Open AccessCompact closed‐loop resonator filters with wide spurious free band and extended common‐mode noise suppression
Author(s) -
Arbelaez Arcesio,
Olvera JoseLuis,
Corona Alonso,
Saavedra Carlos
Publication year - 2020
Publication title -
iet microwaves, antennas and propagation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.555
H-Index - 69
eISSN - 1751-8733
pISSN - 1751-8725
DOI - 10.1049/iet-map.2019.0581
Subject(s) - stopband , resonator , transition band , control theory (sociology) , filter (signal processing) , elliptic filter , noise (video) , spurious relationship , prototype filter , band stop filter , m derived filter , physics , acoustics , topology (electrical circuits) , electronic engineering , low pass filter , mathematics , optics , engineering , computer science , electrical engineering , artificial intelligence , image (mathematics) , statistics , control (management)
A theoretical analysis is presented for miniaturised filters with an extended stopband and extended common‐mode (CM) rejection, using loaded closed‐loop resonators. A numerical method is presented to solve the equations extracted from the ideal transmission line model. Selection of critical resonator parameters to minimise filter area while simultaneously maximising the differential‐mode (DM) stopband or the CM noise suppression is explored. The trade‐off between size, stopband and CM rejection is presented and used to design three filters at 1 GHz, which are designed to verify the proposed concept. First, a differential second‐order filter with an extended DM stopband ( S 21 d < − 20 dB) up to 6.8 f cand extended CM noise suppression ( S 21 c < − 20 dB) up to 6.42 f cis realised to show the parameter trade‐offs. Then optimal resonators are used to develop a compact singled‐ended filter ( 0.011 λ g 2 ) with an extended stopband ( S 21 < − 30 dB) up to 8.2 f cand the smallest size. Lastly, a second order filter with an optimal extended CM rejection ( S 21 c < − 20 dB) up to 6.64 f cis presented. Measured results are presented. All three filters stand out compared to other works by exhibiting the smallest footprint relative to the operating frequency.