Liyana Zahid
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Liyana Zahid
Official Name
Liyana, Zahid
Alternative Name
Zahid, Liyana
Zahid, L.
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Scopus Author ID
55626247800

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Cylindrical Dielectric Resonator as Dielectric Matching on Microwave Amplifier for the Unconditionally Stable and Conditionally Stable Transistor at 5 GHz Frequency

2022-12-01 , Rashidah Che Yob , Mahyuddin N.M. , Ain M.F. , Mohd Aminudin Jamlos , Nur Hidayah Ramli , Norfatihah Bahari , Mohd Wafi Nasrudin , Liyana Zahid

Stability and matching techniques on microwave amplifier have been an important consideration to maintain their required performances, but typically its frequency dependent. Thus, a frequency variable mechanism is required. The dielectric matching employing the stability and matching techniques on microwave amplifier with cylindrical dielectric resonator has been investigated and realized. The cylindrical dielectric resonator (CDR) with parallel microstrip lines is proposed at 5 GHz frequency for unconditionally stable and conditionally stable transistor as dielectric matching. Hence, the proposed dielectric resonator with +2 mm spacing and 155Ëš of curved configuration indicated the best performances for preliminary study. The result improves the performance of the parallel inhomogeneous CDR by 9.77%. Subsequently, the homogeneous CDR is also successfully working as the variable frequency mechanism for unconditionally stable and conditionally stable transistor at 5 GHz frequency in maintaining their stability performances.

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Left-Handed Metamaterial Wearable Antenna at 5G Frequency Range for Wireless Body Area Network

2023-01-01 , Ramli N.H. , Lokman M.A.F. , Norfatihah Bahari , Liyana Zahid , Rashidah Che Yob , Mohd Hafizuddin Mat , Mohd Aminudin Jamlos , Alzubaidi L.H. , Hussein A.H.A.

Wearable antennas are typically required to be small in weight, provide high bandwidth, high gain and efficiency, low price, and be installation-free for many modern applications. Due to the non-static human movement, an antenna with wide-angle scanning is necessary. This project is carried out by designing a small metamaterials wearable antenna at a 5G frequency range. The combination of left-handed metamaterial (LHM) and the wearable antenna is designed to operate for such a system. Results prove that the small wearable metamaterial antenna offers good performances where the gain is 5.8 dBi with an efficiency of 91.86% and provides an omnidirectional radiation pattern compared to the wearable antenna without LHM structure. The communication links of the antenna between the base station and the human body are investigated. The antenna can receive the signals for long distances may be up to 2 meters with wide angles. All the results will be a guideline while designing the systems in the future.

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A switchless pentagon-shaped reconfigurable antenna for radar applications

2020 , Norfatihah Bahari , Rashidah Che Yob , Liyana Zahid

This paper proposes a switchless pentagon-shaped microstrip patch antenna for radar and radionavigation applications. The antenna is built on Rogers RT5880 substrate with five rectangular radiating elements on top. Five ports have been set up to operate at 13.5 GHz resonant frequency. Besides having reflection coefficient below -10 dB, the antenna also offers high gain when about 8.29 dB is achieved. The proposed antenna also has a bi-directional radiation pattern with 360° of beam steering.

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Design of multiple-layer microwave absorbing structure based on rice husk and carbon nanotubes

2017-01-01 , Lee Yeng Seng , Wee Fwen Hoon , Hasliza A Rahim @ Samsuddin , Mohamed Fareq AbdulMalek , Kok Yeow You , Liyana Zahid , Muhammad Ezanuddin Abdul Aziz

This paper presents a multiple-layered microwave absorber using rice husk and carbon nanotube composite. The dielectric properties of each layer composite were measured and analysed. The different layer of microwave absorber enables to control the microwave absorption performance. The microwave absorption performances are demonstrated through measurements of reflectivity over the frequency range 2–18 GHz. An improvement of microwave absorption <−20 dB is observed with respect to a high lossy composite placed at bottom layer of multiple layers. Reflectivity evaluations indicate that the composites display a great potential application as wideband electromagnetic wave absorbers.

