Journal Articles

Permanent URI for this collection

https://hdl.handle.net/20.500.14170/1818

Browse

Browsing Journal Articles by Title

  • Publication
    A 1.5 V, 0.85-13.35 GHZ MMIC low noise amplifier design using optimization technique
    ( 2009)
    Arjuna Marzuki
    ;
    Ali Yeon Md Shakaff
    ;
    Zaliman Sauli
    This paper describes how a broadband, 1.5 V, 0.85-13.35 GHz low noise amplifier in 0.15 μm 85 GHz PHEMT process is synthesized to simultaneously meet multiple design specifications such as bandwidth, noise figure, power gain and power consumption. Power-constrained synthesis technique is used to design the broadband amplifier. The simulated peak S21 is 19.8 dB, maximum noise Figure is 2.5 dB, 3-dB bandwidth is 12.5 GHz and power consumption is 73.5 mW. The calculated Figure of merit (FOM) is better than many reported broadband low noise amplifier (LNA).
      5  13
  • Publication
    A low complexity OFDM modulator/demodulator based on discrete hartley transform
    ( 2011)
    Zakaria Sembiring
    The investigation upon to discrete Hartley transform (DHT) to replace the conventional complex-valued and mature discrete Fourier transform (DFT) as the OFDM modulator and demodulator was carried out in this research. The overall project is divided into two parts as follows: firstly, the proposed system is simulated under various parameters such as BER versus SNR and the quality of image versus given value of SNR. Secondly, the simulation model has been developed using excellent software for simulation, MATLAB. Statistically analysis has been investigated to measure the accuracy of the system performance and also the complexity of the system. Simulation results show that the system complexity is reduced in term of multiplication and addition number. For number of subcarriers, N = 64, 52 % of multiplication and 28 % of addition numbers are reduced. The system performance is measured in term of plotted graph of BER versus SNR and quality of received image versus SNR, where the BER value is 10-3 and quality of image is similar with the original image when the given value of SNR = 30 dB.
      1  1
  • Publication
    A multilayers adaptive ALACO-OFDM for spectral efficiency improvement using PSO algorithm in visible light communication systems
    (De Gruyter, 2023)
    Aymen Abdalmunam Hameed
    ;
    Anuar Mat Safar
    ;
    Montadar Abas
    ;
    Junita Mohd Nordin
    ;
    Norizan Mohamed Nawawi
    In this paper, we propose a new adaptive layered asymmetrically-clipped optical orthogonal frequency division multiplexing (ALACO-OFDM) technique as a method to improve the spectral efficiency of optical system, especially visible light communication (VLC). Particle swarm optimisation (PSO)-based LACO-OFDM method is used for this purpose and the channel capacities are studied. Simulations using variable layers are carried out to validate the theoretical steps. The simulation results indicate that the ALACO-OFDM technique has significantly improve the spectral efficiency compared to previous techniques such as ACO-OFDM. Moreover, it is shown that channel capacities of different layers are significantly improved when electrical power is increased.
  • Publication
    A patch antenna with enhanced gain and bandwidth for sub-6 GHz and sub-7 GHz 5G wireless applications
    (MDPI, 2023)
    Shehab Khan Noor
    ;
    Muzammil Jusoh
    ;
    Ali Hanafiah Rambe
    ;
    Thennarasan Sabapathy
    ;
    Hamsakutty Vettikalladi
    ;
    Ali M. Albishi
    ;
    Mohamed Himdi
    This paper presents a novel microstrip patch antenna design using slots and parasitic strips to operate at the n77 (3.3–4.2 GHz)/n78 (3.3–3.8 GHz) band of sub-6 GHz and n96 (5.9–7.1 GHz) band of sub-7 GHz under 5G New Radio. The proposed antenna is simulated and fabricated using an FR-4 substrate with a relative permittivity of 4.3 and copper of 0.035 mm thickness for the ground and radiating planes. A conventional patch antenna with a slot is also designed and fabricated for comparison. A comprehensive analysis of both designs is carried out to prove the superiority of the proposed antenna over conventional dual-band patch antennas. The proposed antenna achieves a wider bandwidth of 160 MHz at 3.45 GHz and 220 MHz at 5.9 GHz, with gains of 3.83 dBi and 0.576 dBi, respectively, compared to the conventional patch antenna with gains of 2.83 dBi and 0.1 dBi at the two frequencies. Parametric studies are conducted to investigate the effect of the parasitic strip’s width and length on antenna performance. The results of this study have significant implications for the deployment of high-gain compact patch antennas for sub-6 GHz and sub-7 GHz 5G wireless communications and demonstrate the potential of the proposed design to enhance performance and efficiency in these frequency bands.
