Rapidly and continuously frequency-scanning opto-electronic oscillator.

Area of Science:

• Optoelectronics
• Microwave Engineering
• Signal Generation

Background:

• Traditional methods for generating frequency-swept microwave signals often face limitations in phase noise and performance.
• Opto-electronic oscillators (OEOs) offer a promising platform for high-performance signal generation due to their unique properties.

Purpose of the Study:

• To propose and experimentally demonstrate a novel opto-electronic oscillator (OEO) operating in a chirp oscillation mode.
• To generate low-phase-noise, frequency-swept microwave signals with enhanced performance characteristics.

Main Methods:

• The proposed OEO scheme embeds a rapidly frequency-scanning microwave filter within an opto-electronic cavity.
• The filter exhibits a fixed passband with its center frequency rapidly and periodically scanning at the cavity round-trip time.
• This configuration enables coverage of a large frequency range (~GHz) for the generated microwave signal.

Main Results:

• Experimentally, a linear frequency-modulated continuous wave (FMCW) signal was generated, centered at 7 GHz with a 1-GHz bandwidth.
• The instantaneous frequency swept linearly from 6.5 GHz to 7.5 GHz and back in 12.8 μs, achieving a scanning rate of ~156 MHz/μs.
• The single-side-band (SSB) noise was measured at -104 dBc/Hz at a 10 kHz offset frequency, significantly outperforming commercial electronic arbitrary waveform generators (E-AWGs) by up to 23 dB.

Conclusions:

• The demonstrated chirp oscillation OEO successfully generates high-quality, frequency-swept microwave signals.
• This approach offers a significant improvement in phase noise performance compared to existing electronic methods.
• The proposed scheme holds potential for applications requiring precise and low-noise frequency-swept signals.