Milad Ekhteraei

This paper presents a microstrip lowpass filter with compact size, and ultra-wide stopband. The structure consists of a modified hairpin resonator loaded with tapered cells and the circular patches as the suppressing cell. The proposed lowpass filter has −3 dB cut-off frequency at 1.64 GHz. It also has suitable performances such as: ultra-sharp transition-band of 0.09 GHz that is from −3 to −20 dB, an extended stopband bandwidth from 1.73 to 21 GHz with the attenuation level more than −20 dB, low insertion-loss, flat group delay in the passband, and simple structure. The proposed lowpass filter is simulated and fabricated and there is good agreement between the simulation and measurement results.

A compact lowpass filter (LPF) using a lattice‐shaped resonator is presented with a wide rejection band and sharp roll‐off. The designed LPF has −3 dB cut‐off frequency at 4.34 GHz. The fabricated LPF is simulated and tested; there is a good agreement between the simulation and experimental results. Experimental results show that the maximum variation of flat group delay is only 0.3 ns in the passband. Also, the measured return‐loss and insertion loss are more than 19 dB and 2 .

This paper, a compact low-pass filter (LPF) with an Elliptic function response using P-shaped resonators is presented. The LPF with simple structure results in the low insertion loss less than 0.1 dB and high return loss better than 20 dB, in the pass-band. The proposed filter with a −3 dB cutoff frequency of 2.61 GHz is fabricated and measured. The measured results show that the proposed LPF has significant advantages such as a wide stop-band from 2.9 GHz to 17.3 GHz with the suppression level better than −20 dB, and it has an acceptable sharp frequency response in the transition band. The measurement results are in good agreement with the simulation results.

This study presents a novel lowpass filter (LPF) with very sharp roll-off and ultra-high figure-of-merit (FOM). The −3 dB cutoff frequency of the proposed LPF is set nearby 1.39 GHz to eliminate the higher frequencies for wireless applications in communication systems. The measurement results indicated that the transition band of the proposed LPF is 0.04 GHz from −3 dB to −20 dB and 0.06 GHz from −3 dB to −40 dB, which shows a very sharp roll-off. Also, an ultra-wide stopband from 1.39 GHz to 20.2 GHz and low insertion loss and high return loss in the passband region are achieved. The proposed LPF has an ultra-high FOM which is probably the highest FOM ever reached in related works until 2014, thus showing its strong sufficiency. The proposed LPF is fabricated and tested, and there is a good agreement between the simulation and measured results.