Solid state coaxial relay

Or….Options in the “RF switching without the clacky bits”!

A solid-state coaxial relay is basically an RF switch that uses PIN diodes or GaAs FETs instead of a mechanical armature. They flip between paths fast, stay silent, and don’t wear out, but they’ve got their own quirks.

Quick feel for the landscape:

• PIN-diode types handle higher power and are the usual go-to up through L-band and well beyond.
• FET switches shine for low power and very fast switching, especially in SDR setups.
• Insertion loss is typically lower than you expect but still a touch worse than a good mechanical relay.
• Isolation is decent but rarely as absurdly good as a pricey DowKey or Radiall mechanical unit.
• They need a bit of biasing trickery: forward current for “on,” reverse bias for “off,” so you usually get a little driver board with them.
• They’re fantastic if you’re doing rapid switching, time-division interferometry, or protecting an LNA with fast RF muting.