Compact and very sharp roll-off low-pass filter using folded flag resonator

Abstract

In this paper, a microstrip low-pass filter (LPF) using folded-flag-shaped resonators is designed and presented. Its base resonator length is 12.4 mm, and the proposed low-pass filter has a sharpness of 0.08 GHz. The filter cut-off frequency is 1.44 GHz, and the return loss is reduced to a level of −17 dB, indicating a flat pass-band. Also, the suppressing cell is used to weaken the disturbing harmonics by a stepped impedance structure and two high-impedance stubs with an L-shaped structure, which results in a bandwidth of 17.78 GHz. The circuit area of the LPF is 20.9 × 7.5 mm², which it has created a suitable normalized circuit size (NCS) rate due to the −3 dB cut-off frequency. The figure of merit (FOM) of the proposed filter is 114450, and it indicates that the microstrip LPF responses are optimal as compared to previous works.

KEYWORDS:

• Microstrip lowpass filter
• flag resonator
• sharp roll-off
• suppressing cell

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Seyed Hamed Kazemi

Seyed Hamed Kazemi was born in Kermanshah, Iran, in 1993. He received the B.Sc. in telecommunication Engineering from the Kermanshah University of technologies, Kermanshah, Iran, in 2016 and M.Sc. degree in Electronic Engineering in 2018 from Razi University of Kermanshah. He is currently a Ph.D. student at Malek Ashtar University of Technology. His research interests include Pulse power systems and design of the microwave circuits, microstrip filters, and couplers.

Mohsen Hayati

Mohsen Hayati received the B.E. degree in Electronics and Communication Engineering from Nagarjuna University, Andhra Pradesh, India, in 1985, and the M.E. and Ph.D. degrees in Electronics Engineering from Delhi University, Delhi, India, in 1987 and 1992, respectively. He joined the Electrical Engineering Department, Razi University, Kermanshah, Iran, as an Assistant Professor in 1993. Currently, he is a Professor with the Electrical Engineering Department, Faculty of Engineering, Razi University. He has published more than 230 papers in international, domestic journals, and conferences. His current research interests include microwave and millimeter wave devices and circuits, power amplifiers, low noise amplifier design, analog cmos circuit, application of computational intelligence, artificial neural networks, fuzzy systems, neuro-fuzzy systems, electronic circuit synthesis, modeling and simulations.