Research On Near-Field To Far-Field Transformation And The Analisis Of Measurement Error

With the rapid development of modern science and technology, a variety of electronic and electrical device are integrated into the same system and get more and more widely used. And compared to metal materials, more light-weight synthetic material now widely applied is poorer in electromagnetic shielding effect. Under the certain space constraints, when these electrical or electronic devices or system works, on the one hand, they are very sensitive to electromagnetic interference, on the other hand, they themselves will emit electromagnetic interference signals and affect normal operation of other electrical and electronic equipment or system. These electromagnetic interference, intentionally, unintentionally, or electromagnetic leakage through radio waves propagation distance is still likely to cause certain electromagnetic radiation energy. In this paper, the solution of the problem is to calculate the limit far field value through near-field electric field of the radiation of the electronic equipment or system and the near-field to far-field transformation, and to test and analysis the error.Firstly, according to the principle of plane wave spectrum, the near-field- far field extrapolation principle is studied, and the far-field electric field expression is obtained. Utilizing Lorenz reciprocity principle can bring the integrable coupling and compensation methods in the near-field to far field transformation. This paper analyzes the effects of different sampling intervals and it can provide theoretical analysis basis for the follow-up model.Secondly, the dipole array is used as a radiator simulation model. Through the model, the near-field electric field value on a plane are calculated and imported into the near-field to far-field algorithm to obtain the E-plane far-field pattern, and compared the theory E-plane far-field pattern, in a certain error range, they are identical. Considering the actual conditions, the paper has analyzed the effects of the ground conductor plane, discusses the impact of the situation on the different height of the distance from the ground.Finally, the error accuracy problem of the near-field measurement technology is analyzed. And this paper summarizes three error sources: the random amplitude-phase error of measurement, limited truncation error, probe positioning error, analyzes their impact on the measurement results, and then summarizes impact of the far-field pattern function. For each kind of error sources, it will be introduced into the simulation model respectively, and analysis the comparison pattern when different error values are got, then the upper bound of error will be obtained and the error will be modified through the error compensation method.