Characteristic Modes based Antenna Analysis
CMC 2015 (Characteristic Mode Computation):
The graphical user interface is programmed in MATLAB and the aid of the MSDN library. The visualization of the 3D objects and the plots are realized in OpenGL (TaoFramework: freeware, available “www.sourceforge.net/projects/taoframework/”). The software owns a CAD interface and an internal mesh algorithm for the propose of the characteristic mode calculation.
The main features of the software are:
 CAD Interface is included
 Mesh of the surface into triangles
 MoM matrix calculation with EFIE/MFIE and PMCHWT
 Import STL and GMSH files
 Characteristic Mode Decomposition
 Lossy dielectric and magnetic materials
 Lumped sources and plane wave excitation
 Lumped impedances can be added
 Define infinite size ground plane
 QFactor calculation
 Calculate correlation for multi port antenna systems
 Lumped impedance matching network can be connected with lumped feed ports
 Eigenvalue tracking with correlation and orthogonalization based algorithm
 Adaptive frequency control for eigenvalue tracking
 Power coefficient
Theory:
The Theory of Characteristic Modes has been derived by Garbacz in 1971first, and it is a useful method to decompose the complex current distribution of an antenna into its fundamental modes. The radiation properties of these modes are often much simpler to understand than the complex entire current distribution.
Reconstruction:
As other software, e.g. Empire XCcel, are used for antenna design the characteristic modes cannot be calculated, as the impedance matrix is usually not available. In order to overcome this drawback a reconstruction is needed, which approximates the impact of the characteristic modes by the radiated far field. A mathematical concept to reconstruct the characteristic modes of a complex structure, treated with Empire, and the general knowledge about the modes on a simplified structure, treated with MGUI, has been developed. The approach is based on the assumption that the complex antenna contains the same modes as the simplified structure. The envelope correlation allows for a simple estimation of the coefficients of modes and, therefore, the contribution into the overall power budget.
Reconstruction of a rectangular plate excited by a plane wave polarized along the major axis for six significant characteristic modes. The lines denote the normalized coefficient of the reference calculated with CMC. The dashed lines denote the reconstruction with the method. The result is scaled in b_{n} [dB] = 20 log_{10}(b_{n}).
Impedance Matching Network in CMC:
From earlier publications, it is widely known that the placement of lumped elements, e.g. at the port position, have a significant influence on the mode excitation and the impedance matching of the respective ports. In common antenna designs the input impedance at the frontend of the port is matched with an additional impedance matching network to achieve the required bandwidth at the frequency bands of interest. The reactive network, which is typically designed out of capacitances and inductances, shifts the resonance of the characteristic modes down and up in frequency. The characteristic modes under the influence of such network can be calculated with some MoM impedance matrix modifications.
For this, a
simple dipole antenna is assumed, which is placed in free space. The dipole is feed in
the center, as denoted in the below figure.
The matching network is added in the MoM impedance matrix with:
With the aid of this modified matrix the characteristic modes under the influence of the impedance matching network can be analyzed. The same principle can be used if lossy components are included in the network. The next figure shows the eigenvalue of the new modified characteristic modes of the dipole.
 Publications:

 Safin, E., Martens, R. and Manteuffel, D. , "Modal Source Reconstruction Based on Radiated FarField for Antenna Design", In Antennas and Propagation (EUCAP), 2012 6th European Conference on., march, 2012. , pp. 1645 1649. DOI
 [Abstract]
 We present a mathematical technique to reconstruct the modal current distribution on arbitrary antennas from the radiated farfield and general knowledge about the modes involved. The method leads to good results if the radiation mechanism of the actual antenna can be approximated by the current distribution on a simplified structure. The current distribution of the simplified structure is decomposed into its characteristic modes and the related modal farfield is calculated. Assuming that the farfield of the actual antenna contains the same modes, their weighting coefficients are calculated by comparing the farfield of the actual antenna to the modal farfield of the simplified structure. It can be shown that the weighting coefficients of all significant modes can be reconstructed with good accuracy.
 [BibTeX]

@inproceedings{6205814, author = {Safin, E. and Martens, R. and Manteuffel, D.}, title = {Modal source reconstruction based on radiated farfield for antenna design}, booktitle = {Antennas and Propagation (EUCAP), 2012 6th European Conference on}, year = {2012}, pages = {1645 1649}, doi = {10.1109/EuCAP.2012.6205814} }
 Safin E. and Manteuffel, D. , "Resonance Behaviour of Characteristic Modes Due to the Presence of Dielectric Objects", In Antennas and Propagation (EUCAP), 2013 7th European Conference on., April 2013.
 [Abstract]
 In this paper we present a modal analysis of dielectric bodies of arbitrary shape. The problem of a dielectric body is reformulated into equivalent electric and magnetic surface currents. Using the weighed eigenvalue equation the characteristic modes of the equivalent problem are calculated. A physical interpretation of the eigenvalue of the dielectric characteristic modes is presented and discussed.
 Safin, E. and Manteuffel, D. , "Reconstruction of the Characteristic Modes on an Antenna Based on the Radiated Far Field,", Antennas and Propagation, IEEE Transactions on , vol.61, no.6, pp.2964,2971, June 2013.
DOI
 [Abstract]
 In this paper, we present a method to reconstruct the modal current distribution on an antenna from the radiated far field and general knowledge about the modes involved. The method leads to good results if the radiation mechanism of the antenna can be approximated by the current distribution on a simplified structure. The current distribution of the simplified structure is decomposed into its characteristic modes and the related modal far field is calculated. Assuming that the far field of the actual antenna contains the same modes, their weighting coefficients are calculated by comparing the far field of the actual antenna to the modal far field of the simplified structure. It can be shown that the weighting coefficients of all significant modes can be reconstructed with good accuracy even for complex real structures such as mobile phones.
 [BibTeX]

@ARTICLE{6473830, author={Safin, E. and Manteuffel, D.}, journal={Antennas and Propagation, IEEE Transactions on}, title={Reconstruction of the Characteristic Modes on an Antenna Based on the Radiated Far Field}, year={2013}, volume={61}, number={6}, pages={29642971}, abstract={In this paper, we present a method to reconstruct the modal current distribution on an antenna from the radiated far field and general knowledge about the modes involved. The method leads to good results if the radiation mechanism of the antenna can be approximated by the current distribution on a simplified structure. The current distribution of the simplified structure is decomposed into its characteristic modes and the related modal far field is calculated. Assuming that the far field of the actual antenna contains the same modes, their weighting coefficients are calculated by comparing the far field of the actual antenna to the modal far field of the simplified structure. It can be shown that the weighting coefficients of all significant modes can be reconstructed with good accuracy even for complex real structures such as mobile phones.}, keywords={Antennas;Correlation;Current distribution;Eigenvalues and eigenfunctions;Equations;Mathematical model;Surface impedance;Antenna radiation pattern;antenna theory;eigenvalues and eigenfunctions;mobile antennas;numerical analysis}, doi={10.1109/TAP.2013.2251312}, ISSN={0018926X},}, }
 Safin, E., Martens, R. and Manteuffel, D. , "Modal Source Reconstruction Based on Radiated FarField for Antenna Design", In Antennas and Propagation (EUCAP), 2012 6th European Conference on., march, 2012. , pp. 1645 1649. DOI