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

Abstract

A novel scheme that can simultaneously measure the Doppler frequency shift (DFS) and angle of arrival (AOA) of microwave signals based on a single photonic system is proposed. At the signal receiving unit (SRU), two echo signals and the reference signal are modulated by a Sagnac loop structure and sent to the central station (CS) for processing. At the CS, two low-frequency electrical signals are generated after polarization control and photoelectric conversion. The DFS without direction ambiguity and wide AOA measurement can be real-time acquired by monitoring the frequency and power of the two low-frequency electrical signals. In the simulation, an unambiguous DFS measurement with errors of ±3 × 10−3 Hz and a −90° to 90° AOA measurement range with errors of less than ±0.5° are successfully realized simultaneously. It is compact and cost-effective, as well as has enhanced system stability and improved robustness for modern electronic warfare systems.

Photonic Measurement for Doppler Frequency Shift and Angle of Arrival Based on Integrated Dual-Parallel Dual-Drive Modulator

“…Recently, scholars have undertaken a lot of work on microwave photonic measurement technology. In the schemes of simultaneous measurement of DFS and AOA [6][7][8][9][10][11][12][13][14][15], by frequency downconversion, the DFS value is obtained from intermediate-frequency (IF) signals, and there are two main methods for determining the DFS direction. The first way is based on a reference signal with a frequency shift, which adds a small frequency shift to the transmitted signal [6][7][8][9][10][11].…”

“…In [9], the AOA is calculated based on the power of two IF signals, with one channel serving as the measurement channel, while the other channel is used to solve the phase ambiguity problem. The AOA measurement is achieved by calculating the electrical signal power in [11], which introduces an additional phase shift between reference signals. However, the structure is complex and has not been experimentally verified.…”