Zahriladha Zakaria
Universiti Teknikal Malaysia Melaka (UTeM)

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Journal : TELKOMNIKA (Telecommunication Computing Electronics and Control)

A Compact Reconfigurable Dual Band-Notched Ultra-Wideband Antenna using Varactor Diodes Sam Weng Yik; Zahriladha Zakaria; Herwansyah Lago; Noor Azwan Shairi
TELKOMNIKA (Telecommunication Computing Electronics and Control) Vol 16, No 6: December 2018
Publisher : Universitas Ahmad Dahlan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12928/telkomnika.v16i6.11552

Abstract

In this paper, a reconfigurable dual band-notched ultra-wideband (UWB) antenna is presented. The antenna design consists of a circular shape with two pairs of the L-resonator. To realize the notch characteristics in WLAN at 5.2 GHz and 5.8 GHz bands, the half wavelength of the L-resonator is introduced in the design. The T-shaped notch is etched in the ground to enhance the bandwidth which covers the UWB operating frequency range from 3.219 – 10.863 GHz. The proposed reconfigurable dual band-notched UWB antenna shows good impedance matching for the simulated in the physical layout. Furthermore, the proposed antenna has a compact size of 37.6 x 28 mm2. This proposed reconfigurable design can provide an alternative solution for the wireless system in the designing of a band-notched antenna with a good tuning capability.
Dual-band aperture coupled antenna with harmonic suppression capability Faza Syahirah Mohd Noor; Zahriladha Zakaria; Herwansyah Lago; Maizatul Alice Meor Said
TELKOMNIKA (Telecommunication Computing Electronics and Control) Vol 17, No 1: February 2019
Publisher : Universitas Ahmad Dahlan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12928/telkomnika.v17i1.11598

Abstract

The paper presents an aperture-coupled dual-band linearly-polarized antenna with harmonic suppression capability, operating at frequency 2.45 GHz and 5.00 GHz. In purpose of improving the directivity of antenna at the operating frequency of 2.45 GHz and 5.00 GHz, a modified inverted π-shaped slot-etched patch on the lower layer of the stacked antenna is introduced alongside the 50 Ω feed line. The harmonic suppression capability is achieved by the introduction of U-slot and asymmetrical left-right-handed stub at the transmission feed line, suppressing unwanted harmonic signals from 6.00 GHz up to 10.00 GHz. The final design of the antenna has produced very good reflection coefficient of -18.87 dB at 2.45 GHz and -19.57 dB at 5.00 GHz with third and higher order harmonic suppression up to -4 dB.
Energy-efficient user association mechanism enabling fully hybrid spectrum sharing among multiple 5G cellular operators Mothana L. Attiah; A. A. Md Isa; Zahriladha Zakaria; Ahmed M. Dinar; M . K. Abdulhameed; Mowafak K. Mohsen
TELKOMNIKA (Telecommunication Computing Electronics and Control) Vol 17, No 6: December 2019
Publisher : Universitas Ahmad Dahlan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12928/telkomnika.v17i6.13058

Abstract

Spectrum sharing (SS) is a promising solution to enhance spectrum utilization in future cellular systems. Reducing the energy consumption in cellular networks has recently earned tremendous attention from diverse stakeholders (i.e., vendors, mobile network operators (MNOs), and government) to decrease the CO2 emissions and thus introducing an environment-friendly wireless communication. Therefore, in this paper, joint energy-efficient user association (UA) mechanism and fully hybrid spectrum sharing (EE-FHSS) approach is proposed considering the quality of experience QoE (i.e., data rate) as the main constraint. In this approach, the spectrum available in the high and low frequencies (28 and 73 GHz) is sliced into three portions (licensed, semi-shared, and fully-shared) aims to serve the users (UEs) that belong to four operators in an integrated and hybrid manner. The performance of the proposed QoE-Based EE UA-FHSS is compared with the well-known maximum signal-to-interference-plus-noise ratio (max-SINR UA-FHSS). Numerical results show that remarkable enhancement in terms of EE for the four participating operators can be achieved while maintaining a high degree of QoE to the UEs.
Switchable dual-band bandpass filter based on stepped impedance resonator with U-shaped defected microstrip structure for wireless applications Mussa Mabrok; Zahriladha Zakaria; Yully Erwanti Masrukin; Tole Sutikno; A. R. Othman; Nurhasniza Edward
TELKOMNIKA (Telecommunication Computing Electronics and Control) Vol 17, No 2: April 2019
Publisher : Universitas Ahmad Dahlan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12928/telkomnika.v17i2.11637

