Current issue of " International Journal on Communications Antenna and Propagation (IRECAP)"

International Journal on
Communications Antenna and Propagation
(IRECAP)
December 2013 (Vol. 3 N. 6)

of IRECAP:

Analysis and Comparison of Deterministic Power Line Channel Modeling Methods

by R. Nizigiyimana, J.-C. Le Bunetel, Y. Raingeaud, P. Ravier, G. Lamarque, A. Achouri

Abstract - Indoor broadband power line communications (PLC) use home grid as communication media. Many applications exist such as data sharing and internet access. However, the performances achieved differ widely from a home to another because of differences in electrical installations. A software tool able to qualify any household grid versus power line might be developed. There is no today undeniable model and many frameworks exist. To make an informed choice, this paper analyzes and compares frequent deterministic modeling: chain matrices, multipath, infinite impulse response (IIR) filters, and electrical circuits. Multipath model proved to be the most accurate despite its implementation challenge. Chain matrices and electrical circuits are very sensitive to the uncertainty of the propagation coefficient and the impedance characteristic of power cables. Chain matrices and IIR filters based methods are unable to predict accurately the level of a fading due to both two derivations.

Keywords: Chain Matrices, Electrical Circuits, IIR Filters, Multipath, Power Line Communication, Transfer Function Modeling.

Vulnerability and VoIP Threats Survey in Broadband Networks

by S. Reza Chogan, Mostafa Heidarzadeh, Hassan Yeganeh, Hosein Mohammadi

Abstract - VoIP services are a major area in the broadband networks for telecommunication domain. This technology includes positive and negative aspects as other new technologies. Nowadays, the telecom operators provide call waiting, call transfer, conference calling, caller ID and other VoIP services based on IMS solution. Thus, VoIP security is now one of the issues over which many debates take place. In this paper, we decide to concentrate on categories of vulnerability for VoIP services which is implemented by IMS solution in broadband networks. We try to present the common security threats and vulnerabilities of VoIP services. Identifying vulnerabilities, their classification and the risks which these services are threatened by, makes the ways to penetrate in the system to be clear and hence the administrators can solve the problems. The debate on this matter would be a misleading subject without having full recognition of various specifications. In addition, to clarify the importance of identifying these types of vulnerabilities, we classify the probability threats for VoIP.

Keywords: Vulnerability, Classification, Threats, Security, VoIP.

Broadband Impedance Matching Techniques for Microwave Amplifiers [10-12] GHz

by M. Lahsaini, L. Zenkouar, S. Bri

Abstract - In this paper, we have modeled a low noise amplifier that we have adapted by band pass coupled resonator filters, using two adaptation techniques, the first is based on filters on a distributed elements and the second based on a combination of distributed and localized elements. We have used two kinds of transistors that are the FET and the HEMT. The obtained results showed that this amplifier is unconditionally stable in the whole band [10-12] GHz. Moreover, the gain is satisfactory. The reflection coefficients of the input and output S11 and S22 are low. The modeled amplifier in this work can be integrated in radar systems and satellite transmission and reception systems.

Keywords: Amplifier, Impedance Matching, Filters, Coupled Resonators .

Study of Network Access Control System Featuring Collaboratively Interacting Network Security Components

by Li He-Hua, Wu Chun-Ling

Abstract - Draw lessons from Cisco network access control thought, proposed one kind based on the 802.1x protocol of a network component security interaction type network access control system design and implementation, and to the large campus network application background and describes in detail the development and deployment of technology of the system, including identity authentication, billing, network access control, information statistics safety linkage, form a variety of different network components linkage collaboration, the traditional first connection security evaluation network access mode changes for the first safety assessment after connection, significantly improve the security of network.

Keywords: 802.1x, NAC, Network Access Control, Network Security.

Microstrip-Fed Printed Slot Antennas Based on Hilbert-Type Space-Filling Curves for Wireless Communication Systems

by Jawad K. Ali

Abstract - In this paper, two microstrip-fed printed slot antennas have been introduced to be used in modern communication systems, as alternatives for conventional Hilbert slot antenna. The slot structures of the proposed antennas are in the form of the 3rd iteration of two variants of the conventional Hilbert space-filling curves. These antennas are fed with 50 Ω microstrip line printed on the reverse side of the slot structure. The proposed antennas have been modelled and analyzed using the method of moments (MoM) based commercially available software, IE3D from Zeland Software Inc,. Simulation results show that all these antennas possess a multi-resonant behavior with a miniature size of about half the guided wavelength. It has been found that the fundamental resonance depends on the external side length of the slot structure, while higher mode resonances are attributed by the smaller self-similar structures the slot pattern contains. Furthermore, amongst the proposed antennas, the antenna with slot structure based on Moore’s space-filling curve, which is a closed version of Hilbert curve, has been found to offer a multiband behavior with enhanced bandwidths around the multiple resonances as compared with the other two antennas based on other Hilbert space-filling variants.

Keywords: Printed Slot Antenna, Microstrip-Fed Antenna, Multiband Antenna, Hilbert-Type Fractal Curves.

Stepped Impedance Resonators in Triple Band Bandpass Filter Design for Wireless Communication Systems

by Abdullah Eroglu

Abstract - Triple band microstrip tri-section bandpass filter using stepped impedance resonators (SIRs) is designed, simulated, built, and measured using hair pin structure. The complete design procedure is given from analytical stage to implementation stage with details. The coupling between SIRs is investigated for the first time in detail by studying their effect on the filter characteristics including bandwidth, and attenuation to optimize the filter perfomance. The simulation of the filter is performed using method of moment based 2.5D planar electromagnetic simulator. The filter is then implemented on RO4003 material and measured. The simulation, and measured results are compared and found to be very close. The effect of coupling on the filter performance is then investigated using electromagnetic simulator. It is shown that the coupling effect between SIRs can be used as a design knob to obtain a bandpass filter with a better performance for the desired frequency band using the proposed filter topology. The results of this work can used in wireless communication systems where multiple frequency bands are needed.

Keywords: Bandpass, Resonators, Sirs, Microstrip, Filter, Communication, Wireless.