An RF-adaptive array antenna incorporated in a MIMO receiver under interference

In this paper, incorporation of an RF-adaptive array antenna (RF-AAA) is proposed on each receive branch in a multiple-input multiple-output (MIMO) receiver to achieve interference suppression. A criterion is shown for maximizing the output signal-to-interference-plus-noise ratio (SINR) in the RF-AAA with amplitude and phase adjusts. The performance is roughly evaluated with no amplitude adjust and a four-bit phase shift. Computer simulation verifies that the RF-AAA improves the capacity of the MIMO system and the bit-error rate (BER) performance of its receiver by suppressing interference, as the number of RF-AAA elements increases. However, diversity gain is not obtained as the number of RF-AAA elements increases, and the impact of interference suppression is seriously degraded as the angular spread of the interference increases.