RF isolator

　　Radio frequency isolator: An isolator, also known as a unidirectional device, is a device that transmits electromagnetic waves in a unidirectional manner. When electromagnetic waves are transmitted in a forward direction, they can feed power to the load, causing significant attenuation of reflected waves from the load. This unidirectional transmission characteristic can be used to isolate the impact of load changes on the signal source.

　　RF circulators can be used as RF isolators. Directly connected to the antenna, the power amplifier may withstand high voltage or current levels, so the amplifier may be damaged by them. Use isolators to protect PA from the influence of reflected power. The transmitter is connected to port 1, and the antenna is connected to port 2. Port 3 is usually connected to a 50 Ω load - this is necessary because the isolation level depends on good impedance matching presented on different ports. If there is poor matching or open circuit, the isolation performance will be compromised.

　　Isolator: It is generally based on the structure of a ring-shaped device, with the only difference being that the isolator is usually a two port device that connects the three ports of the aforementioned ring-shaped device to a matching load or detection circuit. Thus forming a function where the signal can only go from port 1 to port 2, and cannot return to port 1 from port 2, achieving unidirectional conductivity. If the 3 ports are connected to the detector, it can also achieve the degree of mismatch of the terminal devices connected to the 2 ports and achieve standing wave monitoring function.

　　Isolator indicators:

　　Insertion loss: may be in the range of 0.1 to 0.75dB.

　　Isolation degree: usually between approximately 17 and 35dB. If a higher level of isolation is required, two RF circulators can be placed in series.

　　Power: As wiring and ferromagnetic materials can only handle certain power levels, it is important not to exceed these levels.

　　Packaging type: plug-in, surface mounting technology, etc.

　　Connectors: SMA and N-type

　　VSWR: VSWR or voltage standing wave ratio represents the degree of matching with the required impedance level. It is usually possible to achieve VSWR levels between 1:1.2 and 1:1.5.

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