Comparative studies of the rain attenuation predictions for tropical regions

The radio waves propagating through the earth atmosphere 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 summary of comparative studies on different 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 information for microwave engineers and researchers in making decision over the choice of most suitable rain attenuation prediction for terrestrial 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

Relationship for slots width, antenna directivity, and the 3dB HPBW of an RLSA antenna at 12.4GHz using regression analysis

The quest to optimize performance of the radial line slots array (RLSA) antenna continued to unfold. Attempt is made at studying slots width variation in radial line slot array antenna (RLSA) and its effect on the 3dB half power beam width (3dB HPBW) in this submission. It is aimed at formulating a polynomial equation that best describes the relationship between them. The polynomial equation in turn relates to the directivity of the RLSA antenna. The minimum number of slots in the first ring were restricted to (n1) =12 and, (n1) =14, this is used to manipulate slots concentration on the radiating surface. The restriction is owed to the fact that much cluster of slots in the first ring resulted to a deteriorating performance in terms of directivity values recorded from CST 2012 simulations, for the 12.4 GHz regression analysis in this study. Results obtained from the polynomial equation formed were compared with measured and simulated directivity values and showed good agreement

Comparison of measured rain attenuation and ITU-R predictions on experimental microwave links in Malaysia

This paper presents the results of direct rain attenuation measurements carried out on four experimental microwave links, installed at UTM, Malaysia. The links operate at frequencies of 15, 22, 26, and 38 GHz and the cumulative distribution function for different rain rates have been generated from the measured 4-year rain gauge data. The experimentally measured attenuation data have been compared with International Telecommunication Union-R rain attenuation predictions; and it has been found that the latter have underestimated the measured values, especially at higher rain rates. The deviations have been modeled as a function of rain rate exceedances R%p. It is hoped that the study will provide useful information for estimation of rainfall attenuation on microwave links in tropical regions that have similar situation to Malaysia

Radiation Characteristics Improvement of Monopole Antenna for WBAN Applications

The design, simulation and fabrication of a P-shaped monopole antenna for wireless body area networks (WBAN) applications is presented in this paper. It is noted that the radiation characteristics was improved by attaching a P-shaped element to the ground plane. The simulation of the proposed antenna in the free space and close proximity of body surface has been done using CST Microwave Studio. The proposed antenna is designed on the FR4 substrate with dielectric constant of 4.4 and 1.6mm thickness; and the operating frequency band is between 3.1 to 5.1GHz. The final optimized design has dimensions of 32mm ×28mm. The proposed antenna improves the gain of close proximity of body surface. In addition, the antenna improves the reflection coefficient when placed close human body compared to other antennas. It was observed that there is good agreement between the simulation and measurement results, thereby showing that the antenna is potential to be deployed for WBAN application