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New design of an adjustable compact microstrip lowpass filter using Z‐shaped resonators with low VSWR
Author(s) -
Alizadeh Pahlavani Mahmoud,
Moradkhani Masoud,
Sayadi Ramin
Publication year - 2020
Publication title -
microwave and optical technology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 76
eISSN - 1098-2760
pISSN - 0895-2477
DOI - 10.1002/mop.32503
Subject(s) - stopband , passband , resonator , cutoff frequency , return loss , insertion loss , microstrip , low pass filter , group delay and phase delay , physics , materials science , filter (signal processing) , optics , band pass filter , electrical engineering , engineering , antenna (radio)
In this article, an adjustable microstrip lowpass filter(LPF) with the cut‐off frequency ( f c ) at 1.59 GHz is designed and fabricated. The proposed structure is composed of a Z‐shaped resonator as basic resonator and a combination of modified T‐shaped and Z‐shaped resonators as suppressor units. To describe a theoretical design, the L‐C equivalent circuit of the basic resonator and also its transfer function are calculated precisely; then, the location of the first transmission zero (TZ) is accurately computed. Generating a deep TZ near the cutoff frequency leads to a high roll‐off rate of 195 dB/GH. The LPF also benefits from an extremely wide stopband from 1.72 to 23.67 GHz (15 f c ). In passband region, the insertion loss and return loss of the LPF are 0.62 and 22.9 dB, respectively. The experimental results also show that maximum variation of group delay is only 0.53 ns regarding a negligible figure. The electrical size of the LPF is 0.187 × 0.083 λ g 2 (where λ g is the guided wavelength at 1.59 GHz). Finally, the proposed LPF achieves a high figure of merit of 57 860 deemed a great accomplishment.