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Transmission line or choke baluns can be considered as simple forms of transmission line transformers. This type is sometimes called a current balun, since it ensures equal current on both sides of its output, but not necessarily equal voltage. These are normally called ununs, because they go from unbalanced to unbalanced or un-un.
Choke transformers are sometimes called transmission-line transformers (although see below for a different transformer type with the same name), or Guanella transformers, or current baluns, or line isolators. Although called a "transmission line" transformer, it is distinct from the transformers made from segments of transmission line.
A current balun uses a transformer wound on a toroid or rod of magnetic material such as ferrite. All of the current seen at the input goes into one terminal of the balanced antenna. It forms a balun by choking common-mode current. The material isn't critical for 1:1 because there is no transformer action applied to the desired differential ...
A pair of parallel conductors with current Î 1 and Î 2 flowing on each conductor, which can be decomposed into CM and DM current respectively. Fig. 1. CM and DM Current Illustration on Pair Conductors. As shown in the figure above, the relations between Î 1, Î 2 and modal current are given: Î 1 = Î C + Î D Î 2 = Î C - Î D
The goal is to prevent certain current flows (common mode current in the coax shield) while allowing others (opposing currents in the shield vs. center conductor). I should post a good schematic picture. Each type of balun does its job slightly differently. The choke balun prevents the outside current while the coax allows the inside current.
A transition from a balanced to an unbalanced line requires a balun circuit. An example of this is CPW to slotline. Example D in the diagram shows this kind of transition and features a balun consisting of a dielectric radial stub. The component shown thus in this circuit is an air bridge bonding the two CPW ground planes together.
These form a common-mode choke which inhibits unbalanced current flow, without affecting the differential signal. Coaxial cables used at radio frequencies may be wound several times through a ferrite core to add a useful amount of common-mode inductance. This limits the flow of unwanted high-frequency common-mode current along the cable shield.
Integrated passive devices (IPDs), also known as integrated passive components (IPCs) or embedded passive components (EPC), are electronic components where resistors (R), capacitors (C), inductors (L)/coils/chokes, microstriplines, impedance matching elements, baluns or any combinations of them are integrated in the same package or on the same ...