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A novel compact lowpass filter with sharp roll-off and wide stopband

Published online by Cambridge University Press:  08 August 2019

M. Hayati Open the ORCID record for M. Hayati [Opens in a new window] ,
AS. Abdipour  and
AR. Abdipour
M. Hayati
Affiliation:
Electrical Engineering Department, Faculty of Engineering, Razi University, Tagh-E-Bostan, Kermanshah-67149, Iran
AS. Abdipour
Affiliation:
Electrical Engineering Department, Faculty of Engineering, Razi University, Tagh-E-Bostan, Kermanshah-67149, Iran
AR. Abdipour
Affiliation:
Electrical Engineering Department, Faculty of Engineering, Razi University, Tagh-E-Bostan, Kermanshah-67149, Iran
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Abstract

In this paper, a microstrip lowpass filter adopting two main resonators with steep transition band and wide rejection band has been introduced. The first main resonance cell consists of meandered transmission lines which are loaded by modified T-shaped patches. The second main resonator is composed of high-impedance lines loaded by polygon patches. To obtain a steep skirt performance, the first and second resonators have been combined. Moreover, employing eight high–low impedance folded stubs and two rectangular open-stubs as suppressing cells has resulted in improving the stopband features. To comprehend the frequency behavior of the employed resonators and also their combination, the formulas of the transmission coefficient, reflection coefficient, and the transmission zeros of their equivalent LC circuits have been extracted, separately. According to the measurement results, the −3 dB operating frequency of this filter is 1.65 GHz. Moreover, a relative stopband bandwidth equal to 166% with a corresponding attenuation level of 23 dB and a sharp roll-off rate (393.61 dB/GHz) have been achieved. In the passband region from DC to 1.632 GHz, the insertion loss and return loss are better than 0.0763 and 15.85 dB, respectively, proving an acceptable in-band performance. Finally, the implemented structure brings about a high figure-of-merit equal to 81 672.

Keywords

Microstrip lowpass filtermeandered transmission linesmodified T-shaped patchespolygon patches
Type
Research Papers
Information
International Journal of Microwave and Wireless Technologies , Volume 12 , Issue 1 , February 2020 , pp. 21 - 33
Copyright
Copyright © Cambridge University Press and the European Microwave Association 2019 

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