      4  1
  • Publication
    A Point-of-Care immunosensor for human chorionic gonadotropin in clinical urine samples using a cuneated polysilicon nanogap Lab-on-Chip
    ( 2015)
    S. R. Balakrishnan
    ;
    Uda Hashim
    ;
    Subash Chandra Bose Gopinath
    ;
    Prabakaran A/L Poopalan
    ;
    H. R. Ramayya
    ;
    M. Iqbal Omar
    ;
    R. Haarindraprasad
    ;
    P. Veeradasan
    Human chorionic gonadotropin (hCG), a glycoprotein hormone secreted from the placenta, is a key molecule that indicates pregnancy. Here, we have designed a cost-effective, label-free, in situ point-of-care (POC) immunosensor to estimate hCG using a cuneated 25 nm polysilicon nanogap electrode. A tiny chip with the dimensions of 20.5 × 12.5 mm was fabricated using conventional lithography and size expansion techniques. Furthermore, the sensing surface was functionalized by (3-aminopropyl)triethoxysilane and quantitatively measured the variations in hCG levels from clinically obtained human urine samples. The dielectric properties of the present sensor are shown with a capacitance above 40 nF for samples from pregnant women; it was lower with samples from non-pregnant women. Furthermore, it has been proven that our sensor has a wide linear range of detection, as a sensitivity of 835.88 μA mIU-1 ml-2 cm-2 was attained, and the detection limit was 0.28 mIU/ml (27.78 pg/ml). The dissociation constant Kd of the specific antigen binding to the anti-hCG was calculated as 2.23 ± 0.66 mIU, and the maximum number of binding sites per antigen was Bmax = 22.54 ± 1.46 mIU. The sensing system shown here, with a narrow nanogap, is suitable for high-throughput POC diagnosis, and a single injection can obtain triplicate data or parallel analyses of different targets.
  • Publication
    A reconfigurable WiMAX antenna for directional and broadside application
    ( 2013-04-25)
    Muzammil Jusoh
    ;
    M. F. Jamlos
    ;
    M. R. Kamarudin
    ;
    Thennarasan Sabapathy
    A novel reconfigurable compact patch array antenna for directional and broadside application is proposed. The presented antenna has successfully been able to function for directional beam at 320° or 35° and divisive broadside beam at 43° and 330°. This is realized in the unique form of aperture coupled spiral feeding technique and positioning of the radiating elements at 0°, 90,° and 180°. The switchable feature is effectively performed by the configuration of three PIN diodes. All PIN diodes are positioned at the specific location of the aperture coupled structure. It is discovered in simulation that the switches can be represented with a copper strip line or touchstone (TS) block . The proposed antenna design operates at 2.37 GHz to 2.41 GHz and has a maximum gain of 6.4 dB and efficiency of 85.97%. Such antenna produces a broadside HPBW with a wider bandwidth covering from −90° to 90° compared to the normal microstrip antenna which could only provide HPBW of −50° to 50°. Moreover, the proposed antenna has small physical dimension of 100 mm by 100 mm. The simulation and measurement results have successfully exhibited the idea of the presented antenna performance. Therefore, the antenna is sufficiently competent in the smart WiMAX antenna application.
      9  9
  • 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.
