Photonically enabled coherent spatiotemporal focusing via time-reversal for wideband communications [Invited]

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Abstract
Time-reversal (TR) signal processing is a promising approach for mitigating multipath propagation effects in wideband wireless systems by leveraging channel reciprocity to pre-compensate for propagation-induced symbol delays, phase misalignment, and interference at the transmitter. This enables temporal compression at the receiver, resulting in the constructive combination of multipath components, reduced inter-symbol interference (ISI), and improved spatial focusing, while shifting the signal processing burden away from the receiver. However, the practical implementation of TR in distributed multi-antenna systems is fundamentally limited by the need for tight phase coherence and frequency synchronization across transmitters, which is difficult to achieve with conventional RF architectures that rely on independent oscillators. In this work, we present an RF-photonic distribution architecture that enables distributed coherent multi-transmitter TR operation by driving up to 10 transmit antennas from a single optical source, thereby ensuring phase coherence and frequency synchronization across all paths. Using experimentally measured channel states over the 6G carrier frequency of 20 GHz and an instantaneous bandwidth of 600 MHz, we demonstrate time-reversal transmission with strong temporal compression and spatial focusing. These results highlight the critical role of coherence in distributed TR systems and establish RF-photonic architectures as a scalable solution for multi-antenna time-reversal communication in emerging wireless networks.
Funding Information
  • Office of Naval Research (N00014-23-1-2742)

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