Metasurface-Enabled Superheterodyne Transmitter With Decoupled Harmonic-Free Signal Generation and Precoding

2025-11-16

AI Summary

To address critical bottlenecks in programmable metasurface (PM) transmitters—including limited modulation order, symbol-level spatial inconsistency, and severe harmonic interference—this work proposes the first reflective heterodyne-based mixer array architecture. Leveraging co-designed digital upconversion and amplitude-phase-decoupled reconfigurable reflective mixing, the architecture decouples baseband signal generation from RF beamforming. It enables arbitrary-order QAM modulation, multi-stream interference suppression, and spatial diversity while completely eliminating harmonic distortion. Experimental validation on a 5.8 GHz prototype demonstrates a linear-region throughput of 20 Mbps, isotropic constellation generation, and time-frequency coherent applications such as Doppler spoofing—thereby surpassing the fundamental performance limits of conventional switch-based PM transmitters.

Technology Category

• Search and Optimization: Mixed Discrete/Continuous Search
• Machine Learning: Mixture of Experts (MoE)
• Planning, Routing, and Scheduling: Mixed Discrete/Continuous Planning

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Data management and stream processing for Web, mobile and wireless applications
• Security and Privacy: Data transparency and provenance
• Responsible Web: Machine-in-the-loop, human agency and autonomy

Abstract

The evolution of programmable metasurfaces (PM) from passive beamforming to active information transmission marks a paradigm shift for next-generation wireless systems. However, this transition is hindered by fundamental limitations in conventional metasurface transmitter architectures, including restricted modulation orders, symbol-level spatial inconsistency, and significant harmonic interference. These issues stem from the intrinsic coupling between baseband signal processing and radio-frequency beamforming in monolithic designs reliant on simplistic switching mechanisms. This paper proposes a novel metasurface-enabled superheterodyne architecture (MSA) that fundamentally decouples these functionalities. The MSA introduces a dual-stage up-conversion process, comprising a digital up-conversion module for in-phase/quadrature modulation and baseband-to-intermediate frequency conversion, a precoder module for precoding, and a custom-designed magnitude-phase-decoupled metasurface that acts as a reconfigurable reflective mixer array. This decoupling of harmonic-free waveform generation from spatial precoding overcomes the critical drawbacks of existing approaches. Experimental results from a 5.8 GHz proof-of-concept prototype system validate the MSA's superior performance. The system generates spatially isotropic constellations for arbitrary-order QAM modulations, ensures consistent time-frequency signatures for applications like Doppler-spoofing, and achieves data rates up to 20 Mbps within a linear operating region that minimizes nonlinear distortion. The capability of employing spatial diversity and multi-stream interference cancellation has been demonstrated for the first time in a PM-based transmitter.

Problem

• Decoupling harmonic-free signal generation from spatial precoding in metasurface transmitters
• Overcoming restricted modulation orders and symbol-level spatial inconsistency limitations
• Eliminating significant harmonic interference in conventional metasurface transmitter architectures

Innovation

• Dual-stage up-conversion process for signal modulation
• Precoder module enabling spatial precoding functionality
• Magnitude-phase-decoupled metasurface as reflective mixer array