Showing papers by "Norbahiah Misran published in 2010"

A Novel High-Gain Dual-Band Antenna for RFID Reader Applications

Abstract: A novel high-gain dual-band antenna for radio frequency identification (RFID) reader applications covering free ISM bands of 2.45 and 5.8 GHz is presented in this letter. The antenna is composed of a U-shaped copper strip with unequal arm, a printed rectangular ring, and the ground plane. A good impedance bandwidth of 120 MHz has been achieved from 2.37 to 2.49 GHz for the lower band, while the upper band covers 420 MHz (from 5.55 to 5.97 GHz). The U-shaped feeding strip excites the rectangular ring effectively by providing a good impedance matching with over 85% of total antenna efficiency in both the frequency bands and also 9.56 and 10.17 dBi gain in the lower and higher frequency band, respectively.

Stacked patch antenna with folded patch feed for ultra-wideband application

Abstract: A new stacked patch antenna with a folded patch feed is presented for ultra-wideband (UWB) application. The bandwidth is obtained by a stacked patch fed with a folded patch feed, and the size reduction is realised through the use of shorting wall. The antenna occupies a compact dimension of 0.340λ g ×0.340× g ×0.227× g (where λ g is the guided wavelength of the centre operating frequency). The design achieves an impedance bandwidth of 90% across the frequency range of 3.75%9.86%GHz. The details of the antenna designs are shown, and the results with low-profile characteristics make this antenna suitable for UWB applications.

Study of Specific Absorption Rate (SAR) in the human head by metamaterial attachment

Abstract: The reduction of Specific Absorption Rate (SAR) with metamaterial is performed by the finite-difference time-domain method (FDTD) with Lossy-Drude model by CST Microwave Studio in this paper. The metamaterials can be achieved by arranging split ring resonators (SRRS) periodically. The SAR value has been observed by varying the distances between head model to phone model, different width, different thickness, and different height of metamaterial design. Metamaterial has achieved 42.12% reduction of the initial SAR value. These results can endow with supportive information in designing the wireless communications equipments for safety compliance.

Printed Planar Antenna for Wideband Applications

Abstract: A compact planar antenna operating at a frequency range of 3–16 GHz is presented for wideband applications. The antenna is composed of a square patch fed by a microstrip line and a partial ground plane with a rectangular slot. The proposed antenna is very easy to be integrated with microwave circuitry for low manufacturing cost. The flat antenna has a compact structure and the total size is 29 mm × 22 mm. The result shows that the measured impedance bandwidth (VSWR≤ 2) of the proposed antenna is 3.2–15.44 GHz, with a notch from 4.7 to 5.8 GHz. The effects of the structure parameters on impedance bandwidth are also investigated. Details of the proposed compact planar antenna design are presented and discussed.

Effect of human head shapes for mobile phone exposure on electromagnetic absorption

Abstract: In this paper, the local Specific Absorption Rate (SAR) induced in spherical, cubical, and realistic human head models exposed to a mobile phone is investigated. Three human head models of the highest degree of different shapes but of almost the same volume are considered. Obtained local maximum SAR induced in these three human head models for homogeneous cases are established to have average differences of about 12% and 9% at 900 and 1800 MHz respectively. A comparison analysis of SAR induced in the realistic human head model for homogeneous and inhomogeneous cases are also discussed. From the results, it can be observed that the local maximum SAR induced in the homogeneous human head model is larger than that induced in the inhomogeneous human head model.

Evaluation of Specific Absorption Rate (SAR) Reduction for PIFA antenna Using Metamaterials

Abstract: This paper is analyzed the reduction of specific absorption rate (SAR) with metamaterials attachment. The SAR reduction methodology is discussed and the effects of attaching location, distance, and size of metamaterials, on the SAR reduction are explored. Metamaterials have achieved a 57.75 % reduction of the initial SAR value for the case of 10 gm SAR. Index Terms – antenna, human head model, lossy-Drude model, metamaterials, specific absorption rate (SAR).

