  It is well known that there is inherent radiation pattern distortion for the
commercial base station antenna array, which usually needs three antenna
sectors to cover the whole space. To eliminate pattern distortion and further
enhance beamforming performance, we propose an electromagnetic hybrid
beamforming (EHB) scheme based on a three-dimensional (3D) superdirective
holographic antenna array. Specifically, EHB consists of antenna excitation
current vectors (analog beamforming) and digital precoding matrices, where the
implementation of analog beamforming involves the real-time adjustment of the
radiation pattern to adapt it to the dynamic wireless environment. Meanwhile,
the digital beamforming is optimized based on the channel characteristics of
analog beamforming to further improve the achievable rate of communication
systems. An electromagnetic channel model incorporating array radiation
patterns and the mutual coupling effect is also developed to evaluate the
benefits of our proposed scheme. Simulation results demonstrate that our
proposed EHB scheme with a 3D holographic array achieves a relatively flat
superdirective beamforming gain and allows for programmable focusing directions
throughout the entire spatial domain. Furthermore, they also verify that the
proposed scheme achieves a sum rate gain of over 150% compared to traditional
beamforming algorithms.
