The antenna current Green’s function (ACGF) can be used to consider the mutual coupling effect between multiple arrayed antennas. To obtain the ACGF of antennas, numerical simulations such as moment method (MoM) are mainly used. However, these numerical simulations require a large memory and time consumption to obtain a solution. The computer-aided design (CAD) model for the numerical simulation should be accurately designed. Therefore, we propose an alternative method for obtaining the ACGF based on infinitesimal dipole modeling (IDM). The IDM is a technique to model antennas with a distribution of theoretically expressed dipoles. The infinitesimal dipoles have the form of a current distribution, the same as that of the ACGF. The IDM can be optimized with the radiation pattern of the modeled antenna, which can be measured without a numerical simulation. The CAD model is not required, and only an approximate dimension of the antenna is used. A CAD model of a seven-patch array antenna with a large platform and a manufactured single Yagi antenna are used to verify the proposed scheme. For the verification, we calculate the active element pattern (AEP) based on the ACGF for the antennas. These AEPs calculated based on the ACGF obtained by MoM are compared with those calculated on the basis of the IDM. The AEPs represent a sufficient coincident tendency, and the phase values are even more accurate than the existing scheme.

For accurate beam analysis of a radiating antenna array on a complex platform, the mutual coupling and platform scattering effects are important. We proposed a beam pattern analysis method for an antenna array on a complex platform, which combines the active element pattern method of the receiving mode and hybrid geometrical theory of diffraction antenna current Green's function technique. This proposed method clearly and mathematically divides the beam pattern of the antenna array on a complex platform into mutual coupling and platform scattering components. For a 12 linear dipole array embedded in a complex aircraft, analyses of the beam pattern and boresight error using the proposed method were verified with the method of moment results, which were simulated with FEKO. With reasonably good accuracy, the proposed method can efficiently analyze a beam pattern reflecting the mutual coupling effect and the platform scattering effect. Additionally, convex optimization with the proposed method is simply applied to synthesize the compensated beam pattern.

An improved prediction of the wideband beam patterns of an antenna array is proposed based on the active element pattern (AEP) method and infinitesimal dipole modeling (IDM). In the conventional method, the gain of an antenna array can be easily analyzed. However, the prediction of the shape of the beam pattern is limited due to usage of the slow-varying assumption and the scaling factor. On the contrary, the proposed method uses the free-space dyadic Green's function, which varies for frequencies and all infinitesimal dipole (ID) elements. By eliminating the slow-varying assumption and the scaling factor, the proposed method, predicting the shape of the beam pattern of an antenna array, is more accurate than the conventional method. The proposed method was verified by the wideband beam synthesis problem for a 7-patch antenna array.

There are mainly three issues for Near-Field Focusing (NFF) using an antenna array. First, it is required to know the distribution of the near electric field in 3D space for each antenna element. In general, a huge amount of data is required to express the near-field for each antenna element in a 3D space with high resolution. Second, in the trade-off relationship between efficiency and accuracy for NFF, we require to solve the optimization problem in which energy can be concentrated to the focal point. Solving optimization problems with near-field represented by huge amounts of data is very inefficient. Third, accurate NFF must be performed by reflecting the mutual coupling phenomenon between antennas. In this paper, there are three key ideas to overcome the issues in the NFF by improving both accuracy and efficiency. The first is the extraction of the infinitesimal dipole model (IDM) using the active element pattern. This makes it possible to obtain a mathematical model of the antenna that perfectly reflects the mutual coupling effect. The second is the acquisition of near-field data to an adaptive resolution grid with appropriate resolution using the extracted IDM. This re-radiated near-field data has both accuracy and efficiency by maintaining high resolution only for a focal point. The third is an efficient optimization method for a desired focal area with an arbitrary elliptical shape using convex optimization. Through simulations for the verification, 4 types of grids with various resolutions are used to the same NFF problem. The computational time of the proposed method in optimization for the NFF could be reduced to 8% with a similar focal shift compared to a type of the finest resolution. In addition, the accuracy of the electromagnetic analysis of the proposed method was verified through comparative verification with the MoM results.

This letter presents an antennadiagnosis method using infinitesimal dipole modeling. For antenna diagnosis, it is important to estimate the current distribution of the antenna aperture. By using the measured near-field data of the antenna, the infinitesimal dipole current distribution that can generate the same near-field measurement result is extracted. This current distribution can be considered as a back-projection image on the antenna aperture. Using the infinitesimal dipole modeling, accurate antenna diagnosis is possible even by using only the measured near-field which is limited over the antenna aperture. We compared the results of the conventional antenna diagnosis method based on Fourier transform and the proposed method for the near-field measurement results of the standard gain horn antenna. Although the limited near-field measurement over the antenna aperture, the back-projection image for the antenna diagnosis of the proposed method has a very high resolution.

Jeon P, et al. Anat Cell Biol. 2011 Jun;44(2):135-142. http://dx.doi.org/10.5115/acb.2011.44.2.135