Multi-Mode Optic RF to Digital Conversion
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Solution Overview
Problem
Existing analog-to-digital converters (ADCs) are inadequate for handling wideband signals due to limitations in sampling rate and resolution, leading to inefficiencies in applications like electronic warfare and telecommunications, and rely on high-speed, high-power, and costly electronics.
Innovation Solution
The use of multi-mode optics to convert radio-frequency signals into the digital domain by imposing them onto an optical carrier, processing in the optical domain, and then converting back to the electronic domain using low-cost, low-power ADCs, reducing the need for high-bandwidth electronics and free-space optics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-speed, high-power electronics are used in ADCs to handle wideband signals, then signal processing capability is improved, but device complexity, power consumption, and cost increase
Solution Approach 1:
The patent replaces electronic signal processing with optical signal processing. An optical modulator converts the RF signal to an optical signal, which then passes through a multi-mode optical fiber to generate a speckle pattern. This optical approach substitutes high-speed electronics with optical components, achieving wideband signal handling without the power and complexity penalties of high-speed electronic ADCs
Solution Approach 2:
The patent changes the domain parameter from electrical to optical. By modulating the RF signal onto an optical carrier and processing it in the optical domain, the system exploits optical properties (such as the statistical characteristics of speckle patterns in multi-mode fibers) to achieve signal processing that would be prohibitively complex in the electrical domain
2Productivity
If high-speed, high-power electronics are used in ADCs to handle wideband signals, then signal processing capability is improved, but power consumption increases
Solution Approach 1:
The patent replaces power-hungry high-speed electronic ADCs with a low-power optical processing system. The optical modulator and multi-mode fiber processing consume significantly less power than high-speed electronic sampling, while the final detection stage uses standard low-speed ADCs to digitize the optical signal
Solution Approach 2:
The patent creates an optical copy of the RF signal by modulating it onto an optical carrier. This optical copy is then processed through the multi-mode fiber's speckle pattern, which acts as a random projection matrix. The information is preserved in the statistical properties of the speckle pattern, allowing reconstruction with far lower power consumption than direct electronic sampling
3Measurement precision
If traditional ADCs are used for wideband signals, then direct digital conversion is achieved, but sampling rate and resolution requirements make the system inadequate
Solution Approach 1:
The patent introduces an optical intermediary (the multi-mode fiber and speckle pattern) between the RF signal and the digital domain. Instead of directly sampling the RF signal with a high-speed ADC, the system uses the optical channel to perform random projection, transforming the wideband signal into a form that can be captured by low-speed ADCs while preserving the information needed for accurate reconstruction
Solution Approach 2:
The patent transforms the problem from the time domain to a spatial-statistical domain. By using the multi-mode fiber to create a speckle pattern, the system maps the temporal signal characteristics into spatial intensity distributions. This dimensional transformation allows information from a wideband signal to be captured through multiple lower-rate measurements that can be computationally reconstructed
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 enables efficient conversion of wideband signals into digital form using low-cost, low-power ADCs, reducing the complexity and cost of wideband signal processing while maintaining high performance.
Implementation Method 1
outputting by the multi-mode optic a speckle pattern based on the radio-frequency signal imposed on the optical carrier
Implementation Method 2
irradiating an optical sensor with a first portion of the speckle pattern
Data Source
AI summary
A multi-mode optic can receive as input a radio-frequency (RF) signal imposed on an optical carrier, and can output a speckle pattern. A digital representation of the radio-frequency signal can be obtained based on the speckle pattern. An optical sensor can be irradiated with a first portion of the speckle pattern, the first portion of the speckle pattern including an optical intensity profile that is different than an optical intensity profile of a second, spatially separated, portion of the speckle pattern. The multi-mode optic can impose the optical intensity profile on the first portion of the speckle pattern as a function of wavelength of the optical carrier. The optical intensity profiles of portions of the speckle pattern can define a mixing matrix. The digital representation of the RF signal can be obtained based on an output of the optical sensor and the mixing matrix.