فهرست مطالب

Communication Engineering - Volume:1 Issue: 1, Autumn 2012

Journal of Communication Engineering
Volume:1 Issue: 1, Autumn 2012

  • تاریخ انتشار: 1391/11/18
  • تعداد عناوین: 6
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  • M. Sheikh, Hosseini, M. Molavi, Kakhki, Gh. Abed Hodtani Page 1
    In this paper we propose a new space diversity scheme for broadband PLC systems using orthogonal space-time block coding (OSTBC) transmission combined with single-carrier frequency-domain equalization (SC-FDE). To apply this diversity technique to PLC channels, we first propose a new technique for combining SC-FDE with OSTBCs applicable to all dispersive multipath channels impaired by impulsive noise. The proposed technique is then applied to indoor and outdoor PLC channels under different channel scenarios in the presence of background and impulsive noises. We perform the simulations for SISO, MISO and MIMO configurations and show that a significant SNR gain is achieved when SC-FDE is combined with diversity techniques. We also compare our proposed technique with OFDM using Alamouti code for broadband PLC and show the superiority of our technique.
    Keywords: broadband power line communication, frequency, selective fading channel, impulsive noise, orthogonal space time block coding, single, carrier frequency, domain equalization
  • R. Keneshloo, G. Dadashzadeh, A. Frotanpour, M. Okhovvat Page 18
    Multipactor breakdown analysis is presented in cylindrical dielectric resonator waveguide filter under its dual-mode behavior. The method of effective electron algorithm with combination of Monte-Carlo method is used to perform the simulation and predict multipactor breakdown thresholds. The breakdown thresholds of the proposed structure are presented for different values of frequency-gap product. The results indicate that increasing the radius of filter increases the RF breakdown threshold. The results are compared with the classic parallel plate waveguides.
    Keywords: dielectric resonator, waveguide filters, multipactor breakdown thresholds, effective electron
  • M. Ferdosizadeh Naeiny, M. Habibi Page 25
    Tone Reservation (TR) is one of the well-known methods for PAPR reduction of Orthogonal Frequency Division Multiplexing (OFDM) systems. In this method some sub-carriers are reserved for PAPR reduction and the symbols in these sub-carriers are selected such that the PAPR of the OFDM frame is minimized. In this paper, the iterative algorithm introduced earlier for TR method in single antenna OFDM systems is extended to multiple antenna Spatially Multiplexed OFDM (SM-OFDM) systems. In the proposed method, which is called selective TR, in each iteration the peak reduction symbols of the antenna with maximum PAPR are updated. Simulation results show that using this approach leads to the performance improvement in comparison to the case where TR method is applied independently to all of antennas.
    Keywords: Spatial Multiplexing (SM), OFDM, PAPR, Tone Reservation (TR)
  • V. Rafii, J. Nourinia, J. Pourahmadazar, F. Jalili Page 38
    This paper presents the design, simulation, and measurement of two low-cost broadband circularly polarized (CP) printed antennas: a single element and an array at C band. The proposed single element antenna is excited by an L-shaped strip with a tapered end, located along the circular-slot diagonal line in the back plane. From the array experimental results, the 3 dB axial ratio bandwidth can reach as large as 1900 MHz which covers the 4.7 GHz to 6.6 GHz frequency band. In addition, the measured impedance bandwidth for reflection coefficient of less than -10 dB has the bandwidth with the frequency range from 4.2 GHz to 8 GHz (C Band application). The CP element achieves a bandwidth of 16.6% for an axial ratio less than 3 dB. The proposed antenna array can provide a peak gain of about 8.7 dBic at 5.9 GHz. Acceptable agreements between the simulation and measured results validates the proposed design.
    Keywords: Circularly polarized, Circular Slot antenna, Slot antenna array, sequentially rotated array
  • A.R. Mallahzadeh, S. Mohammad Ali Nezhad Page 47
    A low cross-polarization slot array antenna in the narrow wall of ridge waveguide is presented. A non-angled slot which is created in the narrow wall of the ridge waveguide is considered to be used as radiating resonant slot. The normalized resistance and normalized reactance curves are presented for design purposes. A six element slot array waveguide antenna with ridges on its narrow wall is then designed at frequency of 9 GHz using the normalized conductance of each radiating slot. It is shown that good performance can be achieved even for angled ridge in waveguide. The antenna has the characteristics SLL of -20 dB and cross-polarization equivalent to -60 dB.
    Keywords: slot array antenna, singled ridge waveguide, cross, polarization
  • Y. Zehforoosh, A. Siahcheshm Page 61
    This paper presents the results of a new monopole antenna that exhibits 2.75-10.7 GHz performance. The proposed antenna consists of a radiating patch with notches excited by capacitive coupling feed. Also, the antenna’s truncated ground-plane incorporates a central notch. This modification significantly improves the antenna’s impedance bandwidth by 118% over an ultra-wideband frequency range. These characteristics make the proposed antenna an excellent candidate for numerous UWB applications and next generation communication systems. The key physical parameters affecting the antenna’s frequency characteristics have also been investigated in order to determine optimum antenna performance. The antenna’s simulated return-loss, and E-plane and H-plane radiation patterns show very good correlation with the requirements of UWB applications.
    Keywords: monopole antenna, notch filter, capacitive coupling, UWB