Amplitude-only beam scanning in linear antenna arrays

In phased arrays the mainbeam is scanned by either varying the phase excitations of the elements or varying the frequency of operation. In spite of their extensive use, these methods need either variable phase shifters or frequency sweeping. It is shown here that beam scanning is also feasible by varying magnitudes of the array element excitations thus alleviating the need for phase shifters or frequency variation. In this technique, the amplitude excitations of some side elements are reduced while those of the others are increased by proper power division or weighting in the feed network of the array. Theoretical analysis and computer simulations are presented to verify the proposed idea. A 3-element array is studied first, then the idea is extended to a 7-element array. Simulation results show appreciable scan angles with minor variation in the mainbeam level. Some degradation in the array pattern is noticed at large scan angles.