Frequency-selective Dynamic Scattering Arrays for Over-the-air EM Processing

TL;DR

This work tackles hardware and power challenges in next-generation wireless systems by moving part of the signal processing into the electromagnetic domain using a frequency-selective Dynamic Scattering Array (DSA). The authors develop a multicarrier, end-to-end model in which a small set of active RF chains interact with a large cluster of reconfigurable passive scatterers via varactor-based loads to realize space-frequency beamforming. They formulate and solve an optimization to configure the loads so that the end-to-end response matches a target across $K$ subcarriers, and demonstrate through simulations that the DSA can achieve space-frequency superdirective beams with reduced RF-chain requirements, including joint space-frequency operation. The results suggest substantial potential for energy-efficient, low-latency holographic MIMO in future wireless networks, with practical load models and wideband operation enabling flexible EM-domain processing.

Abstract

In this paper, we investigate frequency-selective dynamic scattering array (DSA), a versatile antenna structure capable of performing joint wave-based computing and radiation by transitioning signal processing tasks from the digital domain to the electromagnetic (EM) domain. The numerical results demonstrate the potential of DSAs to produce space-frequency superdirective responses with minimal usage of radiofrequency (RF) chains, making it particularly attractive for future holographic multiple-input multiple-output (MIMO) systems.

Figures (4)

• Figure 1: Schematic of the DSA.
• Figure 2: Single-carrier beam forming with $N_{\text{A}}=4$RF chains.
• Figure 3: Multi-carrier beam forming with one RF chain ($N_{\text{A}}=1$) and $K=4$ subcarriers.
• Figure 4: Joint angle-frequency beamforming $N_{\text{A}}=2$RF chains and $K=2$ subcarriers.