The Investigation of Polarization Diversity in MIMO System at 2.4 GHz

This paper describes the concept of multiple input multiple output (MIMO) system using polarization diversity that can enhance the channel capacity and increased the data output performance of the system. The microstrip antenna array is designed, fabricated and measured at the desired operating frequency for this measurement. Computer Simulation Technology (CST) software is used to design and simulate the microstrip antenna array. The simulation and measurement data results are compared and discussed. The fabricated microstrip antenna is used to develop the Radio Frequency (RF) MIMO test bed system. The system measurement has been conducted in Microwave Laboratory at Faculty of Electronic and Computer Engineering, University Technical Malaysia Melaka at the operating frequency of 2.4 GHz. The spatial diversity and polarization diversity are applied in measurement campaign to investigate the performance of the wireless MIMO channel. The data obtained from the measurement is processed using MATLAB software in order to calculate the MIMO channel capacity. The analysis has been focused on the effect of the MIMO channel capacity due to the proposed measurement setup configurations. The channel capacity is increased from 0.03 b/s/Hz to 0.09 b/s/Hz when polarization diversity is applied at both transmitter and receive

Risk factors for Nipah virus infection among pteropid bats, Peninsular Malaysia

We conducted cross-sectional and longitudinal studies to determine the distribution of and risk factors for seropositivity to Nipah virus (NiV) among Pteropus vampyrus and P. hypomelanus bats in Peninsular Malaysia. Neutralizing antibodies against NiV were detected at most locations surveyed. We observed a consistently higher NiV risk (odds ratio 3.9) and seroprevalence (32.8%) for P. vampyrus than P. hypomelanus (11.1%) bats. A 3-year longitudinal study of P. hypomelanus bats indicated nonseasonal temporal variation in seroprevalence, evidence for viral circulation within the study period, and an overall NiV seroprevalence of 9.8%. The seroprevalence fluctuated over the study duration between 1% and 20% and generally decreased during 2004–2006. Adult bats, particularly pregnant, with dependent pup and lactating bats, had a higher prevalence of NiV antibodies than juveniles. Antibodies in juveniles 6 months–2 years of age suggested viral circulation within the study period

Agricultural intensification, priming for persistence and the emergence of Nipah virus: a lethal bat-borne zoonosis

Emerging zoonoses threaten global health, yet the processes by which they emerge are complex and poorly understood. Nipah virus (NiV) is an important threat owing to its broad host and geographical range, high case fatality, potential for human-to-human transmission and lack of effective prevention or therapies. Here, we investigate the origin of the first identified outbreak of NiV encephalitis in Malaysia and Singapore. We analyse data on livestock production from the index site (a commercial pig farm in Malaysia) prior to and during the outbreak, on Malaysian agricultural production, and from surveys of NiV's wildlife reservoir (flying foxes). Our analyses suggest that repeated introduction of NiV from wildlife changed infection dynamics in pigs. Initial viral introduction produced an explosive epizootic that drove itself to extinction but primed the population for enzootic persistence upon reintroduction of the virus. The resultant within-farm persistence permitted regional spread and increased the number of human infections. This study refutes an earlier hypothesis that anomalous El Niño Southern Oscillation-related climatic conditions drove emergence and suggests that priming for persistence drove the emergence of a novel zoonotic pathogen. Thus, we provide empirical evidence for a causative mechanism previously proposed as a precursor to widespread infection with H5N1 avian influenza and other emerging pathogens

Socializing One Health: an innovative strategy to investigate social and behavioral risks of emerging viral threats

