New design of an adjustable compact microstrip lowpass filter using Z‐shaped resonators with low VSWR. Issue 11 (22nd June 2020)

• Record Type: Journal Article
• Authors: Alizadeh Pahlavani, Mahmoud; Moradkhani, Masoud; Sayadi, Ramin
• Is Part Of: Microwave and optical technology letters. Volume 62:Issue 11(2020:Nov.)
• Page Start: 3527
• Page End: 3535
• Publication Date: 2020-06-22
• Subjects: lowpass filter -- microstrip filter -- microwave filter -- resonator; Microwaves -- Periodicals; Optics -- Periodicals; 621
• DOI: 10.1002/mop.32503
• Languages: English
• ISSNs: 0895-2477

Abstract

Abstract: 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 λg 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.