5G has attracted much attention due to its application prospect in vehicle networking and industrial IOT, while trade war between China and the United States also promotes the temperature. In fact, 5G has also caused an uproar owing to the mass production of 5G circulator magnet. As an important component of radio-frequency subsystem, circulators have been widely used in wave filter, duplexer and reflection amplifier of 2G ~ 4G wireless base station. 5G has much higher network capacity requirement compared with 4G, and Massive MIMO Technology is one of the critical technology to enhance network capacity. In order to support Massive MIMO Technology, antenna channel of 5G significantly increase to 64-channel from 4-channel and 8-channel in 4G. The consumption of radio-frequency devices has been increased by several times with the increasing channels. Besides, more base station density than 4G due to improvement of working band. Hence, consumption of circulator and relevant 5G circulator will increase sharply.

What is Circulator?

Circulator is a radio-frequency passive device in the mobile communication field that allows microwave or radio-frequency signal transmits in unidirectional ring. The one-way transmission characteristics are based on the gyromagnetic property of gyromagnetic ferrite. Gyromagnetic ferrite is a kind of ferrite material which polarization plane constantly rotates around transmission direction when the plane polarized electromagnetic wave travel through the ferrite in one particular direction under high frequency magnetic field. The one-way transmission characteristics are mainly served for mutual isolation between level and level or between level and system of radio-frequency equipment to ensure working independently, therefore, protect signal source and reduce frequency pulling, interference or unnecessary radiation which will efficiently improve circuit quality.

Isolator is another device that helps electromagnetic wave to achieve one-way transmission. The power is completely transferred to load when electromagnetic wave transfers along the forward direction, then reflected wave from the load generated relatively high attenuation. Such one-way transmission characteristics can be applied to isolate the power reflection from the load, and thus protect the signal source. In reality, the circulator can become isolator as long as one of the port connects to termination resistor.

About 5G Circulator Magnet

Permanent magnets are a key component that applies the constant direct-current magnetic field to gyromagnetic ferrite, and directly affect working band, temperature stability and other parameters of circulator. Both ferrite and Samarium Cobalt magnets can serve as circulator magnets. Ferrite magnets may off-center and the performance of circulator become unstable, in the meanwhile, ferrite also cannot satisfy the miniaturization demand of 5G circulator. In this case, Sm₂Co₁₇ magnets are chosen as 5G circulator magnet even do not have the cost advantage. With the increasing construction of 5G base station, the demand for Sm₂Co₁₇ 5G circulator magnet is experiencing explosive growth.