Remote broadband RF signal down-conversion with stable phase and high efficiency using a sideband optical...

Area of Science:

• Optoelectronics
• Radio Frequency Engineering
• Signal Processing

Background:

• Remote signal transmission often suffers from degradation.
• Efficient down-conversion of broadband radio frequency (RF) signals is crucial for various applications.
• Maintaining signal integrity over long distances presents significant challenges.

Purpose of the Study:

• To propose and demonstrate a phase-stable, high-efficiency down-conversion approach for broadband RF signals from remote sites.
• To enhance conversion gain and spurious-free dynamic range (SFDR) for improved signal quality.
• To enable simple-structured remote ends for weak broadband signal down-conversion.

Main Methods:

• Utilizing a high-power coherent optical local oscillator at the local site.
• Employing a sideband optical phase-locked loop (OPLL) to suppress fiber-induced phase noise and laser frequency drift.
• Experimental demonstration of single-frequency and broadband signal down-conversion.

Main Results:

• Achieved 3 dB gain and 103 dB/Hz^2/3 SFDR for a 16.45 GHz signal down-converted to 250 MHz after 10 km fiber transmission.
• Demonstrated broadband down-conversion of a 1 GHz wide linear frequency modulated (LFM) pulse signal.
• Obtained an average SFDR of 97.6 dB/Hz^2/3 for down-conversion from 5 GHz to 40 GHz with positive gain.

Conclusions:

• The proposed phase-stable down-conversion approach offers high efficiency and improved SFDR.
• The method effectively mitigates phase noise and frequency drift issues in remote signal transmission.
• This technique is well-suited for weak broadband remote signal down-conversion, requiring a simple remote-end structure.