At last fall’s Euronaval, Israel Aircraft Industries (IAI) displayed an important inherent feature of an active-array radar it had developed. Passive phased arrays such as the U.S. Navy’s SPY-1 (the Aegis radar) use antennas consisting of phase shifters connected to radiating elements, all fed by a single power tube. Together, the individual radiators create a beam. Because they are under computer control, and because they can act quickly, the phase shifters can steer that beam electronically. In an active array, there is no single power tube. Instead, each element of the array radiates a signal with a computer-controlled phase. A passive array creates a single beam, because it feeds from a single power tube.
World Naval Developments: Naval Guard Debuts
By Norman Friedman