Fast-Acting Varactors for Sub-Nanosecond Power Limiting in Receiver Protectors

Fast-acting pn junctions were developed to self-limit in less than 1 nsec at relatively high peak levels at X-band frequencies. The cascading of junctions in order of decreasing base region thickness behind high average power plasma limiters resulted in a passive receiver protector capable of limiting 1 nsec risetime multi-kilowatt RF pulses to 1 watt spike levels. It is also shown that 1 watt spikes of less than 10 nsec duration do not degrade the noise figure of balanced mixers employing small-junction (5 to 10 mu diameters) Schottky barrier diodes.