Research On Formation And Performance Of Radiation Field Of Instrument Landing System

Since defined by International Civil Aviation Organization(ICAO)as the standard Precision Approach Landing System,Instrument Landing System(ILS)has always played an important role in aircraft approach landing guidance.Public reports on comprehensive and in-depth research on ILS systems at home and abroad are rare,and the equipment accompanying data on ILS is basically a description of the technical results.Models for various types of ILS are established,with corresponding radiation fields generated in this paper.Then the influence of various parameters of antenna distribution unit(ADU)on the formation and performance of ILS radiation field is studied.Finally multipath effect model and near field effect model are established,with countermeasures given.Firstly,FEKO is used to model and optimize the ILS array antenna named logarithmic periodic dipole antenna(LPDA).The current distribution characteristics,antenna gain and radiation pattern of the LPDA are analyzed,involving the localization of the ILS array antennas.It provides theoretical support and lays the foundation for the modeling of subsequent instrument landing system array antennas.Then the horizontal coverage performance of single-frequency 6/12-unit localizer(LOC)and dual-frequency 12/16/24-unit LOC is analyzed.The dual-frequency 12-unit LOC is taken as an example to study the effects of array parameters such as space with feed amplitude and phase on LOC performance.And the phase changes under near-field effects are studied.Next,the vertical coverage performance of single-frequency and dual-frequency glide slope(GS)is studied.The influence of the forward slide on the vertical coverage of the GS is studied,with the compensation method given.What's more,the beam bending potential(BBP)of single-frequency LOC and dual-frequency LOC is compared and analyzed,BBP of GS is studied,the anti-interference performance of the four GS is compared,a mathematical model formultipath interference is established,and course deviation indication(CDI)caused by multipath effect on LOC is simulated,with the method of weakening the course bend amplitude is given,providing guiding significance for the adjustment work after flight verification.Finally,the system integration of the formation and performance of the ILS radiation field is provided,which provides technical support for the theoretical study and the installation and debugging of the ILS.The research results show that the formation process of radiation field is correct.The research on ADU parameters,multipath effect and near field effect affecting the performance of ILS is well-founded.The integrated system can operate according to the corresponding requirements,and can be used to provide technical support for localization,installation and debugging of ILS equipment,as well as teaching training.