Gain Calibration And Influence Factor Analysis Based On Antenna Measurements

With the development of electronic communication technology,antennas are widely used in mobile communication,self-driving,astronomical detection,defence industry and other fields.The increasing demand for applications makes it increasingly important to verify the accuracy and performance of antennas not only at the design level,but also in the development and production of antennas.As the core index of antennas,high precision antenna measurement is an important part of the development and production,which puts forward higher requirements and challenges on the accuracy and convenience of antenna gain measurement.Microwave darkroom measurements have developed rapidly over the past 20 years due to their all-weather and shielding advantages,but in the actual darkroom measurement process,the bracket,feed line and non-uniformity of quiet field often bring interference to the standard gain antenna,and thus affect the accuracy of the gain measurement,and many measurement agencies are currently difficult to quantitatively describe the degree of impact of this environmental interference on the measurement results.In addition,due to the limitations of darkroom size,cost and measurement conditions,some microwave communication antennas are often difficult to obtain the farfield gain from darkroom measurements,which brings great difficulties to the practical engineering applications.Therefore,this topic focuses on the practical problems in engineering applications,aiming at solving the problem of how to quantitatively analyse the degree of influence of the interference of the bracket,feed line and non-uniformity of quiet field on the standard antenna gain value during the darkroom measurement process,so as to calibrate the standard antenna gain value;and how to measure and detect the antenna by changing the measurement method or introducing the radiation source reconstruction algorithm after being limited by the existing measurement conditions,so as to judge its processing accuracy and ensure that the actual antenna reaches the accurate gain index.Based on this,several standard gain antennas commonly used in darkroom are modelled and simulated to provide antenna models for the subsequent comprehensive simulation of darkroom environment.By combining the relevant antenna manuals and measurement results,four standard gain antennas,namely dipole,log-periodic,horn and double-ridge horn,are modelled and the obtained antenna simulation models meet the working performance requirements of the corresponding standard gain antennas.Then,based on several standard gain antenna simulation models,the antenna bracket and feed line models are introduced,and the actual measurement process of the standard gain antenna is simulated by combining the actual use of the darkroom bracket and feed line and the quiet zone field distribution information.After a large number of comparative analyses,the degree of influence on the gain value by the bracket,the feed line and the fluctuation of the quiet zone field amplitude in the actual measurement process of the darkroom is quantitatively described.Then,for the parabolic reflector antenna with splash-plate feed,which is difficult to measure the gain under the existing conditions,a measurement and detection method for the error of the splash-plate feed is proposed.By introducing a half spherical reflector in the radiation direction of the splash-plate feed,the combination of the half spherical reflector and the splash-plate feed is measured in the near field,and based on the near field measurement results,it is determined whether there is processing error in the splashplate feed in kind.A parabolic reflector antenna with splash-plate feed is used as an example to perform a simulated feed inspection to verify the feasibility of the measurement and inspection method.Finally,in order to better restore the radiation characteristics of the feed itself and the antenna as a whole,a feed reconstruction gain measurement calibration scheme is proposed.The simple equivalent source of the feed is obtained by the solution of the radiation source reconstruction algorithm,and then combined with the parabolic reflector to restore the far-field gain information of the feed and antenna to achieve the purpose of gain measurement and calibration.Through theoretical and simulation analysis,it is clear that the error of the scheme mainly comes from the accuracy of the reconstruction algorithm and the coupling between the feed and the introduced reflecting surface.For the reconstruction algorithm,two types of radiation source reconstruction models are further developed based on genetic algorithm and differential optimisation algorithm,and the accuracy and effectiveness of the two reconstruction models are verified through simulation examples.This provides a new way of thinking for antenna measurements.