A Wideband Balun - How Does it Work?

J. Thaysen, Kaj Bjarne Jakobsen, Jørgen Appel-Hansen

    Research output: Contribution to journalJournal articleResearchpeer-review


    Whenever a balanced antenna such as a dipole, loop or spiral is used, the issue of how to feed the antenna becomes relevant. Because a balanced antenna requires a balanced feed, a balun is needed.

    A balanced antenna fed by a two-wire transmission line is a balanced system with respect to the lines, provided that the two feed points on the balanced antenna have the same orientation and placement with respect to the lines. If the balanced (symmetrical) antenna is connected to a coaxial transmission line, the transition from the feed line to the balanced antenna is an unbalanced (asymmetrical) driven system. The balun is inserted between the feed line and the antenna to provide a transition between the coplanar waveguide (CPW) and the coplanar strip line (CPS). The balun produces a symmetrical radiation pattern. However, this article does not deal with the radiation from a connected antenna.

    In some applications, it is necessary to connect the feed terminals on the balanced antennas to an unbalanced coaxial cable that requires not only a balanced-to-unbalanced transformation circuit, but also an impedance match due to the different characteristic impedances of the antenna and the cable.

    In the literature, different types of baluns are described [1, 2]. In this article, the focus is solely on a planar balun...
    Original languageEnglish
    JournalApplied Microwave & Wireless
    Issue number10
    Pages (from-to)40-50
    Publication statusPublished - Oct 2000

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