Analysis and design of compact dual-mode bandpass filter based on modified CSRR with wide stopband for 5G sub-6 GHz mobile communications

Abstract

In this paper, a dual-mode bandpass filter with a wide stopband
based on modified complementary split-ring resonators for 5G sub-6 GHz mobile
communications is presented. The non-magnetic resonant particle known as a
complimentary split ring resonator is used with a host microstrip line with a series gap
in order to obtain a bandpass response. Since a complementary split-ring resonator
provides a narrow passband, a T-slot has been introduced in the middle of this
resonator to obtain dual-mode behavior with controllable bandwidth. Moreover, a
pair of stubs are added to the host microstrip line in order to achieve a wide stopband
with good out-of-band rejection. The proposed resonator is analyzed, and a bandpass
filter is designed to operate at 3.6 GHz to cover the 5G band from 3.4 to 3.8 GHz.
The results show that the filter has a low insertion loss, good return loss, and a wide
stopband up to 9 GHz with a compact size since its resonator offers a size of 0.1 λg × 0.14 λg where λg is the guided wavelength at 3.6 GHz.