Maximizing firm-track range on low-observable targets

It has been shown that a multifunction radar can initiate firm tracks at ranges well beyond those at which its search function would have sufficient single-scan detection probability to support reliable track initiation and track-while-scan operation. The advantage, attributable to the sequential detection process of alarm followed by validation, represents an increase in range capability corresponding to some four to six decibels in power-aperture product (25% to 40% in range). A disadvantage is that the target must be detected initially in the microwave band that supports the tracking function, and the low-observable target may have very low cross section in that band, requiring a very high search power-aperture product to cover the required volume in space. An alternative system design procedure uses a lower-frequency search radar and a multiple-channel, electronically scanned tracking radar in which an unused fire control channel performs the same validation and track initiation steps as would be used in a multifunction radar, based on an unvalidated alarm from the search radar. The search radar need not obtain the string of three or more detections that would be required for it to establish a firm track, and hence the same four to six decibel advantage is obtained as with the multifunction radar, but with search at the more optimum lower frequency. The result is to combine the sequential-detection gain of the multifunction radar with the RCS enhancement of the lower-frequency search radar to maximize firm-track range on all targets.