Analysis of Utilizing Lossless Networks for Self-Interference Cancellation Purpose

In this paper, novel self-interference cancellation technique is proposed. The technique addresses in particularly the transceivers where dedicated-transmit-and-receive antenna configurations are embraced. The technique, moreover, relies on a lossless decoupling network, which interconnects the transceiver's chains to the antenna elements. The values of the network's reactive components, which are the building blocks of the lossless network, can be computed to suppress the self-interference at the local receivers for the targeted frequency. Thus, the technique provides a self-interference suppression method at the radio-frequency domain, which does not waste energy for cancellation purpose. Moreover, the technique can implicitly assure optimized power delivery among the antenna array elements and the transceiver front-ends. Network analysis of a multiple-input-multiple-output antenna array in a full-duplex transceiver is presented in order to characterize the self-interference in terms of mutual coupling phenomenon among the antenna array elements. Mutual coupling measurements of two identical antennas setup are presented and analyzed. Finally, empirical assessment of the proposed self-interference cancellation technique is provided, to show that the self-interference cancellation levels can exceed 70 dB by employing the proposed technique.