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International Journal of Engineering & Technology Sciences
IJETS 2015, 3(1), 32-44
Design of High Performance LPF with Excellent Return Loss Using Stepped Impedance and Radial Resonators
a Department of Electrical Engineering, Kermanshah Science and Research Branch, Islamic Azad University, Kermanshah, Iran
b Department of Electrical Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran.
c Department of Electrical Engineering, Faculty of Engineering, Razi University, Kermanshah, Iran.
ABSTRACT
In this study, a novel microstrip lowpass filter (LPF) using stepped impedance, radial and open stub resonators is proposed. The insertion loss of the proposed filter is less than 0.4 dB in frequency range from DC up to 1.65 GHz. The transition band is from 1.796 up to 2.060 GHz with -3 and -40 dB attenuation points, respectively. LC equivalent circuit of the proposed main resonator is calculated precisely. The stopband bandwidth with a suppression factor of 25 dB is from 2.023 up to 15.14 GHz is reached; hence, a wide stopband with high suppression is accomplished. The results demonstrate that a roll-off rate of 140 dB/GHz, relative stopband bandwidth of 153% and a high figure-of-merit (FOM) of 24536 have been achieved. Furthermore, the proposed lowpass filter exhibits a small circuit of 0.097ðœ†ð‘”×0.225ðœ†ð‘” where ðœ†ð‘” is the guided wavelength at 3 dB cutoff frequency.
Microwave filters; Microstrip; Lowpass filter; Stepped impedance; T-shaped resonators; Sharp roll-off; Radial resonators.