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The rainfall path attenuation measured at Universiti Sains Malaysia (USM) for 4 years (January 02 to January 06) is presented. The data obtained are useful to investigate the impairment due to rainfall attenuation in satellite links operating in tropical and equatorial climates. It shows that the logarithmic function with ground rain rate deviates at very high rain rate. A rainfall rate of 130 mm/h causes the rainfall attenuation threshold (> 20 dB) to be exceeded. Maximum exceedences for rain rate and attenuation were observed during the wet months. The cumulative distributions of attenuation derived from the measured data are presented and compared with those obtained with existing prediction methods.

Specific attenuation is the fundamental quantity in the calculation of rain attenuation for terrestrial path and slant paths representing as rain attenuation per unit distance (dB/km). Specific attenuation is an important element in developing the predicted rain attenuation model. This paper deals with the empirical determination of the power law coefficients which allow calculating the specific attenuation in dB/km from the knowledge of the rain rate in mm/h. The main purpose of the paper is to obtain the coefficients of k and α of power law relationship between specific attenuation. Three years (from 1st January 2006 until 31st December 2008) rain gauge and beacon data taken from USM, Nibong Tebal have been used to do the empirical procedure analysis of rain specific attenuation. The data presented are semi-empirical in nature. A year-to-year variation of the coefficients has been indicated and the empirical measured data was compared with ITU-R provided regression coefficient. The result indicated that the USM empirical measured data was significantly vary from ITU-R predicted value. Hence, ITU-R recommendation for regression coefficients of rain specific attenuation is not suitable for predicting rain attenuation at Malaysia.

A compact simple structure modified Swastika shape multiband patch antenna is designed and investigated. The antenna, which occupies an overall dimension of 0.305 × 0.305 × 0.012 at lower frequency, has a simple structure which comprises of a planar wide square slot in the ground with four slits and Swastika shape radiation patch with a rectangular slot. The proposed Swastika shape antenna was designed and analyzed by using a finite element method based high frequency structural simulator HFSS. The experimental and numerical results exhibit that the antenna operates over the frequency ranges 950 MHz (2.28-3.23 GHz), 660 MHz (3.28-3.94 GHz), and 1120 MHz (5.05-6.17 GHz) suitable for WLAN (2.4/5.2/5.8 GHz) and WiMAX 2.5/3.5/5.5 GHz applications. It has a good omnidirectional radiation pattern and reaches 3.97 dBi at 2.44 GHz, 4.04 dBi at 3.5 GHz, and 3.25 dBi at the band of 5.98 GHz. A prototype is fabricated and then measured. The experimental and simulation results show good impedance bandwidth, radiation pattern, and stable gain across the operating bands.

A double inverted F-shape patch antenna is presented for dual-band operation. The proposed antenna is comprised of circular and rectangular slots on a printed circuit board of 40 mm × 40 mm × 1.6 mm with a 50 Ω microstrip transmission line. Commercially available high frequency structural simulator (HFSS) based on the finite element method (FEM) has been adopted in this investigation. It has a measured impedance bandwidths (2 : 1 VSWR) of 18.53% on the lower band and 7.8% on the upper band, respectively. It has achieved stable radiation efficiencies of 79.76% and 80.36% with average gains of 7.82 dBi and 5.66 dBi in the operating frequency bands. Moreover, numerical simulations have been indicated as an important uniformity with measured results.

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