Synthesis Of Phased Array Antenna To Realize Wide-angle Scanning

Phased array has been widely used in the wireless communication and radar system due to its characteristic such as high gain and beam scanning. Typically, microstrip antenna phased array can only scan its main beam from-50°~50° in the main plane with gain fluctuation about 4-5d B, which is mainly affected by the beam-width coverage of antenna element and mutual coupling between elements. Grating lobes will appear if the elements of the array are equally spaced and the distance between elements is greater than hale of the wavelength, and the side lobe level will become large when the array scans to the large angle, which obviously restricts the development and application of phased array. Widening the scanning angle of phased array and reduce the side lobe level at the same time is the main technical problems which this thesis is focused on. In this thesis, the application of tinned array, pattern reconfigurable antenna and broad beam antenna in phased array have been studied and analyzed. By introducing a new arrangement rule of antenna array, reconfigurating the radiation pattern and broading the beam-width of antenna element, the phased array can realized the wide-angle scanning and restricts the side lobe level at the same time. The content of the thesis includes five chapters as follows:Chapter I is the introduction, which briefly generalizes the background and meaning, the currently research status at home and abroad. The main task of this thesis in this field is also summarized.Chapter II introduces the basic principle of thinned array and reconfigurable antenna, and a symmetric weighted thinned array has been designed on the basis of this, which can further reduce the side lobe level by symmetrically placing the array and properly selecting the weighted function. A novel symmetric weighted thinned array with pattern reconfigurable antenna as elements has been designed eventually, which can realize the wide-angle scanning and reduce the side lobe level.In chapter III, a pattern reconfigurable magnetic dipole antenna has been designed on the basis of traditional magnetic dipole. The working principle of this antenna is similar to pattern reconfigurable microstrip Yagi antenna, which can control the impedance of the parasitic strip by adjusting the electrical length. The designed antenna can operate in three different modes. By applying this antenna in thinned array, the array can scan its main beam from-70°~70° in principle plane with low side lobe level.In chapter IV, a novel electromagnetic dipole has been designed. The radiation 3dB beam coverage in principle plane is 140°, which makes it a good candidate for wide-angle scanning phased array. And the cross polarization of this antenna is very low. A novel thinned array has been designed based on this antenna, the designed array can scan its main beam from-70°~70° in principle plane with low side lobe level and cross polarization. The gain fluctuation is less than 3dB. A parameter study has been made to analyze the influence of the distance between elements on the radiation characteristics.In Chapter V, a conclusion of the whole thesis has been made, and the trend of the phased array in the future has been analyzed.