There are many components in an RF system. Most people consider the mixers, filters, amplifiers and antennas to be the most important parts of a radio frequency system. However, there is another component whose importance is often undervalued and that is the RF switch. An RF switch is used to route radio frequency signals through alternative transmission paths.RF switches play a crucial role in the successful design of RF systems. Switches are used to change the routing of radio frequency signals. There are three main factors that should be considered when evaluating RF switches: insertion loss, isolation and switching speed.
A device is inserted into a transmission line causes a loss in signal power. This loss is called insertion loss. Insertion loss is the ratio between the input and the output power in the wanted signal path and is generally expressed in decibels. Consequently, a low insertion loss is desired.
Isolation is a term used to describe the degree of attenuation in any unwanted signal path. Isolation is the ratio between the input and output power in an unwanted signal path, expressed in decibels. High isolation is desired.
Switching speed is the time needed to change the routing of an RF signal through the switch. Many applications require a fast switching time.
Broadly speaking, there are three main types of RF switches:
The switching mechanism of electromechanical switches is made up of mechanical contacts. In such switches, the mechanical contacts physically change position during the switching process. These switches can handle high power signals, have high isolation and low insertion loss. However, the switching speed of an electromechanical switch is very low. They are bulky but robust and are hence typically used in industrial applications where their power handling capabilities are of the essence.
MEMS (Microelectromechanical) switches were pioneered by IBM. MEMS switches are a relatively new technology and are still being improved. The major concern is with the reliability of these devices. Improvements are being made to increase the lifetime of such switches.
Solid State Switch
A solid state switch is based on semiconductor technology. These switches do not have any moving parts. The lack of moving parts means that an RF solid-state switch can be designed to be faster, smaller and with an almost infinite lifetime. Such switches are generally used when there is a need for fast switching times. They are also good for applications where repeatability and isolation are important. Because of their light weight and small size these switches can be used in a variety of applications like mobile phones, automotive radars, etc.
A wide range of solid-state RF switches and modules are available with Ranatec. More details regarding capacity are available on the website.
“The above opinions are purely the reflection of the author’s point of view. They do not reflect the position of Ranatec.”