a relay for high frequency instruments and a reverse power protection circuit for high frequency instruments are described herein . the relay is inexpensive to construct , permits good impedance matching up to approximately 5 ghz , and can be easily mounted on a coplanar waveguide transmission line . the circuit can open the relay in response to a reverse power condition in as little as 8 microseconds and provides both good grounding and functions reliably up to 4 ghz .