Microwave linear analog computers (MiLACs) have recently emerged to enable high-performance and efficient beamforming in the analog domain. In this paper, we introduce a dual-functionality framework for MiLAC-aided transceivers. Beyond analog-domain precoding/combining (active beamforming), a MiLAC and its antenna array can simultaneously act as a reconfigurable intelligent surface (RIS) (passive beamforming). This allows the MiLAC to execute beamforming for transmission/reception while reflecting external incident signals. We provide an optimal reconfiguration strategy for this dual-functional MiLAC, and characterize the fundamental limits on the trade-off between active and passive rate, namely the capacity region bounds and the sum-rate capacity.

翻译：微波线性模拟计算机（MiLAC）近期被提出，可在模拟域实现高性能、高效率的波束赋形。本文提出一种面向MiLAC辅助收发机的双功能框架。除模拟域预编码/合并（主动波束赋形）功能外，MiLAC及其天线阵列可同时作为可重构智能表面（RIS）工作（被动波束赋形）。这使得MiLAC在执行发射/接收波束赋形的同时，能够反射外部入射信号。我们针对该双功能MiLAC提出最优重构策略，并刻画了主动与被动速率之间折中的基本极限，即容量区域边界和总速率容量。