1. Field of the Invention
The present invention relates to a balun (Balance to Unbalance transformer), and in particular relates to an easily manufactured balun.
2. Description of the Related Art
FIG. 1a shows a conventional balun 1, which has a cylindrical structure. FIG. 1b is a sectional view of the conventional balun 1. The balun 1 comprises a feed conductor 10, a first ground element 21, a second ground element 22 and a common ground element 30. The first ground element 21 and the second ground element 22 surround the feed conductor 10. The common ground element 30 surrounds the first ground element 21 and the second ground element 22. The first ground element 21 is connected to a first output port 23, and the second ground element 22 is connected to a second output port 24. The common ground element 30 is electrically connected to the first ground element 21 and the second ground element 22.
Conventionally, the feed conductor 10, the first ground element 21, the second ground element 22 and the common ground element 30 are manufactured by a machining process. Thus, it takes a relatively long time to manufacture the conventional balun 1, and costs are relatively high.