Wideband Bandpass Filtering Balun With Perfect In-Band Matching and Isolation

In this brief, a wideband balun with bandpass filtering response is synthesized based on even-/odd-mode analysis. To obtain the desired filtering selectivity, the transfer function of the proposed balun is derived and forced to be the same as the n th-order Chebyshev-transfer function. Thus, with sp...

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Bibliographic Details
Published inIEEE transactions on circuits and systems. II, Express briefs Vol. 67; no. 10; pp. 1884 - 1888
Main Authors Chen, Weijuan, Wu, Yongle, Wang, Weimin
Format Journal Article
LanguageEnglish
Published New York IEEE 01.10.2020
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subjects
Balun/balanced-to-unbalanced
Baluns
Bandpass filters
Bandwidths
Broadband
Chebyshev approximation
Circuit design
Filtering
filtering selectivity
Impedance
Matching
output isolation
Resistors
Selectivity
synthesis design
Transfer functions
Wideband
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Summary:In this brief, a wideband balun with bandpass filtering response is synthesized based on even-/odd-mode analysis. To obtain the desired filtering selectivity, the transfer function of the proposed balun is derived and forced to be the same as the n th-order Chebyshev-transfer function. Thus, with specified parameters (impedance ratio, bandwidth, and in-band return loss), the filtering characteristics of bandpass baluns can be flexibly controlled. Considering favorable in-band output matching and isolation, multiple pairs of resistors are added to the circuit. Finally, complete design procedures are provided. To verify, a 5th-order balun filter at the center frequency of 3 GHz is fabricated and measured. The simulation and measurement are in agreement, proving the correctness of the theory.
ISSN:1549-7747
1558-3791
DOI:10.1109/TCSII.2019.2955145