Free-Space Optical Beamformer for Scalable RF Phased Arrays
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Solution Overview
Problem
RF phased antenna arrays face challenges due to the large volume and weight of RF-electronic beamforming networks, which are overcome by using an optical feed network that transfers phase and amplitude of an optical signal to a microwave signal through coherent detection, but these implementations can be complex and difficult to scale.
Innovation Solution
A free-space optical beamformer supports all RF electrical feed signals for the RF phased antenna array, using a collimating lens and an optical beam steerer to generate and steer optical beams, with photo-detectors converting these signals into RF electrical feed signals, allowing for rapid steering without the need for complex computations like FFTs, and utilizing oversized lenses and photo-detectors to accommodate larger array sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If an optical feed network is used to reduce volume and weight, then the size is reduced, but the device complexity increases
Solution Approach 1:
The patent replaces traditional RF-electronic beamforming components with an optical feed network that uses optical waves to carry multiple RF signals simultaneously. This substitution of mechanical/electronic systems with optical systems reduces the physical volume and weight of the beamforming network while managing complexity through optical domain processing.
Solution Approach 2:
The patent transitions from electrical domain to optical domain, adding a new dimension to the signal processing approach. By using optical frequencies and properties, the system can handle multiple signals in parallel through wavelength division multiplexing and spatial multiplexing, reducing the need for complex electronic beamforming hardware.
2Device complexity
If traditional RF-electronic beamforming is used, then the device is simpler to implement, but the volume and weight increase
Solution Approach 1:
The patent replaces heavy RF-electronic beamforming components with a lighter optical feed network. The optical components such as waveguides, modulators, and detectors have significantly lower weight compared to traditional RF power amplifiers, phase shifters, and antenna feed networks, thus reducing overall system weight while maintaining functionality.
3Adaptability or versatility
If optical feed network is implemented, then scaling to larger arrays becomes difficult, but this limits adaptability
Solution Approach 1:
The patent segments the optical feed network into modular components including multiple optical waveguides, individual modulators for each antenna element, and separate detection channels. This segmentation allows the system to be scaled by simply adding more modular units rather than redesigning the entire network, making it adaptable to larger array sizes.
Solution Approach 2:
The optical feed network is designed with universal components that can serve multiple functions. The same optical waveguide structure and modulator design can be replicated for different array configurations and sizes, providing versatility and ease of scaling across different application scenarios.
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
The optical feed network enables scalable and efficient steering of RF beams, reducing complexity and size compared to traditional implementations, facilitating rapid and flexible beam steering across a wide range of angles while preserving relative phase and amplitude.
Implementation Method 1
A collimating lens collimates the first optical signal to fill an aperture of a free-space optical beamformer
Implementation Method 2
a single free-space optical beamformer supports all of the RF electrical feed signals for the RF phased antenna array to steer an RF beam
Implementation Method 3
The principle of operation uses a coherent detection scheme to directly transfer the phase and amplitude of an optical signal to a microwave signal by mixing this signal with an optical local oscillator (LO) signal
Data Source
AI summary
An optical feed network (OFN) for an RF phased antenna array includes a single free-space optical beamformer that supports all of the RF electrical feed signals for the RF phased antenna array to steer an RF beam. The free-space optical beamformer can more easily scale to accommodate larger array sizes than either the discrete fiber channel or PIC implementations. Furthermore, certain embodiments of the optical beamformer avoid the complexity of having to compute FFTs for each channel to steer the beam, instead relying on the inherent function of an imaging lens to perform the FFT, which in turn facilitates rapid steering.