The Synthesis Of Wideband Phased Array Antenna

Wideband phased-array antenna is studied in this thesis. Based on the property of bandwidth, the technology for optimizing wideband through synthesis of antenna array and design of radiator is discussed.The synthesis of nonuniformly spaced phased arrays is investigated by genetic algorithms. It is known that the element positions and main beam pointing affect the bandwidth of phased array. So during the antenna optimization process in wideband, current amplitudes, current phases and element positions are chosen as optimized variables and modified pattern is defined as the fitness function. As a result, not only the relative bandwidth is broadened to 33% but also the scanning angle is widened to ±60° at the same time of suppressing the sidelobe levels. Further more, the result is proved all-purpose for 25 element phased array antenna with any center frequency. And the antenna will work well over the band which is 5/6~7/6 times of center frequency.And two kinds of wideband printed radiators are designed and simulated. One is a printed dipole antenna with integrated balun. A via-hole through the substrate to the metal of bottom layer is designed to be the via-hole balun structure. Its resonant frequency is about 3GHz and the VSWR is less than two from 2.52 to 3.5GHz. The other is a stripline-fed vivaldi notch antenna with bandwidths in excess of 4 : 1. The VSWR is less than two from 2.2 to 8.8GHz. Comparing the simulated results, the latter has wider bandwidth and main beam, and it is more fit as a phased array antenna element.