Dual-Bandstop Substrate-Integrated-Coaxial Tunable and Static RF Filters

Dimitra Psychogiou,Kunchen Zhao,Roberto Gomez-Garcia

doi:10.1109/lmwc.2021.3098480

Dimitra Psychogiou, Kunchen Zhao + Show 1 more

Open Access

https://doi.org/10.1109/lmwc.2021.3098480

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Abstract

This letter discusses the RF design and practical realization of dual-bandstop filters (BSFs) with compact size and two independently controlled rejection bands. They are based on miniaturized substrate-integrated-coaxial (SIC) resonant stages that are made from two capacitively loaded posts and a thru-line. Each of the stages creates two transmission zeros (TZs) that can be exploited for the realization of dual-bandstop RF filters with approximately half the size of conventional single-post series-cascaded SIC filter configurations. Further miniaturization is achieved by tuning the center frequency of the bands. For proof-of-concept validation purposes, three prototypes were designed, manufactured, and measured. They include a static (rejection bands centered at 4 and 4.5 GHz) and a tunable (between 3.6–4.6 GHz) dual-bandstop second-order RF filters and a third-order dual-bandstop RF filter with bands centered at 4 and 4.4 GHz.

Highlights

M ICROWAVE bandstop filters (BSFs) are fundamental counterparts of ultrawideband communications and radar systems that need to acquire broad parts of the RF spectrum in the presence of interference [1]
Tunable and multi-notch BSFs are being sought for interferenceresilient sub-6-GHz wireless communications due to the large number of co-existing applications [2], [3]
A wealth of planar BSFs have been presented to date

Summary

INTRODUCTION

M ICROWAVE bandstop filters (BSFs) are fundamental counterparts of ultrawideband communications and radar systems that need to acquire broad parts of the RF spectrum in the presence of interference [1]. A wealth of planar BSFs have been presented to date They exhibit multiple rejection bands (e.g., 1–3 in [3] and [4]) and wide center-frequency ( fcen) tuning. SIC-based BSFs exhibit among the smallest physical size and widest tuning range—i.e., one octave of fcen tuning with >40 dB of IS [7], [9] They are only able to suppress a single band, except for the dual-bandstop BSF in [10]. Considering the aforementioned limitations, this letter presents the design and practical development of ultra-compact and tunable dual-bandstop SIC BSFs. The proposed filter concept exhibits significantly smaller size (reduced by about 50%) than that of a conventional dual-band BSF in which two rejection bands are created by cascading two single-post SIC BSFs (e.g., as in [6]).

THEORETICAL FOUNDATIONS

EXPERIMENTAL VALIDATION

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CONCLUSION