TABLE OF CONTENTS An antenna is a device that acts as a transformer to provide a good match between a source of power and free space. If the antenna is not matched to free space, power will be reflected back toward the generator, resulting in a loss in radiated power. In addition, a mismatch produces standing waves on the feed line to the antenna. The voltage at the peaks of these standing waves is (1 + ?? ?) times greater than the voltage of a matched line, where f is the voltage reflection coefficient. This corresponds to an increased power level that is (1 + ?? ?) 2 times as great as the actual incident power. Therefore, while the antenna is radiating less power, individual components must be designed to handle more peak power. With antennas that do not scan, the mismatch may often be tuned out by conventional techniques, preferably at a point as close to the source of the mismatch as possible.
In a scanning array the impedance of a radiating element varies as the array is scanned, and the matching problem is considerably more complicated. Unlike a conventional antenna, where mismatch affects only the level of the power radiated and not the shape of the pattern, spurious lobes in the scanning array may appear as a consequence of the mismatch. Further, there are conditions where an antenna that is well matched at broadside may have...
