Avionics & Radar

One of the broadest uses of RF power amplifiers is detecting objects, and the best examples of this include avionics and radar applications. Avionics transponders generate an amplified electrical response when “interrogated” by a ground station or another aircraft. These are often used for collision avoidance via air traffic control in civilian applications or Identify Friend or Foe (IFF) military applications. Avionics transponders use an RF amplifier to transmit the interrogator signal from the ground station to aircraft or transmit the identifying code from aircraft to ground station. Operating in the L-band frequency range of 960–1215 MHz, avionics transponders range from 250 W to multiple kW power levels but are generally transmitted in short pulses. Radar is quite like avionics transponders, but instead of a communications-style interrogation and reply dynamic, radar systems send pulsed energy and process the returned signals that have bounced off objects. Traditionally, radar transmits very high-power pulses, but for some of the same reasons as the cellular market, system developers are shifting to distributed power via phased array radar AESA systems. Instead of a single, high-power transmitter, a phased-array antenna can consist of hundreds or even thousands of relatively low-power transmit/receive elements. This has created the need for integrated MMIC amplifiers, which is why today, radar developers have access to all three device types−discrete transistors, IMFETs and MMICs.