In an effort to strengthen global capacity to prevent, detect, and control infectious diseases in animals and people, the United States Agency for International Development’s (USAID) Emerging Pandemic Threats (EPT) PREDICT project funded development of regional, national, and local One Health capacities for early disease detection, rapid response, disease control, and risk reduction. From the outset, the EPT approach was inclusive of social science research methods designed to understand the contexts and behaviors of communities living and working at human-animal-environment interfaces considered high-risk for virus emergence. Using qualitative and quantitative approaches, PREDICT behavioral research aimed to identify and assess a range of socio-cultural behaviors that could be influential in zoonotic disease emergence, amplification, and transmission. This broad approach to behavioral risk characterization enabled us to identify and characterize human activities that could be linked to the transmission dynamics of new and emerging viruses. This paper provides a discussion of implementation of a social science approach within a zoonotic surveillance framework. We conducted in-depth ethnographic interviews and focus groups to better understand the individual- and community-level knowledge, attitudes, and practices that potentially put participants at risk for zoonotic disease transmission from the animals they live and work with, across 6 interface domains. When we asked highly-exposed individuals (ie. bushmeat hunters, wildlife or guano farmers) about the risk they perceived in their occupational activities, most did not perceive it to be risky, whether because it was normalized by years (or generations) of doing such an activity, or due to lack of information about potential risks. Integrating the social sciences allows investigations of the specific human activities that are hypothesized to drive disease emergence, amplification, and transmission, in order to better substantiate behavioral disease drivers, along with the social dimensions of infection and transmission dynamics. Understanding these dynamics is critical to achieving health security--the protection from threats to health-- which requires investments in both collective and individual health security. Involving behavioral sciences into zoonotic disease surveillance allowed us to push toward fuller community integration and engagement and toward dialogue and implementation of recommendations for disease prevention and improved health security

Microstrip dipole antenna for VLAN application

This paper describes numerical simulation, fabrication and experimental measurement of microstrip dipole antenna at 2.4 GHz for WLAN application. In this antenna design, Agilent’s ADS software using momentum simulation is employed to analyze the entire structure. The properties of antenna such as bandwidth, radiation pattern and half power beamwidth have been investigated and compared between simulation and measurements. The cross-polar isolation of the microstrip dipole antenna is in the range of 3 to 17.32 dB. The typical half power beamwidth (HPBW) of the microstrip dipole is 60º for E plane and 75º for H plane. Performance comparison between dipole and monopole antenna is also made in term of bandwidth and Input return loss

Microstrip dipole antenna analysis with different width and length at 2.4 GHz

This paper discusses the design and simulation of microstrip dipole antenna at 2.4 GHz. In this antenna design, Agilent's Advanced Design System (ADS) software using momentum simulation is employed to analyze the entire structure. Different width (W = 3, 5, 7, 9 mm) of the arm of dipole antenna is analyzed to study on the performance of frequency resonance. From the simulation, the wider the width will lower the resonance frequency of the antenna. Different width makes the frequency resonance of the antenna shifting lower or higher than 2.4 GHz. In this case, the length (L) of the dipole arm needs changes. Optimization value of the length is needed to make the frequency resonance at 2.4 GHz. The simulation result gives the bandwidth achieved of this microstrip dipole antenna is between 11 and 13 %. Three different width of dipole antenna have been fabricated and presented here in this paper. The properties of antenna such as input return loss and bandwidth have been investigated and compared between simulations

Direct conversion receiver with active integrated antenna

This paper describes numerical simulation, fabrication and experimental measurement of a compact miniature integrated antenna using direct conversion detection at 2.4 GHz. In this receiver design, Agilent's ADS software using momentum simulation and circuit simulation is employed to analyze the entire structure. Microstrip dipole antenna is integrated with 90deg hybrid coupler, oscillator and diodes for direct conversion or zero-IF detection is presented here. Microstrip dipole antenna that is presented here has a wide bandwidth up to 23.85 % bandwidth. The 90deg hybrid coupler can act as a phase shifter to provide the necessary 90deg characteristics to operate with I and Q signal for direct conversions. Two Schottky diodes (HSMS 8101) are mounted onto each of two coupler's output port to act as a mixer. One pin of the diodes is connected to the edge of output port and the other pin is grounded via a small hole to ground plane. One kHz sinusoidal signal act as a baseband has been generated and modulated using signal generator. The demodulated signal is detected using direct conversion receiver circuit and the baseband signal at the output ports is successfully detected using oscilloscope

Microstrip patch antenna array at 5.8 GHz for point to point communication

This paper described the design of microstrip patch array antenna with operating frequency at 5.8GHz for point to point communication. The array of four microstrip rectangular patch antennas with inset feed based on quarter-wave impedance matching technique were designed, simulated, fabricated and measured with the aid of microwave office software. The simulation and measurement result met the IEEE 802.11a standard and able to operate in upper UNII band for point to point communication. The 4times4 array has a return loss of -30.42 dB with 15% bandwidth. The gain obtained from simulation is 16 dB with 9deg half power beamwidth (HPBW)