BAe AN/ALR-94, the most complex piece of equipment on F-22

[Yongpeng Sun-Tastaufen]

The RWR is a passive radar detector with more than 30 antennas are blended into the wings and fuselage for all-round coverage. Tom Burbage, former F-22 program head at Lockheed Martin, described it as "the most technically complex piece of equipment on the aircraft." The range of the RWR (250+ nmi) exceeds the radar's, and can cue radar emissions to be confined to a narrow beam (down to 2° by 2° in azimuth and elevation) to increase stealth.

http://aircraftknowledge.yolasite.com/f-22-rapter.php