Norhawati Ahmad
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Preferred name
Norhawati Ahmad
Official Name
Norhawati, Ahmad
Alternative Name
Ahmad, Norhawati Binti
Ahmad, N.
Ahmad, Norhawati
Main Affiliation
Scopus Author ID
48661864200
Researcher ID
IAW-0777-2023

Research Output

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Remazol orange dye sensitized solar cell

2017-01-03 , Siti Salwa Mat Isa , Muhammad Mahyiddin Ramli , Nor Azura Malini Ahmad Hambali , Muda M.R. , Shahrir Rizal Kasjoo , Muammar Mohamad Isa , Nurul Izza Mohd Nor , Norhawati Ahmad , Nazuhusna Khalid , Nur M. Selamat , Nur Asyikin Mohd Anhar

Water based Remazol Orange was utilized as the dye sensitizer for dye sensitized solar cell. The annealing temperature of TiO2 working electrode was set at 450 °C. The performance of the device was investigated between dye concentrations of 0.25 mM and 2.5 mM at three different immersion times (3, 12 and 24 hours). The adsorption peak of the dye sensitizer was evaluated using UV-Vis-Nir and the device performance was tested using solar cell simulator. The results show that the performance was increased at higher dye concentration and longer immersion time. The best device performance was obtained at 0.2% for dye concentration of 2.5 mM immersed at 24 hours.

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Comprehensive study on gate recess step for the fabrication of high-speed InGaAs/InAlAs/InP pHEMT

2017-01-03 , Muammar Mohamad Isa , Norhawati Ahmad , Siti Salwa Mat Isa , Muhammad Mahyiddin Ramli , Nazuhusna Khalid , Nurul Izza Mohd Nor , Shahrir Rizal Kasjoo , Missous M.

We report a comprehensive etching study on the gate recess step for the fabrication of the novel high speed pHEMT devices. The experiments focused on the elimination of 'hump' structure as a result of an incomplete etching process at the InGaAs cap layer. In this work, two types of test samples were used, namely bulk InGaAs and epitaxial structure together with an etch stop layer. The result showed that the etch rate of bulk InGaAs is about 360 A/min and the percentage of dome height is consistent at approximately 25%. Meanwhile, the study on pHEMT epitaxial layer showed that the etching time of 3 minutes is sufficient in order to completely remove the cap layer. Gate leakage current of magnitude more than 10 times lower is observed on the devices that engaging Succinic Acid as the gate recess etching agent. The optimized processing steps will tailor for highly reproducible pHEMT fabrication process for high speed applications.

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Linear modelling of novel InGaAs/InAlAs/InP pHEMT for low noise applications

2017-01-03 , En A.Y. , Norhawati Ahmad , Muammar Mohamad Isa , Siti Salwa Mat Siti , Muhammad Mahyiddin Ramli , Nazuhusna Khalid , Nurul Izza Mohd Nor , Shahrir Rizal Kasjoo , Missous M.

Linear modelling of novel InGaAs/InAlAs/InP pHEMT for low noise applications is substantial to the future transistors that will operate in high speed and low noise conditions. The novel pHEMT is constructed by sandwiching two different materials together with different lattice constants, for instance InGaAs and InAlAs in order to form a heterojunction in between. However, InP is only utilised to be the substrate base of pHEMT. In the modelling process, extrinsic and intrinsic parameters need to be extracted. Briefly, a high accuracy transistor modelling enables designers to predict the real output of a circuit before it can be fabricated onto an actual chip.

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Low voltage low power FGMOS based current mirror

2017-11-22 , Nurulain D. , Musa F.A.S. , Muammar Mohamad Isa , Norhawati Ahmad , Shahrir Rizal Kasjoo

This paper presents the comparison of a conventional current mirror with the one utilizing floating gate MOSFET transistors (FGMOS) to achieve low power (LP) and low voltage (LV) design. The device structure has been simulated with 0.1μ CMOS technology and 1.2V voltage supply by using SAED 90nm PDK with the Synopsys Custom Designer tool. The FGMOS circuit has shown to have low power consumption of 9.62mW, smaller threshold voltage of 0.2V and Iout of 20 mA. The improvement of 40.1% from conventional current mirror has shown the LV and LP capability of FGMOS transistor.

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Review of mixer design for low voltage - Low power applications

2017-09-26 , Nurulain D. , Musa F.A.S. , Muammar Mohamad Isa , Norhawati Ahmad , Shahrir Rizal Kasjoo

A mixer is used in almost all radio frequency (RF) or microwave systems for frequency translation. Nowadays, the increase market demand encouraged the industry to deliver circuit designs to create proficient and convenient equipment with very low power (LP) consumption and low voltage (LV) supply in both digital and analogue circuits. This paper focused on different Complementary Metal Oxide Semiconductor (CMOS) design topologies for LV and LP mixer design. Floating Gate Metal Oxide Semiconductor (FGMOS) is an alternative technology to replace CMOS due to their high ability for LV and LP applications. FGMOS only required a few transistors per gate and can have a shift in threshold voltage (VTH) to increase the LP and LV performances as compared to CMOS, which makes an attractive option to replace CMOS.

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Design and analysis of two stage CMOS operational amplifier using 0.13 μm technology

2020-01-08 , Tan K.T. , Norhawati Ahmad , Muammar Mohamad Isa , Musa F.A.S.

