Systematic Pattern Synthesis for Single Antennas Using Characteristic Mode Analysis

In this work, a systematic and generally applicable method to synthesize patterns for single antennas is proposed based on characteristic mode analysis (CMA). Both the theoretical analysis and real implementations are taken into consideration. To obtain a desired pattern, we first calculate the weighting coefficient of each mode using the correlation between the characteristic field and the desired pattern. Afterwards, the synthesized current and the feeding vector are solved using CMA, providing feeding information, such as feeding numbers, locations, amplitude and phase. The feeding vector is non-sparse, making practical feeding impossible. In this circumstance, the theory of compressed sensing is applied so that the number of the ports can be greatly reduced, the synthesized pattern is still highly correlated with the desired one. The method is applied to two-dimensional (2D) and three-dimensional (3D) structures, where a mobile handset and a scaled model of the shipboard are utilized as representatives. The prototype of the handset antenna was fabricated and measured, with the desired pattern achieved, having null in the boresight direction and being almost omni-directional on the plane of the chassis. The measured results agree well with the simulated ones. With the synthesized pattern, the handset antenna is robust to the user effects. The method can be generally applied to pattern synthesis for planar and 3D antennas.