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International Journal on Communications Antenna and Propagation - June 2011 (Vol. 1 N. 3) - Papers

A New Method for Calculation of Impedance in Straight and Ring Wires in Various Frequencies
Estimation of Band-Limited AC Signals from Irregular Samples
Optimum Design of Wideband Multilayered Parallel Coupled-Line Microstrip Filters with the Suppression of Spurious Harmonics
A New Six-Port Receiver for Wave-Radio
Design and Performance Characterization of Waveguides
Information Coding and Steganography Using Fractal in Multimedia's
Analysis of Multiconductor Transmission Line Loaded by Multi MESFET Transistors Modeled by their Large Signal Scheme: an FDTD Approach
Loaded Dipole Antenna Using DPS and DNG Materials
A Rigorous Study of Complex Modes of Higher Order in the Rectangular Waveguides Filled with Longitudinally Magnetized Ferrite
Azimuth Radiation Pattern Shaping and Control for FM Broadcast
Simulation of a Multi-band Class E PA with a PWM Envelope-coded Signal, for a Multi-radio Transmitter
Radiation and Gain Characteristics of Log Periodic Antenna

International Journal on Communications Antenna and Propagation - Papers

A New Method for Calculation of Impedance in Straight and Ring Wires in Various Frequencies
by S. A. Fazljoo, M. R. Besmi

Vol. 1. n. 3, pp. 211-218

Abstract - In this paper a new method for Impedance Calculation by Fazljoo and Besmi (ICFB) is presented to calculate frequency-dependent impedance in a straight and ring wires. The new method is compared with Impedance Calculation by Ramo-Whinnery (ICRW) and Impedance Calculation by Mesh (ICM) method which are conventionally used in high frequencies impedance calculation. The new method is fast and simple and its results are admissibly accurate and conform with the conventional methods.

Keywords: Coilgun, High Frequency, Inductance, Linear Motor, Skin Depth.

Estimation of Band-Limited AC Signals from Irregular Samples
by Predrag B. Petrović

Vol. 1. n. 3, pp. 219-229

Abstract - The paper deals with the estimation of amplitude and phase of an analogue multi-harmonic band-limited signal from irregularly spaced sampling values. To this end, assuming the signal fundamental frequency is known in advance (i.e., estimated at an independent stage), a complexity-reduced algorithm for signal reconstruction in time domain is proposed. The reduction in complexity is achieved owing to completely new analytical and summarized expressions that enable a quick estimation at a low numerical error. The proposed algorithm for the calculation of the unknown parameters requires O((2M+1)2) flops, while the straightforward solution of the obtained equations takes O((2M+1)3) flops (M is the number of the harmonic components). It is applied in signal reconstruction, spectral estimation, system identification, as well as in other important signal processing problems. The proposed method of processing can be used for precise RMS measurements (for power and energy) of a periodic signal based on the presented signal reconstruction. The paper investigates the errors related to the signal parameter estimation, and there is a computer simulation that demonstrates the accuracy of these algorithms.

Keywords: Band-limited signals, Fourier coefficient estimation, Analytical solutions, Signal reconstruction, Time-domain.

Optimum Design of Wideband Multilayered Parallel Coupled-Line Microstrip Filters with the Suppression of Spurious Harmonics
by H. Oraizi, N. Azadi-Tinat

Vol. 1. n. 3, pp. 230-237

Abstract - In this paper the optimum design of multilayered parallel coupled-line microstrip bandpass filters is developed based on the theory of multiconductor coupled lines in multilayered dielectric media and the method of least square. Stub lines are also connected to the circuit for the suppression of spurious response in the filter stopbands. Furthermore, impedance matching between the filter input and output ports is incorporated in the filter design. An error function is constructed for the specified filter scattering parameters through the evaluation of related transmission matrices of the network. The minimization of error function gives the optimum values of the filter dimensions. A prototype model of a third order two layer bandpass filter is designed and optimized by the proposed method and is fabricated. It's performance as obtained by the proposed design algorithm, computer simulation results and measurement data agree very well and verity the efficacy of the proposed method.

Keywords: Multilayer Microstrip filter, Parallel Coupled, Method of least square.

