Bilal Khawaja - Academia.edu (original) (raw)

Papers by Bilal Khawaja

2021 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting (APS/URSI), Dec 4, 2021

This paper investigates dual-band Metamaterial (MTM) Sierpinski carpet antenna (SCA) with and wit... more This paper investigates dual-band Metamaterial (MTM) Sierpinski carpet antenna (SCA) with and without MTM superstrate for 5G applications. The proposed antenna design is based on the second iteration of SCA, and the cross-slot MTM unit-cell is incorporated in the slots of the SCA. The MTM-SCA has been designed on a Rogers TMM4 substrate boldsymbol(varepsilonr=4.5,h=\boldsymbol{(\varepsilon_{r}=4.5, h=}boldsymbol(varepsilonr=4.5,h= 1.524mm), and the simulation was done using CST Microwave studio. The simulation results indicate that the proposed antenna operates at 3.5GHz and 5.6GHz with a gain of 4.2dB and 3.6dB, respectively. The overall dimension of the SCA is boldsymbol25times30textmm2\boldsymbol{25\times 30\text{mm}^{2}}boldsymbol25times30textmm2, which refers to a size reduction of 45% compared to the conventional microstrip patch antenna (MPA). A boldsymbol5times4\boldsymbol{5\times 4}boldsymbol5times4 cross-slot MTM superstrate was loaded above the MTM-SCA with different spacing to identify and study the gain variation. The MTM superstrate has been kept 3.9mm above the MTM-SCA, which gives an improved gain characteristic of 4.67 dB and 7.4dB at 3.5GHz and 5.6GHz, respectively. The proposed MTM- SCA with and without MTM superstrate shows dual-band characteristics, an excellent size reduction, high-gain and efficiency, and leads to an easy fabrication process, which makes them an excellent candidate for 5G applications.

IEEE Antennas and Wireless Propagation Letters, Nov 1, 2021

A low-profile, compact, four-element, eight-port multiple-input--multiple-output and diversity an... more A low-profile, compact, four-element, eight-port multiple-input--multiple-output and diversity antenna for 5G Internet of Things and cellular handheld applications is presented in this letter. This antenna structure contains four antenna elements, which are same in its configuration. The antenna ground dimensions are taken similar to a modern mobile handset, i.e., 60 mm × 120 mm. The four antenna elements are situated at four corners of antenna ground structure. Each antenna element has two feeding ports, thus making a total of eight-port antenna. A single antenna element has two feeding plates, which are placed perpendicular to one another so that they become cross polarized, thus exploiting polarization diversity, whereas spatial diversity also exists between different antenna elements. For reducing mutual coupling between different antenna ports, slots are cut in ground plane, including a small strip etched along the entire length of ground plane and rectangular slots cut in ground plane under every antenna element. The minimum bandwidth attained by all eight ports for S11 < –10 dB is more than 1.4 GHz from 2.4 GHz to more than 3.8 GHz, which testify that it covers majority of frequency bands allocated for 5G sub-6 GHz spectrum. The isolation obtained between different ports has a minimum value of –13 dB, and the maximum value goes below –30 dB. For the covered frequency bands by this antenna structure, the correlation coefficient is found to be below 0.03, whereas the measured peak gain is in the range of 3.2--5 dB.

Fractal and fractional, Feb 5, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

International journal of electrical and computer engineering systems, Jul 12, 2023