  • Publication
    ABCS antenna for wireless body area network at 26 GHz
    (AIP Publishing Ltd., 2023)
    Muhammad Afifi
    ;
    Saidatul Norlyana Azemi
    ;
    Amiza Amir
    ;
    Soh Ping Jack
    The paper presents the design and investigation of a wearable textile antenna (receiver) and transmitter antenna operating in the wireless body area network (WBAN) of 26 GHz band for 5G mobile networks. The wearable antenna with an overall size of 30 mm x 40 mm x 1.26 mm achieves good impedance matching, high gain, and directive radiation pattern. Both antennas were designed using CST Microwave Studio to validate the simulation results. A rectangular radiating patch comprises a Shieldit electrotextile situated on one side of a non-conductive substrate panel with the ground plane. The bed sheet cotton fabric is used as the non-conductive substrate due to its widespread use in daily clothing with a dielectric constant is 3.2 and the loss tangent is 0.0027. In addition, the wearable antenna successfully achieved the high gain and efficiency of 12 dB and 90.83% respectively. Moreover, the antenna operating at 26 GHz with -40.48 dB return loss, which is less than the -10 dB in requirement. The simulated results show that this proposed wearable antenna is best suited for wireless body area network applications. Hence, the wearable antenna is simple, compact and easy to fabricate.
  • Publication
    An introduction to double stain normalization technique for brain tumour histopathological images
    ( 2024)
    Fahmi Akmal Dzulkifli
    ;
    Mohd Yusoff Mashor
    ;
    Rafikha Aliana A Raof
    ;
    Hasnan Jaafar
    Stain normalization is an image pre-processing method extensively used to standardize multiple variances of staining intensity in histopathology image analysis. Staining variations may occur for several reasons, such as unstandardized protocols while preparing the specimens, using dyes from different manufacturers, and varying parameters set while capturing the digital images. In this study, a double stain normalization technique based on immunohistochemical staining is developed to improve the performance of the conventional Reinhard’s algorithm. The proposed approach began with preparing a target image by applying the contrast-limited adaptive histogram equalization (CLAHE) technique to the targeted cells. Later, the colour distribution of the input image will be matched to the colour distribution of the target image through the linear transformation process. In this study, the power-law transformation was applied to address the over-enhancement and contrast degradation issues in the conventional method. Five quality metrics comprised of entropy, tenengrad criterion (TEN), mean square error (MSE), structural similarity index (SSIM) and correlation coefficient were used to measure the performance of the proposed system. The experimental results demonstrate that the proposed method outperformed all conventional techniques. The proposed method achieved the highest average values of 5.59, 3854.11 and 94.65 for entropy, TEN, and MSE analyses.
  • Publication
    Android-based timetable manager for university students using rule-based algorithm
    (AIP Publishing Ltd., 2023)
    Lim Yan Yi
    ;
    Norfadila Mahrom
    ;
    Calvin Lim
    Currently, there are several drawbacks in the existing university timetable system, including students do not know the class hour of subjects that they are going to register during the registration period. This situation has resulting in clashing in the class hour of the registered subjects. In addition, some students are not aware of this situation until it is too late from them to drop and register other subjects. This particularly happened to those who has more than two registered subjects clash and resulting in overlook at the rest of clashed subjects. Besides, students find it is inconvenient to view the timetable through the current timetable system. Thus, the development of an Android based mobile application that able to notify students if the class hour of the subjects they registered are overlapping is presented in this paper. The application also able to manage the student timetable by reporting details such as venue, day and the time of clashed subjects. Then, the application will suggest student to select elective subjects or subjects that students wish to retake to prevent clashing in class hour. The software development of the application is based on the Agile model and using rule-based algorithm. The application is developed in Android Studio by using Java as the programming language and all data is stored in Firebase Realtime Database. In conclusion, this paper presents results of the application that has successfully designed and developed.