Specific absorption rate analysis using metal attachment

Abstract: Specific absorption rate (SAR) reduction with metal attachment is analysed in this paper. The SAR reduction technique is discussed and the effects of attaching location, distance, and size of metal on the SAR reduction are investigated. The remarkable improvement has been achieved for SAR reduction of the initial SAR value for the case of 1 gm SAR. These results suggest a guideline to choose various types of metals with the maximum SAR reducing effect for a portable telephone. Analiza parametra SAR pri uporabi kovinske zaščite Kjučne besede: SAR, prenosni telefon, kovinski nastavek, zmanjšanje SAR Izvleček: V članku analiziramo vpliv kovinskega nastavka na zmanjšanje vrednosti parametra SAR. Raziščemo vpliv položaja, velikosti in razdalje le-tega na zmanjšanje SAR. Še poseben napredek smo dosegli v primeru 1gm SAR. Rezultati nam služijo kot smernica pri izbiri različnih vrst kovinskih materialov, ki najbolj vplivajo na zmanjšanje SAR pri uporabi prenosnega telefona. UDK621.3:(53+54+621+66), ISSN0352-9045 Informacije 40(2010)3, Ljubljana

Compact dual band microstrip antenna for Ku-band application

Abstract: 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.

Evaluation of em absorption in human head with metamaterial attachment

Abstract: ─ The reduction of electromagnetic (EM) absorption with metamaterial is performed by the finite-difference time-domain method with lossyDrude model by CST Microwave Studio in this paper. The metamaterials can be achieved by arranging split ring resonators (SRRS) periodically. The SAR value has been observed by varying the distances between head model to phone model, different distance, different thickness, and different size of metamaterial design. Metamaterial has achieved 53.94% reduction of the initial SAR value for SAR 10 gm. Index Terms ─ Antenna, human head model, lossy-Drude model, metamaterial, symmetry, SAR, SRRS.

Coplanar Waveguide Fed Printed Antenna with Compact Size for Broadband Wireless Applications

Abstract: A novel and simple coplanar waveguide fed compact antenna is introduced in this paper. The antenna structure combines the advantages of CPW with those of the broadband antenna and simplifies the structure of the antenna by reducing the number of metallization level to construct uni-planar antenna. Prototype of the proposed antenna have been constructed and studied experimentally. The measured results agrees well with the simulated prediction and shows a broad bandwidth of 6 GHz ranging from 3.5 GHz to 9.5 GHz with VSWR ≤2 (return loss ≤−10 dB), which is equivalent to 92.3% impedance bandwidth centered at 6.5 GHz. The proposed antenna shows stable radiation characteristics, gain and axial ratio of less than 1 dB over the whole operating bandwidth. Furthermore, an extensive parametric study was performed to realize the relationship between the resonance frequencies of the broadband antennas and different parameters which is helpful for advancement of the antenna design.

Printed circular ring antenna for UWB application

Abstract: A printed circular ring antenna for UWB application is proposed in this paper The antenna structure is composed of a circular ring patch and a partial ground plane The proposed antenna has a total size of 39 × 40 mm2 The measurement shows that the antenna has an impedance bandwidth (VSWR≤ 2) of 954 GHz (254 to 1208 GHz) A nearly stable bidirectional radiation pattern with low cross polarization makes the proposed antenna suitable for being used in wireless communication system Details of the proposed compact planar antenna design are presented and discussed

Design of microstrip patch antenna using novel U-shaped feeding strip with unequal arm

Abstract: A novel feeding technique is developed for the microstrip patch antenna. The U-shaped feeding strip with an unequal arm is proposed to feed a printed rectangular ring patch antenna to achieve high gain. Measured results of the prototype antenna agree very well with simulated results. According to the measured results, the antenna shows good impedance bandwidths satisfying ISM 2.45/5.8 GHz with good impedance matching. Stable radiation patterns are achieved with maximum gains of 9.56 and 10.17 dBi for both bands.

Compact planar antenna for UWB applications

Abstract: In this paper, a planar antenna for UWB applications has been proposed. The antenna consists of a square patch, a partial ground plane and a slot on the ground plane. The proposed antenna is easy to be integrated with microwave circuitry for low manufacturing cost. The flat type antenna has a compact structure and the total size is 14.5×14.5mm2. The result shows that the impedance bandwidth (VSWR≤ 2) of the proposed antenna is 12.49 GHz (2.95 to 15.44 GHz), which is equivalent to 135.8%. Details of the proposed compact planar UWB antenna design is presented and discussed.

High gain W-shaped microstrip patch antenna

Abstract: A high gain W-shaped microstrip patch antenna is proposed and experimentally investigated. The patch antenna employs a new inverted W-shaped patch structure with meander probe feed technique. A prototype of the proposed antenna is fabricated and tested for validation. This low-profile antenna is operating for the frequency band of 1.84GHz to 2.29GHz. It exhibits an impedance bandwidth (2:1 VSWR) of 21.79% and a high gain of 10.46dBi at the frequency of 2.11GHz. The measured result shows the stable radiation characteristics, including a low cross-polarization level below -20dB in both planes.

