A Hadamard Matrix Feed Network for a Dual-Beam Forming Array Antenna

We propose a novel 4 times 4 Hadamard matrix feed network for a 4 times 1 array antenna to form a dual beam. If each element of the array is excited following the elements in a row of the Hadamard matrix, a two-lobed antenna beam can be obtained. The angle between the two lobes can be controlled by selecting the appropriate row of the matrix. The Hadamard matrix feed network consists of four 90deg hybrids, one crossover, and four phase shifters. The array antenna, including the Hadamard matrix feed network, was fabricated on a microstip structure. The measured beam directions of the two lobes are 0deg, plusmn 5deg, plusmn 33deg, and plusmn 45deg depending on the choice of the input port of the feed network.