Abstract

This paper presents a new technique in designing the switchable dual-band bandpass filter at 2.4 GHz and 3.5 GHz for WLAN and WiMAX applications. Wideband bandpass filter designed based on stepped impedance resonator at frequency of 3 GHz. To eliminate the interference from existing system that operates in the same frequency band, a defected microstrip structure applied and implemented to produce the notch response. In order to generate the switchable characteristic, the PIN diode was introduced at the dual-band filter. It exhibits that the measured results for switchable attributes when the diode is at OFF state, the wide passband is produced with the fractional bandwidth of 62.1 % centered at 2.9 GHz. Meanwhile, for the diode in ON state, the dual-passband has produced which centered at 2.5 GHz and 3.45 GHz. The experimental results showed good agreement with the simulation results. This structure is very useful for wireless communication systems and its applications.
Using Alpha-cuts and Constraint Exploration Approach on Quadratic Programming Problem Yosza Dasril; Zahriladha Zakaria; Ismail Bin Mohd
TELKOMNIKA (Telecommunication Computing Electronics and Control) Vol 16, No 6: December 2018
Publisher : Universitas Ahmad Dahlan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12928/telkomnika.v16i6.11584

Abstract

In this paper, we propose a computational procedure to find the optimal solution of quadratic programming problems by using fuzzyalpha-cuts and constraint exploration approach. We solve the problems in the original form without using any additional information such as Lagrange’s multiplier, slack, surplus and artificial variable. In order to find the optimal solution, we divide the calculation in two stages. In the first stage, we determine the unconstrained minimization of the quadratic programming problem (QPP) and check its feasibility. By unconstrained minimization we identify the violated constraints and focus our searching in these constraints. In the second stage, we explored the feasible region along side the violated constraintsuntil the optimal point is achieved. A numerical example is included in this paper to illustrate the capability of alpha-cuts and constraint exploration to find the optimal solution of QPP.
Analysis and investigation of a novel microwave sensor with high Q-factor for liquid characterization Ammar Alhegazi; Zahriladha Zakaria; Noor Azwan Shairi; Tole Sutikno; Rammah A. Alahnomi; Ahmed Ismail Abu-Khadrah
TELKOMNIKA (Telecommunication Computing Electronics and Control) Vol 17, No 2: April 2019
Publisher : Universitas Ahmad Dahlan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12928/telkomnika.v17i2.11901

Abstract

In this paper, a new design of microwave sensor with high Q-factor for liquid characterization is analyzed and investigated. The new microwave sensor is based on a gap waveguide cavity resonator (GWCR). The GWCR consists of upper plate, lower plate and array of pins on the lower plate. The liquid under test (LUT) is characterized by placing it inside the GWCR where the electric field concentrates using a quartz capillary that is passing through microfluidic channels. The results show that the proposed sensor has a high Q-factor of 4832. Moreover, the proposed sensor has the ability to characterize different types of liquids such as oils, ethanol, methanol and distilled water. The polynomial fitting method is used to extract the equation of the unknown permittivity of the LUT. The results show that the evaluated permittivity using the proposed sensor has a good agreement with the reference permittivity. Therefore, the proposed sensor is a good candidate for food and pharmaceutical applications.
Enhanced Antenna Design for Rectenna Application in the 2.45 GHz ISM Band Sharif Ahmed; Zahriladha Zakaria; Mohd Nor Husain; Azahari Salleh; Ammar Alhegazi
TELKOMNIKA (Telecommunication Computing Electronics and Control) Vol 14, No 4: December 2016
Publisher : Universitas Ahmad Dahlan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12928/telkomnika.v14i4.4137

