| 摘要 |
The present disclosure relates to a balun suitable for realising a wideband transition in the radio frequency band from an unbalanced transmission line to a balanced transmission line. The balun comprises an input terminal; a two conductor output terminal; and a layered structure comprising a number of conducting layers and dielectric layers alternatingly arranged on top of each other. The layered structure comprises at least one ground plane layer and at least one signal transmission layer. The input terminal has a signal connection point and a screen connecting point. An unbalanced signal path is connected to the signal connection point and the screen connecting point of the input terminal. A balanced signal path is connected to the output terminal and being part of the layered structure. A balun transition region transforms the signal from an unbalanced signal to a balanced signal. The balun transition region comprises a non-conducting gap between the screen of the unbalanced signal and a dummy screen structure. The dummy screen structure is a mirror structure, mirrored in a plane of the gap, of a horizontal portion of the unbalanced signal path before the gap. A central conductor or signal conductor of the unbalanced signal path traverses the gap and enters a volume defined by the dummy screen structure. The screen of the unbalanced signal in the vicinity of the gap forms a first balanced conductor being part of the layered structure and the screen of the dummy screen structure, in vicinity of the gap, forms a second balanced conductor being part of the layered structure. |
