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

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  • 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
    A Review of Antennas for Picosatellite Applications
    ( 2017)
    Abdul Halim Lokman
    ;
    Ping Jack Soh
    ;
    Saidatul Norlyana Azemi
    ;
    Herwansyah Lago
    ;
    Symon K. Podilchak
    ;
    Suramate Chalermwisutkul
    ;
    Mohd Faizal Jamlos
    ;
    Azremi Abdullah Al-Hadi
    ;
    Prayoot Akkaraekthalin
    ;
    Steven Gao
    Cube Satellite (CubeSat) technology is an attractive emerging alternative to conventional satellites in radio astronomy, earth observation, weather forecasting, space research, and communications. Its size, however, poses a more challenging restriction on the circuitry and components as they are expected to be closely spaced and very power efficient. One of the main components that will require careful design for CubeSats is their antennas, as they are needed to be lightweight, small in size, and compact or deployable for larger antennas. This paper presents a review of antennas suitable for picosatellite applications. An overview of the applications of picosatellites will first be explained, prior to a discussion on their antenna requirements. Material and antenna topologies which have been used will be subsequently discussed prior to the presentation of several deployable configurations. Finally, a perspective and future research work on CubeSat antennas will be discussed in the conclusion.
      26  1