Broadband stepped-frequency radar waveform generation by Fourier domain mode-locking period-one laser dynamics

Area of Science:

• Photonics and Optics
• Radar Systems Engineering
• Signal Processing

Background:

• Traditional stepped-frequency (SF) radar waveform generation faces limitations in signal quality and resolution.
• Semiconductor laser dynamics and optoelectronic feedback loops are key areas for advanced radar signal generation.

Purpose of the Study:

• To propose and demonstrate a new SF radar waveform generation method using Fourier domain mode-locking (FDML).
• To enhance the frequency stability, accuracy, and signal-to-noise ratio of SF radar signals.
• To achieve high-resolution inverse synthetic aperture radar (ISAR) imaging.

Main Methods:

• Utilizing period-one laser dynamics in FDML by controlling semiconductor laser optical injection strength via electro-optical modulation.
• Implementing an optoelectronic feedback loop synchronized with the SF signal's temporal period to enable FDML.
• Generating broadband SF signals with specific bandwidth and frequency step parameters.

Main Results:

• Successfully generated SF signals with a 6 GHz bandwidth (12-18 GHz) and a 150 MHz frequency step.
• FDML significantly improved frequency stability, accuracy, and in-band signal-to-noise ratio compared to non-FDML methods.
• Demonstrated high-resolution 2D ISAR imaging with a resolution of 2.6 cm × 3.82 cm.

Conclusions:

• The proposed FDML-based SF radar waveform generation method offers superior performance.
• This technique effectively enhances radar signal quality and enables advanced imaging capabilities.
• The method holds promise for future high-resolution radar applications.