Title: Compact microstrip lowpass filter with wide stopband and very‐sharp roll‐off
Abstract: Electronics LettersVolume 52, Issue 10 p. 830-831 Microwave technologyFree Access Compact microstrip lowpass filter with wide stopband and very-sharp roll-off M. Hayati, Corresponding Author M. Hayati [email protected] Department of Electrical Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, IranSearch for more papers by this authorM. Akbari, M. Akbari Department of Electrical Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, IranSearch for more papers by this authorR. Salahi, R. Salahi Department of Electrical Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, IranSearch for more papers by this author M. Hayati, Corresponding Author M. Hayati [email protected] Department of Electrical Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, IranSearch for more papers by this authorM. Akbari, M. Akbari Department of Electrical Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, IranSearch for more papers by this authorR. Salahi, R. Salahi Department of Electrical Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, IranSearch for more papers by this author First published: 01 May 2016 https://doi.org/10.1049/el.2016.0191Citations: 14AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Abstract A novel microstrip lowpass filter (LPF) with good specifications such as wide stopband and sharp roll-off is reported. The filter structure consists of split ring resonator loaded by folded polygene patches. The proposed filter with −3 dB cut-off frequency at 1.57 GHz has been designed, fabricated and measured. The LPF has a wide stopband from 1.67 to 14 GHz with a rejection level greater than −20 dB, sharp roll-off rate equal to 170 dB/GHz and low insertion loss lower than 0.13 dB in 94% of the passband. Finally, a high figure of merit of 51,178 is obtained. Introduction The compact microstrip lowpass filters (LPFs) with wide stopband, sharp roll-off, high figure of merit (FOM) and good performance are widely being applied in modern communication systems. For obtaining wide stopband and relatively sharp roll-off rate, an LPF has been reported in [1]. Among all of the references, the presented LPF [2] has the best normalised circuit size (NCS) but the disadvantage of this LPF is a gradual cut-off frequency. The only benefit of the presented work in [3] is its sharp roll-off. In [4], the presented LPF has a relatively good SF but the other factors are not appropriate. In [5], the presented filter has a wide stopband and compact size but the cut-off frequency and roll-off rate are not suitable in this design. An LPF with sharp transition band has been fabricated in [6] but it has a very narrow rejection band. In this Letter, the proposed LPF has a wide stopband, good return loss, very-sharp roll-off rate and compact size. Fig 1Open in figure viewerPowerPoint Layout of proposed LPF and its dimensions (unit: millimetres) Fig 2Open in figure viewerPowerPoint Layout and simulated S-parameters a Filter with resonator-1 b Filter with resonator-2 c Filter with resonator-3 d Filter with all of resonators Filter design Fig. 1 shows the configuration of the proposed filter consisting of three resonators, which are composed of high impedance transmission folded polygene patches. The filter includes four resonators. To depict the design process of the filter, all of the used resonators are studied below. The frequency response of resonator-1 is illustrated in Fig. 2a. As can be seen in Fig. 2a, one transmission zero at 2.8 GHz with −38 dB attenuation level is created by resonator-1, which provides a narrow stopband. Fig. 2b illustrates the simulated frequency response of filter with resonator-2, which generates two transmission zeros located at 2.8 and 5 GHz with the attenuation level of −29 and −48 dB, respectively. So the roll-off rate can be improved. In Fig. 2c, resonator-3 has more transmission zeros and better sharp roll-off rate but the stopband is still narrow. In Fig. 