Distributed-element circuit: Difference between revisions

Revision as of 21:48, 26 December 2018

Revision as of 22:53, 26 December 2018

Line 105:

An unusual application of a circulator is in a reflection amplifier, where the [[negative resistance]] of a [[Gunn diode]] is used to reflect back more power than it received. The circulator is used to direct the input and output power flows to separate ports.<ref>Roer, pp. 255–256.</ref>

Passive circuits, both lumped and distributed, are nearly always [[Reciprocity (network theory)|reciprocal]]; however, circulators are an exception. There are several ways to define or represent reciprocity. A convenient one for circuits at microwave frequencies (where distributed element circuits are used) is in terms of their [[S-parameters]]. A reciprocal circuit will have an S-parameter matrix, [''S''], which is [[Symmetric matrix|symmetric]]. From the definition of a circulator, it is clear that this will not be the case,

:<math>[S] = \begin{pmatrix}

Line 113:

\end{pmatrix}</math>

for an ideal three-port circulator;, showing that circulators are non-reciprocal, therefore,by definition. It follows andthat it is impossible to build a circulator from standard passive components (lumped or distributed). The presence of a ferrite, or some other non-reciprocal material or system, is essential for the device to work.<ref>Maloratsky, pp. 285–286.</ref>

== Active components ==