Hasliza A. Rahim

Development of a New Approach for High-Quality Quadrupling Frequency Optical Millimeter-Wave Signal Generation Without Optical Filter

In this paper, we propose a new approach to generate quadrupling-frequency optical millimeter-wave (mm-wave) signal with carrier suppression by using two parallel Mach-Zehnder modulators (MZMs) in Radio-over-flber (RoF) system. Among the numerous properties of this approach, the most important is that a fllterless optical mm-wave at 60GHz with an optical sideband suppression ratio (OSSR) as high as 40dB can be obtained when the extinction ratio of the MZM is 25dB. Simplicity and cost-efiectiveness have made this approach a compelling candidate for future wave-division-multiplexing RoF systems. Theoretical analysis is conducted to suppress the undesired optical sidebands for the high-quality generation of frequency quadrupling mm-wave signal. The simulation results show that a 60GHz mm-wave is generated from a 15GHz radio frequency (RF) oscillator with an OSSR as high as 40dB and an radio frequency spurious suppression ratio (RFSSR) exceeding 35dB without any optical or electrical fllter when the extinction ratio of the MZM is 25dB. Furthermore, the efiect of the non-ideal RF-driven voltage as well as the phase difierence of RF-driven signals applied to the two MZMs on OSSR and RFSSR is discussed and analyzed. Finally, we

Low Complexity OFDM Modulator and Demodulator Based on Discrete Hartley Transform

The investigation on discrete Hartley transform (DHT) as an alternative to replace the conventional complex valued and mature discrete Fourier transform (DFT) as OFDM modulator and demodulator was carried out in this research. The random binary data was generated and transmitted via the dispersive channel with using additive white Gaussian noise(AWGN) channel model. The performance of the system was evaluated by calculating the number of bit errors for several value of signal to noise ratio (SNR). The measurements of parameters were repeated five times to obtain and to calculate the accuracy of the new system. The plotted graph of average BER verses SNR showed that the BER was decreased with the increasing of given value SNR. The analysis of system performance was also evaluated for several numbers of sub carriers used and the results showcased some advantages. The modification of DHT algorithm is expected to reduce the complexity and time consuming for long-length of computational on the performing of OFDM modulator and demodulator based on DHT.

Effect of different substrate materials on a wearable textile monopole antenna

In this paper the investigation of the effect using different substrate materials on a textile monopole antenna is discussed. This textile monopole antenna is designed to be used for Body-Centric Wireless Communications (BCWC) at 2.45 GHz. Three types of non-conductive materials were selected: felt, fleece and foam. The textile monopole was benchmarked against a conventional FR-4 monopole antenna. The results demonstrated a good agreement between simulated return loss of all three substrates used for textile monopole antenna and conventional monopole antenna. The felt-based textile monopole antenna offered higher return loss compared to other substrates and conventional monopole antenna. Moreover, the substrate materials gained bandwidths of up to 1000 MHz in free space where fleece fabric produced broader bandwidth compared to other substrates. The simulated gain characteristics for all three types of substrates agreed reasonably well with conventional monopole antenna.

Effect of Short-Term Mobile Phone Base Station Exposure on Cognitive Performance, Body Temperature, Heart Rate and Blood Pressure of Malaysians.

Individuals who report their sensitivity to electromagnetic fields often undergo cognitive impairments that they believe are due to the exposure of mobile phone technology. The aim of this study is to clarify whether short-term exposure at 1 V/m to the typical Global System for Mobile Communication and Universal Mobile Telecommunications System (UMTS) affects cognitive performance and physiological parameters (body temperature, blood pressure and heart rate). This study applies counterbalanced randomizing single blind tests to determine if sensitive individuals experience more negative health effects when they are exposed to base station signals compared with sham (control) individuals. The sample size is 200 subjects with 50.0% Idiopathic Environmental Intolerance attributed to electromagnetic fields (IEI-EMF) also known as sensitive and 50.0% (non-IEI-EMF). The computer-administered Cambridge Neuropsychological Test Automated Battery (CANTAB eclipseTM) is used to examine cognitive performance. Four tests are chosen to evaluate Cognitive performance in CANTAB: Reaction Time (RTI), Rapid Visual Processing (RVP), Paired Associates Learning (PAL) and Spatial Span (SSP). Paired sample t-test on the other hand, is used to examine the physiological parameters. Generally, in both groups, there is no statistical significant difference between the exposure and sham exposure towards cognitive performance and physiological effects (P’s > 0.05).