A New Six-Port Receiver for Wave-Radio
by Hamzé Alaeddine, Ali Alaeddine, Oussama Bazzi, Yasser Mohanna

Vol. 1. n. 3, pp. 238-242

Abstract - A new processing hardware is proposed for the direct-conversion wide-band (3–4 GHz) six-port receiver using wave radio interferometer transmitter/receiver (WRI) integrated system. Compared to the previous module using digital signal processing (DSP), the new architecture, based on a High Speed Real Time Circuit (HSRTC), has the advantage of being robust, low cost, simple mean for demodulation, instantaneously response for a specific signal input. The proposed HSRTC hardware is suitable for use in wave radio receiver (RF or optical) for high data rates. Results show that the WRI architecture, in conjunction with the proposed HSRTC, operates efficiently in the range of 3 to 4 GHz band. As a testing criterion for overall wave-radio performance, it is shown that the wave-radio interferometer architecture exhibits a favorable bit error rate (BER) performance compared with other wide-band radio communication systems utilizing QPSK modulation. Data rates of 40, 80 and 120 Mbps were used for the considered measurement.

Keywords: Radio communication, Digital signal processing, High speed integrated circuits.

Design and Performance Characterization of Waveguides
by Abdullah Eroglu

Vol. 1. n. 3, pp. 243-253

Abstract - The design and performance characterization of commercial rectangular waveguides, WR-430, when filled with general anisotropic material including gyrotropic, uniaxally anisotropic media are given in detail. The walls of the waveguide are assumed to be perfect conductors. Uniaxially anisotropic filling materials are chosen to be Sapphire and ceramic impregnated Teflon to represent positively and negatively uniaxial anisotropies, respectively. The gyrotropic material is chosen to be ferrite which is magnetically gyrotropic and biased at different magnetization levels. The design equations are derived and performance tables, and plots illustrating cut off frequencies are presented. The overall performance of the waveguide using general anisotropic media as filling material is compared with the performance of isotropic material. The results of this work can be used in RF communication systems where waveguide performance carries importance.

Keywords: Waveguides, anisotropic, ferrite, uniaxial, isotropic, RF, communications.

Information Coding and Steganography Using Fractal in Multimedia's
by Kourosh Kiani, Amir Hassan Firoozi

Vol. 1. n. 3, pp. 254-257

Abstract - The information age brings some unique challenges to society. New technology and new applications bring new threats and force us to invent new protection mechanism. So every few years, computer security needs to reinvent itself. In this paper we present a new kind of encoding in which the Hilbert fractal is characterized be function. The filling properties of this Fractal type are remarkable. Mentioned properties of the Hilbert could increase the volume of coded message in an image. Also this produces an increase in the security of decoding. We try to change 1th to 6th LSB of RGB bits an image and replace it with codes as they be on Hilbert fractal path .as we know LSB method is not robust a lots. We placed the message either out of commonly three bits (3 bits are LSB in 8 bits image) such as 4th – 6th bits of an image. We know the eye less sensitive to Blue, Red and Green successively thus could changing LSB to 5 or 6 bits in Blue and less in other colors. We utilized of DCT as robust method, in this method we changed mean coefficients, not high/low coefficients. Also we could use the idea on video clip, so as it will be separate to certain frame. Also we regard more elements in each string that describe a character. It’s necessary to mention for each character there are three forms as string. We consider more in follow sections.

Keywords: Steganography, Fractal, Encoding, Hilbert, LSB, DCT transformation.

Analysis of Multiconductor Transmission Line Loaded by Multi MESFET Transistors Modeled by their Large Signal Scheme: an FDTD Approach
by A. Amharech, H. Kabbaj

Vol. 1. n. 3, pp. 258-264

Abstract - This paper deals with electromagnetic compatibility domain and coupling in microwave circuits using a purely temporal method, the centered-points finite-difference time-domain (FDTD). We present a study of multiconductor transmission lines loaded by multiple complex nonlinear components such as the metal semiconductor field-effect transistors (MESFET). The FDTD method has several positive aspects such as the ease to introduce nonlinear components in the algorithm, the gain in simulation time and memory space. Systematic comparisons of the results of this method with those obtained by PSpice and literature are presented to validate this study.

Keywords: FDTD, MTL, nonlinear loads, multi MESFETs, Large signal scheme, Coupling.

Loaded Dipole Antenna Using DPS and DNG Materials

by A. Jafargholi, M. Kamyab

Vol. 1. n. 3, pp. 265-271

Abstract - In this paper, a loaded biconical antenna with reactive elements is investigated. The reactive loading of the bicone is inspired by DPS (Double Positive material) and DNG (Double Negative material) metamaterial (MTM) inclusions, which enables the loaded bicone to operate in multiband. The mode-matching technique is utilized while the boundary conditions are enforced to obtain simultaneous equations for the discrete modal coefficients inside all antenna regions. Computation is performed to illustrate impedance behavior in terms of geometries and frequency. A conventional Dipole and Biconical antennas are treated as special cases. Investigations reveal that the DNG loaded dipole radiates at two or multiple separated bands depending on DNG plasma frequency and geometrical parameters. The new resonant frequencies are lower than the natural resonance frequency of the conventional half wavelength dipole. The comparison between simulation results and the CST Microwave Studio shows good agreement. To validate the simulation results, a prototype is fabricated and tested. The agreement between the simulated and measured results is quite good.

