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SUMMARY We present an efficient rectenna capable of harvesting ambient radio frequency energy to obtain utilizable direct current power at a frequency of 2.45 GHz. The rectifying antenna incorporates a fractal structure at its antenna section. The unique space‐filling property of fractals is implemented to develop an antenna with a significant size reduction. A Sierpinski carpet, which is a simple and effective fractal design, is edge‐fed and iterated up to the 3rd order. The received signal from the 2nd‐order fractal iterated patch antenna is rectified using a rectifier circuit that uses an HSMS 8202 (Avago Technologies, California, USA) diode. The realized rectenna has the capacity to exhibit a maximum efficiency of 57% at an input power level of 20 dBm. Simulations for the fractal iterated patch antennas and rectifier circuit are performed in Ansoft HFSS, Ver. 10 (Ansys, Canonsburg, USA) and ADS (Agilent Technologies, Mississauga, Canada), respectively. The simulated antenna and rectenna are experimentally tested to verify the simulation results. The simulation and experimental results for the antenna and rectenna design are found to be in good agreement with each other. Copyright © 2013 John Wiley & Sons, Ltd.

Rain plays a major impairment factor for propagation of electromagnetic waves in atmosphere for systems operating at frequencies above 10 GHz. Several effects are noted such as depolarization, scintillation, interference due to scattering and extra attenuation which seems to increase with frequency. To mitigate its effect in satellite communication, knowledge of local rainfall statistics is necessary which act as milestone for design of radio link. Rain attenuation is best visualize by the 1-min rainfall rate statistic but the measurement of this rain rate distribution is rare on a worldwide basis and observation of rain rate are done with longer integration times typically 30 min or more. In this paper, efforts have been made to develop model that can convert rain rate complementary cumulative distribution function to shorter integration times. The average relative error margin of about 5, 14, 43, 71 and 115 % are noted for 5 to 1-, 10 to 1-, 20 to 1, 30 to 1- and 60 to 1-min respectively from ITU-R P.837-6 method which have been analyzed in further section of this article. The empirical natures of conversion methods as such Segal method, Burgueno’s method, Chebil and Rahman method and Logarithmic model are studied along with the proposed new model that seems to be applicable in derivation of 1-min rain rate of the South Korea rain rate statistics. International Telecommunication Union-Radio communication Sector (ITU-R) has developed a recommendation ITU-R P.837-6 that enables the user to estimate the local 1-min rainfall rate statistical distribution which is compared with calculated 1-min rain rate distribution from experimental 1-min rainfall accumulation. Unfortunately, ITU-R P.837-6 estimated 1-min values show greater error percentages. In order to get better approximation of local 1-min rain rate estimation, a novel method is proposed and it’s efficiency have been compared with rainfall rate statistics obtained from nine different locations in the South Korea.

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This study proposed a patch antenna with a MIMO structure which is applicable for wireless communication equipment by combining a single patch antenna with a multi port. The proposed MIMO patch antenna was designed through the TRF-45 substrate with a relative permittivity of 4.5, loss tangent equal to 0.0035 and dielectric high of 1.6 ㎜, and the center frequency of the antenna was 2.45 ㎓ in the ISM (Industrial Scientific and Medical) band. The proposed MIMO patch antenna had a 500 ㎒ bandwidth from 2.16 ∼ 2.66 ㎓ and 24.1% fractional bandwidth. The return loss and VSWR were -62.05 ㏈, 1.01 at the ISM bandwidth of 2.45 ㎓.The Wibro band of 2.3 ㎓ was -17.43 ㏈, 1.33, the WiFi band of 2.4 ㎓ was -31.89 ㏈, 1.05, and the WiMax band of 2.5 ㎓ was -36.47 ㏈, 1.03. The radiation patterns included in the bandwidth were directional, and the WiBro band of 2.3 ㎓had a gain of 4.22 ㏈i, the WiFi band of 2.4 ㎓ had a gain of 4.12 ㏈i, the ISM band of 2.45 ㎓ had a gain of 4.06㏈i, and the WiMax band of 2.5 ㎓ had a gain of 3.9 6㏈i.