Open AccessCompact coupled‐line balun with complex impedances transformation and high isolation
Author(s) -
Zhang Weiwei,
Wu Yongle,
Liu Yuanan,
Yu Cuiping,
Chen Wenhua
Publication year - 2015
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.2014.0775
Subject(s) - balun , transmission line , microstrip , impedance matching , stub (electronics) , electrical impedance , electronic engineering , planar , electric power transmission , topology (electrical circuits) , computer science , engineering , electrical engineering , computer graphics (images) , antenna (radio)
A planar microstrip circuit is proposed to design a kind of coupled‐line balun with good ports matching and high output‐ports isolation for complex source to complex load impedance transformation. This balun prototype essentially consists of three coupled‐line sections, a tapped open transmission‐line stub (TOTS) on the left‐hand side, and a tapped complex equivalent‐impedance part (TCEP) on the right‐hand side. The TCEP is the key to realise high output isolation and all ports matching. Based on the traditional even‐odd mode technique and the transmission‐line theory, closed‐form mathematical equations for circuit electrical parameters are obtained. To demonstrate this proposed design theory, a practical microstrip coupled‐line balun is designed, simulated and measured to operate at approximately 2 GHz, indicating high isolation and balanced output. Good agreements between the simulated and measured results verify this design.