RF isolator type

　　Mechanical and electrical switch

　　In RF systems, there are two basic types of switches: electromechanical and solid-state. Mechanical and electrical switches are similar to wall switches used to control lights in a cafeteria. In the electromechanical switch, the control signal causes contact and changes the physical position during the exchange process. The advantage of electromechanical switches is that they can handle high-power RF signals because of their low insertion loss and high insulation. For this reason, they are often used in RF testing equipment. In contrast, the other performance of the electromechanical switch is poor. They are large and heavy, with slow conversion speed and high losses. The conversion speed is on the order of milliseconds, which is eternal in RF.

　　Solid state switch

　　Another type of solid-state switch, which means that the core of this switch is some kind of semiconductor device. Unlike electromechanical switches, when this type of switch is switched, there is nothing really moving inside the solid-state switch, which makes their workstations very fast, although they cannot process large signals like electromechanical switches. The conversion time of solid-state switches is one billionth of a second in the nanosecond range.

　　Electrode and Range

　　All RF switches are classified into different types based on their electrodes and range, and the large circular dot in the center of the switch is called the electrode. The electrode is the calibration chain that connects the active part of the switch. A switch can have one or more electrodes. Essentially, each electrode represents a separate switch within the switch, but different electrodes within a single switch are not independent and are converted simultaneously.

　　System application

　　Assuming a cellular phone wants to use its antenna to both receive and send. The phone will use a T/R switch, with the antenna connected to path N, the receiver connected to path A, and the transmitter connected to path B. Each time a signal enters, the antenna will be switched to the receiver path, and each time a signal exits, it will be switched to the transmitter path. The T/R switch not only works well, but also eliminates the need for another antenna, which is exactly the real situation of many mobile phones working. Any switch that is connected to both the transmitter and receiver is called a transmit receive switch, or simply a T/R switch.

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