Basic theory of RF circulator and RF isolator

In microwave technology, RF circulator and RF isolator are two important ferrite devices mainly used for regulating and isolating microwave signals.
The core characteristic of these devices lies in their non reciprocity, which means that the signal loss is small during forward transmission, while it absorbs most of the energy during reverse transmission.
This characteristic is determined by the interaction between the magnetic field and the microwave ferrite.
The magnetic field provides the basis for non reciprocity, while the ferrite determines the resonant frequency of the device, that is, its response to a specific microwave frequency.

The working principle of RF circulator is to use a magnetic field to control microwave signals. When a signal enters from one input port, it is guided to another output port, while reverse transmission is almost blocked.
Isolators go further on this basis, not only blocking reverse signals, but also effectively isolating two signal paths to prevent interference between signals.

It is worth noting that if there is only a magnetic field without microwave ferrite, the transmission of signals will become reciprocal, that is, the effect of forward and reverse transmission will be the same, which obviously does not conform to the design intention of RF circulator and RF isolator. Therefore, the presence of ferrite is crucial for achieving the functionality of these devices.