Compact Planar Tunable Filter With Constant Absolute Bandwidth and Wide-Frequency Tuning Range Using DGS Coupling Structure

In this study, defected ground structures (DGSs) are applied in the coupling schemes of a planar tunable filter to achieve constant absolute bandwidth (CAB). The filter consists of parallel-coupled quarter-wavelength resonators loaded with varactor diodes, and the DGSs are implemented to enhance the...

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Autores principales:	Yun Liu, Lingyun Liu, Chen Liang, Irfan Majid
Formato:	article
Lenguaje:	EN
Publicado:	IEEE 2021
Materias:	Tunable filter defected ground structure constant absolute bandwidth Electrical engineering. Electronics. Nuclear engineering TK1-9971
Acceso en línea:	https://doaj.org/article/f01ce533de664af3a99ac26be4004161
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spelling	oai:doaj.org-article:f01ce533de664af3a99ac26be40041612021-12-02T00:00:48ZCompact Planar Tunable Filter With Constant Absolute Bandwidth and Wide-Frequency Tuning Range Using DGS Coupling Structure2169-353610.1109/ACCESS.2021.3124218https://doaj.org/article/f01ce533de664af3a99ac26be40041612021-01-01T00:00:00Zhttps://ieeexplore.ieee.org/document/9594848/https://doaj.org/toc/2169-3536In this study, defected ground structures (DGSs) are applied in the coupling schemes of a planar tunable filter to achieve constant absolute bandwidth (CAB). The filter consists of parallel-coupled quarter-wavelength resonators loaded with varactor diodes, and the DGSs are implemented to enhance the coupling at a certain part. This method enables controlling the ratio between electric coupling and magnetic coupling and makes the total coupling coefficient inversely proportional to frequency, as required to achieve CAB. With the DGSs, the tunable resonators can be equalized to stepped-impedance tunable resonators, which bring wider-frequency tuning range. Moreover, due to the help of the DGS in adjusting the coupling coefficient curve versus frequency, the resonators maintain their universal widths and are coupled at full length. Thus, the tunable filter is as compact as a traditional combline filter. Meanwhile, each external coupling scheme contains a series capacitor and a short-ended stub that is parallel coupled to the first or last resonator, resulting in external <inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> factor being proportional to frequency. A second-order tunable filter is designed and measured, and a wide tuning range from 0.63 GHz to 1.09 GHz together with a constant bandwidth of 65±4 MHz are achieved. Besides, a transmission zero generated by coupling zero of the DGS-loaded coupling structure can be observed at the high stopband. The total dimension of the filter is 0.05 <inline-formula> <tex-math notation="LaTeX">$\lambda _{\mathrm {g}}^{\ast }~0.15 \lambda _{\mathrm {g}}$ </tex-math></inline-formula>, which is more compact than solutions with partial-length coupling schemes. Owing to the simple structures of the resonators and coupling schemes, the filter solution has the potential to design high-order tunable filters with CAB, and a compact fourth-order tunable filter with ABC is given with simulation results.Yun LiuLingyun LiuChen LiangIrfan MajidIEEEarticleTunable filterdefected ground structureconstant absolute bandwidthElectrical engineering. Electronics. Nuclear engineeringTK1-9971ENIEEE Access, Vol 9, Pp 157259-157266 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Tunable filter defected ground structure constant absolute bandwidth Electrical engineering. Electronics. Nuclear engineering TK1-9971
spellingShingle	Tunable filter defected ground structure constant absolute bandwidth Electrical engineering. Electronics. Nuclear engineering TK1-9971 Yun Liu Lingyun Liu Chen Liang Irfan Majid Compact Planar Tunable Filter With Constant Absolute Bandwidth and Wide-Frequency Tuning Range Using DGS Coupling Structure
description	In this study, defected ground structures (DGSs) are applied in the coupling schemes of a planar tunable filter to achieve constant absolute bandwidth (CAB). The filter consists of parallel-coupled quarter-wavelength resonators loaded with varactor diodes, and the DGSs are implemented to enhance the coupling at a certain part. This method enables controlling the ratio between electric coupling and magnetic coupling and makes the total coupling coefficient inversely proportional to frequency, as required to achieve CAB. With the DGSs, the tunable resonators can be equalized to stepped-impedance tunable resonators, which bring wider-frequency tuning range. Moreover, due to the help of the DGS in adjusting the coupling coefficient curve versus frequency, the resonators maintain their universal widths and are coupled at full length. Thus, the tunable filter is as compact as a traditional combline filter. Meanwhile, each external coupling scheme contains a series capacitor and a short-ended stub that is parallel coupled to the first or last resonator, resulting in external <inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> factor being proportional to frequency. A second-order tunable filter is designed and measured, and a wide tuning range from 0.63 GHz to 1.09 GHz together with a constant bandwidth of 65±4 MHz are achieved. Besides, a transmission zero generated by coupling zero of the DGS-loaded coupling structure can be observed at the high stopband. The total dimension of the filter is 0.05 <inline-formula> <tex-math notation="LaTeX">$\lambda _{\mathrm {g}}^{\ast }~0.15 \lambda _{\mathrm {g}}$ </tex-math></inline-formula>, which is more compact than solutions with partial-length coupling schemes. Owing to the simple structures of the resonators and coupling schemes, the filter solution has the potential to design high-order tunable filters with CAB, and a compact fourth-order tunable filter with ABC is given with simulation results.
format	article
author	Yun Liu Lingyun Liu Chen Liang Irfan Majid
author_facet	Yun Liu Lingyun Liu Chen Liang Irfan Majid
author_sort	Yun Liu
title	Compact Planar Tunable Filter With Constant Absolute Bandwidth and Wide-Frequency Tuning Range Using DGS Coupling Structure
title_short	Compact Planar Tunable Filter With Constant Absolute Bandwidth and Wide-Frequency Tuning Range Using DGS Coupling Structure
title_full	Compact Planar Tunable Filter With Constant Absolute Bandwidth and Wide-Frequency Tuning Range Using DGS Coupling Structure
title_fullStr	Compact Planar Tunable Filter With Constant Absolute Bandwidth and Wide-Frequency Tuning Range Using DGS Coupling Structure
title_full_unstemmed	Compact Planar Tunable Filter With Constant Absolute Bandwidth and Wide-Frequency Tuning Range Using DGS Coupling Structure
title_sort	compact planar tunable filter with constant absolute bandwidth and wide-frequency tuning range using dgs coupling structure
publisher	IEEE
publishDate	2021
url	https://doaj.org/article/f01ce533de664af3a99ac26be4004161
work_keys_str_mv	AT yunliu compactplanartunablefilterwithconstantabsolutebandwidthandwidefrequencytuningrangeusingdgscouplingstructure AT lingyunliu compactplanartunablefilterwithconstantabsolutebandwidthandwidefrequencytuningrangeusingdgscouplingstructure AT chenliang compactplanartunablefilterwithconstantabsolutebandwidthandwidefrequencytuningrangeusingdgscouplingstructure AT irfanmajid compactplanartunablefilterwithconstantabsolutebandwidthandwidefrequencytuningrangeusingdgscouplingstructure
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Compact Planar Tunable Filter With Constant Absolute Bandwidth and Wide-Frequency Tuning Range Using DGS Coupling Structure

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