Editing Circulator (section)

===Lumped-element circulators===
[[File:Lumped Mesh.jpg|thumb|100px|Woven mesh conductor wrapped around the ferrite of a lumped-element circulator.]]

[[File:Lumped Constant Isolators.jpg|left|thumb|200px|Internal construction of two different lumped-element isolators.  One type of isolator is a circulator having one port internally terminated.  The termination in each of these isolators is a rectangular film resistor.]]

Lumped-element circulators<ref name="Konishi">{{cite journal|title=Lumped Element Y Circulator|journal= IEEE Transactions on Microwave Theory and Techniques|date=November 1965|issn=0018-9480|pages=852–864|volume=13|issue=6|doi= 10.1109/tmtt.1965.1126116 |first1=Yoshihiro|last1=Konishi|bibcode= 1965ITMTT..13..852K}}</ref> are small-size devices that are typically used at frequencies in the [[High frequency|HF]] through [[UHF]] bands.  In a junction circulator, the size of the ferrite(s) is proportional to signal wavelength, but in a lumped-element circulator, the ferrite can be smaller because there is no such wavelength proportionality.<ref name="Dunn & Roberts">{{cite conference|title=New Design Techniques for Miniature VHF Circulators|last1=Dunn|first1=V. E.|last2=Roberts|first2=R. W.|date=1965|pages=147–151|conference=International Microwave Symposium Digest|doi=10.1109/GMTT.1965.1122495}}</ref>

In a lumped-element circulator, conductors are wrapped around the ferrite, forming  what is typically a woven mesh.  The conductor strips are insulated from each other by thin dielectric layers.  In some circulators, the mesh is in the form of traces on a [[printed wiring board]] with metallized vias to make connections between layers.  The conductive strips can be thought of as non-[[Reciprocity (electrical networks)|reciprocally]] coupled inductors.  Impedance matching circuitry and broad-banding circuitry in lumped-element circulators are often constructed using discrete ceramic capacitors and air-core inductors.

This class of circulator offers a considerable size reduction compared with the junction circulators.  On the other hand, lumped-element circulators generally have lower RF power handling capacity than equivalent junction devices and are more complex from a mechanical perspective.  The discrete lumped-element inductors and capacitors can be less stable when exposed to vibration or mechanical shocks than the simple [[Distributed-element circuit|distributed]] impedance transformers in a stripline junction circulator.