A -Transform Method for Synthesis of Unequal-Length Multisection Transmission Lines for Multiband Applications

A method based on the Z-transform is demonstrated to cascade transmission line sections of unequal lengths and achieve multiband and/or wideband properties. Unlike previous methods based on the Z-transform, the proposed method associates the z -1 term with the infinitesimal length of the unit segmen...

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Bibliographic Details
Published in:IEEE transactions on microwave theory and techniques 2017-09, Vol.65 (9), p.3200-3210
Main Authors: Kim, Joonsuk, Lee, Yongshik
Format: Article
Language:English
Subjects:
Broadband
Dual band
Impedance
Impedance transformer
Microwave circuits
multiband
multisection
Polynomials
Power dividers
Power transmission lines
stepped impedance
Transmission lines
unequal length
Wideband
Wilkinson power dividers
Z transforms
Z-transform
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Summary:A method based on the Z-transform is demonstrated to cascade transmission line sections of unequal lengths and achieve multiband and/or wideband properties. Unlike previous methods based on the Z-transform, the proposed method associates the z -1 term with the infinitesimal length of the unit segment. Consequently, any electrical length can be expressed in the z -1 form. Therefore, while the previous methods are restricted to cascading lines of a commensurate length only, the proposed method can be applied to those of incommensurate lengths. Furthermore, the z-polynomials for triple or more bands can be constructed by multiplying a combination of single-and dual-band polynomials, which remarkably simplifies the entire procedure to develop multiband and/or wideband circuits with virtually no limitation in terms of the number and/or combination of frequencies. The validity and practicality of the proposed method is verified with experimental results for various impedance transformers for real loads and Wilkinson power dividers; the results show the independence in the number and combination of operating frequencies as well as a dual-band operation with a center frequency ratio as large as 7.75.
ISSN:0018-9480
1557-9670
DOI:10.1109/TMTT.2017.2678474