Active-array antenna beam shaping for direct broadcast satellites and other applications

Current direct broadcast satellites use high-power traveling-wave-tube amplifiers and a multiple-horn feed array and reflector antenna to achieve the downlink high power required. The desirability of replacing the traveling-wave-tube amplifier with a solid-state power amplifier is well established. However, no high-efficiency, 250-W, Ku-band solid-state power amplifier now exists. The high power required can be achieved by using a large number of low-power solid-state amplifiers to drive the elements in an active-array antenna. This paper addresses the mathematical problem of determining, for each element in an active-array antenna, the amplitude and phase drive signals required to produce the desired antenna pattern on earth.