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Selected Abstracts

Combined resonance phenomena due to earth wires grounding and conductor sagging effects in overhead transmission lines

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 4 2003
J. A. Brand Ãofaria
The periodic discrete bonding of earth wires to ground, on the one hand, and the distributed conductor sagging between towers, on the other, are mechanisms that have been reported before to be individually responsible for abnormal high-frequency responses of overhead power lines. In this paper we consider both effects superposed and then evaluate, as a function of the frequency, the even and odd mode propagation parameters characterizing a given transmission line section. We show that the two interacting mechanisms being combined do not annihilate each other; on the contrary, wave interference effects accumulate giving rise to broadband noticeable resonance phenomena for frequencies such that the line span gets close to one half wavelength, typically in the 400,600 kHz range. [source]

Harmonic suppressed and size-reduced bandstop and bandpass filters

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2009
Majeed A. S. Alkanhal
Abstract New bandstop/bandpass microstrip structures with harmonic suppression are presented in this article. By replacing the series quarter-wavelength connecting lines of conventional open-stub bandpass/bandstop filters with the equivalent ,-shaped line section, compact open-stub bandstop/bandpass filters with second harmonic suppression are achieved. Transmission-line theory is used to derive the design equations of the equivalent ,-shaped lines. Simulation and experiments have also been done to validate the proposed design concept. When compared with the conventional open-stub Bandpass/Bandstop filters, the second harmonic is suppressed and size reduction is achieved in both the Bandstop/bandpass structures. Moreover, results confirm that the proposed shaped bandpass filter achieves a further third harmonic rejection. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2109,2114, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24580 [source]

Design and optimization of multi-band Wilkinson power divider

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 1 2008
Nihad Dib
Abstract In this paper, a general and easy procedure for designing the symmetrical Wilkinson power divider that achieves equal-power split at N arbitrary frequencies is introduced. Each quarter-wave branch in the conventional Wilkinson divider is replaced by N sections of transmission lines, and the isolation between the output ports is achieved by using N resistors. The design parameters are the characteristic impedances and lengths of the N transmission line sections, and the N isolation resistors. The even,odd modes of analysis are used to derive the design equations. Closed-form expressions, which are suitable for CAD purposes, are derived for the dual-band divider. For N , 3, closed-form expressions are not available, and therefore, the powerful particle swarm optimization method is used to obtain the design parameters. Examples of the dual-, triple-, and quad-band dividers are presented to validate the proposed design procedure, and the results are compared, wherever possible, with published results using other methods. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008. [source]

Three-dimensional coplanar waveguide lowpass filters for MMIC applications

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2003
Laleh Lalehparvar
Abstract Shielded single and multilayer coplanar waveguide lowpass filter on GaAs and Si substrates in MMIC technology is presented and their performance is investigated with electromagnetic simulations. The filters are both Chebyshev type. The stepped-impedance method is used in the design of the lowpass filter, where high- and low-impedance line sections are cascaded together. The shielded single-layer lowpass filter consists of three low- and two high-impedance sections with characteristic impedances of 20, and 100,. The multilayer filter makes use of three low- and two high-impedance lines with characteristic impedances of 5, and 120,, respectively. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 403,405, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10931 [source]