      2  4
  • Publication
    Camera motion estimation and object extraction using multiple consecutive frames with ghost and noise removal for Pan-Tilt-Zoom camera
    ( 2014)
    Syaimaa' Solehah Mohd Radzi
    This research presents a new algorithm for extracting moving objects using Pan-Tilt- Zoom (PTZ) camera. Previously, system that uses moving camera faces some problems, including misalignment between current and template frames, appearance of unwanted objects (ghost), illumination changes, shadow and crowd. This research developed an algorithm to avoid misalignment images, remove ghost and noises. The proposed algorithm consists of six steps, which are camera motion estimation, object extraction, removing ghost, detecting shadow, refining shadow and noises elimination. This research proposed to apply camera motion estimation twice, which is between three consecutive frames. Keypoints of each image are detected using Speed-up Robust Features (SURF) detector, then produces homography matrix. The homography contains rotation and translation of one image from another image. It is used to warp previous frames with respect to the current frame. In object extraction, current frame is compared to both compensated previous frame 1 and compensated previous frame 2 using Wronskian Change Detector (WCD). Detecting changes using multiple frames produces ghost, which is actually moving objects in previous frames. Then, this research has developed a ghost removal technique, in which two output images of object extraction are compared each other, pixel by pixel. Then the existing method of shadow removal, Normalized Cross-Correlation (NCC) technique is applied to refine the output image. Some pixels may be misclassified as shadow pixels. Therefore, refinement of shadow detection is done so that the actual shadow is removed, while the false detected shadows are returned to be background entities. To remove other noises, a 3x3 noise filter has been created. The filter is used to scan the output image where the centre of the 3x3 window will look for white pixel. Number of white pixel in the whole window (filter) will be compared to the threshold. Finally, morphological operator is used to remove undesirable foreground pixels. The developed algorithm had been tested on seven image conditions; striped background, objects move slowly, camouflage object, small moving object, multiple moving objects, objects move towards the camera and shadow. The developed algorithm has successfully extracted moving object, removed ghost, removed shadow, noises and detected illumination changes. Based on the manual calculation and visual observations, this system has the highest average accuracy which is 95.13%, followed by single WCD 93.99%, Background Subtraction 93.42%, Luminance Ratio 92.92%, HSV Histogram 91.85% and Greyscale Histogram 91.47%.
      2  1
  • Publication
    Comparative analysis on virtual private network in the internet of things gateways
    ( 2022-10-01)
    Mohd Idzaney Zakaria
    ;
    Mohd Natashah Norizan
    ;
    Muammar Mohamad Isa
    ;
    Mohd Faizal Jamlos
    ;
    Mustapa Muslim
    A virtual private network (VPN) connects a private network to the internet, primarily the public network, through a secure tunnel. Using a local area network (LAN) segment, users can send and receive data from their colleagues in different locations on the network. The development of VPN allows users to gain access to company applications and databases. Therefore, data can be transmitted through a secure tunnel without the need to configure port forwarding for the internet of things (IoT) gateway, allowing users to access it from any location in the world. A method such as dataplicity and pitunnel was examined to compare with the conventional setting. This research paper examines the current deployment of VPN connections in IoT gateways, discussing their characteristics, benefits, and drawbacks, as well as comparing them. The advantage of this method is that the IoT gateway is always accessible and has internet connectivity, which is a significant benefit. Dataplicity is a more trustworthy option because they offer excellent assistance for both the backend and frontend environments.
      4  2
  • Publication
    Comparison between conventional OCDMA and subcarrier multiplexing SAC OCDMA system based on single photodiode detection
    ( 2017-12-11)
    N. A. A Ahmad
    ;
    Junita Mohd Nordin
    ;
    Syed Alwee Aljunid Syed Junid
    ;
    Mohd Rashidi Che Beson
    ;
    Rosdisham Endut
    This paper demonstrates the comparison between conventional OCDMA system and subcarrier multiplexing (SCM) SAC-OCDMA system by applying Recursive Combinatorial (RC) code based on single photodiode detection (SPD). SPD is used in the receiver part to reduce the effect of multiple access interference (MAI) which contributes as a dominant noise in incoherent SAC-OCDMA systems. From this analysis, the performance of SCM OCDMA network could be improved by using lower data rates and higher received power. The hybrid SCM OCDMA system shows better performance compare to conventional OCDMA system although the number of users involved is very high. This is because, for hybrid SCM OCDMA system, the number of users can be increased by increasing the number of subcarriers without affect the number of code length and optical codes. Increasing the number of subcarriers will enhance the power consumption by applying hybrid SCM system in OCDMA compared to the conventional OCDMA system. This is because increasing the number of users for hybrid SCM system does not affects the number of code length and the number of optical codes but only increase the number of subcarriers. Thus, hybrid SCM OCDMA system has to increase spectral efficiency and produce better performance compared to conventional of OCDMA system
  • Publication
    Coverage extension and balancing the transmitted power of the moving relay node at LTE-A cellular network
    ( 2014)
    Jaafar A. Aldhaibani
    ;
    Abid Yahya
    ;
    R Badlishah Ahmad
    The poor capacity at cell boundaries is not enough to meet the growing demand and stringent design which required high capacity and throughput irrespective of user’s location in the cellular network. In this paper, we propose new schemes for an optimum fixed relay node (RN) placement in LTE-A cellular network to enhance throughput and coverage extension at cell edge region. The proposed approach mitigates interferences between all nodes and ensures optimum utilization with the optimization of transmitted power. Moreover, we proposed a new algorithm to balance the transmitted power of moving relay node (MR) over cell size and providing required SNR and throughput at the users inside vehicle along with reducing the transmitted power consumption by MR. The numerical analysis along with the simulation results indicates that an improvement in capacity for users is 40% increment at downlink transmission from cell capacity. Furthermore, the results revealed that there is saving nearly 75% from transmitted power in MR after using proposed balancing algorithm. ATDI simulator was used to verify the numerical results, which deals with real digital cartographic and standard formats for terrain.
