Mohd Najib Mohd Yasin
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Preferred name
Mohd Najib Mohd Yasin
Official Name
Mohd Najib , Mohd Yasin
Alternative Name
M. Yasin, M. Najib
Yasin, Mohd Najib
Yasin, Mohd Najib M.
Yasin, M. N.Mohd
Mohd Yasin, M. N.
Main Affiliation
Scopus Author ID
57210314287
Researcher ID
AAQ-6242-2021

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Size-Reduction of a Dual-Band Circularly Polarized Dielectric Resonator Antennas

2021-01-01 , Mohd Najib Mohd Yasin , Ali A. , Zambak M.F. , Radzi M.F.

In this paper, a circularly polarized rectangular DRA has been designed and simulated for WiMAX, satellite, 5G NR band applications. The design uses an F-shaped conducting patch with a parasitic patch to excite the design. The bandwidth enhancement of the design has been achieved thorough the optimization of the patch placement and gap distance for both conducting patch and parasitic patch to cover the desired operating frequency. The S11<10 dB and axial ratio< -3 dB result covers the operating frequency range. The designing and optimization of the design has been carried out using the CST Studio Suite software.

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Development of cascaded voltage doubler rectifier for RF energy harvesting

2022-02-21 , Ismahayati Adam , Mohd Najib Mohd Yasin , Ibrahim S.Z. , Haris N.

Radio Frequency (RF) energy harvesting is a process where RF energy from the ambient source is collected and converted into an electrical energy by using a rectifier circuit. However, the collected RF energy only supplies very low input power. Therefore, it is important to design a circuit that not only rectified the RF signal, but also with amplified characteristic to obtain a higher output voltage from a low input power. Driven by the increasing use of Internet of Things (IoT) devices operating in the 2.4 GHz Industrial, Scientific, and Medical (ISM) band, the presented rectifier circuit in this paper is designed in the same band as well. Initially, the voltage doubler circuit is chosen as the primary rectifier circuit, afterward cascaded into several stages until the most optimized result is obtained. The optimization is investigated across-30 dBm to 0 dBm of RF input power by varying the value of capacitor and resistor at a single stage. Based on the topology analysis, Dickson topology yields slightly higher voltage compared to Villard. In turn, the optimized number of stages is 6 because higher stages resulted to less output power. The measured reflection coefficient of the fabricated prototype is better than 40 dB at the center frequency with 240 MHz bandwidth. The rectified voltage is 3.4 V with 0 dBm input power. When it is supplied by 5 dBm input power, the green LED that connected to rectifier circuit output is light-up, confirming the RF energy harvesting application.

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Publication

A Review of Circularly Polarized Dielectric Resonator Antennas: Recent Developments and Applications

2022-12-01 , Abd Rahman N.A. , Mohd Najib Mohd Yasin , Ibrahim I.M. , Muzammil Jusoh , Noor S.K. , Ekscalin Emalda Mary M.R. , Zamin N. , Nurhayati N.

A comprehensive review on recent developments and applications of circularly polarized (CP) dielectric resonator antennas (DRAs) is proposed in this paper. DRAs have received more considerations in various applications due to their advantages such as wide bandwidth, high gain, high efficiency, low losses, and low profile. A broad justification for circular polarization and DRAs is stated at the beginning of the review. Various techniques such as single feed, dual, or multiple feeds used by different researchers for generating circular polarization in DRAs are briefly studied in this paper. Multiple-input-multiple-output (MIMO) CP DRAs, which can increase channel capacity, link reliability, and data rate, have also been analyzed. Additionally, innovative design solutions for broadening the circular polarization bandwidth and reducing mutual coupling are studied. Several applications of DRA are also discussed comprehensively. This paper finishes with concluding remarks.

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Modeling superconducting critical temperature of 122-iron-based pnictide intermetallic superconductor using a hybrid intelligent computational method

2021-08-02 , Akomolafe O. , Owolabi T.O. , Rahman M.A.A. , Kechik M.M.A. , Mohd Najib Mohd Yasin , Souiyah M.

