Stepped Impedance Hairpin Resonator (SIHR) based Compact Lowpass Filter with Wide Attenuation Band

ABSTRACT

In this article, a compact (0.29 λ_g x 0.10 λ_g) low-pass filter (LPF) using a trisection stepped impedance hairpin resonator (SIHR) with a low insertion loss and a wide attenuation band is proposed. The microstrip structure is loaded with an L-shaped spur-line resonator and folded T-shaped stub for generating additional transmission zeroes to obtain a wider attenuation band. Moreover, an open stub is introduced into the existing structure to enrich the stopband performance of the LPF with a relative stopband rejection of almost 142 %. The proposed LPF that operates at a cut-off frequency of 1.7 GHz is suppressed up to −46 dB at the resonant frequency with a passband insertion loss of 0.35 dB. The suppression of harmonics is achieved up to 10 GHz with a suppression factor of 2. A well-matched behavior is observed in between the EM simulated, measurement, and circuit simulated results. The proposed LPF is suitable for mobile phones (1850 MHz), a global system for mobile communications (1800 MHz), and LTE communications (1700 MHz).

KEYWORDS:

• Folded T-shaped stub
• stepped impedance hairpin resonator (SIHR)
• spur-line resonator
• LPF
• open stub

Acknowledgments

The authors would like to acknowledge the ISRO project on “Applicability of Electromagnetic Metamaterials in Antennas and Microwave Circuits for use in Space Applications” and Mr. Dipesh Debnath, Lab technician,National Institute of Technology, Agartala, for their great support.

Disclosure statement

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