Photonic Doppler frequency shift measurement based on a dual-polarization modulator

Area of Science:

• Photonics
• Optical Engineering
• Signal Processing

Background:

• Doppler frequency shift (DFS) is crucial for radar and communication systems.
• Accurate measurement of DFS value and orientation is essential for target tracking and velocity estimation.
• Existing DFS measurement techniques may face limitations in accuracy or complexity.

Purpose of the Study:

• To propose and demonstrate a novel photonic-assisted DFS measurement scheme.
• To achieve simultaneous measurement of DFS value and orientation.
• To investigate the frequency tunability and accuracy of the proposed scheme.

Main Methods:

• Utilizing an integrated dual-polarization Mach-Zehnder modulator for optical frequency conversion.
• Transforming DFS into a low-frequency electrical signal via an optical frequency-conversion link.
• Analyzing the spectrum of the electrical signal to determine DFS value and employing a 90° hybrid coupler for orientation detection.

Main Results:

• The proposed scheme successfully measures both the value and orientation of DFS.
• Experimental demonstration covered DFS from -100 to 100 KHz for microwave signals at 10, 15, and 18 GHz.
• Measurement errors were within ±5×10^-6 Hz, demonstrating high accuracy.

Conclusions:

• The presented photonic-assisted DFS measurement scheme offers a robust and accurate solution.
• The integrated approach simplifies DFS measurement, providing both magnitude and direction.
• The scheme exhibits excellent frequency tunability and precision, suitable for advanced applications.