A waveguide circulator used as an isolator by placing a matched load on port 3. The label on the permanent magnet indicates the direction of circulation

A circulator is a passive non-reciprocal three- or four-port device, in which microwave or radio frequency power entering any port is transmitted to the next port in rotation (only). Thus, to within a phase-factor, the scattering matrix for an ideal three-port circulator is

S = \begin{pmatrix}
  0 & 0 & 1\\
  1 & 0 & 0 \\
  0 & 1 & 0

When one port of a three-port circulator is terminated in a matched load, it can be used as an isolator, since a signal can travel in only one direction between the remaining ports.[1]

There are circulators for LF, VHF, UHF, microwave frequencies and for light, the latter being used in optical fiber networks. Circulators fall into two main classes: 4-port waveguide circulators based on Faraday rotation of waves propagating in a magnetised material, and 3-port "Y-junction" circulators based on cancellation of waves propagating over two different paths near a magnetised material. Waveguide circulators may be of either type, while more compact devices based on striplines are of the 3-port type. Sometimes two or more Y-junctions are combined in a single component to give four or more ports, but these differ in behaviour from a true 4-port circulator.

In radar, circulators are used to route outgoing and incoming signals between the antenna, the transmitter and the receiver. In a simple system, this function could be performed by a switch that alternates between connecting the antenna to the transmitter and to the receiver. The use of chirped pulses and a high dynamic range may lead to temporal overlap of the sent and received pulses, however, requiring a circulator for this function.

Radio frequency circulators are composed of magnetised ferrite materials. A permanent magnet produces the magnetic flux through the waveguide. Ferrimagnetic garnet crystal is used in optical circulators.

There have also been investigations into making "active circulators" which are based on electronics rather than passive materials. However, the power handling capability and linearity and signal to noise ratio of transistors is not as high as those made from ferrites. It seems that transistors are the only (space efficient) solution for low frequencies.


  1. ^ For a description of a circulator, see Jachowski (1976)

Wikimedia Foundation. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • circulator — CIRCULATÓR, OÁRE, circulatori, oare, adj. Care aparţine circulaţiei sângelui, privitor la circulaţia sângelui. ♢ Aparat (sau sistem) circulator = ansamblu anatomic format din inimă, vene, artere şi capilare, care asigură circulaţia sângelui în… …   Dicționar Român

  • Circulator — Cir cu*la tor, n. [Cf. L. circulator a peddler.] One who, or that which, circulates. [1913 Webster] …   The Collaborative International Dictionary of English

  • Circulātor — (lat.), 1) Marktschreier; 2) so v. w. Circitor 2) …   Pierer's Universal-Lexikon

  • Circulātor — (lat.), Marktschreier; in der katholischen Kirche derjenige Geistliche, der die Kirchen zu visitieren hat, jetzt Ruraldekan; in der protestantischen Kirche soviel wie Kircheninspektor …   Meyers Großes Konversations-Lexikon

  • CIRCULATOR — et Circumforaneus Medicus, vide supra Charlattanus, et infra, in voce Periodeuta: uti de Circulatoribus Cybeliis, infra Cybele …   Hofmann J. Lexicon universale

  • circulator — noun a) A person or thing that causes something to circulate Who is the circulator of this rumor? b) A local transit system that provides regular service within a closed loop You can ride the airport circulator to the next terminal …   Wiktionary

  • circulator — /serr kyeuh lay teuhr/, n. 1. a person who moves from place to place. 2. a person who circulates money, information, etc. 3. a talebearer or scandalmonger. 4. any of various devices for circulating gases or liquids. 5. Obs. a mountebank. [1600… …   Universalium

  • circulator — cirkuliatorius statusas T sritis radioelektronika atitikmenys: angl. circulator vok. Ringleiter, m; Zirkulator, m rus. циркулятор, m pranc. circulateur, m …   Radioelektronikos terminų žodynas

  • circulator — circulate ► VERB 1) move continuously through a closed system or area. 2) pass from place to place or person to person. 3) move around a social function and talk to many people. DERIVATIVES circulator noun …   English terms dictionary

  • Circulator (disambiguation) — Circulator may refer to: Optical circulator Circulator pump DC Circulator often referred to as the Circulator Downtown circulator This disambiguation page lists articles associated with the same title. If an …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”