Development of a high-speed full digital processing phase detector for interferometry

Area of Science:

• Plasma Physics
• Digital Signal Processing
• Interferometry

Background:

• Plasma interferometry is crucial for diagnostics, but conventional analog phase detectors struggle with small or rapidly changing signals.
• Accurate phase shift measurement is essential for understanding plasma dynamics, especially during events like pellet injection.

Purpose of the Study:

• To develop a fully digital phase detector for plasma interferometry.
• To overcome limitations of analog detectors in handling rapid phase changes and weak signals.

Main Methods:

• The digital phase detector directly processes the intermediate frequency (IF) signal waveform.
• Hilbert transformation converts the IF signal to in-phase and quadrature-phase components.
• Digital low-pass filtering and coordinate rotation digital computer algorithm extract the phase shift from the entire waveform.

Main Results:

• Simulations show the detector can handle phase change rates up to 0.8 × 10^6 rad/s without fringe jumps.
• The method accurately calculates phase signals from real interferometer data, even when conventional methods fail.
• The digital approach provides reliable phase derivation from challenging IF signals.

Conclusions:

• The developed fully digital phase detector offers superior performance for plasma interferometry.
• This technology enables accurate phase shift measurements in dynamic plasma conditions.
• The digital processing method represents a significant advancement over traditional analog techniques.