Investigation On Wide Angle Coverage Beam Scanning Linear Array Antenna

As an important component of wireless communication system,antenna is a kind of converter between traveling wave and free space wave.Antennas with high gain can save transmit power and improve sensitivity of receiver.Antennas with wide beamwidh can cover a wide angle range.Therefore,antennas not only with high gain but also with wide angle coverage have drawn more and more attentions.It has been investigated initially by using nonuniformly arranged phased array and smart antenna technology in this thesis.The thesis is arranged as follows:In first chapter,background of the investigations is elaborated and researches about phased array and smart antenna are summarized and reviewed.In second chapter,the theory of antenna array is introduced as well as the analysis method for uniform and nonuniform array.A model for nonuniformly arranged linear array is proposed in this chapter,which is the basis for the chapters below.In third chapter,a phased array for wide angle scanning is invested.The distance between each element is set as variable and the side lobe level(SLL)is set as fitness function in the optimization by genetic algorithm(GA)during the full wide angle beam scanning.The nonuniformly arranged linear array is simulated by full wave electromagnetic software with feeding network composed by phase shifters and power dividers based on substrate integrated waveguide(SIW).To lower SLL when the array scanning at elevation angle further,two dummy elements are placed on each side of the linear array to weak the side effect.To validate the accuracy of the design,two linear arrays are fabricated and tested with main beam pointing at 0° and 70°,respectively.The measurement results verified simulation,showing a low gain fluctuation and SLL during the wide angle beam scanning.In fourth chapter,the beam scanning performance of sparse linear array has been investigated.Two sparse linear arrays with the aperture of 4.5 wavelength are designed based on genetic algorithm and SIW technology with number of element of 8 and 7,respectively.The arrangement of sparse array is optimized by GA and the feeding network is verified by full wave electromagnetic simulation,where the beam scanning performance is studied.To validate the accuracy of the design,two linear arrays are fabricated and tested with main beam pointing at 0° and-15°.The measurement results verified simulation,showing the sparse array with fewer elements can maintain a same beamwidth and low SLL and a good performance within a small range phase scanning.In fifth chapter,a beam switched smart antenna is designed with low cost single layer FR-4 substrate and printed circuit board technology,which including wideband microstrip patch antenna,RF circuits and controlling circuits.After assembling and measured,the beam can be switched to track transmit signal successfully and the gain fluctuation lower than 3.5dB within 360°.The achievement of this chapter is accepted and exhibited in international conference 2017 APCAP.In sixth chapter,investigations of this thesis are summarized and some suggestions on future works are given.