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In telecommunications and electrical engineering in general, an unbalanced line is a pair of conductors intended to carry electrical signals, which have unequal impedances along their lengths and to ground and other circuits. Examples of unbalanced lines are coaxial cable or the historic earth return system invented for the telegraph, but ...
However, connecting an unbalanced circuit to, for instance, a twisted pair line, which is an intrinsically balanced format, makes the line susceptible to common-mode interference. [citation needed] For this reason, balanced lines are normally driven from balanced circuits. One option is to redesign the circuit so that it is properly impedance ...
The circuit shown in the bottom diagram only can model the differential mode. In the top circuit, the voltage doublers, the difference amplifiers, and impedances Z o (s) account for the interaction of the transmission line with the external circuit. This circuit is a useful equivalent for an unbalanced transmission line like a coaxial cable.
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.
For example, in order to match an inductive load into a real impedance, a capacitor needs to be used. If the load impedance becomes capacitive, the matching element must be replaced by an inductor. In many cases, there is a need to use the same circuit to match a broad range of load impedance and thus simplify the circuit design.
If an unbalanced circuit is required, we have to accept some overall loss. By choosing k 1 = k 2 = a = 0.5, then the network shown below is obtained. This circuit has an overall loss of four times, whereas the conventional L-C ladder network [1]: 605 has no loss (but is not a constant resistance network).
The first example gives the circuit for a 6th order maximally flat delay. Circuit values for z a and z b for a normalized lattice (with z b the dual of z a) were given earlier. However, in this example the alternative version of z b is used, so that an unbalanced alternative can be easily produced. The circuit is
There are several approaches to understanding reflections, but the relationship of reflections to the conservation laws is particularly enlightening. A simple example is a step voltage, () (where is the height of the step and () is the unit step function with time ), applied to one end of a lossless line, and consider what happens when the line is terminated in various ways.