Hybrid multiobjective optimization using modified cuckoo search algorithm in linear array synthesis

In this study, we postulated the hybridization of modified cuckoo search (MCS) with two evolutionary algorithms (EAs), which were particle swarm optimization (PSO) and genetic algorithms (GA) in weighted-sum multiobjective optimization towards synthesizing symmetric linear array geometry with minimum side lobe level (SLL) and/or nulls mitigation. The newly nature-inspired MCS algorithm was principally based on the natural obligate brood parasitic behavior of some cuckoo species in combination with the Lévy flight behavior of some birds. Through the integration with the Roulette wheel selection operator and the inertia weight controlling the exploration of host nest position (solution), the proposed hybrid MCS-based approach optimized simultaneously three element excitation components including locations, amplitudes, and phases, respectively. The optimal solutions obtained were then analyzed for relative performance comparisons against the conventional, original CS, individual MCS, and hybrid GAPSO-based linear arrays.

Reconfigurable beam steer antenna (RBSA) design for WiMAX application

A reconfigurable antenna design for beam steer capability (RBSA) is proposed in this research. The RBSA has successfully achieved beam steer functionality at three angle direction of -42°, -28° and -15°. This is achieved by certain PIN diode configuration. The PIN diode is positioned at the specific location of the RBSA feed network. The proposed antenna consists of an array of three rectangular radiating elements. Aperture coupled feed technique applied in order to reduce the deterioration of power due to the presence of the PIN diode. RBSA has a small dimension of 100 mm × 100 mm that design on Taconic substrate. All designs and simulations have been carried out using CST Microwave Studio. This antenna is potentially useful for Wireless Interoperability Microwave (WiMAX) smart antenna system.

Power harvesting using dual transformations of piezoelectricity and magnetism: A review

This paper discusses the recent progress in micromachined energy harvesting for low power applications. Especially, the combination of piezoelectric and magnetic energy harvesting technologies are focused here. From the review, it is evident that, using the combined platform of piezo and magnetic device is more beneficial compared to the standalone system. It is found that, the proposed combined platform can achieve the output ranged from 40.8μW to 176μW based on the given load mass. Most of the cases it is proven that, the outcome of the hybrid harvester is superior than that of the standalone ones.

Assessment of wireless power transfer technology for emergency power response

The impact of the natural disaster is devastating. Wireless power transfer technology is very promising to reduce this impact by providing power backup for communication devices. This paper presents the assessment of the wireless power transfer technologies for long distance energy transfer. The review of several wireless power transfer technologies (WPTT), namely inductive, capacitive, acoustic, and optical, are presented. The WPTTs are evaluated in the context of several criteria, specifically, propagation area, power level, and efficiency. From the evaluation, it is evident that, optical WPTT is highly suitable for long distance power transfer. It can cover a large area with considerable power. Moreover, it can be merged with the PV technology on the receiving end, which proves its superiority over other technologies in the context of application compatibility.

Basic characteristics of a textile monopole antenna for body-centric wireless communications

This paper presents a light-weight, compact and simple textile monopole antenna structure for body-centric wireless communications (BCWC), applications operating in the 2.45 GHz Industrial, Scientific and Medical (ISM) band. Three different conductive textile materials are chosen: Pure Copper Polyester Taffeta, ShieldIt Super and Nora RS. The result obtained in this investigation showed that all three textile monopoles produced higher reflection coefficient and directivity values compared to the conventional FR-4 monopole antenna. It was found that the simulated gain and radiation pattern characteristics agreed well with the conventional FR4 monopole antenna. The result has also shown that the Nora RS gave better performance in terms of return loss and gain characteristics compared to the other two electrotextiles.

Design and simulation of Orthogonal Frequency Division Multiplexing transceiver system using Differential Phase Shift Keying (DPSK) for Wireless Local Area Network

Orthogonal Frequency Division Multiplexing (OFDM) is predicted to be implemented in future broadcasting and Wireless Local Area Network (WLAN) systems due to its robustness in transmitting a high data rate. Some examples of current applications using OFDM include ETSI BRAN in Europe, IEEE802.11 in United States, and ARIB MMAC in Japan have adopted the OFDM transmission technology as a physical layer for future broadband WLAN systems. This paper presents the design and implementation of an OFDM transceiver system for high speed Wireless Local Area Network (LAN) using MATLAB simulation. Differential M-ary Phase Shift Keying (Mary DPSK) modulation scheme such as Differential Quadrature Phase Shift Keying (DQPSK), Differential 16-Phase Shift Keying (D16PSK) and Differential 256-Phase Shift Keying (D256PSK) have been implemented in the proposed OFDM. The bit error rate (BER) performances for DQPSK, D16PSK and D256PSK have been evaluated in additive white Gaussian noise (AWGN) channel and compared to the theoretical BER.