Channel Estimation Technique for Eliminating Spurious Peaks in Ultra-Massive Hybrid-Field MIMO

‍ ‍Ultra-massive MIMO （Multiple-Input Multiple-Output） is a potential key technology for 6G mobile communications. Most of the existing channel models assume that all the scatterers are in the far-field region， and adopt the far-field channel model based on the plane wave assumption； Or they are all in the near-field region， using the near-field channel model based on the spherical wave hypothesis. In practice， ultra-massive MIMO systems are more likely to produce hybrid-field channel environments. Existing channel models cannot match the characteristics of this far-field and near-field mixed channel well， so existing channel models and channel estimation schemes cannot be directly used. In this paper， the hybrid-field channel was modeled. Aiming at the problem of spurious peaks in the spatial spectrum of the hybrid-field channel， a channel estimation scheme was proposed to eliminate the spurious peaks. At the same time， this scheme also took into account the spatial non-stationary problem of the ultra-massive MIMO antenna array. Simulation results show that the proposed channel estimation scheme for eliminating spurious peaks in ultra-massive hybrid-field MIMO systems has better channel estimation performance.