The function of the circulator is to transfer the incident wave entering any port into the next port in sequence according to the direction determined by the static bias magnetic field. The circulator is a non-reversible device with several terminals. For example: the signal input from port 1 can only be output from port 2. Similarly, the signal input from port 2 can only be output from port 3, and so on, so it is called a circulator. The outstanding feature of the circulator, also called the isolator, is the unidirectional transmission of high-frequency signal energy. It controls the transmission of electromagnetic waves along a certain circular direction. This characteristic of unidirectional transmission of high-frequency signal energy is mostly used between the output end of the high-frequency power amplifier and the load, and plays a role of being independent and "isolating" each other. The load impedance does not affect the working state of the power amplifier even in the case of open circuit or short circuit, thereby protecting the power amplifier.

 

The principle of the one-way transmission of the circulator is to use the characteristics of the ferrite gyromagnetic material. This material produces gyromagnetic characteristics (also known as tensor permeability characteristics) under the combined action of an external high-frequency wave field and a constant DC magnetic field. It is this gyromagnetic characteristic that causes the electromagnetic wave propagating in the ferrite to rotate polarized (Faraday effect), and the electromagnetic wave energy is strongly absorbed (ferromagnetic resonance), using this gyromagnetic phenomenon to create junction isolation Circulator, circulator. It has the characteristics of small size, bandwidth, and small insertion loss, so it is widely used.