5G base station core device：circulator
Time:2023-08-17
Views:1204
The circulator is also called a circulator, and its notable feature is that it can transmit high-frequency signal energy in one direction. A general circulator has several ports, and the signal is transmitted to the next port sequentially according to the direction determined by the static bias magnetic field. It can only propagate along this determined direction and cannot be transmitted in reverse order. In view of this characteristic, circulators are used to isolate the transmitted signal from the received signal, and are commonly used in radar, active electronically scanned antenna (AESA) arrays, satellite communications, and telecommunications.
The principle of one-way transmission of the circulator is due to the use of ferrite gyromagnetic material. This material produces gyromagnetic properties (also known as tensor magnetic permeability properties) under the combined action of an external high-frequency wave field (measurement signal from a network analyzer) and a constant magnetic field.
It is this gyromagnetic property that causes the rotation of the polarization of electromagnetic waves propagating in ferrite (Faraday effect), and the strong absorption of electromagnetic wave energy (ferromagnetic resonance), precisely because ferrite isolators utilize electromagnetic waves in The Faraday rotation effect in which the plane of polarization rotates during transmission in a gyromagnetic ferrite material with an external DC magnetic field.
After proper design, the electromagnetic wave polarization plane is perpendicular to the grounding resistive board during forward transmission, so the attenuation is very small. During reverse transmission, the electromagnetic wave polarization plane is parallel to the grounding resistance board and is almost completely absorbed. Gyromagnetic phenomenon, make a junction circulator, and add a load (attenuation sheet) to any end of the circulator to form an isolator.
If two or more isolators and circulators are connected in series or in parallel, they are called ring isolation components. It has the characteristics of small size, wide frequency band and low insertion loss, so it is widely used.
In the wireless access network, the circulator is mainly used to isolate the output signal of the base station antenna from the input signal. For specific purposes, the circulator cooperates with other devices to achieve the following functions:
(1) Used as an antenna duplexer;
(2) Combined with BPF with rapid attenuation for splitting circuit;
(3) Connect the terminal resistor to the outside of the circulator as an isolator, that is, the signal is input and output from the designated port;
(4) Connect an external ATT and use it as a circulator with reflected power detection function.
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