The FDD method is normally used for the stability of the Tx and the Rx links in a fast-varying channel. It is required to physically separate the Tx and Rx arrays for independent Tx and Rx beam control. In this system, it is important to reduce the Tx self-interference (SI) that causes the problem of active element saturation and ADC dynamic range in the Rx beamformer. To suppress Tx SI, we proposed two simple techniques. The first is the general soft-surface which attenuates the surface current flow from the Tx tile array to the Rx array. The second is the sub-array structure of the Rx hybrid beamforming system. Based on the Cauchy–Schwartz inequality, the electrical sum by the sub-array acts as a destructive interference of the complex SI signals, and it can be shown as an additional isolation effect. The proposed idea was validated through measurement.

FDD方法通常用于快速通道中Tx和Rx链路的稳定性。需要将Tx和Rx阵列物理分开，以实现独立的Tx和Rx波束控制。在该系统中，重要的是减少Tx自干扰（SI），该干扰会导致Rx波束形成器中的有源元件饱和和ADC动态范围问题。为了抑制Tx SI，我们提出了两种简单的技术。第一个是一般的软表面，它会衰减从Tx瓦片阵列到Rx阵列的表面电流。第二个是Rx混合波束成形系统的子阵列结构。基于Cauchy-Schwartz不等式，子阵列的电和对复杂SI信号起破坏性干扰的作用，并且可以显示为附加的隔离效果。