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Articles by N. Misran
Total Records ( 13 ) for N. Misran
  M. Abdullah , A.F.M. Zain , M.H. Jusoh , N. Misran and W.A. Mubarak
  Problem statement: Ionospheric precursors of earthquake have been studied by scientists and seismologists. This study aims at examining the relationship between the ionosphere and earthquake precursors. The effects of the anomalous electric field that penetrates the ionosphere on the electron concentration can be measured experimentally. This study reports on the variability of the Total Electron Content (TEC) during the December 26, 2004 earthquake in North Sumatra (epicentre: 3.295°N, 95.982°E) which measured 9.3 on the Richter scale. Approach: The ionospheric TEC near North Sumatra between December 19 to 31 was calculated between 22:00 and 24:00 and between 02:00 and 06:00 local time (LT) using a dual frequency Global Positioning System (GPS) receiver. It was recorded for a period of 13 days, which is seven days before and five days after the earthquake. The GPS data was taken from the Department of Survey and Mapping Malaysia in the north of Malaysia (4.1°N, 99.8°E), which is near North Sumatra. Four sets of data were selected from different GPS satellites that passed near the epicentre. Results: Results show good agreement with the existence of earthquake precursors. TEC variability was detected at night and in the early morning of 21 December 2004 (five days before the earthquake) and 25 December 2004 (a day before). Findings show an increase in the electron concentration level at the station closest to the epicentre and the TEC varies from 2-10 TEC unit. Conclusion/Recommendations: The findings correspond with previous research and literature in this field. Further studies on the parameters that cause the change in the ionospheric TEC due to earthquakes are needed if this is to be used as part of an earthquake early warning prediction system.
  M.T. Islam , N. Misran and A.T. Mobashsher
  A new design of dual band compact microstrip antenna is proposed for Ku-band applications. Dual band is achieved using three pairs of thin slits from the sides of a rectangular patch and feeding with a microstrip feedline. The antenna has a compact structure and the total size is 9.50 by 10 by 0.254 mm. The result shows that the return loss of -23.83 dB is achieved at the first resonant frequency of 12.54 GHz and -14.04 dB is obtained at the second resonant frequency of 14.15 GHz. The antenna gives a stable radiation performance with gain greater than 4 dBi over the frequency band.
  M.T. Islam , N. Misran , M.N. Shakib and Y. Bahrin
  In this study, a new Compact Coplanar Waveguide (CPW) fed antenna is presented. The impedance matching and the radiation characteristics of this proposed structure is studied using method of moment techniques. The proposed antenna is based on CPW feed configuration with C shaped patch and two notches. The achievable bandwidth of the proposed antenna obtained about 400 MHz (5.02-5.42 GHz) at -10 dB return loss which corresponds to WLAN 5.2 GHz frequency band and the achievable gain is 8.5 dBi. Stable radiation characteristics are obtained across the operating band.
  M.T. Islam , N. Misran , M.N. Shakib and M.N.A. Zamri
  In this study, a new compact Circularly Polarized (CP) antenna is presented. The impedance matching and the radiation characteristics of this proposed structure is studied using method of moment techniques. The proposed antenna is based on L-probe fed with thick air-filled substrate, truncated corners and two L-shaped slits on the patch. The achievable bandwidth of the proposed antenna obtained is 27% (2.14-2.81 GHz) at -10 dB return loss. The radiation pattern of the antenna shows that the antenna radiates in Right Hand Circular Polarization (RHCP) with achieving an Axial Ratio (AR) bandwidth of 4.3% at 3 dB and a maximum gain of 8.7 dBi. The proposed antenna is suitable for the application in Wireless Local Area Network (WLAN) 2.4 GHz frequency band. The details of the proposed design method is presented and discussed.
  M.T. Islam , R. Azim and N. Misran
  The design of a dual linearly polarized patch antenna for Ku-band is presented in this study. The square patch with triangular slots is adopted in this design. The antenna has a compact structure and the total size is 15x15 mm2. The result shows that the impedance bandwidth (VSWR≤2) of the proposed antenna is 6.0% (from 14.13 to 15 GHz). The antenna has achieved a stable radiation performance with a maximum gain of 6.2 dBi in the operating band. The present design provides a good isolation level between the two ports and a stable cross polarization level around -14 dB for both E- and H-planes. Details of the proposed antenna design and results are presented and discussed. The patch shows a high matching level in Ku-band and isolation elements that makes it suitable for satellite communication.
  A.L. Yusof , M. Ismail and N. Misran
  The objective of this research is to propose an adaptive handoff algorithm which can effectively deal with hotspot cells in next-generation cellular networks. Under the proposed algorithm, the signaling burden is evenly distributed and the regional network boundary is dynamically adjusted according to the traffic load, handoff type and speed of mobiles in advance, before handoff execution. A simulation model is developed to investigate the handoff performance. The simulation results find that the proposed algorithm is better than traditional handoff algorithm. Therefore, this algorithm enhances the service quality of users by flexibly manage the overloaded cells.
