A new photonics-based microwave angle of arrival (AOA) measurement system is presented. It is based on a single-laser, single dual-drive Mach Zehnder modulator (DDMZM) and single-photodetector structure. The AOA of a microwave signal can be determined by simply measuring the system output DC voltage. The proposed system is suitable for determining the AOA of a microwave signal with a single frequency or a band of frequencies, and has a wide AOA measurement range. Experimental results are presented that demonstrate an AOA measurement range of 0° to 76.8° and 12.6° to 90° without and with introducing a time delay to one of the DDMZM input RF ports respectively, and measurement errors of less than 2°. Results also demonstrate an AOA measurement for a pseudorandom binary sequence signal upconverted into a microwave frequency.

Simple Approach to Measure Angle of Arrival of a Microwave Signal

A novel photonic approach for simultaneously measuring both the Doppler frequency shift (DFS) and the angle of arrival (AOA) of a microwave signal in a radar system is presented. It has the same structure as a fiber optic link consisting of a laser, an optical modulator and a photodetector. The incoming microwave signal and a reference signal are applied to the optical modulator. Beating of the echo and reference signal sidebands at the photodetector generates a low-frequency electrical signal. The DFS and the AOA can be determined from the frequency and the power of the low-frequency electrical signal measured on an electrical spectrum analyzer. The system has a very simple structure and is low-cost. It has a wide operating frequency range and a robust performance. Experimental results demonstrate a DFS measurement at around 15 GHz with errors of less than ±0.2 Hz, and a 0° to 90° AOA measurement with less than ±1° errors.

Simple photonics-based system for Doppler frequency shift and angle of arrival measurement.

Abstract The revolutionary 5G cellular systems represent a breakthrough in the communication network design to provide a single platform for enabling enhanced broadband communications, virtual reality, autonomous driving, and the internet of everything. However, the ongoing massive deployment of 5G networks has unveiled inherent limitations that have stimulated the demand for innovative technologies with a vision toward 6G communications. Terahertz (0.1-10 THz) technology has been identified as a critical enabler for 6G communications with the prospect of massive capacity and connectivity. Nonetheless, existing terahertz on-chip communication devices suffer from crosstalk, scattering losses, limited data speed, and insufficient tunability. Here, we demonstrate a new class of phototunable, on-chip topological terahertz devices consisting of a broadband single-channel 160 Gbit/s communication link and a silicon Valley Photonic Crystal based demultiplexer. The optically controllable demultiplexing of two different carriers modulated signals without crosstalk is enabled by the topological protection and a critically coupled high-quality ( Q ) cavity. As a proof of concept, we demultiplexed high spectral efficiency 40 Gbit/s signals and demonstrated real-time streaming of uncompressed high-definition (HD) video (1.5 Gbit/s) using the topological photonic chip. Phototunable silicon topological photonics will augment complementary metal oxide semiconductor (CMOS) compatible terahertz technologies, vital for accelerating the development of futuristic 6G and 7G communication era driving the real-time terabits per second wireless connectivity for network sensing, holographic communication, and cognitive internet of everything. 

https://www.nature.com/articles/s41467-022-32909-6.pdf

Phototunable chip-scale topological photonics: 160 Gbps waveguide and demultiplexer for THz 6G communication

Photonic angle-of-arrival measurement without direction ambiguity based on a dual-parallel Mach-Zehnder modulator

A new microwave photonic system for determining the angle of arrival (AOA) of a continuous wave (CW) or pulsed microwave signal is presented. It is based on a dual-polarisation dual-drive Mach–Zehnder modulator followed by an optical notch filter for carrier suppression. Two orthogonal-polarised carrier- suppressed optical signals are detected by low-frequency photodetectors that generate two DC voltages. An incoming microwave signal AOA can be obtained from the ratio of the two DC voltages, without the need of a calibration procedure or measuring the incoming microwave signal power level, which are required in previously reported structures. The proposal system can be incorporated with a conventional radar receiver front end consists of mixers and filters, for measuring the AOA of a pulsed microwave signal. Experimental results demonstrate 0°–63° AOA measurement with less than 2° errors for an input microwave signal having different frequencies and different power levels.

Photonics-Based CW/Pulsed Microwave Signal AOA Measurement System

A new technique for determining the angle of arrival (AoA) of an RF signal is presented. It is based on a cascaded modulator structure, where continuous wave light from an optical source is modulated by an incoming RF signal twice. The AoA of an RF signal can be determined by the system output RF signal power. The proposed structure is capable for measuring the AoA of both narrow and broadband RF signals. This overcomes the limitation in all previously reported photonics-based AoA measurement systems, which are applicable to either a single-frequency RF signal or a broadband RF signal. It also does not involve electrical components and high extinction ratio modulators, which are required in reported structures. Experimental results are presented that show an AoA measurement range of 0° to over 65° with errors of less than 1.9° for a microwave signal at 2.65 and 12.62 GHz. Results also show that the system is capable to measure the AoA of a pseudorandom binary sequence signal at a microwave frequency.

Angle-of-Arrival Measurement System Using Double RF Modulation Technique

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.

/pdf/photonic-approach-for-measuring-aoa-of-multiple-signals-with-1frm5y4v1g.pdf

Hao Chen

Papers

Simple Approach to Measure Angle of Arrival of a Microwave Signal

Angle-of-Arrival Measurement System Using Double RF Modulation Technique

Simple photonics-based system for Doppler frequency shift and angle of arrival measurement.

Photonics-Based CW/Pulsed Microwave Signal AOA Measurement System

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