On Analytical Solution of Channel Spatial Correlation for Efficient MIMO OTA Testing

This letter presents an analytical (closed-form) expression for computing the channel spatial correlation in multiple-input–multiple-output over-the-air (OTA) testing. Specifically, by leveraging the Jacobi–Anger expansion, the target channel spatial correlation can be accurately characterized using finite-order Bessel functions. Compared to conventional approaches that require complex integration to determine the channel spatial correlation, the proposed method significantly reduces computation time with minimal impact on accuracy. This improvement is crucial for enhancing the efficiency of OTA testing, especially in dynamic channel scenarios where spatial correlation must be calculated for each snapshot. Simulation results show that our method can reduce computation time to 1.4% of that required by the conventional integration method while achieving more than 99.99% computational accuracy.