A compact and low-cost eight-port (2x4 configuration) tapered-edged antenna array (TEAA) with sym... more A compact and low-cost eight-port (2x4 configuration) tapered-edged antenna array (TEAA) with symmetrical slots and reduced mutual-coupling is presented in this paper using the inset-feed technique. The 8-port TEAA is designed and simulated using CST microwave studio, fabricated using the flame-resistant (FR4) substrate having a dielectric constant (ε r) = 4.3 and thickness (h) = 1.66mm and characterized using Keysight technologies vector network analyzer (VNA). The designed 8-port TEAA operates at the 5.05-5.2GHz frequency band. Various performance design parameters, like return-loss, bandwidth, gain, 2D/3D radiation patterns, surface current distributions, and isolation-loss, are briefly studied, and the results are summarized. The eight-port TEAA has featured the bandwidth/ gain characteristic of 195MHz/10.25dB, 3dB beam-width of 52.8 o , and excellent mutual-coupling (high isolation-loss) of less than-20dB, respectively. The 8-port TEAA is proposed and characterized to work for next-generation high-throughput WLANs like IEEE 802.11ax (WiFi-6E), Internet-of-Things (IoT), and the upcoming 5G wireless communication systems.

2022 International Symposium on Antennas and Propagation (ISAP), Oct 31, 2022

IEEE Access, 2018

A novel coplanar waveguide-fed rectenna with high efficiency is proposed and implemented in this ... more A novel coplanar waveguide-fed rectenna with high efficiency is proposed and implemented in this paper for 2.45-GHz Bluetooth/ wireless local area network applications. The antenna has compact dimensions of 18 mm × 30 mm, which is simulated and manufactured using a low-cost FR4 substrate with a thickness of 1.6 mm. A tuning stub technique with rectangular slots is used for better impedance matching and enhancing the impedance bandwidth of the antenna with a peak gain of 5.6 dB. The proposed novel antenna for RF energy harvesting applications exhibits dipolelike radiation pattern in H-plane and omnidirectional pattern in E-plane with improved radiation efficiency. Single-stage Cockcroft-Walton rectifier with L-shaped impedance-matching network is designed in advance design system and fabricated on FR4 substrate. The dc output of the rectenna is measured as 3.24 V with a load resistance of 5 k. A simulated peak conversion efficiency of 75.5% is attained, whereas the measured one is observed to be 68% with an input signal power of 5 dBm at 2.45 GHz. INDEX TERMS Rectennas, printed antennas, Wi-Fi, WLAN, ultrawideband, wireless energy harvesting.

International Journal of Electrical Engineering Education, Sep 17, 2020

In this paper, we present a detailed action plan under continuous quality improvement (CQI) exerc... more In this paper, we present a detailed action plan under continuous quality improvement (CQI) exercise of outcomes based education framework related to Mathematics concerns highlighted by the Electrical Engineering (EE) Department. Failing and low performed student learning outcomes (SOs) and course learning outcomes (COs) in range of core EE courses were observed to be linked with weak Mathematics basis of students. This feedback was achieved through an automated CQI system in EvalTools under Faculty Class Assessment Report (FCAR) tab, where each instructor is required to make reflections about failing as well as low performed SOs and COs. Feedback was reviewed comprehensively, and mathematical concepts which significantly affect the performance of students in the core EE courses were derived. Moreover, a high level of Mathematics prerequisite covering required mathematical concepts is identified for the range of core EE courses. Consequently, well-defined tasks were assigned to continuously evaluate and monitor improvement in required Mathematics concepts to ensure SOs and COs achieved in core EE courses. Results are given to exhibit the effectiveness of continuous improvement management system (CIMS).

Micromachines, Jan 27, 2022

This paper focuses on the design of flexible and wearable antennas using textile substrates for w... more This paper focuses on the design of flexible and wearable antennas using textile substrates for wireless/satellite based communication and control systems supporting Internet of Things (IoT). The same are based on on-body communication in Wireless body area network (WBANs). The antennas are designed using two different textile substrates i.e. Jeans and Polyester with εr of 1.7 and 2.8 respectively. The substrates are selected for the ease of wearability and the compact size of the designed antennas. The antennas are designed to operate in the C-Band (4-8 GHz) which is popular for satellite communications. The reason that a higher frequency band is selected is to overcome the congestion issues in the lower satellite frequency bands. Various simulation parameters like bandwidth, reflection coefficient (S11), 2D and 3D radiation patterns, directivity, gain and efficiency of both the antennas are compared and analysed. The maximum achieved gain, bandwidth and efficiency are 3.8dBi, 9.8GHz and 88.4 % for jeans substrate antenna and 3.1dBi, 6.7GHz and 77.5% for polyester substrate antenna respectively. The antennas are designed using Agilent Advance Design System simulator.

