Validity Analysis of the Near-Field Equivalent Method in Simulation

In this paper, the validity of the near-field equivalent method is studied to solve the problem of distortion in simulations. To analyze the validity, the condition of the principle of equivalence is reconsidered. The relationship between the principle of equivalence and the methods of near-field equivalence and far-field equivalence is studied, results show that the distance between the antenna and its platform is the key factor affecting the validity. To verify it, the 2D radiation patterns of the three-knife antenna above the curved platform are analyzed with full modeling simulation method and near-field equivalent method, respectively. Results indicate that the near-field equivalent method can still be used to simulate the radiation patterns of antennas above the platform, but the accuracy of this method is closely related to the distance between the antenna and its platform. That is, the longer the distance is, the more accurate the results are; when the distance is longer than 1/3 wavelength, high-precision results can be achieved with near-field equivalent method; However, when the distance is shorter than about 1/30 wavelength, this method is no longer appropriate for the simulation.