Recent Submissions

Now showing 1 - 5 of 23
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    Monthly and Diurnal Variability of Rain Rate and Rain Attenuation during the Monsoon Period in Malaysia
    (Společnost pro radioelektronické inženýrství, 2014-06) Ulaganathen, Kesavan; Rafiqul, Islam Md; Rahman, Tharek A.; Assis, Mauro S.
    Rain is the major source of attenuation for microwave propagation above 10 GHz. In tropical and equatorial regions where the rain intensity is higher, designing a terrestrial and earth-to-satellite microwave links is very critical and challenging at these frequencies. This paper presents the preliminary results of rain effects in a 23 GHz terrestrial point-to-point communication link 1.3km long. The experimental test bed had been set up at Skudai, Johor Bahru, Malaysia. In this area, a monsoon equatorial climate prevails and the rainfall rate can reach values well above 100mm/h with significant monthly and diurnal variability. Hence, it is necessary to implement a mitigation technique for maintaining an adequate radio link performance for the action of very heavy rain. Since we now know that the ULPC (Up Link Power Control) cannot guarantee the desired performance, a solution based on frequency band diversity is proposed in this paper. Here, a secondary radio link operating in a frequency not affected by rain (C band for instance) is placed parallel with the main link. Under no rain or light rain conditions, the secondary link carries without priority radio signals. When there is an outage of the main link due to rain, the secondary link assumes the priority traffic. The outcome of the research shows a solution for higher operating frequencies during rainy events.
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    Estimation of Most Favorable Optical Window Position Subject to Achieve Finest Optical Control of Lateral DDR IMPATT Diode Designed to Operate at W-Band
    (Společnost pro radioelektronické inženýrství, 2014-06) Acharyya, Aritra; Goswami, Jayabrata; Banerjee, Suranjana; Banerjee, J. P.
    The optimum position of the optical window (OW) of illuminated lateral double-drift region (DDR) impact avalanche transit time (IMPATT) device has been determined subject to achieve the finest optical control of both DC and RF properties of the device. The OW is a tiny hole that has to be created on the oxide layer through which the light energy of appropriate wavelength can be coupled to the space charge region of the device. A non-sinusoidal voltage is assumed to be applied across the diode and the corresponding terminal current response is obtained from a two-dimensional (2-D) large-signal (L-S) simulation technique developed by the authors for illuminated lateral DDR IMPATT diode. Both the DC and L-S properties of the illuminated device based on Si, designed to operate at W-band frequencies (75 – 110 GHz) are obtained from the said L-S simulation. Simulation is carried out for different incident optical power levels of different wavelengths (600 – 1000 nm) by varying the position of the fixed sized OW on the oxide layer along the direction of electrical conduction of the device. Results show that, the most favorable optical tuning can be achieved when the OW is entirely created over the p-type depletion layer, i.e. when the photocurrent is purely electron dominated. Also the 700 nm wavelength is found to be most suitable wavelength for obtaining the maximum optical modulation of both DC and RF properties of the device.
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    A Novel T-Fed 4-Element Quasi-Lumped Resonator Antenna Array
    (Společnost pro radioelektronické inženýrství, 2014-06) Olokede, Seyi Stephen; Adamariko, Clement Anowe; Almohamad, Tarik Adnan; Jiya, Enoch Adama
    In this paper, electrically small corporately T-fed quasi-lumped element resonator antenna array is investigated. The radiating element, a quasi-lumped element resonator is excited by a novel semi hybrid ring-like T-shaped corporate feed network. The characteristics losses due to Ohmic and discontinuities along the feed line which invariably constitutes complex feed structures are mitigated at the instance of the proposed antenna. Technique to implement the compact array with the intent to enhance the gain is presented. The operation dynamics of the feed along with its theoretical explanation is also reported. Findings indicates that the measured gain is 10.97 dBi for antenna of an estate area of about 0.677λ_0 × 1.257λ_0 sq. mm. Valuable insight to the optimum design in terms of compactness, good gain, and ease of fabrication is documented.
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    An Improved NSGA-II and its Application for Reconfigurable Pixel Antenna Design
    (Společnost pro radioelektronické inženýrství, 2014-06) Li, Yan-Liang; Shao, Wei; Wang, Jing-Ting; Chen, Haibo
    Based on the elitist non-dominated sorting genetic algorithm (NSGA-II) for multi-objective optimization problems, an improved scheme with self-adaptive crossover and mutation operators is proposed to obtain good optimization performance in this paper. The performance of the improved NSGA-II is demonstrated with a set of test functions and metrics taken from the standard literature on multi-objective optimization. Combined with the HFSS solver, one pixel antenna with reconfigurable radiation patterns, which can steer its beam into six different directions (θDOA = ± 15°, ± 30°, ± 50°) with a 5 % overlapping impedance bandwidth (S11 < − 10 dB) and a realized gain over 6 dB, is designed by the proposed self-adaptive NSGA-II.
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    Design of Multi-Antenna System for UMTS Clamshell Mobile Phones with Ground Plane Effects Considerations
    (Společnost pro radioelektronické inženýrství, 2014-06) Addaci, Rafik; Diallo, Aliou; Luxey, Cyril; Le Thuc, Philippe; Staraj, Robert
    In this paper, the influence of the ground plane dimensions on the port-to-port isolation of two closely-spaced Universal Mobile Telecommunications System (UMTS) Planar Inverted-F Antennas (PIFAs) with and without neutralization line is first presented. Parametric studies show the existence of an optimal size of the ground plane allowing optimizing the isolation and the efficiency of the considered antenna-system. The results obtained with this study are used in the second part to develop an efficient neutralized multi-antenna system for clamshell-type mobile phones. The obtained results, in terms of isolation, matching and diversity for the two possible configurations of the clamshell system in use namely the open and the closed states, show that good performance are obtained in the open state and preserved in the closed state. Prototypes of these two configurations are realized and measurement results are in good agreement with the simulations.