Nowadays, low power operational amplifiers (op-amp) are highly demand for most of the applications such as in medical and communication system. In this project, two stage op-amp is designed and operated at 1.8 V supply voltage. The supply voltage is scaled down to reduce the power dissipation of the op-amp. This is because the power will be high when there is a large supply voltage. The design is simulated and analysed using Mentor Graphic Pyxis software. This two stage op-amp is designed using the Silterra 0.13 μm process technology. The operational amplifier provides a Direct Current (DC) gain of 21.18 dB and a unity gain bandwidth of 6.31 MHz. The gain margin obtained from the op-amp is 14.07 dB and the phase margin of the op-amp is 94.26 ° for 3 pF compensation capacitor and 10 pF load capacitor. The result shows that circuit able to work at 1.8 V power supply voltage and the total power dissipation for the op-amp is 5.35 mW.

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IoT Monitoring System for Fig in Greenhouse Plantation

2023-07-01 , Mohd Firdaus Ibrahim , Muammar Mohamad Isa , Razaidi Hussin , Syed Muhammad Mamduh Syed Zakaria , Norhawati Ahmad , Yuan C.K.J. , Abdullah A.F.T.

Fig is rich in nutrients and has a high market value due to its extensive application in promoting a nutritious food supply and supporting various medical disciplines. However, the equatorial climate in Malaysia poses significant difficulties for the large-scale cultivation of figs. Therefore, a Smart Monitoring System for controlled Greenhouse Plantation was proposed in this study to enable more efficient cultivation. The proposed system was equipped with LoRa and GSM to overcome the distance and data transmission limitations, developed using the Arduino Uno microcontroller. The proposed system consists of sensors to measure soil moisture, temperature, and humidity, while the data is transmitted using long-range LoRa communication to the control unit. The sensors circuit also has a solar power supply for convenient application in rural areas. The control unit is placed at a location with good data coverage. The system functioned well, and the monitoring parameter was accurately read, collected, and updated every 30 minutes. The optimal temperature, humidity, and soil moisture for growing fig is 22°C-33°C, > 60%, and 50%-60%, respectively. Real-time data monitoring enabled the sensors and control unit to achieve LoRa data transmission over a distance of 2.5 km. Any data exceeding the controlled parameters will trigger an alarm so that the user can perform corrective actions.

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Novel march WY approach for dynamic fault detection in memory BIST

2024-01 , Wan Ying Loh , Weng Fook Lee , Razaidi Hussin , Aiman Zakwan Jidin , Norhawati Ahmad , Nor Azura Zakaria

Dynamic fault detection has shown an increasingly important role in the DPM level for embedded memories in SoC. Memory testing is directly related to the reliability of the whole SoC since embedded memories occupy a large area in the SoC and are used to store data for application usage. However, it is essential to bring down the test complexity of the March-based test algorithm for dynamic fault detection to maintain the test time and expenses within an acceptable economic range. March WY1 (66n) is proposed as the minimal March algorithm targeting unlinked two-operation single-cell dynamic faults and double-cell faults of types Sw and Saa to enhance the test efficiency for dynamic fault detection in SRAM. The proposed March WY1 (66n) has reduced test complexity by 4n compared to the well-known March MD2 (70n) while maintaining the same 100% dynamic fault coverages.

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Film bulk acoustic wave resonator in 10-20 GHz frequency range

2017-01-03 , Nurul Izza Mohd Nor , Nazuhusna Khalid , Muhammad Mahyiddin Ramli , Muammar Mohamad Isa , Norhawati Ahmad , Siti Salwa Mat Isa , Shahrir Rizal Kasjoo

This paper presents the design and optimisation of film bulk acoustic wave resonator (FBAR) using nano electro mechanical systems (NEMS) technology in 10-20 GHz frequency band. The effect of thickness, width and length and damping factor of the FBAR are analysed. The air-gap FBAR are designed due its ability to achieve high quality (Q) factor in 10-20 GHz frequency band. The proposed designs achieve a constant electromechanical coupling coefficient for 10-20 GHz. Analysis shows the Q varies highly dependent on the damping factor. The results show that the proposed design achieves almost double the Q factor at 15 GHz and 20 GHz operation when compared to similar designs.

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Analytical Modeling of Depletion-Mode MOSHEMT Device for High- Temperature Applications

2024-01-01 , Islam N. , Packeer Mohamed M.F. , Norhawati Ahmad , Muammar Mohamad Isa , Rahim A.F.A. , Ahmeda K.

An analytical model for depletion-mode MOSHEMTs for high-temperature applications is compared against the experimental GaN HEMT data of the AlGaN/GaN MOSHEMT for temperature dependence of 2DEG simulated at 75 °C and 125 °C. Both temperatures reduce the 2DEG density by 4 %in the GaN HEMT and 3 %in the AlGaN/GaN MOSHEMT. The cause of this diminishing effect is determined to be the decrease of the conduction band offset at high temperatures. Additionally, the device performance degrades at high temperatures due to the immature behaviour of GaN material when it operates at high-power dissipation with poor thermal conductivity. The simulated AlGaN/GaN MOSHEMT performance is comparatively improved compared to the experimental AlGaN/GaN HEMT devices. This improvement could be used to understand the nature of the 2DEG density vs the temperature, hence could enhance the experimental performance of the AlGaN/GaN MOSHEMT.

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