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Characteristic analysis of a wideband balun transformer having a delay line element for phase compensation
Author(s) -
Li Yingdan,
Nishizuka Norio,
Nakashima Yoshio
Publication year - 1999
Publication title -
electrical engineering in japan
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.136
H-Index - 28
eISSN - 1520-6416
pISSN - 0424-7760
DOI - 10.1002/(sici)1520-6416(19990130)126:2<1::aid-eej1>3.0.co;2-g
Subject(s) - wideband , balun , transformer , transmission line , electrical engineering , impedance matching , electric power transmission , electronic engineering , electrical impedance , engineering , acoustics , physics , voltage , antenna (radio)
The balanced‐unbalanced transformer (balun) is extensively used in radio communication and measuring instruments. In recent years, with the development of television and portable telephones, wideband transformers tend to be miniaturized. In this paper, the wideband transformer is analyzed in terms of distributed coupled‐line theory. A main result of the analysis is that the balance and unbalance transmission characteristics of the balun are markedly improved in the high‐frequency range by using a delay line element for compensation. If the connection point S w between the coil winding and delay line is off the ground, the balance transmission band is about doubled in the low‐frequency range. If the point S w is grounded and if the impedance ratio m 2 is small, a higher degree of unbalance attenuation can be obtained. Better balance transmission characteristics can be obtained when the matching factor K approaches half the optimum. In addition, we show that an in‐phase or anti‐phase transformer can be made on the basis of our isolation wideband transformer. The equivalent circuits of in‐phase and anti‐phase wideband n :1 transformers are obtained from our theoretical analysis and these can be formed by the same transformer. The transmission characteristics of in‐phase and anti‐phase wideband transformers are analyzed and improved characteristics are obtained in the high‐frequency range. The theoretical and experimental values agree well over the wide frequency range of 100 KHz to 1000 MHz. ©1998 Scripta Technica, Electr Eng Jpn, 126(2): 1–14, 1999