Function:

Isolator:

• An isolator is a 2 port device which provides very small amount of attenuation for transmission from port 1 to port 2 but provides maximum attenuation for transmission from port 2 to port 1.
• This is very desirable when we want to match a source with a variable load.
• When an isolator is inserted between the microwave generator and the load, generator is coupled to the load with zero attenuation and reflections if any from the load side are completely absorbed by the isolator without affecting generator output.

Circulator:

• A circulator is a 4 port microwave device which has a property that each terminal is connected only to the next clockwise terminal.
• They are useful in parametric amplifiers, tunnel diode, amplifiers and duplexers in radars.