  A. Saad , M. Ismail and N. Misran
  This research aims to study the effect of Channel State Information (CSI) at the transmitter on the overall channel capacity. The capacity of MIMO correlated Rayleigh channels for different antenna configurations with and without channel knowledge (CSI) at the transmitter is simulated. When CSI is available at the transmitter (i.e., informed transmitter), waterfilling algorithm is used to allocate the power among the transmitter antennas. Simulations show that capacity is improved significantly when CSI is known at the transmitter. It also shows that the lack in channel knowledge (i.e., uninformed transmitter) can be compensated for by increasing the number of antennas in the receiver (Mr). When the number of antennas in the transmitter is larger than those in the receiver, using waterfilling becomes necessary to get the optimum capacity.
  M. Tariqul Islam and N. Misran
  In this study, a Matrix Inversion Normalized Least Mean Square (MI-NLMS) adaptive beamforming algorithm is described with tracking. The MI-NLMS was developed by combining the Sample Matrix Inversion (SMI) and the Normalized Least Mean Square (NLMS) algorithms taking the individual good aspects of both algorithms. Simulation results showed that the improvement in Bit Error Rate (BER) performances is proportional to the number of antenna elements employed in the antenna array. The MI-NLMS algorithm demonstrates an outstanding tracking ability with respect to LMS algorithm in the various signal environments.
  F. Sayadi , M. Ismail , N. Misran and K. Jumari
  In this study, tunnels radio coverage utilizing leaky coaxial cable has been described. This cable can be deployed as a base station antenna for indoor wireless system such as tunnels. The older type of leaky cables is called coupled mode, while latest type is called radiation mode. These two modes can be distinguished by their radiation pattern, method of radiation (i.e., wave or energy) and class of slot on outer conductor. To obtain the field radiation patterns, we use two models; diffuse and deterministic models. Then a modified ray tracing algorithm has been used and simulated to predict radio coverage in tunnels by leaky cable deployment. Simulations show that leaky cables achieve better RF coverage than distributed antennas in term of received signal level versus frequency for various lengths and cross section of tunnels.
  N. Misran , M. Tariqul Islam and K.J. Ng
  This research presents a beamforming feed network for a novel E-H shaped microstrip patch antenna array. The broadband microstrip antenna array was developed based on the novel L-probe fed inverted hybrid E-H (LIEH) shaped element design arranged into 4x1 uniform linear array antenna, fed by a feed network. The corporate 4-ways Wilkinson power divider which was fabricated in-house covering the frequency range from 1.83-2.29 GHz (460 MHZ) were integrated to form the beamforming feed network. The beamforming feed network comprises of commercial variable attenuators (KAT1D04SA002), variable phase shifters (KPH35OSC000) and the corporate 4-ways Wilkinson power divider which was developed in-house. The developed 4-ways Wilkinson power divider achieves bandwidth of 22.33% at VSWR 1.25. The measured isolation and insertion loss are 30.72 and 0.32 dB correspondingly. The feed network developed and fabricated in-house has been shown to function well within its design ability.
  M. Salem , M. Ismail and N. Misran
  The indoor wireless environments suffer from the coverage disconnection. The trends in the future wireless networks are to enable the mobile terminal to be connected anytime and anywhere. An efficient location management will solve the problem of frequent location registration in the small area of indoor environment. This study treats the problem by developing an indoor location registration with sequential paging algorithm for future heterogeneous wireless networks. The algorithm is based on the RSS signal that received from the surrounding sources. The proposed algorithm has been compared with conventional registration with blanket paging algorithm in terms of the performed location registration and paging messages.
  M. Ramli , A. Selamat , N. Misran , M.F. Mansor and M.T. Islam
  The design of reconfigurable reflectarray with a single varactor to provide capacitance effect embedded inter-patch are presented. The essence of this concept lies in the behavior of the capacitance variation contributes to phase changes of element. Simulated radiation patterns with single element phase characteristics as a reference are reported to demonstrate reconfigurability of elements for beam scanning at Ku-band. The consistency in pattern and value of single and 2x2 sub-array will provide guideline and indicator on how to get promising beam scanning result for full reflectarray fabrication and measurement. The radiation pattern of linear array by three different elements with 35° scanning angle at Ku-band is analyzed and has confirmed the important of single and sub-array characteristics in array realization.
  A. Selamat , M. Ramli , N. Misran , M.F. Mansor and S.H. Zaidi
  A low profile solar cell integrated with reflectarray element composed of multilayer materials is presented in this study. A unit cell consist of triangular loop shape element is varied in size to get the required phase range. Some modification is then introduced to the triangular loop element aimed to optimize the bandwidth. A wide bandwidth range over 15% has been achieved. A prototype of the solar reflectarray cell was fabricated and measured. The measured results show good agreement with simulation. The element is designed to be operated at Ku-band frequency and formed a solar reflectarray antenna used for terrestrial applications.
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