Amplification-Free Electro-Optical Oscillator Phase Noise Reduction
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Solution Overview
Problem
Existing electro-optical oscillators face challenges in minimizing phase noise, particularly at mm-wave and THz frequency ranges, due to noise contributions from electrical components, laser relative intensity noise, and photodiode shot noise, which limits their application in high-resolution imaging and small form-factor radars.
Innovation Solution
The electro-optical oscillator design incorporates a modulator, signal splitter, multiple photodiodes, and filters, with variable optical gain/attenuation and delay components in each optical path, eliminating the need for electrical amplification and reducing phase noise by splitting and processing the modulated optical signal across multiple paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional electro-optical oscillator design with electrical amplification is used, then electrical signal gain is achieved, but phase noise increases due to noise contributions from electrical components, laser relative intensity noise, and photodiode shot noise
Solution Approach 1:
The patent extracts and removes the electrical amplifier component from the conventional electro-optical oscillator design. By eliminating the electrical amplification stage, the system removes the primary source of electrical noise contributions. Instead, the invention uses direct optical-to-electrical conversion through photodiodes to achieve signal generation without the intermediate electrical amplification that introduces phase noise.
Solution Approach 2:
The patent substitutes the electrical amplification mechanism with an optical-based approach. Rather than using electrical components to amplify and regenerate the signal, the system relies on optical signal splitting and direct photodetection, replacing the electrical amplification subsystem with an optical processing architecture that inherently reduces noise.
2Object-affected harmful factors
If multiple photodiodes and optical paths are used to reduce phase noise, then device complexity increases
Solution Approach 1:
The patent segments the optical signal into multiple parallel paths, each containing a photodiode. By dividing the single optical signal into N separate optical signals that travel through distinct paths and are detected by individual photodiodes, the system achieves noise reduction through statistical averaging while maintaining a modular and manageable structure.
Solution Approach 2:
The patent combines the outputs of multiple photodiodes through electrical signal addition or averaging. By merging the N electrical signals from the separate optical paths, the system achieves coherent signal addition while the uncorrelated noise components from each photodiode average out, reducing overall phase noise by a factor related to the number of photodiodes used.
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 reduces phase noise, making it independent of oscillation frequency and suitable for mm-wave and THz applications, while maintaining or exceeding the gain of conventional oscillators, achieving phase noise better than -140 dBc/Hz at 1 MHz offset at 80 GHz.
Implementation Method 1
Each of the N photodiodes is adapted to convert the optical signal it receives to a current signal
Implementation Method 2
The modulator is adapted to modulate an optical signal in accordance with a feedback signal
Data Source
AI summary
An electro-optical oscillator includes, in part, a modulator, a signal splitter, N photodiodes with N being an integer greater than one, a signal combiner, and a filter. The modulator modulates an optical signal in accordance with a feedback signal. The splitter splits the modulated optical signal into N optical signals each delivered to a different one of N photo-diodes. Each of the N photo-diodes converts the optical signal it receives to a current signal. The signal combiner combines the N current signals received from the N photo-diodes to generate a combined current signal. The filter filters the combined current signal and generates the feedback signal. The electro-optical oscillator optionally includes, in part, N variable optical gain/attenuation components each amplifying/attenuating a different one of the N optical signals generated by the splitter.