Keywords: Loaded Dipole Antenna, Metamaterials, Biconical Antenna, Mode Matching.

A Rigorous Study of Complex Modes of Higher Order in the Rectangular Waveguides Filled with Longitudinally Magnetized Ferrite
by Hedi Sakli, Hanen Ltaifi, Taoufik Aguili

Vol. 1. n. 3, pp. 272-283

Abstract - In this paper, we formulate the study of propagation in the homogeneous anisotropic wave-guide by the transverse-operator method (TOM). We deal with the case of the rectangular metal guides completely filled with longitudinally magnetized ferrite (LMF). Our contribution consists in creating a graphical interface with Matlab dedicated to the simulation of dispersion in this type of structure. As a matter of fact, the application of the formalism of the transverse operator followed by the Galerkin method gives us a system with eigenvalues. Additionally, the propagation constant and the distribution of the electromagnetic fields will then be analyzed. Hence, we obtain a good agreement with the literature. Moreover, the existence of complex modes of higher order will be highlighted.

Keywords: Complex modes of higher order, Ferrite, Galerkin method, Graphic interface, TOM.

Azimuth Radiation Pattern Shaping and Control for FM Broadcast
by Gerino P. Mappatao, Felicito S. Caluyo

Vol. 1. n. 3, pp. 284-289

Abstract - FM broadcast stations must transmit power only in areas where the signal is needed. This paper presents a simpler method of shaping the azimuth electric field pattern of an antenna system for FM broadcast applications to exhibit a radiation pattern similar to a directional desired radiation pattern without minor lobes. The method is simpler than the trial-and-error method of adding parasitic elements to achieve a certain desired pattern. It makes use of a uniform linear antenna array composed of two basic antennas or bays with omnidirectional pattern. Radiation patterns are realized by determining the optimum value of the distance between bays and their phase relationship. Genetic Algorithm (GA) is used in determining these optimum values assuring a radiation pattern that resembles the desired pattern. Some GA parameter values fitted for pattern shaping are first determined to improve accuracy and consistency before the GA optimization process is run. Two sample directional patterns are presented to demonstrate the performance of the method. Results show that the proposed method produces near zero cost function values resulting to radiation patterns having very close semblance to the desired pattern. An antenna simulation software is used to validate the results in each sample desired pattern.

Keywords: array factor, cost function, Genetic Algorithm, Linear Array, Pattern Optimization.

Simulation of a Multi-band Class E PA with a PWM Envelope-coded Signal, for a Multi-radio Transmitter
by A. Diet, M. Suarez-Peñaloza, F. Robert, M. Villegas, G. Baudoin

Vol. 1. n. 3, pp. 290-295

Abstract - This paper focuses on the design of a highly efficient multi-band Power Amplifier (PA), for high Peak to Average Power Ratio (PAPR) signals in the context of a multi-radio transmitter design. Solutions are currently based on polar decomposition of the signal and constant power signal amplification. A simple methodology based on the tuning of an LC network is presented. The goals are to provide high efficiency at several frequency bands. This method implies the collaboration between transient non-linear simulations and frequency simulations/optimization techniques. Once the PA is optimized with a given frequency profile, we tested the amplification of Orthogonal Frequency Division Modulation (OFDM) signal, with Pulse Width Modulation (PWM) envelope coding, and compare with the results of the harmonic simulations. Conclusions are given about such these architectures for multi-radio.

Keywords: multi-radio architecture, EER/polar linearization, class E RF PA.

Radiation and Gain Characteristics of Log Periodic Antenna
by B. I. Neelgar, G. S. N. Raju

Vol. 1. n. 3, pp. 296-302

Abstract - Log Periodic array Antenna is one of the most important and commercially used antennas for T.V. reception. It is used in VHF and UHF bands. Although the analysis of this antenna is reported in literature, the data of self impedance, mutual impedance and radiation characteristics is not fully available. But, this data is useful for the optimal design of the antenna. In view of this the above array is considered and the analysis is carried out in the present work. The computed data on radiation pattern both, in linear and polar form for different range of frequencies is presented.

Keywords: Log-Periodic, Self-Impedance, Mutual-Impedance, Power Gain, Radiation Pattern.