Structural transformation and magnetic ordering interplays for emergence as well as suppression of superconductivity in 122-iron-based superconducting materials. Electron and hole doping play a vital role in structural transition and magnetism suppression and ultimately enhance the room pressure superconducting critical temperature of the compound. This work models the superconducting critical temperature of 122-iron-based superconductor using tetragonal to orthorhombic lattice (LAT) structural transformation during low-temperature cooling and ionic radii of the dopants as descriptors through hybridization of support vector regression (SVR) intelligent algorithm with particle swarm (PS) parameter optimization method. The developed PS-SVR-RAD model, which utilizes ionic radii (RAD) and the concentrations of dopants as descriptors, shows better performance over the developed PS-SVR-LAT model that employs lattice parameters emanated from structural transformation as descriptors. Using the root mean square error (RMSE), coefficient of correlation (CC) and mean absolute error as performance measuring criteria, the developed PS-SVR-RAD model performs better than the PS-SVR-LAT model with performance improvement of 15.28, 7.62 and 72.12%, on the basis of RMSE, CC and Mean Absolute Error (MAE), respectively. Among the merits of the developed PS-SVR-RAD model over the PS-SVR-LAT model is the possibility of electrons and holes doping from four different dopants, better performance and ease of model development at relatively low cost since the descriptors are easily fetched ionic radii. The developed intelligent models in this work would definitely facilitate quick and precise determination of critical transition temperature of 122-iron-based superconductor for desired applications at low cost with experimental stress circumvention.

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Comparison of rectifier performance using different matching technique

2017-01-03 , Ismahayati Adam , Mohd Najib Mohd Yasin , Mohammad Shahrazel Razalli

This paper describes the design and implementation of the 4-stage Villard multiplier for RF energy harvesting. Each stage is a combination of two HSMS 2850 Schottky diodes and two capacitors for each stage. For ambient energy harvesting, the incident power is extremely small, thus an efficient rectifier is needed. The designed rectifier with the matching circuit is a good candidate since it is able to enhance the rectified output power up to 300% during -40dBm input power compared to the rectifier circuit alone.

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A Review of Orbital Angular Momentum Vortex Waves for the Next Generation Wireless Communications

2022-01-01 , Noor S.K. , Mohd Najib Mohd Yasin , Ismail A.M. , Osman M.N. , Soh Ping Jack , Ramli N. , Rambe A.H.

The next-generation wireless technology that can fulfill such a demand, namely the fifth-generation (5G) technology, should provide 1000 times larger capacity. Moreover, sixth-generation (6G) communication, which represents a significant upgrade from the fifth-generation (5G) network and is anticipated to operate from 100 GHz to 3 THz band, will be required in the years after 2030 due to newly developed data-hungry applications and the greatly expanded wireless network. To meet the ever-growing demands of wireless carriers, an efficient wireless access method that can improve wireless area throughput without expanding bandwidth or cell size is required. Radio Frequency (RF) Orbital Angular Momentum vortex waves (which is now on referred to as OAM waves) to address the concerns mentioned above have attracted much attention in recent years. Due to their orthogonality, different OAM waves of different modes can be multiplexed in the same frequency channel, which can greatly increase the channel capacity. Using the orthogonal modes, a new type of multiple access scheme known as Mode Domain Multiple Access (MDMA) can be used by multiple users using the same frequency channel without additional resources such as frequency and time. As a result, the channel capacity for the next generation wireless communication systems can be enhanced as well as the overall spectrum efficiency can be improved. This review paper begins with an overview of the next generation communication such as 5G communication technology and beyond. This paper first briefly discusses the theory of OAM waves and several methods to generate OAM waves. Various different designs have also been analyzed for their ability to generate OAM waves and discussion on several restrictions and solutions to resolve. Open concerns and development trends are discussed for possible future RF OAM antenna upgrades. This study also proposes that for next generation wireless communication employing OAM, the typically used Uniform Circular Array (UCA) could be paired with the Multiple-Input-Multiple-Output (MIMO) system to improve performance in dense or urban areas for multiusers. In addition, the purity of OAM-modes needs to be considered for efficient utilization of the OAM system for future communications at the radio domain.

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Higher-order-mode triple band circularly polarized rectangular dielectric resonator antenna

2021-04-02 , Zambak M.F. , Mohd Najib Mohd Yasin , Ismahayati Adam , Iqbal J. , Osman M.N.

