In this letter, a microstrip lowpass filter with 3 dB cutoff frequency at 1.286 GHz is proposed. By using two main resonators which are placed symmetrically around (Y) axis a sharp roll-off rate (250 dB/GHz) is obtained. The proposed resonators are consisted of two asymmetric high-low impedance patches. To achieve a high relative stopband bandwidth (1.82) four high-low impedance resonators and four radial stubs as suppressing cells are employed. Furthermore, a flat insertion loss in the passband and a low return loss in the stopband can prove desired in-band and out-band frequency response. The proposed lowpass filter has a high gure of merit about 63483.
In this paper, a microstrip lowpass filter with-3dB cutoff frequency of 1.8 GHz consisting of two resonators with different triangular patches and four high-low impedance resonators as suppressing cells has been designed. To design this filter, the influence of each transmission line on the frequency response of the utilized resonators has been clarified by calculating the equations of S 21 and S 11 based on the lumped circuit of them separately. The designed filter has been constructed and tested, and a good agreement between the simulation and measurement results has been achieved. The stopband covers an ultra-wide frequency range from 1.94 to 34.556 GHz with a suppression level of-21.2 dB. Furthermore, the insertion loss in the passband region is close to zero from DC to 1.68 GHz and an acceptable return loss (17.44 dB) in this band can prove desired in-band character. Moreover, the proposed filter provides a sharp transition band equal to 228 dB/GHz. The designed lowpass filter has a high figure of merit equal to 26583.4.
In this paper, a microstrip lowpass filter adopting two main resonators with steep transition band and wide rejection band has been introduced. The first main resonance cell consists of meandered transmission lines which are loaded by modified T-shaped patches. The second main resonator is composed of high-impedance lines loaded by polygon patches. To obtain a steep skirt performance, the first and second resonators have been combined. Moreover, employing eight high–low impedance folded stubs and two rectangular open-stubs as suppressing cells has resulted in improving the stopband features. To comprehend the frequency behavior of the employed resonators and also their combination, the formulas of the transmission coefficient, reflection coefficient, and the transmission zeros of their equivalent LC circuits have been extracted, separately. According to the measurement results, the −3 dB operating frequency of this filter is 1.65 GHz. Moreover, a relative stopband bandwidth equal to 166% with a corresponding attenuation level of 23 dB and a sharp roll-off rate (393.61 dB/GHz) have been achieved. In the passband region from DC to 1.632 GHz, the insertion loss and return loss are better than 0.0763 and 15.85 dB, respectively, proving an acceptable in-band performance. Finally, the implemented structure brings about a high figure-of-merit equal to 81 672.
In this paper, a microstrip lowpass filter with-3 dB cutoff frequency of 2.1 GHz consisting of three cascaded resonators with different semicircle patches and four suppressors employing radial stubs has been proposed. To indicate the role of each employed microstrip transmission line in the structure of its resonance cell, the equations of the transfer function and transition zero of the resonator have been calculated, separately. The designed filter has been constructed and tested, and a good agreement between the results of simulation and measurement has been achieved. In the whole rejection region, a return loss better than +0.28 dB and a 19.656 GHz stopband bandwidth with high rejection level of 32 dB have been obtained. Moreover, a flat insertion loss close to zero in the passband and sharp cutoff slope (203.57 dB/GHz) can verify the desired frequency response. The proposed filter has a high figure of merit equal to 24241.69.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.