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There is an emerging need for millimeter-wave capabilities on military vehicles; in order to make such capabilities more affordable, we have been experimenting with the notion of combining multiple functions into a single device. The functions to be performed simultaneously include: 1) active protection (AP) radar for point defense against antitank threats; 2) surveillance radar for airborne and ground targets; 3) trunking radio for mobile ad hoc networking at a high data rate (>100 Mb/s); and 4) combat identification (ID). Due to a unique combination of characteristics, millimeter-wave radios, radars, and other sensors are attractive for military vehicle use. These characteristics include: 1) smaller profile/footprint of the high-gain antennas; 2) adequate weather penetration; 3) antijam, low probability of intercept, low probability of detection; and 4) wide bandwidth. For the combination of applications identified, this need is best met via a system operating near the 35-GHz atmospheric transmission window. Current mobile millimeter-wave ground-based systems (AP radar, wide-band communication, and combat ID) utilize highly directional steerable beams. Mechanical beam steering is usually done, resulting in restricted beam agility. Nevertheless, mechanical beam-steering performance is acceptable for AP radar and combat ID systems (but not for Joint Tactical Radio networked communications). A true multifunction system, however, requires beam-steering speeds that far exceed capabilities of even the best mechanical technologies. This is due to the need to support either networking or simultaneous multifunctions via time-shared beam steering. Thus, a true multifunction system must steer its beam anywhere in the upper hemisphere in less than 1 ms. Phased arrays are the obvious solution to these needs. Unfortunately, past phased-array technologies were unaffordable for Army vehicle application-hence, the multiplicity of systems. However, a new trend in development of affordable phased-array Ka-band antennas enables development of affordable Ka-band multifunction systems.