Multipath Parameters Acquisition Method Based On Assisted Measurement System

Electromagnetic situation refers to the electromagnetic signals spatial distribution of a radiation source’s radiation electric field or radiation magnetic field under the complex electromagnetic environment.Nowadays,electromagnetic situation assessment has occupied an important position in People’s daily life,such as the abatement of electromagnetic radiation pollution and the design of wireless communication system.In addition,it is also widely used in military fields,such as the development of electronic countermeasures,electromagnetic defense.However,existing prediction models have their own disadvantages and limitations.Represented by the ray tracing,the calculation is extremely large.Moreover,the exact geographical distribution of full path is difficult to obtain in actual measurement.The computational efficiency and timeliness has become the bottleneck of the engineering application.Therefore,there is no practical method for the electromagnetic situation evaluation.It is urgent to relieve the dependence on the full-path terrain by means of auxiliary test methods.It is very important to use a real-time and efficient situation assessment model without GIS support.The skeleton of this paper as follows.First,according to the current research progress of radio waves,the radio wave propagation environment is described.Those static landform and topography that affect communication channels are analyzed.The geometric characteristics are classified,and the geomorphology electromagnetic characteristics are introduced.The dielectric constant of some building materials and existing basic research methods for obtaining electromagnetic parameters are given.Some propagation theories are summarized,such as line-of-sight propagation,non-line-of-sight propagation and Fresnel theory.Several propagation modes of multipath effect are studied and the influence of multipath effect on situation assessment is described.Then,three kinds of assistant measurement methods used to obtain multipath parameters are introduced.They are environmental geometric parameter acquisition,receiver original data acquisition and electromagnetic characteristic parameter acquisition.When using radio wave propagation model to predict signals,it is not realistic to measure the whole propagation environment.At this time,a simple method is needed to build a three-dimensional model of the environment.In this paper,the geometric parameters are obtained by laser ranging and image recognition method.In order to acquire the test point original data,a method based on USRP is adopted in this paper.The overall framework and core technology of USRP system are introduced.The sampling and signal processing methods used in this paper are analyzed.The data acquisition program based on GRC is compiled,and the collected data is transformed by matlab.The electromagnetic characteristics of objects in different environments are quite diverse at different frequencies.Therefore,on the basis of summing up the previous research on electromagnetic characteristic parameters,the calculation method of complex dielectric constant is improved.The inverse function of complex permittivity is constructed and the method is verified.Finally,a theoretical calculation model for obtaining multipath parameters is established.When the spatial coordinate of the signal source and the propagation path of the radio wave are unknown,the environment around the receiver is located in the consistent region of the direct wave.According to the mirror principle,the spatial coordinates of the propagation reflection points are calculated,the radio channel is determined by ray tracing,and an improved field intensity superposition model is established.Based on the space domain of radio wave propagation,the non-linear equations are simplified,and the multipath parameters are solved by means of the auxiliary measurement method introduced.The real scene is simulated and the experimental results are analyzed.The multipath parameter acquisition method based on the auxiliary measurement system introduced in this paper has the advantages of small calculation,easy operation and high accuracy.It will be of great reference significance for the actual engineering electromagnetic situation assessment.