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Costas-coded linear frequency modulation waveform generation based on a VCO-controlled Fourier domain mode locking
Optics Express
|November 23, 2021
Summary
Researchers developed a new method to create tunable Costas-coded linear frequency modulation waveforms (LFMWs) using an optoelectronic oscillator (OEO). This technique offers agile broadband radar waveform generation with excellent coherence.
Area of Science:
- Photonics and Optics
- Signal Processing
- Radar Systems
Background:
- Optoelectronic oscillators (OEOs) are crucial for generating microwave signals.
- Fourier domain mode locking enables precise control over OEO oscillation modes.
- Costas coding is essential for robust radar signal detection and ranging.
Purpose of the Study:
- To propose and demonstrate a novel method for generating tunable Costas-coded linear frequency modulation waveforms (LFMWs) from an OEO.
- To explore the tunability of bandwidth and center frequency for these waveforms.
- To assess the pulse-to-pulse coherence and phase noise characteristics of the generated waveforms.
Main Methods:
- Utilizing an OEO under Fourier domain mode locking.
- Employing a fast-scanning microwave bandpass filter based on stimulated Brillouin scattering for mode selection.
- Implementing an open-loop voltage-controlled oscillator (VCO) for Costas coding and agile frequency shifting.
Main Results:
- Successfully generated Costas-coded LFMWs with a 12-bit sequence, a period of 20.39 µs, and a tunable frequency range.
- Demonstrated excellent pulse-to-pulse coherence through cross-correlation analysis.
- Confirmed negligible influence of open-loop VCO phase noise on the generated waveforms.
Conclusions:
- The proposed approach enables direct generation of agile broadband multi-format radar waveforms from an OEO.
- The method offers low phase noise and excellent pulse-to-pulse coherence.
- This technique holds significant potential for advanced radar applications requiring flexible and high-performance waveforms.
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