Photonics-Based Simultaneous DFS and AOA Measurement System without Direction Ambiguity

Area of Science:

• Photonics
• Microwave Engineering
• Signal Processing

Background:

• Accurate measurement of Doppler frequency shift (DFS) and angle of arrival (AOA) is crucial for modern electronic warfare (EW) systems.
• Existing methods often require multiple systems or suffer from ambiguity and limited range.

Purpose of the Study:

• To propose and validate a novel, single photonic system capable of simultaneously measuring both DFS and AOA of microwave signals.
• To achieve unambiguous DFS measurement and wide AOA measurement range with high accuracy.

Main Methods:

• A Sagnac loop structure is employed at the signal receiving unit (SRU) to modulate echo and reference signals.
• Signals are processed at the central station (CS) involving polarization control and photoelectric conversion.
• Real-time DFS and AOA are acquired by monitoring the frequency and power of generated low-frequency electrical signals.

Main Results:

• Simulations demonstrate unambiguous DFS measurement with errors as low as ±3 × 10^-3 Hz.
• A wide AOA measurement range from -90° to 90° with errors less than ±0.5° was successfully achieved.
• The system simultaneously acquired both DFS and AOA in real-time.

Conclusions:

• The proposed photonic system offers a compact, cost-effective solution for simultaneous DFS and AOA measurement.
• The system exhibits enhanced stability and improved robustness, making it suitable for advanced EW applications.
• This approach overcomes limitations of existing methods, providing unambiguous and wide-ranging measurements.