Azremi Abdullah Al-Hadi
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Preferred name
Azremi Abdullah Al-Hadi
Official Name
Azremi, Abdullah Al-Hadi
Alternative Name
Abdullah Al-Hadi, Azremi
Al-Hadi, Azremi A.
Al-Hadi, A. A.
Azremi, A. A. H.
Main Affiliation
Scopus Author ID
57194469675
Researcher ID
A-6983-2015

Research Output

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Now showing 1 - 10 of 12
  • Publication
    Deployable Linear-to-Circular Polarizer Using PDMS Based on Unloaded and Loaded Circular FSS Arrays for Pico-Satellites
    ( 2019)
    Hidayath Mirza
    ;
    Toufiq Md Hossain
    ;
    Ping Jack Soh
    ;
    Mohd Faizal Jamlos
    ;
    Muhammad Nazrin Ramli
    ;
    Azremi Abdullah Al-Hadi
    ;
    Emad S. Hassan
    ;
    Sen Yan
    In this paper, flexible and deployable double-sided linear-to-circular polarizers designed on polydimethylsiloxane are proposed for the first time to the best of our knowledge. ShieldIt textile is used as the conducting element of the two designs based on two different unit cell arrays: a loaded circular patch unit cell or an unloaded circular patch unit cell, both backed by a generic rectangular element on its reverse side. This is in contrast to conventional frequency-selective structure-based linear-to-circular polarizers implemented using rigid substrates, which are multi-layered and requires inter-layer physical spacing. This complicates their implementation using flexible substrates and in a deployable format. Upon implementation of this double-sided polarizer, their final performances are evaluated in terms of the phase difference, conversion efficiency, 3-dB axial ratio (AR), and ellipticity bandwidth (from 40° to 45°). Measurements indicated good agreements with simulations, and both structures exhibited more than 90% of conversion efficiency from 2.34 to 3 GHz (for the loaded circular unit cell) and from 2.36 to 3 GHz (for the unloaded circular unit cell). In terms of ellipticity, a bandwidth of 8.67% is observed for the unloaded design and 13.82% for the loaded design. The unloaded structure exhibited a fractional 3-dB AR bandwidth of 36.36% (from 1.98 to 2.86 GHz) in simulations, and 32.64 % (from 2.00 to 2.78 GHz) when evaluated experimentally. Conversely, the loaded design showed only 12.58%. An equivalent circuit model is proposed and validated via a comparison between the circuit and full-wave simulations. Finally, the performances of these polarizers are also assessed under different bending conditions due to the use of flexible materials, prior to the proposal of a suitable deployment mechanism.
  • Publication
    A flexible wearable linear-to-circular polarizer for GNSS application
    (Institute of Electrical and Electronics Engineers (IEEE), 2020)
    Hidayath Mirza
    ;
    Ping Jack Soh
    ;
    Rais Ahmad Sheikh
    ;
    Azremi Abdullah Al-Hadi
    ;
    Toufiq M Hossain
    ;
    Sen Yan
    This paper presents a single-layered fabric-based flexible linear-to-circular polarizer for GNSS application operating at 1.575 GHz. The structure presented here is based on a square aperture with an E-shaped patch structure on the reverse side. The size of the structure is 0. 21λ0 ×0. 26λ0 × 0. 01λ0 The complete structure is flexible, and the frequency of operation is centered at 1.575 GHz, with a minimum value of the axial ratio achieved is 0.06 dB. The 3 dB axial ratio fractional bandwidth is 3.81% (1.54-1.60 GHz) and the conversion efficiency fractional bandwidth covering 90% is 5.09% (1.53 to 1.61 GHz).
