biff44 said:For times when you do not know a pulse is coming, you will need a passive limiter. A thin PIN diode will turn on all by itself (assuming there is a DC path to ground for self bias currents). But it has some capacitance that is a bother at higher frequencies. Matching with series inductors to form a lowpass structure (bond wires make good inductors!) is one way. Using a thicker PIN diode (less capacitance) and a detector diode scheme to provide bias to it is possibly a better way. Another scheme is to use two PIN diodes, a thick one up front, and a thinner one quarter wave further down the line, works too.