Dual Band Microstrip Patch Antenna for Sar Applications

Abstract: Microstrip patch antennas offer the advantages of thin profile, light weight, low cost, ease of fabrication and compatibility with integrated circuitry, so the antennas are widely used to satisfy demands for polarization diversity and dual-frequency. This paper presents a coaxilly-fed single-layer compact dual band (C- and X-band) microstrip patch antenna for achieving dual-polarized radiation suitable for applications in airborne synthetic aperture radar (SAR) systems. The designed antenna consists of three rectangular patches which are overlapped along their diagonals. Full-wave electromagnetic simulations are performed to accurately predict the frequency response of the antenna. The fabricated antenna achieves an impedance bandwidth of 154 MHz (f0 = 6.83 GHz) and 209 MHz (f0 = 9.73 GHz) for VSWR < 2. Simultaneous use of both frequencies should drastically improve data collection and knowledge of the targets in the SAR system.

A Novel Feeding Technique for a Dual Band Microstrip Patch Antenna

Abstract: In this paper, a novel feeding technique is proposed to feed a printed rectangular ring patch antenna that attains high gain in two bands simultaneously. The prototype antenna exhibits good impedance bandwidths satisfying ISM 2.45/5.8 GHz achieving maximum gain of 9.56 and 10.17 dBi, respectively, with a stable radiation pattern.

Design of material attachment for SAR reduction in human head

Abstract: In this paper, reducing specific absorption rate (SAR) with materials attachment is investigated. The finite-difference time-domain method with lossy-Drude model is adopted in this study. The methodology of SAR reduction is addressed and the effects of attaching location, distance, and size of ferrite sheet material on the SAR reduction are investigated. Materials have achieved a 47.68% reduction of the initial SAR value for the case of 1 gm SAR. These results suggest a guideline to choose various types of materials with the maximum SAR reducing effect for a phone model.

Compact wideband microstrip antenna for universal 5GHz wlan applications

Abstract: A microstrip-fed compact antenna with omnidirectional radiation patterns in the azimuth plane is proposed. It provides an impedance bandwidth of 41% (from 4.5 to 6.82GHz) below 10dB and below 14dB it attains 37.3% (from 4.62 to 6.74GHz), so that it easily covers the required universal 5GHz bandwidths for wireless local area network applications (WLAN) The proposed antenna is composed of a square spiral patch and a partial ground plane with a small rectangular stub. It occupies an area of only 14 × 15mm when printed on an FR4 substrate with a thickness of 1.6mm.

Assessment of specific absorption rate (SAR) and temperature increases in the human head of portable telephones

Abstract: The bioheat equation is solved for an anatomically based model of the human head with a resolution of 2.5× 2.5 ×2.5 mm to study the thermal implications of exposure to electromagnetic (EM) fields typical of cellular telephones at 900 MHz. Attention has first been posed on a particular phone model, and a comparison between the absorbed power distribution and steady-state temperature increases has been carried out. The antenna output power was set to be consistent with the portable telephones of 600 mW, maximum SAR values, averaged over 1 gm, from 2.1 to 3.6 W/kg depending on the considered phone. The maximum temperature increases are obtained in the ear and vary from 0.22 °C to 0.39 °C, while the maximum temperature increases in the brain lie from 0.07 °C to 0.17 °C. These steady-state temperature increases are obtained after about 48 min of exposure, with a time constant of approximately 6 min. Application of the ANSI/IEEE safety guidelines restricting the 1 gm averaged spatial peak SAR to 1.6 W/kg results in the maximum temperature rise in the brain from 0.07 °C to 0.15 °C at 900 MHz. Finally, considerations about the exposure limits in the considered frequency are made.

An efficient FPGA-based hardware implementation of MIMO wireless systems

Abstract: Emerging multiple-input multiple-output (MIMO) systems are regarded to play a key role in 4G wireless systems in order to achieve higher data rate while maximizing spectral efficiency. This paper presents a proficient hardware realization of MIMO systems that is designed and implemented on a Xilinx Virtex™-4 XC4VLX60 Field Programmable Gate Arrays (FPGA) device. The MIMO encoder implementation is straight forward; however, the decoder implementation is little more complex as it requires resource utilization. The hardware, presented in this paper, utilizes the resources by adopting the technique of parallelism. A comprehensive explanation of the complete design process is provided, including a highlight on the tools used in its development. The results are obtained for 2×2 MIMO system for encoding and decoding at the transmitter and the receiver. The system is developed based on modular design which simplifies system design, eases hardware update and facilitates testing the various modules in an independent manner.