  • Publication
    Coverage extension and balancing the transmitted power of the moving relay node at LTE-A cellular network
    ( 2014)
    Jaafar A. Aldhaibani
    ;
    Abid Yahya
    ;
    R. Badlishah, Ahmad
    The poor capacity at cell boundaries is not enough to meet the growing demand and stringent design which required high capacity and throughput irrespective of user’s location in the cellular network. In this paper, we propose new schemes for an optimum fixed relay node (RN) placement in LTE-A cellular network to enhance throughput and coverage extension at cell edge region. The proposed approach mitigates interferences between all nodes and ensures optimum utilization with the optimization of transmitted power. Moreover, we proposed a new algorithm to balance the transmitted power of moving relay node (MR) over cell size and providing required SNR and throughput at the users inside vehicle along with reducing the transmitted power consumption by MR. The numerical analysis along with the simulation results indicates that an improvement in capacity for users is 40% increment at downlink transmission from cell capacity. Furthermore, the results revealed that there is saving nearly 75% from transmitted power in MR after using proposed balancing algorithm. ATDI simulator was used to verify the numerical results, which deals with real digital cartographic and standard formats for terrain.
      1  6
  • Publication
    Cross-Talk in mechanomyographic signals from the forearm muscles during sub-maximal to maximal isometric grip force
    ( 2014)
    Md. Anamul Islam
    ;
    Kenneth Sundaraj
    ;
    R. Badlishah, Ahmad
    ;
    Sebastian Sundaraj
    ;
    Nizam Uddin Ahamed
    ;
    Md. Asraf Ali
    This study aimed: i) to examine the relationship between the magnitude of cross-talk in mechanomyographic (MMG) signals generated by the extensor digitorum (ED), extensor carpi ulnaris (ECU), and flexor carpi ulnaris (FCU) muscles with the sub-maximal to maximal isometric grip force, and with the anthropometric parameters of the forearm, and ii) to quantify the distribution of the cross-talk in the MMG signal to determine if it appears due to the signal component of intramuscular pressure waves produced by the muscle fibers geometrical changes or due to the limb tremor. METHODS: Twenty, right-handed healthy men (mean ± SD: age  = 26.7±3.83 y; height  = 174.47±6.3 cm; mass  = 72.79±14.36 kg) performed isometric muscle actions in 20% increment from 20% to 100% of the maximum voluntary isometric contraction (MVIC). During each muscle action, MMG signals generated by each muscle were detected using three separate accelerometers. The peak cross-correlations were used to quantify the cross-talk between two muscles. RESULTS: The magnitude of cross-talk in the MMG signals among the muscle groups ranged from, R2(x, y) = 2.45-62.28%. Linear regression analysis showed that the magnitude of cross-talk increased linearly (r2 = 0.857-0.90) with the levels of grip force for all the muscle groups. The amount of cross-talk showed weak positive and negative correlations (r2 = 0.016-0.216) with the circumference and length of the forearm respectively, between the muscles at 100% MVIC. The cross-talk values significantly differed among the MMG signals due to: limb tremor (MMGTF), slow firing motor unit fibers (MMGSF) and fast firing motor unit fibers (MMGFF) between the muscles at 100% MVIC (p<0.05, η2 = 0.47-0.80). SIGNIFICANCE: The results of this study may be used to improve our understanding of the mechanics of the forearm muscles during different levels of the grip force.
