Design Of Omnidirectional Filtering Antenna For Multi-Rotor Drone Pattern Measurement System

With the rapid development of UAV technology,a multi-rotor UAV measurement system carrying an omnidirectional antenna has gradually emerged that can measure the radiation characteristics of fixed antennas or radio devices.Antennas and filters are particularly important in such a measurement system,but they both occupy a large volume,which contradicts the compact carrying space and limited payload of UAVs.The filtering antenna can integrate the radiation function and filtering function into one,meeting the demand for an integrated and low-loss UAV measurement system.Therefore,this thesis focuses on the filtering antenna and designs omnidirectional filtering antennas suitable for UAV antenna measurement system.The main research work of the thesis is as follows.In order to realize the integrated design of RF front-end,a broadband omnidirectional filtering antenna is proposed.Firstly,by introducing a stepped impedance resonator at the monopole antenna feed,radiation nulls can be generated at the upper and lower stopbands of the antenna respectively,thus improving the radiation suppression level of the stopband;secondly,by etching a stepped slot on the antenna floor,additional radiation null can be introduced in the high-frequency stopband to further improve the antenna’s high-frequency stopband filtering response.The final impedance bandwidth of the antenna is 59.5%(1.9～3.51GHz),and the frequency selectivity of the antenna is good,the radiation suppression level in the high-frequency stopband is 13 dB,the radiation suppression level in the low-frequency stopband is 28 dB,and the gain variation of the antenna in the band is less than 3dB.Aiming at the problem that the antenna profile is too high and the wind resistance is large when the multi-rotor UAV performs the task,a low-profile omnidirectional filtering antenna is proposed.Firstly,based on the dielectric waveguide model theory,a cross-coupled feed is used to excite a cylindrical dielectric resonator,so that the antenna generates a radiation null at the high-frequency edge of the passband and enhances the radiation suppression level in the high-frequency stopband;then four metal pins are symmetrically distributed inside the dielectric resonator,so that the antenna generates a null at the low-frequency edge of the passband and enhances the radiation suppression level in the low-frequency stopband;Secondly,the antenna profile height is reduced by loading a metal patch on top of the dielectric resonator.Finally,the impedance bandwidth of the antenna is 1.82～3.28 GHz,the relative impedance bandwidth is 57.2%,and the out-of-band radiation suppression of the antenna reaches more than 15 dB,which has excellent frequency selectivity and the gain variation in the band is less than 3dB.For the multi-rotor UAV mission,the multi-rotor UAV measurement system has a certain tilt angle relative to the measured antenna on the ground with the problem of the low received signal,a conical beam filtering antenna is proposed.Firstly,the magnetoelectric dipole antenna is formed into a toroidal array,While the antenna achieves conical beam radiation,it produces a radiation null in the low-frequency stopband;then,by etching an opening slot on the antenna metal radiation patch,a radiation null is generated in its high-frequency stopband;secondly,four symmetrical driving parasitic branches are printed on the bottom of the dielectric,which can further generate additional radiation null at the edge of the highfrequency passband,improving the radiation suppression level of the antenna highfrequency stopband and the frequency selection characteristics of the high-frequency passband edge.The impedance bandwidth of the antenna is 1.49～2.9 GHz,with a relative bandwidth of 64.2%,and maintains a suppression level of more than 15 dB in the highfrequency and low-frequency stopbands,respectively,and the gain variation in the band is less than 3dB.