Small multi-band microstrip antenna for wireless applications

Abstract: A simple microstrip line fed antenna with thin substrate is proposed in this letter for multi-band wireless applications. The multi-band characteristic was achieved by overlapping an annular slot antenna with two concentric fan shaped patches. The antenna demonstrates three wide impedance bandwidths (VSWR ≤ 2) of 36.3, 63.4 and 25.5% with stable polarization and radiation characteristics.

Traffic Driven Handoff Management Scheme for Next Generation Cellular Networks (NGCN)

Abstract: In NGCN, mobile users can move between heterogeneous networks. In this kind of environment, handoff management is the essential issue that supports the handoff of users between various wireless technologies. Handoff decision, one of the handoff management issues consists of finding the appropriate time to perform the handoff and which cell to hand over in cellular networks. Traditionally, the need for initiating the handoff arises when the RSS of the serving base station deteriorates below a certain threshold value. However, in a heterogeneous network environment, more criteria (not only RSS) are needed to initiate the appropriate time to perform the handoff. This research presents a traffic driven handoff management scheme which adopts a hard handoff scheme to adaptively control the handoff time according to the load status of cells. Before accepting a new user, it requests the load information of the target cell in advance before handoff execution. Then, the value of adaptive RSS is applied in the scheme to initiate the right handoff time. The results show that how the handoff initiation criteria might be set in accordance with the quality of services requested by users. It was found that the proposed scheme can support better service quality than the scheme compared. The scheme could efficiently manage overloaded traffic in the system.

Performance and Complexity Improvement of Least Squares Channel Estimation in MIMO Systems

Abstract: i in terms of bit error rate (BER). Simulation results indicate that the proposed method considerably improves the system performance and significantly reduces the complexity caused by matrix inversion. The performance and complexity of the proposed method clearly outperforms the conventional LS channel estimation method and proves itself a smart solution for MIMO channel estimation.

Design analysis of a dual frequency RFID reader antenna

Abstract: In this paper, the analysis of design, fabrication and measurement of a high gain dual frequency RFID reader antenna, proposed for ISM bands of 2.45GHz and 5.8GHz, is discussed with overall explanations. The antenna is composed of a U-shaped copper strip with unequal arm, a printed rectangular ring and the ground plane. The antenna operates over 2.37GHz to 2.49GHz, of 120MHz for the lower band; while the upper band exhibits good impedance bandwidth of 420MHz (from 5.55GHz to 5.97GHz), where return loss of -10dB is taken as the reference for both bands. The U-shaped feeding strip excites the rectangular ring effectively by providing a good impedance matching with over 98% of efficiency in both the frequency bands and also 9.56 and 10.17dBi gain in the lower and higher frequency band, respectively. Furthermore, the analytical parametric study facilitates more elaboration of the design and optimization processes for the antenna researchers.

An enhanced macro diversity handover technique for IEEE 802.16j

Abstract: In this paper, we propose an enhanced macro diversity handover (MDHO) technique for TDD-OFDMA-based interference-limited IEEE 802.16j multi-hop relay cellular networks. The proposed MDHO ensures that the topology of the diversity set members is always fully exploited. Evaluation results show that the proposed MDHO significantly outperforms the conventional MDHO and offers a CINR gain of as much as 4.13dB.

Reflectarray antenna with radar cross-section reduction

Abstract: This paper presents the design of a low RCS reflectarray at 8.52 GHz by replacing the solid metal sheet behind the antenna with a band stop frequency selective surface. A 50 element linear array of omni-directional elements was used to simulate the far field pattern of a reflectarray with f/D=0.325 in the plane of the elements to assess the effect of an imperfect aperture distribution on the gain and sidelobe levels. It is found that the reflection loss variation across the aperture does not have a significant effect on the radiation pattern of the antenna, because for the layout that was studied, only a few of resonant loops were predicted to give a significantly different loss than the others in the array. Simulated and measured results show that the ‘in-band’ reflection phase response of the structure with metal ground plane and with a periodic FSS ground plane is very similar, however the periodic ground plane reduces the ‘out of band’ reflectivity by more than 4 dB, thereby decreasing its RCS profile to these signals.