Micromachines, Dec 12, 2022

IEEE Access, 2020

The performance of conventional repetitive controller (RC) deteriorates under frequency variation... more The performance of conventional repetitive controller (RC) deteriorates under frequency variations and system uncertainties. Due to limited bandwidth, it is also a trivial task to stabilize the conventional RC. This paper proposes a higher-order repetitive controller (HORC) with linear phase lead as a stabilizing compensator and zero-phase tracking error (ZPTE) compensator. The periodic signal generator, used by the HORC, offers relatively high gains in the neighborhood of tuned frequency and its harmonics. Stability conditions for higher-order repetitive (HOR) control system, including the phase lead compensator, are presented. The proposed solution is applied to repetitive current control of a two-level gridconnected inverter. Simulation and experimental results show that the HORC designed using the phase lead compensation is robust to frequency variation in reference/disturbance and system uncertainties. INDEX TERMS Repetitive controller, frequency variation, higher-order repetitive controller, phase lead.

Modelling and Simulation in Engineering, Dec 14, 2021

The Arabian Peninsula is an arid zone with a hot desert climate and severe water scarcity. The lo... more The Arabian Peninsula is an arid zone with a hot desert climate and severe water scarcity. The low humidity, elevated ambient temperatures, and high evaporation rates in the region deemed conventional surface irrigation unsustainable. The IoT-based subsurface smart irrigation systems can be essentially developed for these regions to avoid surface evaporation losses. In this research, the sandy soil conditions of western Saudi Arabia have been considered in numerical simulations to evaluate the performance of a subsurface smart irrigation system. The influence zone of saturation generated by subsurface diffusers in the target root region has been analysed for two different types of sandy soils. The simulation results generated by the COMSOL Multiphysics program reveal that the subsurface smart irrigation system can be effectively applied to simultaneously manage the target root zone at the ideal saturated conditions and prevent surface evaporation losses.

This paper explores two metamaterial fractal antenna (MFA), in which one has complete ground plan... more This paper explores two metamaterial fractal antenna (MFA), in which one has complete ground plane and other uses defective ground structure (DGS) with square split ring resonator (SSR) are designed for 5G applications. The radiating layer of both antennas based on first iteration of minkowski fractal structure with complimentary split ring resonator (CSSR). The proposed antennas are simulated using CST microwave studio. The MFA with complete ground plane/DGS is operating between 3.48GHz-3.52GHz and 3.3GHz-3.7GHz, respectively. Both antennas show an excellent gain of 5.1dB and 4.5dB, respectively. The results show that MFA with DGS structure has an excellent bandwidth improvement with good gain, which can be an ideal candidate for 5G application.

The existing and emerging next generation of wireless communication standards assume that the end... more The existing and emerging next generation of wireless communication standards assume that the end-users use omni-directional antennas, radiating in all directions. This has been a barrier to network capacity and efficiency. Multiple input multiple output (MIMO) is considered as a key smart-antenna technology, to improve the capacity of a communication channel at a greater extent as compared to single input single output (SISO) and single input multiple output (SIMO) techniques. MIMO is a technology which uses multiple antennas both at transmitter and receiver ends to increase the overall data transmission rate and provide higher spectral efficiency. The MIMO antennas have been an area of extensive research all over the world during recent years because of their ability to increase the system capacity without increasing the channel bandwidth. The LTE based mobile devices recommend the use of small-scale and multi-band MIMO antennas. The primary aim of this book is to design, simulate and characterize a dual-band antenna array for LTE and MIMO applications. The antennas cover two 4G LTE frequency bands of 2.1GHz (LTE Band-1) and 3.5GHz (LTE Band-22).