The paper presents a triband circular polarized rectangular dielectric resonator antenna. A single coaxial cable feeds the DRA to a double stub strip on the DRA side. A patch strip coupled to the feed assists in widening the bandwidth of the proposed DRA. The degenerate mode pair TEx∂11 and higher-TEx∂23 has been excited to achieve CP and enhance the antenna gain. The higher-order mode has been excited using a low-cost simple excitation mechanism without compromising on the size and shape of the DRA. An impedance bandwidth of 48% with a gain ~6–9 dBic was achieved in all resonance frequencies. Additionally, the AR bandwidth of 5.5%, 4.2%, and 2.76% was obtained at three different frequencies. Note that the proposed DRA exhibits a wide beamwidth of 112o, which is good for better signal reception. A comparison between the measured with simulated results shows that the measured results are matched by the simulated result trends.

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Essential semiconductor films in micro-/nano-biosensors: Current scenarios

2021-10-01 , Subash Chandra Bose Gopinath , Ramanathan S. , Mohd Najib Mohd Yasin , Shapiai M.I. , Ismail Z.H. , Subramaniam S.

Background: Engineering nanoscale matter in a controlled functional system has expanded the area of science in the state-of-art of nanotechnology. The urgency in introducing real-time health monitoring sensors and rapid diagnostic tools in medical health is indeed high and crucial to date. The efforts are accompanied by nanotechnology to improve the sensors performances. In this line, semiconductor materials (Silicon/Silica) have been in well-focus to develop micro-/nano-sensors. Methods: Further, additional layering such as metal oxide and graphene material have elevated the current scenario in biosensor developments. Among these, two-dimensional graphene nanomaterial owns its remarkable mechanical, electronic, electrochemical, and optical properties, has excited the medical field to develop graphene-based biosensors for human health diagnosis and monitoring. The oxygen rich graphene materials enhance the bio-functionalization of recognition bio-elements for excellent graphene-based biosensor development. Significance: This review encloses the excellence of semiconductor materials in conjunction with biosensors for monitoring health and diagnosis. The advances and challenges encountered with developing semiconductors for nanobiosensors from laboratory set-up to the novel hand-held device for rapid and accurate human health care are outlined.

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Orbital Angular Momentum Vortex Waves Generation Using Textile Antenna Array for 5G Wearable Applications

2022-01-01 , Noor S.K. , Mawardi Ismail A. , Mohd Najib Mohd Yasin , Mohamed Nasrun Osman , Ramli N.

The development of wireless systems for fifth-generation technology (5G) has enabled the use of textile antennas for a wide range of applications, and it has now become one of the world's most in-demand technology. As the number of wireless devices and users increase, operators would need higher channel capacity to deliver better possible service to their customers. This paper presents the generation of Orbital Angular Momentum (OAM) vortex waves with mode 1 using a wearable textile antenna. OAM introduces a new scheme called Mode Domain Multiple Access (MDMA). OAM mode is an orthogonal mode with each mode carrying individual signals. Therefore, multiple signals can be sent using the same carrier frequency without additional resources. This allows the channel capacity and spectrum efficiency to be enhanced. The proposed antenna array comprises rectangular microstrip patch elements with an inset fed technique. Felt textile fabric was used as an antenna substrate. A carefully planned feeding phase shift network was used to excite the elements by supplying similar output energy at output ports with the required phase shift value. The generated OAM waves were confirmed by measuring the null in the boresight direction of their 2D radiation patterns as well as simulated phase distribution, intensity distribution and mode purity. The antenna covered portions of the 5G n77 band with a bandwidth of 81.7 MHz and an overall gain of 2.9 dBi. This is, to the best of our knowledge, the first work on generating OAM waves using a flexible textile material.

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The design of wideband circularly polarized hemispherical DRA using conformal open halfloop excitation

2017-12-15 , Mohamad Ismail Sulaiman , Mohd Najib Mohd Yasin , Hafiz Basarudin , Aizat Faiz Ramli , Mohd Azlan Abu

A circularly polarized (CP) hollow hemispherical dielectric resonator antenna (DRA) is presented. The CP DRA that is excited using conformal open half loop metal strips has been studied theoretically and experimentally. The proposed antenna configuration has provided a measured CP and return loss bandwidths of ∼11.i5%, and 10.32% respectively. The DRA has been simulated using Method of Moments (MoM) model, where a good agreement has been obtained between the experimental and theoretical results.

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