  • Publication
    Design of a quad band CPW-fed compact flexible patch antenna for wearable applications
    (IEEE, 2020)
    Bashar Bahaa Qas Elias
    ;
    Ping Jack Soh
    ;
    Azremi Abdullah Al-Hadi
    ;
    Rahil Joshi
    ;
    Yuepei Li
    ;
    Symon K. Podilchak
  • Publication
    Performance study of a MIMO mobile terminal with upto 18 elements operating in the sub-6 GHz 5G band with user hand
    (IEEE, 2020-01)
    Ahmed Mohamed Elshirkasi
    ;
    Azremi Abdullah Al-Hadi
    ;
    Ping Jack Soh
    ;
    Mohd Fais Mansor
    ;
    Rizwan Khan
    ;
    Xiaoming Chen
    ;
    Prayoot Akkaraekthalin
    This paper investigates the performance variation when a different number of antenna elements (AEs) is integrated onto a single MIMO mobile terminal, both in free space and when held in a user hand in data mode. Starting with a minimum of two AEs, this investigation assessed the performance of the MIMO terminal with every additional two AEs (up to 18 AEs) in terms of envelope correlation coefficient (ECC), efficiency, multiplexing efficiency, capacity and maximal ratio combining (MRC). The integrated MIMO antennas are identical and operate between 5 and 6 GHz for 5G applications. Results indicated that ECC increased with the number of AEs. However, ECC remains less than 0.32 for the case of 18 AEs in both free space and with a user hand. Meanwhile, the free space efficiency of about 90 % for the two AEs is observed to decrease with the increasing number of AEs to about 50 % with 18 AEs. However, the efficiency of elements changes with user hand depending on the level of interaction between each element and the hand. Direct blockage of AEs by the hand resulted in efficiencies of as low as 5 %, while at the same time, other AEs retained an efficiency of up to 75 %. At the center frequency of 5.5 GHz, the free space capacity is 11.1, 49.5 and 83.2 bit/s/Hz with two, ten and 18 AEs, respectively. However, the use of the mobile terminal in the proximity of the user hand degraded these levels by 11 % (two AEs), 35 % (10 AEs) and 31 % (18 AEs). Finally, multiplexing efficiency showed that capacity degradation is caused mainly by the degradation of AEs efficiency, whereas the impact of low correlation between AEs is found to be an insignificant factor. In addition to the capacity analysis, gain and diversity gain of the maximal ratio combining technique was also investigated.
  • Publication
    A triband wearable antenna for location tracking using cospas-sarsat and GNSS
    (IEEE, 2025)
    Rais Ahmad Sheikh
    ;
    Azremi Abdullah Al-Hadi
    ;
    Roy B. V. B. Simorangkir
    ;
    Thennarasan Sabapathy
    ;
    Rizwan Khan
    ;
    Prayoot Akkaraekthalin
    ;
    Surentiran Padmanathan
    ;
    Toufiq Md Hossain
    ;
    Che Muhammad Nor Che Isa
    ;
    Ping Jack Soh
    This paper presents the design of a tri-band antenna operating in the Cospas-Sarsat (C-S) and GPS/GNSS bands applicable for the Internet of Things (IoT). Implemented with flexible and robust materials, the antenna operates in three distinct frequencies: 406 MHz for C-S applications and 1227 MHz (L2) and 1575 MHz (L1) for GPS/GNSS applications. The measured 10-dB impedance bandwidth is from 1.517-1.587 MHz (in L1 band) and from 1.192-1.232 MHz (in L2 band). In C-S band, the measured 6-dB bandwidth is from 393 to 406.5 MHz. The 3 dB axial ratio (AR) bandwidth in the L1 and L2 bands are 17 MHz (1.08%) and 18 MHz (1.47%), respectively. The antenna demonstrates a measured gain of 1.61 dB at 406 MHz, exceeding the simulated gain of 0.573 dB, and features a beamwidth of 140°. The measured gains for the L2 and L1 bands closely align with the simulations, although a slight reduction in gain is observed for the L2 band. In the H-plane, zenith-directed main lobes produce measured gains of 1.61 dB for 406 MHz, 2.71 dB for L2, and 3.51 dB for L1. On the other hand, the measured efficiency for the antenna is 36.32% (in the C-S band), 54% (in L1 band) and 60.12% (in L2 band). Both measured and simulated results consistently showed good agreements in terms of gain, polarization, and efficiency. Moreover, the antenna design incorporates effective shielding against electromagnetic radiation, conforming to specific absorption rate (SAR) values of 0.046, 0.077, and 0.035 W/Kg in C-S, L1 and L2 bands respectively. Antenna integration into the life vest foam prior to placement on the human chest significantly influenced axial ratio variations. In the L1 band, the AR increased from 0.43 dB to 3.34 dB, while in the L2 band, it rose from 0.56 dB to 8.66 dB. This indicates a more pronounced effect on polarization characteristics at the lower frequency. Overall, the proposed tri-band antenna presents promising capabilities for location tracking applications, with potential for integration into wearable devices for enhanced safety and tracking functionalities.
