FaA-CAF: Modular Single-RF-Chain Near-Field mmWave Sensing via Clip-On Antenna Fabric

2026-02-06

AI Summary

This work addresses the high hardware complexity of near-field millimeter-wave sensing, which typically relies on large antenna arrays or multiple RF chains. The authors propose a hardware-efficient architecture based on the “Frequency-as-Aperture” (FaA) principle, enabling switch-free, fully analog spatial aperture synthesis using only a single RF chain and clip-on textile antennas. By exploiting frequency-domain coordination, the approach extends spatial observability without additional hardware, while an online self-calibration mechanism compensates for variations caused by modular attachment. The system integrates FMCW excitation, frequency-selective clip-on modules, a shared guided-wave substrate, and fully analog passive multiplexing. Two case studies demonstrate the method’s robustness and quantify the predictable trade-off between sensing margin and modular deployment, offering a novel pathway toward embodied sensing and integrated communication-sensing systems.

Technology Category

• Machine Learning: Hardware-aware ML
• Intelligent Robots: Multimodal Perception & Sensor Fusion
• Humans and AI: Brain-Sensing and Analysis

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Applied ML and AI for Web-based mobile applications
• Security and Privacy: Large-scale security measurements
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs

Abstract

Near field mmWave sensing is poised to play a key role in future wireless systems, enabling environment-aware, embodied, and application adaptive operation under stringent form-factor and hardware constraints. However, achieving high spatial resolution in the near field typically requires large antenna arrays, multiple radio frequency (RF) chains, or mechanical scanning, creating a fundamental tension between spatial observability and system simplicity. This paper presents frequency as aperture clip on antenna fabric (FaACAF), a hardware efficient sensing by design architecture that synthesizes spatial aperture through the FaA paradigm using a single RF chain. FaACAF realizes a modular clip on aperture fabric, in which frequency selective clip on modules (CMs) are attached to a shared guided-wave substrate and implicitly coordinated by the instantaneous frequency modulated continuous wave (FMCW) excitation frequency. In this fabric, FMCW signaling simultaneously indexes the sensing aperture and orchestrates uplink/downlink signal distribution and echo multiplexing in a switch free, fully passive, and all analog manner, eliminating RF switching and multichannel front ends. An online self calibration mechanism stabilizes the frequency to aperture mapping under practical attachment variability without requiring full matrix calibration. Two case studies illustrate the robustness of the proposed approach and quantify the predictable sensing margin tradeoffs introduced by modular deployment. Overall, FaACAF demonstrates that near field spatial observability can be scaled through architectural coordination in the frequency domain rather than hardware expansion, providing a reconfigurable and hardware efficient pathway toward embodied sensing and integrated sensing and communication (ISAC) in future wireless systems.

Problem

• near-field mmWave sensing
• spatial resolution
• single RF chain
• hardware constraints
• aperture synthesis

Innovation

• Frequency-as-Aperture
• Clip-on Antenna Fabric
• Single RF Chain
• Near-field mmWave Sensing
• Integrated Sensing and Communication