A. Y. Abdulrahman

Empirically Derived Path Reduction Factor for Terrestrial Microwave Links Operating at 15 Ghz in Peninsula Malaysia

This paper describes the technique of deriving path reduction factor from experimental rain rate and rain attenuation data over seven DIGI MINI-LINKs operating at 15 GHz in Malaysia (Lat.: 1.45°N and Long.: 103.75°E). The relationship between experimental path reduction factors with different link lengths has been studied, using multiple non-linear curve-fitting techniques. Based on these studies, an empirical path reduction factor model has been proposed and compared with the ITU-R model. The test results have shown that the ITU-R prediction model may not be appropriate for predicting rain-induced attenuation for the tropical Malaysian climate.

TRANSPARENT ANTENNA DESIGN FOR WiMAX APPLICATION

A transparent monopole antenna operating at 2.30GHz is presented in this paper. The radiating element and ground plane are both designed using AgHT-4, while the substrate is made of glass. The simulated and measured impedance bandwidths (BWs) are 41.89% (2.00{3.06GHz) and 90.91% (1.5{4.00GHz), respectively. These results were obtained by using a suitable arc-shape slot on the ground plane; and the BWs cover the IEEE 802.16e standard for WiMAX application in the 2.30GHz band. The gain of proposed antenna is 3.16dBi, and there is close agreement between measurement and simulation results, in terms of return loss and radiation patterns.

Comparative studies of the rain attenuation predictions for tropical regions

The radio waves propagating through the earth atmo- sphere will be attenuated due to the presence of atmosphere particles, such as water vapor, water drops and the ice particles. Meanwhile, the atmospheric gases and rain will both absorb and scatter the radio waves, and consequently degrade the performance of the link. The results of various studies conducted in temperate and tropical regions have been published in research papers. This paper presents the sum- mary of comparative studies on difierent rain attenuation prediction methods for terrestrial microwave links tropical regions. Basically the models described in this paper include those of the ITU-R, revised Moupfouma, revised Silva Mello and Lin model. The objective of this study is to reveal the most suitable rain attenuation prediction model for the Malaysian tropical region. This paper will provide useful in- formation for microwave engineers and researchers in making decision over the choice of most suitable rain attenuation prediction for ter- restrial links operating in a tropical region. Even though the ITU-R model underestimates the rain attenuation at higher frequencies, the test results have clearly indicated that it is most suitable for predicting terrestrial rain attenuation in tropical Malaysia, compared to others.

Bandwidth enhancement and miniaturization of dielectric resonator antenna for 5.8 GHz WLAN

This paper presents the design of Dielectric Resonator Antenna (DRA) operating at 5.8 GHz, using the techniques of Two Segments DRA (TSDRA) and High-Aspect Ratio Structure. The aim of the paper is to reduce the size of the DRA while still maintaining its large impedance bandwidth. The requirements for WLAN applications are carefully taken into considerations in the design of the proposed structure. Comparison has been made between the proposed design and single layer DRA (SLDRA); and it has been found that the former has better performances than the latter.

Fade Margins Prediction for Broadband Fixed Wireless Access (BFWA) from Measurements in Tropics

The fade margins for 15, 23, 26 and 38GHz frequency bands are predicted based on one-minute rain rate measurements for four years at Universiti Teknologi Malaysia (UTM) Skudai and the speciflcations of the given four MINI-LINKS. The availabilities of terrestrial microwave links are also investigated based on rain attenuation data collected from seven operational microwave links at 15GHz and one at 23GHz for more than one year. The fade margins for all eight links are measured based on the rain attenuation data collected with difierent hop lengths. In this paper, the feasibility to design outage-free wireless broadband radio link also highlighted. These results will contribute to the better design of outage-free Broadband Fixed Wireless Access (BFWA) system such as, Local Multipoint Distribution Service (LMDS) and IEEE802.16 in tropical regions.

Rain attenuation measurements over terrestrial microwave links operating at 15 GHz in Malaysia

This paper presents the experimental results of rain rate and rain attenuation measurements on six terrestrial microwave links in tropical Malaysia. The rain attenuation data were collected from six DIGI MINI-LINKs (DiGi Telecommunications Sdn. Bhd., Malaysia, Shah Alam, Selangor Darul Ehsan, Malaysia) operating at 15 GHz with 99.95 % availability. The experimental results were compared with the International Telecommunication Union Radiocommunication Sector (ITU-R) method and other existing rain attenuation prediction models. The main focus is on the ITU-R prediction method, which underestimates the measured rain attenuation, more especially at extremely higher rain rates. The relationship between ITU-R prediction errors and rainfall rates was studied, and it is shown that the two quantities are related by a quadratic function. The study will provide useful information on the design and planning of terrestrial radio links in Malaysia and similar tropical environments. Copyright

A 6.0GHZ small printed monopole antenna for wireless implantable body area network applications

Wireless implantable body area network (WiBAN) is useful for monitoring vital human parameters in medical diagnosis such as breast cancer, heart attack and high blood pressure. The main objective of this paper is to design a small printed monopole antenna for WiBAN applications at 6.0GHz. The small implantable antenna was tested in a lossy environment by being submerged into canola oil that mimics the dielectric properties of human breast fat tissue. The antenna performances were measured by using vector network analyzer (VNA) in order to evaluate the return loss and operating bandwidth of the antenna. The other parameters such as e-ciency, radiation pattern and gain are evaluated by simulation of CST Studio 2012 software. When compared, there is good agreement between the simulation and measurement results. The simulated antenna gain and e-ciency are 5.8dBi and 97%, respectively, when submerged into canola oil. The antenna radiation pattern is directional, and it has 6 lobes implying its coverage in more directions which is of good beneflt due to body movement. The antennas polarization was tested by placing a wideband antenna at several degrees around the proposed