  • Publication
    Gain Optimization of Low-Profile Textile Antennas Using CMA and Active Mode Subtraction Method
    ( 2021)
    Bashar Bahaa Qas Elias
    ;
    Ping Jack Soh
    ;
    Azremi Abdullah Al-Hadi
    ;
    Prayoot Akkaraekthalin
    This paper presents an active mode subtraction method based on the characteristic mode analysis to estimate the forward directivity based on the difference in modal significance curves. This made the optimization of the antenna gain in the design process to be more efficient. To the best of the authors' knowledge, such method is innovative and proposed in literature for the first time. This method is derived on the basis that the total radiated field of the antenna, and consequently, the directivity is mainly contributed by the excited dominant modes. To demonstrate its effectiveness, three compact, planar, and wearable antennas with increasing complexity will be designed and optimized using this method. The first is a conventional circular patch antenna operating at 5.3 GHz, whereas the second one is a planar loop antenna operating at 3.08 GHz. The third design is a crown-shaped planar antenna (CPA) with a 3 × 3 artificial magnetic conductor (AMC) plane integrated underneath to reduce potential coupling effects from the body. All three antennas are made fully using textiles with the same thicknesses: felt fabric as its substrate and ShieldIt Super as its conductive textile. For all designs, the use of the proposed method, which is validated using the method of moments, has predicted the maximum direction of radiation and its respective gain at the desired frequencies with good accuracy. Besides that, the design of the AMC plane for the CPA is also optimized using CMA prior to the integration with the antenna and a leather wrist strap. Measurements of the final crown-shaped antenna design indicated a good agreement with simulations, with an operating bandwidth of more than 240 MHz, FBR of 15.73 dB and a directional radiation pattern outward from the body.
      3  26
  • Publication
    Dual-band, dual-sense textile antenna with AMC backing for localization using GPS and WBAN/WLAN
    (IEEE, 2020)
    Rahil Joshi
    ;
    Ezzaty Faridah Nor Mohd Hussin
    ;
    Ping Jack Soh
    ;
    Mohd Faizal Jamlos
    ;
    Herwansyah Lago
    ;
    Azremi Abdullah Al-Hadi
    ;
    Symon K. Podilchak
    A wearable textile antenna with dual-band and dual-sense characteristics is presented in this work. It operates at the 2.45 GHz band for WBAN and WLAN applications, and at the 1.575 GHz band for Global Positioning System (GPS) applications. An antenna backing based on an artificial magnetic conductor (AMC) plane operating at 2.45 GHz band is introduced to reduce the backward radiation and to improve antenna gain. It consists of a 3×3 array of square patch unit cells, where each unit cell is integrated with four square slits and a square ring. A square-shaped patch is then located on top of the substrate as its radiator. To enable dual-band operation, two corners of this radiator are truncated, with each of the four corners incorporated with a rectangular slit to enable its circular polarization characteristic in the GPS band. Simulation and experimental results are in good agreement and indicate proper antenna operation with linear polarization in the 2.45 GHz band and circular polarization in the 1.575 GHz band, with realized gain of 1.94 dBi and 1.98 dBic, respectively.
