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

In this article, a compact (0.29 lambda(g) x 0.10 lambda(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).