2d, using all of the illustrated resonators rejection bandwidth increased significantly; furthermore sharp roll-off and good return loss are obtained for the presented filter. Simulation and measurement results The filter is fabricated on Reinforced Teflon (RT)/Duroid 5880 substrate with (εr = 2.2, h = 0.508 mm, loss tangent = 0.0009) as shown in Fig. 3a. The circuit is simulated using Advanced Design System (ADS) software and measurement results are carried out by Agilent HP8757A network analyser. Simulated and measured S-parameters are shown in Fig. 3b. The −3 dB cut-off frequency of the filter is ∼1.57 GHz. The stopband region is extended from 1.67 up to 14 GHz with attenuation level higher than −20 dB and the insertion loss is equal to 0.13 dB in 94% of the passband. Fig 3Open in figure viewerPowerPoint Fabricated LPF a Photograph b Simulated and measured S-parameters Table 1 depicts a comparison among the proposed filter and some published LPFs with ring structures. In this table, the roll-off rate (ξ) is defined with considering −20 dB suppression level as maximum cut-off point and −3 dB attenuation as minimum cut-off point for the transition band. The RSB factor is defined as relative stop bandwidth and SF is the considered suppression factor for the considered rejection bandwidth. The NCS factor is defined, represented by λg, where λg is the wave-guide length at the 1.57 GHz. Also, the architecture factor (AF) is considered as 1 and 2 for a planar and 3D structure, respectively. Finally, FOM is the figure of merit for an LPF. All of these parameters have been defined in [1]. Table 1. Performance comparisons between proposed filter and other LPFs with ring structures Refs. fc (GHz) ξ (dB/GHz) NCS (λg2) SF RSB AF FOM [1] 1.76 94.9 0.01279 2.3 1.60 1 27,292 [2] 1.18 36.3 0.00624 1.5 1.32 1 11,543 [3] 4.24 130.7 0.01400 2 1.26 1 23,526 [4] 2.4 92.5 0.03721 3 1.35 1 10,106 This work 1.57 170 0.01035 2 1.59 1 52,232 On the basis of Table 1, it can be seen that the proposed filter has highest FOM of (51,178) between other mentioned LPFs. Conclusion A novel microstrip LPF with sharp roll-off and wide stopband consisting of radial split ring resonator loaded by folded polygene patches has been designed, fabricated and measured. The filter has –3 dB cut-off frequency of 1.57 GHz and has a return loss higher than 16 dB in the passband region. This filter has many desirable features such as compact size, wide stopband and high roll-off rate of 170 dB/GHz, which provide a very good FOM of 52,232. The proposed filter with these suitable characterisations will be a good choice to implement in modern microwave communication systems. References 1Hayati, M., Asadbeigi, H., Sheikhi, A.: 'Microstrip lowpass filter with high and wide rejection band', Electron. Lett., 2012, 48, (19), pp. 1217– 1219 (https://doi/org/10.1049/el.2012.0884) 2Wang, J., Xu, L.J., Zhao, S., Guo, Y.X., Wu, W.: 'Compact quasi-elliptic microstrip lowpass filter with wide stopband', Electron. Lett., 2010, 46, (20), pp. 1384– 1385 (https://doi/org/10.1049/el.2010.1569) 3Hayati, M., Naderi, S., Jafari, F.: 'Compact microstrip lowpass filter with sharp roll-off using radial resonator', Electron. Lett., 2014, 50, (10), pp. 761– 762 (https://doi/org/10.1049/el.2014.0648) 4Li, J.L., Qu, S.W., Xue, Q.: 'Compact microstrip lowpass filter with sharp roll-off and wide stopband', Electron. Lett., 2009, 45, (2), pp. 110– 111 (https://doi/org/10.1049/el:20093246) 5Ma, K., Yeo, K.S., Lim, W.M.: 'Ultra wide rejection band lowpass cell', Electron. Lett., 2012, 48, (2), pp. 99– 100 (https://doi/org/10.1049/el.2011.2405) 6Xiano, Y., Li, L.: 'A very compact and sharp roll-off low-pass filter with four transmission zeros', Act. Passive Electron. Compon., 2015, 2015, pp. 1– 6 Citing Literature Volume52, Issue10May 2016Pages 830-831 FiguresReferencesRelatedInformation
Publication Year: 2016
Publication Date: 2016-03-08
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 18
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