AN/APQ-181

The AN/APQ-181 is a Ku-band multimode airborne radar system developed by Hughes Aircraft (now Raytheon) in the early 1980s for the Northrop Grumman B-2 Spirit stealth bomber. It features 21 distinct modes for terrain-following and terrain-avoidance, navigation updates, target search, location, identification, acquisition, and weapon delivery, augmented by a GPS-aided targeting system. The radar is a fully redundant modular system, incorporating two separate radar sets and two liquid-cooled active phased array antennas, which are conformally mounted below the leading wing edges and covered by stealthy dielectric panels. Utilizing sophisticated software and advanced Low Probability of Intercept (LPI) techniques, the AN/APQ-181's amplifier-type transmitter employs a liquid-cooled, high-power gridded traveling wave tube, ensuring compatibility with the B-2's stealth characteristics. A significant upgrade was completed in 2014, replacing the original active antenna to prevent interference with commercial satellite systems.

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