Photonics-based coherent wideband linear frequency modulation pulsed signal generation.

Area of Science:

• Photonics
• Radar Systems Engineering
• Signal Processing

Background:

• Coherent radar systems require wideband linear frequency modulation (LFM) pulses with tunable carrier frequencies.
• Existing methods face challenges in reconfiguring pulse bandwidth and carrier frequency while maintaining phase coherence.

Purpose of the Study:

• To propose and demonstrate a photonics-based scheme for generating wideband LFM pulses with broadly tunable carrier frequencies.
• To enable reconfiguration of pulse bandwidth and carrier frequency for coherent radar applications.
• To maintain pulse-to-pulse phase coherence for improved radar performance.

Main Methods:

• Integration of microwave-photonic multiplication and coherent beating techniques.
• Implementation of an optical phase-locked loop (OPLL) for phase fluctuation suppression.
• Demonstration of a Ka-band coherent radar system including signal generation, wireless transmission, and echo detection.

Main Results:

• Successful generation of wideband LFM pulses with tunable bandwidth and carrier frequency.
• Achieved pulse-to-pulse phase coherence through OPLL stabilization.
• Demonstrated coherent integration of radar echo signals, yielding an 8 dB signal-to-noise ratio improvement per tenfold increase in integration time.
• Obtained a range resolution of approximately 3.75 cm, closely matching theoretical predictions.

Conclusions:

• The proposed photonics-based scheme effectively generates reconfigurable wideband LFM pulses for coherent radar.
• The system demonstrates significant improvements in signal-to-noise ratio and range resolution.
• This approach offers a promising solution for advanced coherent radar applications.