RF Circulators and Isolators are defined as RF Ferrite component, transfer RF signals by control of the ferrites. An RF signal experiences a low loss in the direction of arrow and high loss in reverse due to its non-reciprocal.
RF Circulators and Isolators non-reciprocal work on the magnetic fields. RF signal can still be reciprocal in the magnetic fields without RF Ferrite. Resonant frequency was based on the RF Ferrite in the device.
The connection of RF Circulators:
RF Circulator is featured by its non-reciprocal with transmitting electromagnetic waves. The ideal insertion lossless N port Circulator only allows the electromagnetic waves from one port in, and all from next port out.
As picture of three-port circulator below, the electromagnetic wave input from port 1 can only be output from port 2, and input from port 3 can only be output from port 1
Ideally, wave cannot go in reverse.
The Applications of RF Circulators
Usually, three-port circulator can be used as duplexer. Port1 connect with transmitter, Port2 connect to antenna and Port3 connect to receiver as to achieve the purpose of sharing the same antenna.
In order to prevent the reflected electromagnetic wave from burning the receiver, when using it in a high-power system, it is quite common to connect a Limiter between the port3 and the receiver.
Another application of the circulator is to connect several circulators together to function as a parametric amplifier. For example, connect the three circulators together to the dummy load at the terminal.
The applications of RF Isolators:
When one port of circulator connects with a matching load, the component can be used as RF isolator.
RF isolators are widely used in the protection of high-power RF generator in order to prevent the generator from being unstable or even burned due to load changes caused by reflected power. Use isolator to take out the reflected power between antenna and transmitter or between communication systems and radar system.
An RF isolator can also be used on the receiver port.