فهرست مطالب

Majlesi Journal of Telecommunication Devices
Volume:5 Issue: 4, Dec 2016

  • تاریخ انتشار: 1395/10/03
  • تعداد عناوین: 6
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  • Ali Ghasemi Khah, Yosef Seifi Kavian Pages 119-123
    In communication systems, ensuring correct information reception is very important, Error Correction Coding methods have been developed in order to achieve this goal. Convolutional Code is used in Wireless, Satellite, mobile phones and Deep-Space communications, it is one of the most powerful Error Correction code, and the Viterbi algorithm is robust way to decode it. Power conception and speed are two important feature of Viterbi decoders, in many communications the power consumption is most important. In this paper, by removing extra decoding cycles, the SMU registers are reduced by 20%, the power consumption reduced by 14.5% and the speed increased 6 times without error correction performance loss. The proposed design is described by VHDL and it is implemented on Xilinx Spartan3, Xc3s400 FPGA chip.
    Keywords: Convolutional code, Viterbi Decoder, FPGA, Deep-Space Communication
  • Zohreh Dorrani Pages 125-127
    The genetic algorithm is one of the most powerful optimization algorithms in electromagnetism. In this paper, we optimized gain of a microstrip patch antenna using genetic algorithms. The cavity method used for the analysis of this antenna. The simulation results were compared with results obtained in previous work. The resulting gave gain more than the previous one.
    Keywords: genetic optimization, microstrip antennas, gain, input impedance, resonant frequency
  • Frederick Ojiemhende Ehiagwina, Titus Olugbenga Adewunmi, Emmanuel Oludare Seluwa, Olufemi Oluseye Kehinde, Nafiu Sidiq Abubakar Pages 129-137
    Reliability prediction is vital in the conception, definition, design, development, operation and maintenance phase of electronic devices. It is needed at various system levels and degrees of detail, in order to evaluate, determine and improve the dependability measures of an item when designing electronic devices in view of the high level competition among device manufacturers. Different reliability prediction methods or models are available for electronic devices. This paper comparatively examined the commonly used methods such as empirically based failure rate modeling methodologies used in reliability prediction handbooks, and physics of failure (PoF) based models. Three empirical approaches such as MIL-HDBK-217F – a conservative standard applicable principally to military equipment, and Bellcore TR-332/Telcordia SR-332, which are applicable to commercial devices are reviewed in closer details. Also reviewed is Recueil de Donnes de Fiabilite (RDF) 2000, used in Telecom industry. Some PoF based methods such as Arrhenius law; Eyring model, Black Model for Electromigration, and Coffin Manson Model for fatigue are also examined. Additionally, the respective merits and demerits of the prediction methods which provide the basis for use are noted. The paper also attempts to highlight future trends and challenges in RP of electronic devices.
    Keywords: Bellcore TR, 332, Empirical Methods, Life Test, MIL-HDBK-217F, Physics of Failure, RDF 2000, Reliability Prediction, Telcordia SR-332
  • Navid Daryasafar, Omid Borazjani Pages 139-145
    In high capacity systems, as the bit transmission rate increases, Intersymbol Interference (ISI) caused by the multi-path channel reduces the system efficiency. The technique of OFDM acts very well against this phenomenon. On the other hand, an accurate estimation of the communication channel coefficients improves the performance of communication systems effectively. In this paper, the estimation algorithms of the MIMO-OFDM channel are investigated to compare them in terms of estimation error and calculation complexity. In the following, a method is proposed to improve the estimation of the MIMO-OFDM channel. In this method, combining the LS algorithm with adaptive algorithms improves the estimation performance at different Doppler frequencies. We observe in the simulations that the use of adaptive algorithms improves the estimation of the channel at Doppler frequencies.
    Keywords: Multiple Input Multiple Output Systems (MIMO), LS Algorithm, LMS Algorithm, RLS Algorithm
  • Meysam Azimi Roein Pages 147-150
    A new ultra-wideband 3.1-10.6 GHz low noise amplifier(LNA), designed in chartered 0.18μm technology, is presented in this paper.By using series inductive peaking in the feedback loop is used to improve the basndwidth of the LNA. Based on the noise-canceling technique,voltage gain is increased. Measurements show that the S11 and S22 are less than -10 dB, and the maximum amplifier gain S21 gives 12.9dB, and the minimum noise figure is 2.6dB, and the power consumption is 13.6 mW from 1.8V supply voltage.
    Keywords: CMOS, Low noise amplifier, Ultra, wideband, Gain
  • Mohammad Reza Khosravi, Mohammad Kazem Moghimi Pages 151-153
    This letter is about a principal weakness of the published article by Li et al. in 2014. It seems that the mentioned work has a terrible conceptual mistake while presenting its theoretical approach. In fact, the work has tried to design a new attack and its effective solution for a basic watermarking algorithm by Zhu et al. published in 2013, however in practice, we show the Li et al.'s approach is not correct to obtain the aim. For disproof of the incorrect approach, we only apply a numerical example as the counterexample of the Li et al.'s approach.
    Keywords: Remote sensing, Digital watermarking, Counterexample, Li et al.'s approach for Zhu et al.'s watermarking algorithm