IEEE Access, 2023

Diversity measures exploited by blind source separation (BSS) methods are usually based on either... more Diversity measures exploited by blind source separation (BSS) methods are usually based on either statistical attributes/geometrical structures or sparse/overcomplete (underdetermined) representations of the signals. This leads to some inefficient BSS methods that are derived from either a mixing matrix (mm), sparse weight vectors (sw), or sparse code (sc). In contrast, the proposed efficient method, sparse spatiotemporal BSS (ssBSS), avoids computational complications associated with lag sets, deflation strategy, and repeated error matrix computation using the whole dataset. It solves the spatiotemporal data reconstruction model (STEM) with l 1-norm penalization and l 0-norm constraints using Neumann's alternating projection lemma and block coordinate descent approach to yield the desired bases. Its specific solution allows incorporating a three-step autoencoder and univariate soft thresholding for a block update of the source/mixing matrices. Due to the utilization of both spatial and temporal information, it can better distinguish between the sources and yield interpretable results. These steps also make ssBSS unique because, to the best of my knowledge, no mixing matrix based BSS method incorporates sparsity of both features and a multilayer network structure. The proposed method is validated using synthetic and various functional magnetic resonance imaging (fMRI) datasets. Results reveal the superior performance of the proposed ssBSS method compared to the existing methods based on mmBSS and swBSS. Specifically, overall, a 14% increase in the mean correlation value and 91% reduction in computation time over the ssICA algorithm was discovered.

Fractal and Fractional

A compact triple-band operation ultra-wideband (UWB) antenna with dual-notch band characteristics... more A compact triple-band operation ultra-wideband (UWB) antenna with dual-notch band characteristics is presented in this paper. By inserting three metamaterial (MTM) square split-ring resonators (MTM-SSRRs) and a triangular slot on the radiating patch, the antenna develops measured dual-band rejection at 4.17–5.33 GHz and 6.5–8.9 GHz in the UWB frequency range (3–12 GHz). The proposed antenna offers three frequency bands of operation in the UWB range, which are between 3–4.17 GHz (~1.2 GHz bandwidth), 5.33–6.5 GHz (~1.17 GHz bandwidth), and 8.9–12 GHz (~3.1 GHz bandwidth), respectively. The higher resonating frequency band can be tuned/controlled by varying the width of the triangle slot, while the medium operational band can be controlled by adjusting the width of the SSRR slot. Initially, the simulated S-parameter response, 2D and 3D radiation patterns, gain, and surface current distribution of the proposed UWB inverted triangular antenna has been studied using epoxy glass FR4 subst...

IEEE Access, 2022

Smart agriculture techniques have recently seen widespread interest by farmers. This is driven by... more Smart agriculture techniques have recently seen widespread interest by farmers. This is driven by several factors, which include the widespread availability of economically-priced, low-powered Internet of Things (IoT) based wireless sensors to remotely monitor and report conditions of the field, climate, and crops. This enables efficient management of resources like minimizing water requirements for irrigation and minimizing the use of toxic pesticides. Furthermore, the recent boom in Artificial Intelligence can enable farmers to deploy autonomous farming machinery and make better predictions of the future based on present and past conditions to minimize crop diseases and pest infestation. Together these two enabling technologies have revolutionized conventional agriculture practices. This survey paper provides: (a) A detailed tutorial on the available advancements in the field of smart agriculture systems through IoT technologies and AI techniques; (b) A critical review of these two available technologies and challenges in their widespread deployment; and (c) An in-depth discussion about the future trends including both technological and social, when smart agriculture systems will be widely adopted by the farmers globally. INDEX TERMS Smart agriculture, Internet of Things (IoT), smart irrigation, organic farming, artificial intelligence (AI), big data.

