Photonics-Fed Phased Array Antenna RF Power Scaling
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Solution Overview
Problem
Integrated photodetectors face limitations in optical-to-electrical conversion gain due to restrictions on optical input power and saturation effects, which are exacerbated by higher frequency carriers used in wireless communication systems, requiring innovative solutions to enhance signal transmission efficiency.
Innovation Solution
A method involving an optical modulator to generate a high power transmit modulated optical carrier signal, split into multiple reduced power paths for photodetection, followed by constructive combination to produce a high power RF signal, utilizing integrated photonics and multi-chip material integration for efficient optical-to-electrical conversion and phase control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high optical power is used to drive photodetectors, then optical-to-electrical conversion gain is improved, but photodetector saturation occurs and waveguide damage may result
Solution Approach 1:
The patent divides a single high-power optical path into multiple parallel lower-power paths using optical splitters. Each photodetector receives a fraction of the total optical power (e.g., 1/N of total power for N photodetectors), preventing saturation while maintaining high total RF output power through constructive combination of all photodetector outputs.
Solution Approach 2:
The patent combines the electrical outputs from multiple photodetectors using RF combiners to achieve high total RF power output. By coherently combining N photodetector outputs, the system achieves total RF power proportional to the sum of individual photodetector powers, effectively scaling beyond what a single photodetector could produce.
2Power
If multiple photodetectors are used to handle high optical power, then power handling capability is improved, but device complexity increases
Solution Approach 1:
The patent employs identical photodetector modules that can be replicated and interconnected. Each module performs the same function (optical-to-electrical conversion), and they are combined using standard RF combiners. This modular approach allows scaling to higher power handling capabilities while maintaining design simplicity through repetition of standardized components.
Solution Approach 2:
The patent introduces optical splitters and RF combiners as intermediary components that manage the distribution and combination of signals. These intermediaries enable multiple photodetectors to work together in a coordinated manner, handling high total power while keeping individual component designs simple and manageable.
3Power
If optical power is distributed to multiple photodetectors, then RF power output is improved, but optical loss in waveguides increases
Solution Approach 1:
The patent segments the optical power distribution into multiple parallel paths using low-loss optical splitters. By distributing power through optimized waveguide structures and minimizing the number of splitting stages, optical losses are kept minimal while still achieving effective power distribution to multiple photodetectors for high total RF output.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly enhances optical-to-electrical conversion gain, allows for dynamic phase control, and increases the power level of the RF signal beyond the maximum handling capacity of individual photodetectors, effectively addressing the limitations of existing technologies.
Implementation Method 1
using an optical modulator at an RF source location to modulate a high power optical carrier signal with a source RF signal
Implementation Method 2
In each of the N optical paths, a photodetection operation is performed upon the reduced power TMOC signal to obtain N reduced power S′RF signals
Data Source
AI summary
Delivering a radio frequency (RF) signal to a remote phased array antenna system involves using an optical modulator at an RF source location to modulate a high power optical carrier signal with a source RF signal SRF so as to produce a high power transmit modulated optical carrier (TMOC) signal. An optical link communicates the high power TMOC signal to a remote antenna location, where the high power TMOC is split into N optical paths to obtain N reduced power TMOC signals. In each of the N optical paths, photodetection operations are performed upon the reduced power TMOC signal to obtain N reduced power S′RF signals which are then constructively combined to obtain a high power S′RF signal which is communicated to at least one antenna element.