  • Publication
    Cross-Talk in Mechanomyographic Signals from the Forearm Muscles during Sub-Maximal to Maximal Isometric Grip Force
    ( 2014)
    Md. Anamul Islam
    ;
    Kenneth Sundaraj
    ;
    R Badlishah Ahmad
    ;
    Sebastian Sundaraj
    ;
    Nizam Uddin Ahamed
    ;
    Md. Asraf Ali
    Purpose This study aimed: i) to examine the relationship between the magnitude of cross-talk in mechanomyographic (MMG) signals generated by the extensor digitorum (ED), extensor carpi ulnaris (ECU), and flexor carpi ulnaris (FCU) muscles with the sub-maximal to maximal isometric grip force, and with the anthropometric parameters of the forearm, and ii) to quantify the distribution of the cross-talk in the MMG signal to determine if it appears due to the signal component of intramuscular pressure waves produced by the muscle fibers geometrical changes or due to the limb tremor. Methods Twenty, right-handed healthy men (mean ± SD: age  = 26.7±3.83 y; height  = 174.47±6.3 cm; mass  = 72.79±14.36 kg) performed isometric muscle actions in 20% increment from 20% to 100% of the maximum voluntary isometric contraction (MVIC). During each muscle action, MMG signals generated by each muscle were detected using three separate accelerometers. The peak cross-correlations were used to quantify the cross-talk between two muscles. Results The magnitude of cross-talk in the MMG signals among the muscle groups ranged from, R2(x, y) = 2.45-62.28%. Linear regression analysis showed that the magnitude of cross-talk increased linearly (r2 = 0.857-0.90) with the levels of grip force for all the muscle groups. The amount of cross-talk showed weak positive and negative correlations (r2 = 0.016-0.216) with the circumference and length of the forearm respectively, between the muscles at 100% MVIC. The cross-talk values significantly differed among the MMG signals due to: limb tremor (MMGTF), slow firing motor unit fibers (MMGSF) and fast firing motor unit fibers (MMGFF) between the muscles at 100% MVIC (p<0.05, η2 = 0.47-0.80). Significance The results of this study may be used to improve our understanding of the mechanics of the forearm muscles during different levels of the grip force.
  • Publication
    Cylindrical shape slug heat conduction numerical analysis using copper material
    ( 2013)
    High power light emitting diodes have the edge over the conventional lighting system in terms of efficiency, low energy consumption and long operational lifetime. Nevertheless, the heat dissipation issue of the high power LED bottlenecks the fulfilment of the potential possessed by the LED. The heat dissipation of LED is evaluated in terms of junction temperature. In this work, simulation was carried out to evaluate the heat dissipation of a single chip LED attached to a copper based cylindrical heat slug. The junction temperature and the stress of the LED chip were scrutinized under natural convection condition with applied input power of 0.1 W and 1 W. Ansys version 11 was utilized for the simulation. For input power of 1 W, the maximum junction temperature and Von Mises of 117.44°C and 229.21MPa was exhibited by the GaN based chip.
  • Publication
    Data-driven audiogram classifier using data normalization and multi-stage feature selection
    (Elsevier, 2023)
    Abeer Elkhouly
    ;
    Allan Melvin Andrew
    ;
    Nidhal Abdulaziz
    ;
    Hasliza A Rahim @ Samsuddin
    ;
    Mohd Fareq Abd Malek
    ;
    Shafiquzzaman Siddique
    Audiograms are used to show the hearing capability of a person at different frequencies. The filter bank in a hearing aid is designed to match the shape of patients’ audiograms. Configuring the hearing aid is done by modifying the designed filters’ gains to match the patient’s audiogram. There are few problems faced in achieving this objective successfully. There is a shortage in the number of audiologists; the filter bank hearing aid designs are complex; and, the hearing aid fitting process is tiring. In this work, a machine learning solution is introduced to classify the audiograms according to the shapes based on unsupervised spectral clustering. The features used to build the ML model are peculiar and describe the audiograms better. Different normalization methods are applied and studied statistically to improve the training data set. The proposed Machine Learning (ML) algorithm outperformed the current existing models, where, the accuracy, precision, recall, specificity, and F-score values are higher. The reason for the better performance is the use of multi-stage feature selection to describe the audiograms precisely. This work introduces a novel ML technique to classify audiograms according to the shape, which, can be integrated to the future and existing studies to change the existing practices in classifying audiograms.
  • 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.