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Review on Patch Antennas for Unmanned Aerial Vehicle Application

2023-11-01 , Nur Hidayah Ramli , Seng L.Y. , Liyana Zahid , Hazry Desa

The wide-ranging Unmanned Aerial Vehicle (UAV) applications make them one of the Internet of Things promising technologies. The vast potential of monitoring and surveillance for public safety threats using drones is a current issue for researchers. Antennas play an important part in UAV to create reliable communication links. There are different types of antennas that can be used for UAV application depending on antennas size, efficiency, gain, angle of radiation pattern, polarization, etc. This paper mainly focuses on patch antennas for UAV applications. In general, there are two types of patch antenna described which are single patch antenna and array antenna. The review of patch antennas can be a useful guideline to choose or design antenna for UAV applications in the future.

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Design and development of microwave absorber using waste materials

2017 , Liyana Zahid

Sugarcane bagasse is a potential agricultural waste to design the pyramidal microwave absorber to be used in radio frequency (RF) anechoic chamber for testing application. An RF anechoic chamber is a shielded room covered with absorbers to eliminate unwanted reflection signal. In this work, sugarcane bagasse from the sugar industry and rubber tire dust from tire wear have been used. Both of the wastes have lossy carbon contents naturally, which has made them suitable as the raw materials for the fabrication of the low cost microwave absorbers. The dielectric constant of the sugarcane bagasse had been measured using the Dielectric Probe Technique and Software of Agilent 85071E using Transmission Line Technique. Microwave absorbers are made of two main components, a filler material that does the absorption, and a material matrix to hold the filler. In dielectric materials, the most crucial properties that enable them to be applicable as microwave absorbers are the dielectric constant and the loss factor which is the dissipation of energy in the material. Generally, dielectric material absorbers are fabricated by the combination of fillers in a polymer matrix. In this work, the fillers are the agricultural waste which is sugarcane bagasse (SCB) and rubber tire dust (RTD) from tire wear whereas the polymer matrix is unsaturated Polyester Resin RP9509 (UPR) which is rigid, flexible and electromagnetically transparent polymer. In this work, the sugarcane bagasse also has been mixed with rubber tire dust (RTD) to investigate their performance. The microwave absorber using sugarcane bagasse had been designed and simulated in the CST Microwave studio software. The measurement of waveguide technique has been used to check the reflectivity performance. The microwave absorber has been investigated in microwave frequency range between 1 GHz to 18 GHz. The results show that the sugarcane bagasse has the potential used as the base material in developing the microwave absorber and can operate in that range of frequency successfully. The adding of the filler which is rubber tire dust increased the performance of the microwave absorber. These absorbers were designed on the basis of the wave attenuation and depth of penetration data and their EMC performance was evaluated in terms of bi-static reflectivity performance. The performance of the absorbers was found to be below -10 dB. The different concentration of the filler were being measured and the reflectivity was found to be better then -20 dB when the increasing value of rubber tire dust were added.

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Dual-Band MIMO Decagonal C-Shaped CSRR Metamaterial Textile Antenna for WLAN and 5G Applications

2023-01-01 , Mashagba H.A. , Hasliza A Rahim @ Samsuddin , Mohd Najib Mohd Yasin , Narongkul S. , Liyana Zahid , Nur Hidayah Ramli

This study proposed an enhanced two-port dual-band textile Multiple-Input Multiple-Output (MIMO) antenna integrated with a metamaterial unit cell of symmetric decagonal C-shaped Complementary Split-Ring Resonator (CSRR) structure in terms of gain. The proposed MIMO antenna achieves an impedance bandwidth of 6.3% and a maximum up to 18.2% for lower and upper bands, respectively, at port 1. Mutual Coupling (MC) of less than -20 dB for both ports is obtained. The proposed antenna offers high realized gain of 5.6 dBi and 8 dBi at 2.45 GHz and 3.5 GHz, respectively, compared to existing dual-band MIMO textile antenna. Good diversity characteristics in respect of Envelope Correlation Coefficient (ECC) less than 0.001, and Diversity Gain (DG) of about 10 dB are achieved.

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