A review of solid-state radar receiver protection devices

A review is presented of solid-state radar receiver protection devices. The protectors are based on PIN diodes where a layer of intrinsic (I) material is sandwiched between P and N doped layers. At zero bias, the diode impedance is greater than 1 kohm, but under forward bias, charge is injected into the I layer that reduces the impedance to a level of 1 ohm typically. This biased impedance change gives the PIN diode its switching action. For waveguide devices, the diode is usually mounted in a coaxial line that is turned to the waveguide impedance using a capacitive element. The maximum power handling capability of the PIN diodes is discussed. In order to maximize the power handling of the diode mounting structure, the RF current shunt through the diode transferred impedance with the diode forward biased must be minimized. The reliability requirements of the diodes are discussed when used under military environmental conditions with ambient temperatures up to 85 C.