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http://dx.doi.org/10.4218/etrij.15.0114.0188

Analysis of Novel Approach to Design of Ultra-wide Stopband Microstrip Low-Pass Filter Using Modified U-Shaped Resonator  

Karimi, Gholamreza (Department of Electrical Engineering, the Faculty of Engineering, Razi University)
Lalbakhsh, Ali (Department of Engineering, Kermanshah Branch, Islamic Azad University)
Dehghani, Khatereh (Department of Electrical Engineering, Kermanshah Branch, Islamic Azad University)
Siahkamari, Hesam (Department of Electrical Engineering, the Faculty of Engineering, Razi University)
Publication Information
ETRI Journal / v.37, no.5, 2015 , pp. 945-950 More about this Journal
Abstract
A novel microstrip low-pass filter is presented to achieve an ultra-wide stopband with 11 harmonic suppression and very sharp skirt characteristics. The filter is composed of a modified U-shaped resonator (which creates two fully adjustable transmission zeroes), a T-shaped resonator (which determines a cut-off frequency), and four radial stubs (which provide a wider stopband). The operating mechanism of the filter is investigated based on a proposed equivalent-circuit model, and the role of each section of the proposed filter in creating null points is theoretically discussed in detail. The presented filter with 3 dB cut-off frequency ($f_c=2.35GHz$) has been fabricated and measured. Results show that a relative stopband bandwidth of 164% (referred to as a 22 dB suppression) is obtained while achieving a high figure-of-merit of 15,221.
Keywords
Microstrip low-pass filter; U-shaped resonator; ultra-wide stopband;
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