Reliability of Microwave Mixer Diodes

Microwave mixer diodes designed for X-band frequencies and above have a small active region and therefore are limited in power handling capability. Many applications for these types of diodes are in high power radar systems. The sensitive mixer diodes are protected from any high power reflected signals by gaseous or solid state limiters. These limiters allow low level incoming signals to reach the mixer diodes but reflect unwanted high powers. However, RE pulses of 1 to 50 watts peak with pulse width varying 1 - 10 ns are often incident on the mixer diode due to "turn on" behavior of the gaseous limiter TR tube. Both this pulse height and pulse width are important in diode failure (although not directly interchangeable). The reliability feature of the mixer diodes which we will discuss will involve the diodes' capability to withstand RF spikes of energy typically in the pulse width range of 3 to 10 nanoseconds.