Here we will discuss both solid-state and mechanical switches, including design considerations as well as laboratory switch operation. If you are looking for RF switches, click here.
Here is a clickable outline for our Microwaves101 web pages on microwave switches:
There are many things you must consider when you design or buy a microwave switch. Let's try to list all of them all here, before we get into details below:
Reflective versus non-reflective (terminated) switches
A reflective switch does not provide a "good" fifty-ohm termination to the arm(s) that are switched off. A non-reflective switch provides terminations, and is a more complicated network.
Terminations: do the isolated ports of your switch need to present 50 ohms to your system? Can they handle the intended power?
Bandwidth: not just the upper frequency of a switch is limited by the technology you choose. PIN diode switches don't switch down to DC, but FETs do. Capacitive MEMS switches also have a high-pass response.
Insertion loss: will a dB or two of switch loss kill your system performance?
Isolation: how much RF signal can your switch leak before you are in trouble?
Power handling: is your switch going to be positioned on the output of a power amplifier?
Driver requirements: the driver circuits for PIN diode switches and FET switches are quite different, since the former requires a DC current while the latter requires a DC voltage, usually negative polarity.
Switching speed: how fast does your switch need to change state?
Expected lifetime: how many switching cycles do you expect your switch to handle? This is no concern for solid-state switches, but a big consideration for mechanical and MEMS switches.
Size: can you fit a connectorized switch, or do you need to look at a chip or surface mount IC switch?