Also found in: Dictionary, Thesaurus, Medical, Legal, Idioms, Wikipedia.
Related to circulator: magic tee, Directional coupler, Circulator pump


A three- or four-port electronic device in which signals entering port number 1 appear only at port number 2, while signals entering port number 2 emerge only at port number 3, and so on. It is used, for example, in a radio telescope employing a negative-resistance preamplifier, such as a parametric amplifier or a maser amplifier; the circulator isolates the preamplifier from the antenna, which, if connected directly, might oscillate.



(also microwave circulator), a multiarm—that is, multiport—device for transmitting the power of high-frequency electromagnetic oscillations, usually microwaves, in a particular direction. The power that enters one of the ports is transmitted to another, strictly specified port in sequence. Circulators are classified as electronic and ferrite.

Electronic circulators make use of the ability of certain phase shifters to produce a nonreciprocal phase shift of π radians (see alsoPHASE INVERTER). Such circulators consists of discrete components, for example, transistors, diodes, or resistors. Three-port Y-shaped electronic circulators have lumped elements and are used in the frequency band from less than ten to several tens of megahertz.

The operation of ferrite circulators is based on the ability of ferrites that are magnetized in a constant applied magnetic field to produce—when they interact with an electromagnetic field or wave—a nonreciprocal phase shift, a nonreciprocal rotation of the plane of polarization (seeFARAD AY EFFECT), or a combination of waves such that the waves propagate in only one arm of the circulator. Several different types of ferrite circulators are distinguished. Phase-shift Y circulators have lumped elements and are used in the frequency band from hundreds to thousands of megahertz; in this type of circulator, the nonreciprocal phase shift is achieved by means of a magnetized ferrite rod or cylinder and a system of inductively coupled windings. Other types of ferrite circulators are based on junctions of rectangular or circular wave guides or on strip transmission lines, including microstrip lines. Such circulators may be Y-, T-, or X-shaped; they have distributed elements and are used in the frequency band from thousands to tens of thousands of megahertz. The X-shaped circulators are usually called four-port circulators. Examples of waveguide circulators include the four-port circulator known as a polarization rotator (see Figure 1) and the phase-shift circulator, which consists of two wave-guide bridges and two nonreciprocal ferrite phase shifters.

Figure 1. Polarization rotator based on a circular wave-guide section: (1), (2), (3), and (4) circulator ports, which are conventional rectangular wave-guide sections positioned in sequence at an angle of 45° with respect to the preceding port. The broken line represents the ferrite, which rotates the wave’s plane of polarization by 45° in the direction indicated by the arrow. As a result of the rotation, power entering port (4) is transmitted only to port (1), power entering port (3) is transmitted only to port (4), and so forth.

Ferrite circulators are the most promising. For example, they are used as switches, since the port sequence is reversed whenever the direction of the constant magnetic field is changed. In antenna feed lines, four-port and Y ferrite circulators are employed to switch an antenna or a phased-array module from the transmitting mode to the receiving mode. Y ferrite circulators in which one arm contains an absorbing load are used as electric valves. If several Y circulators are connected in series, a circulator array with any desired number of arms may be obtained. In conjunction with bandpass filters, circulator arrays make it possible to construct devices for the combination or separation of signals with different carrier frequencies; such devices require a minimum number of filters.


Lebedev, I. V. Tekhnika i pribory SVCh, 2nd ed., vol. 1. Moscow, 1970.
Vol’man, V. I., and Iu. V. Pimenov. Tekhnicheskaia elektrodinamika. Moscow, 1971.
Knerr, R. H. “An Annotated Bibliography of Microwave Circulators and Isolators, 1968–1975.” IEEE Transactions on Microwave Theory and Techniques, 1975, vol. 23, no. 10 (October).



A waveguide component having a number of terminals so arranged that energy entering one terminal is transmitted to the next adjacent terminal in a particular direction. Also known as microwave circulator.
References in periodicals archive ?
Tender notice number : Rotary Evaporator with chiller circulator, vacuum
a global supplier of on-demand microwave and RF components, releases new RF Circulators and Isolators which are commonly used in radar systems, wireless communications, distributed antenna systems (DAS), test labs and amplifier systems where sensitive RF equipment would require protection from reflected signals.
The purpose of teaching Principle and Function of Surgery Technician as Circulator course is being familiar with the performance and duties of Circular in operation room.
Additionally, the fiber optic circulator market is presented by the following port-count configurations:
Positively, however, Grundfos Sunderland is the only Grundfos facility worldwide which manufactures the 'A' rated UPS2 circulator and the company expects sales volumes to steadily increase through 2014 when it also starts to support the wider European sales region with the product.
A team of researchers at The University of Texas at Austin's Cockrell School of Engineering has built the first-ever circulator for sound.
The Zoom circulator replaces a contract Phoenix Start bus route that was expected to cost the city $6.
The Electronic Foot Massager and Circulator uses electromagnetic impluses to stimulate the nerve endings in the soles of your feet.
currently operates Georgetown Metro Connection, as well as the city s Circulator buses, under a contract worth roughly $12 million each year.
The agency has announced that Charm City Circulator (CCC) has added a new free transportation route, the Purple Route, on June 7, 2010, which will run from Penn Station to Federal Hill, in Baltimore.
New economical circulator pump In recent innovations, the company launched what it said was a new economical circulator pump for universal use.
Hicks said the building, constructed in the mid-1950s, had problems with one boiler and two failed circulator pumps, which accounted for the low temperatures in the older wing.