2019 8th International Conference on Information and Communication Technologies (ICICT), 2019

Nobody can deny the importance of technology in every sphere of life. The latest trends in techno... more Nobody can deny the importance of technology in every sphere of life. The latest trends in technology ensure better surveillance which could not be possible ever before. Drones with attached cameras also known as Unmanned Aerial Vehicles (UAVs) are one of the example used in surveillance operations. These camera mounted spies have the ability to capture real-time video of targeted areas in the monitored zone and stream the captured video to the location where all activities are observed by the administrative body. This setup provides the platform of taking prompt action in time if required. To enhance the efficiency of UAVs in a surveillance framework, it is very essential to understand the circumstances where the video-streaming capacity of UAVs are affected. In this paper, we propose a UAV-based surveillance architecture over 4G-LTE Network and we try to explore the fact that how variation in transmitting channel effects the video streaming capacity of UAVs. For this purpose, we take advantage of the physical layer attribute Reference Signal Receive Power (RSRP) which is used to measure the channel strength of wireless link at UAVs. This cross-layer information is helpful in upgrading the performance of the upper layer application used for surveillance purposes. For simulation, we have selected NS-3 which is the most trusted network simulator in the research community. Simulation results prove that variation in the channel has a direct link with the transmitting capacity of UAVs.

Electronics, 2019

This research focuses on intelligent unmanned aerial vehicle (UAV)-based, real-time video surveil... more This research focuses on intelligent unmanned aerial vehicle (UAV)-based, real-time video surveillance to ensure better monitoring and security of remote locations over 4G-LTE cellular networks by maximizing end-user quality of experience (QoE). We propose a novel server-based crosslayer rate-adaptive scheme (SCRAS) for real-time video surveillance over 4G-LTE networks using UAVs. Our key contributions are: (1) In SCRAS, mobile UAVs having preprogrammed flight co-ordinates act as servers, streaming real-time video towards a remote client; (2) server-side video rate adaptation occurs in 4G-LTE based on the physical characteristics of the received signal conditions due to variations in the wireless channel and handovers; (3) SCRAS is fully automated and independent of client assistance for rate adaptation, as it is intended for real-time, mission-critical surveillance applications; (4) SCRAS ensures that during rate adaptation, the current video frame should not be damaged by completi...

TURKISH JOURNAL OF ELECTRICAL ENGINEERING & COMPUTER SCIENCES, 2019

In this work, a no-reference framework is proposed for the video quality estimation streamed thro... more In this work, a no-reference framework is proposed for the video quality estimation streamed through the wireless network. The work presents a comprehensive survey of the existing full reference (FR), reduced reference (RR), and no-reference (NR) algorithms. A comparison has been made among existing algorithms, i.e. in terms of subjective correlation and feasibility to use these algorithms in wireless architecture, to describe the necessity of the proposed framework to overcome the limitations of the existing algorithms. A brief summary of our previously published algorithms, i.e. NR blockiness, NR blur, NR network, NR just noticeable distortion, and RR, has also been presented. These algorithms have also been used as function modules in the proposed framework. The proposed framework is able to measure the video quality by taking into account major spatial, temporal, network impairments, and human visual system effects for a comprehensive quality evaluation. The proposed framework is able to measure the video quality compressed by different codecs, i.e. MPEG x / H.264x, Motion JPEG/Motion, and JPEG2000, etc. The framework is able to work with two different kinds of received data, i.e. bit streams and decoded pixels. The framework is an integration of the RR and NR method, and can work in three different modes depending on the availability of the RR data, i.e. 1) only RR measurement, 2) hybrid of RR and NR measurement, and 3) only NR estimation. In addition, any individual function block, i.e. blurring, can also be used independently for particular specific distortion. A new subjective video quality database containing compressed and distorted videos (due to channel induced distortions) is also developed to test the proposed framework. The framework has also been tested on publicly available LIVE Video Quality Database. Overall test results show that our framework demonstrates a strong correlation with subjective evaluation of the two separate video databases as compared with other existing algorithms. The proposed framework also shows good results while working only in NR mode as compared with existing RR and FR algorithms. The proposed framework is more scalable and feasible to use in any kind of available network bandwidth as compared with other algorithms, as it can be used in different modes by using different function modules.