Microwave Linear Analog Computer (MiLAC) for Simultaneous Active and Passive Beamforming
2026-05-29 • Information Theory
Information Theory
AI summaryⓘ
The authors study a special computer called MiLAC that uses microwaves to help with beamforming, which is directing signals to specific places efficiently. They show that MiLACs can do two things at once: actively send and receive signals while also acting like a smart mirror (RIS) that reflects outside signals. The paper explains the best way to control this dual function and explores how well it can work, focusing on the balance between active and passive signal handling. They also define limits on the combined data rates achievable by the MiLAC system.
Microwave linear analog computersBeamformingPrecodingCombiningReconfigurable intelligent surfacePassive beamformingActive beamformingCapacity regionSum-rate capacityTransceiver
Authors
Matteo Nerini, Bruno Clerckx
Abstract
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.