Photonic Approach for Measuring AOA of Multiple Signals With Improved Measurement Accuracy

Abstract

The objective of this paper is to present a microwave photonic system that can measure the angle of arrival (AOA) of multiple microwave signals with improved measurement accuracy. It is based on a photonic mixer approach to down convert the incoming microwave signals into IF signals, which enables a low-frequency electrical spectrum analyser to be used for measuring the power of the IF signals to determine the incoming microwave signal AOAs. AOA measurement errors can be reduced by operating the optical modulator at a different transmission point for a different range of microwave signal AOA. The system also has the ability to remove the incoming microwave signal amplitude dependence in the AOA measurement. Measured results demonstrate 0°−81.5°AOA measurement with less than ±2°errors over the 0°−30°and 30°−81.5°AOA measurement range when the optical modulator is biased at the minimum and maximum transmission point respectively. The errors remain below ±2°even when there is a ±0.1 dB change in the output IF signal power. AOA measurement of two microwave signals is also demonstrated.

Photonic Frequency Down Conversion Approach to Measure Microwave Signal Angle of Arrival

“…Hence, a small measurement error for an IF signal phase difference of around 360°will lead to a large AOA measurement error. Note that several reported AOA measurement systems show the ability of measuring microwave signal AOA with errors of less than ±2° [7], [8], [13]. However, the small AOA measurement errors are obtained in a small AOA measurement range, these AOA measurement systems cannot be used in a long baseline interferometer antenna system, and/or an expensive and bulky ESA is needed to measure the microwave signal AOA.…”

“…This solves the incoming microwave signal power dependent AOA measurement problem in the reported AOA measurement systems [5]- [8]. A DPD is compact and low cost compared to an ESA or an oscilloscope used in the reported AOA measurement systems [9]- [11], [13].…”

“…Furthermore, this approach requires a wideband electrical spectrum analyser (ESA). The AOA of a microwave signal can also be found by using an optical phase scanning technique [11], a wavelength division multiplexing technique [12] and a frequency conversion technique [13]. These techniques enable the microwave signal AOA to be measured without knowing the incoming microwave signal power.…”

A Simple Photonics-Based Measurement Method for Microwave DFS and AOA

“…uring intelligent driving, radar detection, wireless communication, internet of things and other emerging fields, it is critical to determine the real-time location of moving objects [1][2], which involves doppler frequency shift (DFS) as well as angle of arrival (AOA) measurements [3][4][5][6]. DFS is the frequency shift between the back and come signals [7], and is applied to obtain the velocity of the object.…”

“…DFS is the frequency shift between the back and come signals [7], and is applied to obtain the velocity of the object. The angle of the moving target can be estimated by AOA, which can be calculated through the phase difference between the echoes received by spatially-separated antennas [1][2][3][4][5][6][7]. However, the narrow bandwidth and poor stability of key electronic devices limit the application of traditional electrical systems.…”