Design Of Probe Antenna For Multi-rotor Drone Pattern Measurement

With the rapid development of multi-rotor drone technology,a measurement system is developed.The system uses the multi-rotor drone equipped with a probe antenna to measure characteristics of radiated performances of large reflector and array antennas on the ground.However,the measurement system is susceptible to factors such as communication signals,flight attitude of the multi-rotor drone and probe antenna polarization.These effects lead to a reduction in measurement accuracy and efficiency.In order to improve the precision and efficiency of the system,this thesis starts with the probe antenna,and mainly analyzes the mutual interference between communications antenna and the probe antenna of the multirotor drone,the received signal changes are caused by the flight attitude change in the air,and the polarization reconfigurable probe antenna,etc.,the probe antenna for multi-rotor drone pattern measurement is designed.The main contributions of this thesis can be summarized as follows: 1.When multi-rotor drone flies in a straight line,there are two problems: one is signal interference;the other is that the received signal changes are caused by the flight attitude change in the air.In order to solve these problems,a broadband dual band-notched dielectric resonator omnidirectional antenna is designed.Firstly,the antenna’s Y-shaped microstrip feed line excites a rectangular dielectric resonator to produce omnidirectional radiation pattern,which overcomes the effects of attitude changes in the air.Secondly,adding stub and rectangular spiral next to the feed line,so that the antenna generates band-notched in the multirotor drone communication bands 2.408 GHz～2.440 GHz and 5.725 GHz～5.825 GHz,respectively,which overcomes the problem of signal mutual interference.Finally,the measured impedance bandwidth is of 99%(2.03 GHz～6.02 GHz),the gain variation in the band is between 1.5 dBi and 3.3 dBi.2.When a multi-rotor drone is hovering,there are two problems: one is signal interference;the other is that the probe antenna has a certain inclination relative to the ground antenna to be measured,but the omnidirectional probe antenna gain decreases in this inclination direction,which leads to low received signal strength.In order to solve these problems,a broadband band-notched conical beam antenna is designed.Firstly,the antenna adopts the structure of a single cone antenna and a reflective metal plate,so that it generates a conical beam.Secondly,The addition of top-coupled load patch and short-circuited cylinder not only improves impedance matching,but also generates band-notched in the multirotor drone communication bands 2.408 GHz～2.440 GHz and 5.725 GHz～5.825 GHz,respectively,which overcomes the problem of signal mutual interference.Finally,the measured impedance bandwidth is of 58.1%(2.10 GHz～3.82 GHz).At an elevation of 30°,the gain variation in the band is between 3.5 dBi and 5.5 dBi,the gain variation in the plane is less than 3 dB.3.When multi-rotor drone is measuring in the air,there is a problem that the co-polarization and cross-polarization of the antenna cannot be measured simultaneously with one antenna during limited flight time.In order to solve this problem,a dual-line polarization reconfigurable broadband omnidirectional antenna is designed.Firstly,based on the theory of characteristic mode analysis,it is analyzed that two kinds of modal currents with orthogonal and omnidirectional radiation pattern exist in the dual-ring patch.Secondly,the above two modal currents are excited by designing multiple dipoles feeding networks.Then,the reconfigurable characteristic of the antenna is achieved by adding four PIN diodes to the feeding network and adjusting the diode switches.The antenna achieves an overlapped bandwidth of 49.6%(from 480.2 to 797.5 MHz),and the gain variation ranges between-1 dBi and 0.4 dBi.the gain variation in the vertical plane is less than 3 dB.