Photonic Generation of Radar Signals with 30 GHz Bandwidth and Ultra-High Time-Frequency Linearity

TL;DR

This paper introduces a novel photonic waveform generation method that produces ultra-wideband, highly linear radar signals exceeding 30 GHz bandwidth, improving resolution and sensing accuracy over traditional electronic approaches.

Contribution

The authors demonstrate, for the first time, a photonic SF waveform scheme with MHz electronics achieving over 30 GHz bandwidth and intrinsic linearity, avoiding complex digital components.

Findings

Achieved >30 GHz tunable bandwidth

Demonstrated high time-frequency linearity

Confirmed improved radar imaging performance

Abstract

Photonic generation of radio-frequency signals has shown significant advantages over the electronic counterparts, allowing the high precision generation of radio-frequency carriers up to the terahertz-wave region with flexible bandwidth for radar applications. Great progress has been made in photonics-based radio-frequency waveform generation. However, the approaches that rely on sophisticated benchtop digital microwave components, such as synthesizers and digital-to-analog converters have limited achievable bandwidth and thus resolution for radar detections. Methods based on voltage-controlled analog oscillators exhibit high time-frequency non-linearity, causing degraded sensing precision. Here, we demonstrate, for the first time, a photonic stepped-frequency (SF) waveform generation scheme enabled by MHz electronics with a tunable bandwidth exceeding 30 GHz and intrinsic time-frequency linearity. The ultra-wideband radio-frequency signal generation is enabled by using a polarization-stabilized optical cavity to suppress intra-cavity polarization-dependent instability; meanwhile, the signal's high-linearity is achieved via consecutive MHz acousto-optic frequency-shifting modulation without the necessity of using electro-optic modulators that have bias-drifting issues. We systematically evaluate the system's signal quality and imaging performance in comparison with conventional photonic radar schemes that use high-speed digital electronics, confirming its feasibility and excellent performance for high-resolution radar applications.