A.G.; Flavell, J.C.; Bennett, S.J.; Buckley, John G.; Harris, J.M.; Scally, Andy J. (2020-08)
    The issue of whether visually-mediated, simple reaction time (VRT) is faster in elite athletes is contentious. Here, we examined if and how VRT is afected by gaze stability in groups of international cricketers (16 females, 28 males), professional rugby-league players (21 males), and non-sporting controls (20 females, 30 males). VRT was recorded via a button-press response to the sudden appearance of a stimulus (circular target—diameter 0.8°), that was presented centrally, or 7.5° to the left or right of fxation. The incidence and timing of saccades and blinks occurring from 450 ms before stimulus onset to 225 ms after onset were measured to quantify gaze stability. Our results show that (1) cricketers have faster VRT than controls; (2) blinks and, in particular, saccades are associated with slower VRT regardless of the level of sporting ability; (3) elite female cricketers had steadier gaze (fewer saccades and blinks) compared to female controls; (4) when we accounted for the presence of blinks and saccades, our group comparisons of VRT were virtually unchanged. The stability of gaze is not a factor that explains the difference between elite and control groups in VRT. Thus we conclude that better gaze stability cannot explain faster VRT in elite sports players.
  • Effects of mould wear on hydrophobic polymer surfaces replicated using plasma treated and laser-textured stainless steel inserts

    Dimov, Stefan; Romano, J.-M.; Sarasa, J.F.; Concheso, C.; Gülçür, Mert; Dashtbozorg, B.; Garcia-Giron, A.; Penchev, P.; Dong, H.; Whiteside, Benjamin R. (2020)
    The mass production of polymeric parts with functional surfaces requires economically viable manufacturing routes. Injection moulding is a very attractive option however wear and surface damage can be detrimental to the lifespan of replication masters. In this research, the replication of superhydrophobic surfaces is investigated by employing a process chain that integrates surface hardening, laser texturing and injection moulding. Austenitic stainless steel inserts were hardened by low temperature plasma carburising and three different micro and nano scale surface textures were laser fabricated, i.e. submicron triangular LaserInduced Periodic Surface Structures (LIPSS), micro grooves and Lotus-leaf like topographies. Then, a commonly available talc-loaded polypropylene was used to produce 5000 replicas to investigate the evolution of surface textures on both inserts and replicas together with their functional response. Any wear orsurface damage progressively built up on the inserts during the injection moulding process had a clear impact on surface roughness and peak-to-peak topographies of the replicas. In general, the polymer replicas produced with the carburised inserts retained the wetting properties of their textured surfaces for longer periods compared with those produced with untreated replication masters.

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