A Method for Measuring the Full Tx-to-Rx Coupling Matrix of Large Active Antenna Arrays

In this paper, a Hadamard matrix based approach is used to capture the individual coupling coefficients from each transmit element to every receive element of large active antenna arrays. The full coupling matrix contains information that can be used to mitigate isolation problems of the full-duplex phased array systems where a high-power transmitter sits in close prox-imity to a low-noise-figure receiver. However, it is challenging to characterize the full coupling of each antenna element in systems with many active antennas due to their common connections to a single fed port. The Hadamard matrix-based method has the ability to characterize every antenna element, a methodology that has long been used in phased array calibration applications. Moreover, this method can maximize signal-to-noise ratio of the measurement and closely mimics operational conditions of the phased array transceiver. Experimental validation using a 1024-element transmitter and 1280-element receiver full-duplex system demonstrates the effectiveness of the proposed method. Measurement results are used to calculate the spatial distribution of signal and noise power coupled to the Rx array, providing insights into coupling behavior across various scan angles and environmental conditions, including the presence of a radome. These findings provide valuable information for performance enhancement such as improving isolation, receiver sensitivity and G/T.