Circulator Working and Its Applications

The circulator is a ferrite device including two or more ports. When the input signal enters into any port then the signal will transmit in a particular direction. There are different models of circulators available in the market from different manufacturing companies. These components are mainly used in different applications like radar systems, amplifier systems, transmitting or receiving from the antenna. The different models of these mainly include two port circulator; three port circulator with waveguide packages & frequency range will be up to 40 GHz, VSWR, insertion loss and isolation.

Working of Circulator

To understand how the circulators control the flow of signal, let’s think a cup of water and place a spoon in it then stir it in the direction of clockwise. If we drop a pinch of pepper into the cup and stir continuously, so we can observe that the pepper can easily follow the motion of water because of the motion of water is strong. The communication of the magnetic field toward the ferrite material within circulator makes magnetic fields related to the flow of water in the cup. The rotating field is extremely strong & will cause any RF signals inside the frequency band at one port to track the magnetic flow toward the nearby port but not in the reverse direction.


The schematic diagram of a circulator is shown above. The arrows within the circulator signify the direction of the magnetic field when the signal is applied to one of the ports of these devices. For instance, If a signal is applied at port-A, & port-B is well-suited, then the applied signal will exit from port B with 0.4dB loss. If there is a difference at port-B, the signal can be reproduced from port-B that will be directed toward port C.

Types of Circulators

The circulators are classified into two types namely ferrite circulators and non-ferrite circulators.

Ferrite Circulators

These circulators are frequently used as a duplexer, and the working of this can be contrasted with a rotating door including three entrances & one compulsory turning sense. This revolving can depend on the communication of the electromagnetic signal by magnetized ferrite.

This signal enters through one particular entry to follow the fixed rotating sense & leaves the circulator through the next door. The transmitter energy turns in an anticlockwise direction toward the antenna port. Almost all circulators are used in radar applications include ferrite.

Non-ferrite Circulators

Non-ferrite circulators are energetic circulators and thus need extra power. The main disadvantage of circulators is based on transistors, limitation of power as well as the degradation of the signal to noise (S/N). The main solution for this drawback is varactors.

Circulator Characteristics

The characteristics of circulator include the following.

  • Insertion loss is < 1 dB
  • Isolation range is approximately from 30dB to 40 dB
  • VSWR (voltage standing wave ratio) is <1.5

Applications of Circulators

The applications of circulators include the following

  • Duplexer
  • Isolator
  • Reflection amplifier
  • Radar systems
  • Amplifier systems
  • Antenna transmitting or receiving

Thus, this is all about circulators, working, types, characteristics, and applications. The selection of circulator can be done using features like frequency, isolation, power & insertion loss. Here is a question for you, what is the function of a circulator?

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