Abstract

In this paper a two layers microstrip antenna design at 2.45 GHz ISM band with Harmonic rejection filter embedded on the ground plane is presented. The two roger substrates with relative permittivity of 2.2 are separated by an air gap which enhances the antenna gain. The design is simulated using Computer Simulation Technology (CST) Studio Suite 2015. Different aperture couplings slots such as rectangular and triangular aperture coupling slots are studied and compared. It is found that the antenna with triangular aperture coupling slot enhances the antenna performance by suppressing 2nd and 3rd harmonics at 5 GHz and 8 GHz, respectively, increasing the antenna gain and providing a better circular polarization behavior. The simulated antenna design achieves a gain of 9 dB, return loss of -23.6dB, axial ratio of 1.27dB and axial-ratio bandwidth of 40.8% (2 ~ 3 GHz). The proposed antenna shows an enhancement in the antenna performance which makes it a suitable candidate for rectifying antenna or rectenna application as it can increase the total conversion efficiency resulting in a high output DC voltage used to power low power electronic and electrical devices such as wireless sensor.
Hybrid multi-independent mmWave MNOs assessment utilising spectrum sharing paradigm for 5G networks Mothana L. Attiah; A. A. Md Isa; Zahriladha Zakaria; M. K. Abdulhameed; Mowafak K. Mohsen; Ahmed M. Dinar
TELKOMNIKA (Telecommunication Computing Electronics and Control) Vol 17, No 3: June 2019
Publisher : Universitas Ahmad Dahlan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12928/telkomnika.v17i3.11131

Abstract

Spectrum sharing paradigm (SSP) has recently emerged as an attractive solution to provide capital expenditure (CapEx) and operating expenditure (OpEx) savings and to enhance spectrum utilization (SU). However, practical issues concerning the implementation of such paradigm are rarely addressed (e.g., mutual interference, fairness, and mmWave base station density). Therefore, in this paper, we proposed ultra-reliable and proportionally fair hybrid spectrum sharing access strategy that aims to address the aforementioned aspects as a function of coverage probability (CP), average rate distributions (ARD), and the number of mmWave base stations (mBSs). In this strategy, the spectrum is sliced into three parts (exclusive, semi-pooled, and fully pooled). A typical user that belongs to certain operator has the right to occupy a part of the spectrum available in the high and low frequencies (28 and 73 GHz) based on an adaptive multi-state mmWave cell selection scheme (AMMC-S) which associates the user with the tagged mBS that offers a highest SINR to maintain more reliable connection and enrich the user experience. Numerical results show that significant improvement in terms of ARD, CP, fairness among operators, and maintain an acceptable level of mBSs density.
2.45 GHz rectenna with high gain for RF energy harvesting Maizatul Alice Meor Said; Zahriladha Zakaria; Mohd Nor Husain; Mohamad Harris Misran; Faza Syahirah Mohd Noor
TELKOMNIKA (Telecommunication Computing Electronics and Control) Vol 17, No 1: February 2019
Publisher : Universitas Ahmad Dahlan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12928/telkomnika.v17i1.11592

Abstract

This paper presents a high gain rectenna at 2.45 GHz. Two layers low cost FR4 substrate has been used with air-gap technology for this fabricated rectenna. The proposed designs contain antenna and  open stub rectifying circuits with feedline. With the dimension of 100 x 100 x 5 mm3, this rectenna can perform high gain. The technique of air gap approach has been used for this proposed rectenna design so as to increase the antenna gain. Second and third harmonics has been eliminated by the introducing of triangular slot and ground plane to the developed design. The proposed rectenna successfully achieved the output voltages reaches 0.46 V when the input power is 0 dBm respectively when  the input power range is between -25 to 30 dBm. It is also can reach up to 6V when the maximum input power is applied. High gain, simple design, low profile and easy integration are the main advantages of this design of the rectenna when compared to past researchers.