Reprogrammable Metasurface Achieves Direct Radio-Frequency Calculations in Electromagnetic Space

The demand for more efficient and less complex electronic systems is driving innovation in how radio-frequency signals are processed. Shao Nan Chen, Zhan Ye Chen, and Si Ran Wang, alongside colleagues from Southeast University and City University of Hong Kong, have developed a new approach to radio-frequency calculation that moves processing directly into the electromagnetic wave domain. Their research details a reprogrammable metasurface system capable of performing calculations , specifically Fourier transforms and convolutions , without the need for digital conversion. This advancement promises to reduce hardware complexity and power consumption, offering a significant step towards more streamlined and cost-effective next-generation electronic devices, and is demonstrated through successful radar target detection. The team’s theoretical, simulated, and experimental results confirm the precision and efficiency of this novel space-time-coding metasurface system.

Dynamically Controlling Waves for RF Systems

Programmable metasurfaces are engineered surfaces capable of dynamically controlling electromagnetic waves by manipulating amplitude, phase, and polarization. This programmability allows them to perform complex signal processing functions directly in the physical domain, offering potential advantages in energy efficiency and speed compared to traditional digital signal processing. These surfaces have applications in RF computing, enabling analog operations like solving matrix equations and Fourier transforms, and in wireless communication, facilitating advanced multiplexing and beam steering. Beyond communication, metasurfaces can be employed for secure communication through information camouflage, harmonic manipulation for improved signal quality, and the generation of specific radar signatures for sensing and target identification.

Applications extend to bioelectronics, healthcare, material identification, and the creation of dynamic holographic projections. Integration with materials like memristors and graphene further enhances performance and functionality. The benefits of this technology include energy efficiency, increased processing speed, compactness, and versatility through reconfigurability. This approach leverages concepts like Fast Fourier Transforms and convolution, and has potential for integration into edge computing architectures, representing a shift towards wave-based computing and a move beyond the limitations of traditional digital signal processing.

RF Calculation via Space-Time-Coding Metasurface

Researchers developed a reprogrammable radio-frequency (RF) calculation system utilising a space-time-coding metasurface (STCM) to perform direct RF calculations within the electromagnetic spectrum, reducing the hardware complexity and power consumption associated with digital signal processing. The system implements fundamental signal operations, including Fourier transforms and convolutions, directly in the electromagnetic domain, and was validated in radar scenarios, accurately detecting target velocity and range. The STCM was constructed with vias to maintain stable reflection characteristics, and scientists developed a spatial encoding method to expand the metasurface’s capabilities beyond the limitations of four reflection states. This modulation strategy allowed conventional metasurfaces to meet the demands of RF calculations, mapping and characterising the In-phase & Quadrature (IQ) distribution of the equivalent reflection coefficient.

Detailed modulation protocols and implementation results are available in supplementary materials. A programmable RF calculation system was assembled, comprising a data transceiver module and a spatiotemporal modulation module. The transceiver employed a vector signal transceiver coupled with pyramidal horn antennas, while the modulation module integrated the STCM with an FPGA controller to dynamically adjust the metasurface’s reflection coefficient. Experiments using 5GHz RF signals demonstrated accurate modulation of the target reflection coefficient, maintaining constant amplitude with varying phase over time, as confirmed by comparisons with theoretical predictions.

The reflected echoes were captured to retrieve the RF calculation results, and the system’s functionality was demonstrated through STCM-based Fourier transforms and convolution operations using various signals. The Fourier transform was performed with N = 512 points, achieving a frequency resolution of 100kHz. Minor deviations, attributed to control signal precision and environmental noise, did not significantly impact the overall computation results.

Reprogrammable Metasurface Performs Direct RF Calculations

Information metasurfaces are increasingly vital in advanced electronic systems, and scientists have developed a reprogrammable RF calculation system based on a space-time-coding metasurface (STCM) that directly manipulates wave interactions within the electromagnetic (EM) space. This innovative approach bypasses traditional digital conversion, reducing hardware complexity and power consumption in signal processing systems, and successfully implements fundamental signal operations, such as Fourier transforms and convolutions, directly in the EM-wave domain. The team validated the RF calculation capabilities in radar scenarios, demonstrating accurate detection of target velocity and range. Theoretical analysis, numerical simulations, and experimental results confirm the STCM-based system delivers superior precision and enhanced operational efficiency, with potential for cost-effectiveness in next-generation electronic deployments.

The research builds upon advances in electromagnetic physics, utilising subwavelength artificial units to precisely control wave properties. By integrating EM wavefront control with space-time-coding strategies, the team created the STCM, enabling direct signal processing at the physical layer and minimising the need for analog-to-digital and digital-to-analog conversions. The STCM achieves complex calculations by integrating multidimensional EM wave manipulations with direct signal processing on the metasurface itself, realising both Fourier transforms and convolution operations. Results demonstrate strong agreement between measured data and theoretical predictions, validating the proposed architecture and its feasibility for programmable RF calculations in the wave domain.

RF Metasurface Performs Direct Wave Domain Calculations

This research demonstrates a reprogrammable radio-frequency (RF) calculation system based on a space-time-coding metasurface (STCM), enabling direct RF calculations within the electromagnetic spectrum. The system successfully implements fundamental signal operations, specifically Fourier transforms and convolutions, directly in the wave domain, bypassing traditional digital conversion processes and achieving accurate detection of target velocity and range in radar scenarios. The work establishes that the STCM-based system offers improved precision, operational efficiency, and cost-effectiveness. While acknowledging minor deviations potentially stemming from control signal precision and environmental noise, the authors note these factors have a negligible impact on overall computational accuracy. Further experimentation confirmed the system’s programmability and ability to maintain spectral characteristics, even with reduced resolution, and a unified coding sequence proved capable of handling diverse input signals. Future research could explore expanding the range of RF calculations and refining the system to minimise environmental interference.