Time-gated filter for sideband suppression

Area of Science:

• Photonics
• Electrical Engineering
• Signal Processing

Background:

• Electrical modulation technologies for single-sideband (SSB) waveforms are limited to radio frequencies (RFs) below 20 GHz.
• Photonic time-stretch analog-to-digital converters (TS-ADCs) suffer from frequency fading due to dispersion, limiting input signal bandwidth and time aperture.
• The presence of both upper and lower sidebands in TS-ADCs exacerbates frequency fading.

Purpose of the Study:

• To demonstrate a time-gated filter capable of converting double-sideband (DSB) RF waveforms to SSB waveforms.
• To apply this filter in TS-ADCs to mitigate frequency fading and extend the operational RF range.
• To show significant reduction in frequency fading and enable digitization of higher frequency signals.

Main Methods:

• Development and demonstration of a time-gated filter operating on a pulsed optically chirped carrier.
• Integration of the time-gated filter into a photonic time-stretch analog-to-digital converter architecture.
• Characterization of the filter's performance in reducing frequency fading and enabling high-frequency signal digitization.

Main Results:

• The demonstrated time-gated filter successfully converts DSB RF waveforms to SSB waveforms.
• Frequency fading in the TS-ADC was reduced by over 20 dB.
• The enhanced TS-ADC successfully digitized electrical signals with RFs exceeding 100 GHz.

Conclusions:

• The time-gated filter overcomes the RF limitations of existing SSB modulation technologies.
• This filter significantly improves the performance of photonic time-stretch analog-to-digital converters by reducing frequency fading.
• The developed system enables high-frequency signal digitization beyond 100 GHz using photonic approaches.