      1  11
  • Publication
    A wideband wearable antenna using inverse partial ground designed using characteristic mode analysis
    (IEEE, 2020)
    Bashar Bahaa Qas Elias
    ;
    Ping Jack Soh
    ;
    Azremi Abdullah Al-Hadi
    ;
    Saidatul Norlyana Azemi
    The design of a wearable wideband textile antenna based on a loop structure and fed using a coplanar waveguide line is proposed in this work. Characteristic mode analysis is used to first estimate the radiating modes on the structure. This is to ensure that the optimal mode significance is chosen. Analysis of modal significance enabled the first four modes to be identified from the structure. In this paper, the antenna is proposed to designed with an inverse partial ground (IPG) to enhance the bandwidth. It is shown that this IPG method improved impedance bandwidth to 1560 MHz (60.57%), indicating a bandwidth broadening of about 370 MHz (11.61%). A compact size of 70×70 mm2(0.57 × 0.57 ?g) is also maintained, with a realized gain of 4.23 dBi. Finally, the proposed antenna is fabricated and measured to validate the analysis experimentally, indicating a good agreement with simulations.
      3  11
  • Publication
    User Influence on Mobile Terminal Antennas: A Review of Challenges and Potential Solution for 5G Antennas
    ( 2018)
    Rizwan Khan
    ;
    Azremi Abdullah Al-Hadi
    ;
    Ping Jack Soh
    ;
    Muhammad Ramlee Kamarudin
    ;
    Mohd Tarmizi Ali
    This paper presents a comprehensive review of mobile terminal antenna researches performed in the past seven years and the current challenges related to the user's influence on the performance of fifth generation (5G) terminal antennas. The main challenges for the designing of mobile terminal antennas are to meet the compact size requirements of built-in structures and their multiband capabilities. The antenna design techniques that are used to achieve broader operating bandwidths with smaller antenna dimensions will be first discussed. This is followed by the effects of user interactions with the head/hand for mobile antennas in terms of radiation efficiency and, consequently, the correlation of multiple input multiple output (MIMO) antenna systems. The ultimate aims of this paper are as follows: 1) to highlight the different frequencies of mobile terminal antennas for different applications; 2) to highlight mobile terminal antennas that have been developed for 5G application; 3) to study and discuss the effects of user's hand on 5G mobile terminal antennas; and 4) to discuss the research gap, issues, and challenges in the field of user's effects on mobile terminal antennas for 5G applications. In addition to that, an investigation of the users' hand effects on two MIMO mobile terminal antennas operational in the sub-6-GHz 5G band is presented. This investigation performed using two MIMO antennas is an attempt to formulate guidelines on efficient mobile terminal antenna design in the presence of user's hand in C Band (from 3.4 to 3.6 GHz) and LTE-U Band 46 (from 5.15 to 5.925 GHz).
      6  23
  • Publication
    Design and optimization of a flexible CPW–Fed slotted planar monopole for WLAN/WBAN and 5G
    (IEEE, 2020)
    Bashar Bahaa Qas Elias
    ;
    Ping Jack Soh
    ;
    Mohamad Kamal A. Rahim
    ;
    Azremi Abdullah Al-Hadi
    ;
    Hadi Aliakbarian
    ;
    Sen Yan
    A flexible Kapton-based coplanar waveguide-fed (CPW) patch antenna has been designed in this work to operate in different wireless applications. The wideband operation and compact size of the antenna is enabled using a simple rhombic-shaped integrated onto the monopole which was designed using a rectangular patch. The proposed broadband antenna model operated below -10dB at 2.45 GHz and 3.5 GHz for the WLAN/WBAN and 5G band, respectively. The antenna optimization process is explained when varying the ground structure, patch dimensions, feed width, and substrate thickness using FEKO software. The performance of the antenna is studied in terms of radiation efficiency, gain, bandwidth and current distributions. Results indicate that the proposed antenna operates throughout the 2.45 and 3.5 GHz bands, with a bandwidth of1710 MHz.
      7  1