Reflective versus non-reflective
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?
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?