Broadband Wide-angle Scanning Circularly Polarized Phased Array Antenna

Phased array antennas have advantages such as wide bandwidth,high gain,fast response,anti-interference,and large-angle scanning,making them widely used in military and 5G technologies.In comparison to linearly polarized phased array antennas,circularly polarized phased array antennas not only aim to expand the impedance bandwidth but also seek to improve axial ratio performance.Therefore,this thesis focuses on the research goal of achieving wideband and wide-angle scanning using a circularly polarized phased array antenna,exploring its broadband characteristics,axial ratio characteristics,and reducing the port isolation in dual-circularly polarized antennas.The main contents of this thesis are as follows:1.A dual-circularly polarized antenna with an L-shaped probe feeding structure is designed,and the antenna unit consists of a rectangular patch,air layer,and bottomwideband coupler.The operating frequency range of the antenna unit is in the Ku-band,with a 27.3% impedance bandwidth and a 24.1% axial ratio bandwidth.The antenna unit also exhibits good polarization isolation characteristics,with isolation levels of both polarizations better than 15 d B within the frequency range.A 4x4 dual-circularly polarized phased array is formed using dual-sequential rotation feeding technology,and the metal back cavity is used to improve the coupling effect between units.Finally,a wide-angle dual-circularly polarized scan of ±50 ° is achieved,with a sidelobe level lower than 7.2 d B within the design frequency range.In addition,the antenna has good scanning gain flatness,with a 5 d B decrease in gain when scanning to 50 °.2.A circularly polarized scanning grid array based on a wideband 90 ° balun is designed,and the antenna unit consists of a rectangular patch,air layer,and bottom ultra-wideband power splitter network.The proposed feeding structure can greatly achieve wideband phase shifting,thereby expanding the axial ratio bandwidth of circularly polarized antennas.The antenna operates in the S-band of 2.9 GHz to 5.1GHz,with a 53% impedance bandwidth and a 44% 3 d B axial ratio bandwidth.The antenna unit has one feeding port and is arranged in a grid planar array,enabling circularly polarized wide-angle scanning within the operating bandwidth.The scanning beam coverage range reaches ±50 °,with good scanning characteristics.