Photonic Delay Phase Noise Measurement System
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Solution Overview
Problem
Current methods for measuring phase noise in RF, microwave, or millimeter signals face challenges in achieving low noise measurements, particularly in characterizing oscillators, as existing devices often rely on high noise components and require reference oscillators or phase locking loops.
Innovation Solution
The proposed solution involves a photonic delay-based system that uses shared optical modules, photonic signal processing branches, and optical polarization techniques to measure phase noise in RF, microwave, or millimeter signals, employing dual homodyne setups with cross-correlation to reduce noise floors and eliminate the need for reference oscillators or phase locking loops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement methods are used, then reference oscillators or phase locking loops are required, but the noise floor increases and measurement precision deteriorates
Solution Approach 1:
The measurement system is divided into multiple independent photonic branches (first photonic branch and second photonic branch), each processing the oscillation signal separately through its own laser and optical modulator. This segmentation allows the system to measure phase noise without requiring a reference oscillator, as each branch independently characterizes the signal under test.
Solution Approach 2:
Optical components (optical modulators, optical delay lines, photodetectors) serve as intermediaries to transfer the electrical oscillation signal into the optical domain for processing. The optical domain provides a low-noise environment for signal manipulation, and the photodetectors convert the optical signals back to electrical signals for analysis, eliminating the need for direct electrical reference oscillators.
2Measurement precision
If multiple independent photonic branches are used, then uncorrelated noise is suppressed, but device complexity increases
Solution Approach 1:
Multiple photonic branches share common components including the same optical modulator, optical delay line, and photodetector. This merging approach reduces the overall device complexity compared to having completely independent measurement systems, while still providing multiple measurement paths that enable noise suppression through cross-correlation analysis.
Solution Approach 2:
The system creates multiple copies of the oscillation signal by routing the input signal through separate photonic branches. Each branch processes an independent copy of the signal, allowing parallel measurement and subsequent cross-correlation to eliminate uncorrelated noise while maintaining the original signal characteristics.
3Object-generated harmful factors
If optical components are used for signal processing, then noise is reduced, but manufacturing and alignment complexity increases
Solution Approach 1:
The system replaces direct electrical signal processing with optical signal processing. Optical components handle the signal in the optical domain, where noise is inherently lower, and then convert back to electrical signals for analysis. This substitution of domains eliminates the need for high-precision electrical reference oscillators and reduces measurement noise.
Solution Approach 2:
The system changes the operating parameters by translating the oscillation signal from the electrical domain to the optical domain. Optical signals operate at frequencies and noise characteristics that are fundamentally different from electrical signals, providing a cleaner measurement environment. The optical delay line and modulators manipulate the signal parameters in this transformed domain.
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 effectively suppresses uncorrelated noise, improving the phase noise floor by 5 log(N) dB units, allowing for low noise measurements without relying on reference oscillators or phase locking loops, and enables direct phase noise measurements with reduced system complexity and cost.
Implementation Method 1
a shared optical modulator that modulates the laser light at the first and second wavelengths to produce modulated laser light that carries the oscillation signal
Implementation Method 2
a wavelength-selective optical device that separates the modulated laser light output by the shared optical delay into a first modulated laser beam at the first wavelength and a second modulated laser beam at the second wavelength
Implementation Method 3
a photodetector coupled to receive light from the third port of the photonic beam combiner to generate a detector signal
Implementation Method 4
a Faraday rotator mirror coupled to the fiber delay line to reflect light back to the fiber delay line by rotating optical polarization by 90 degrees
Implementation Method 5
a voltage controlled phase shifter that receives a copy of the oscillation signal and changes a phase of the copy of the oscillator signal to produce a phase-shifted oscillator signal
Implementation Method 6
a signal mixer that mixes the detector signal and the phase-shifted oscillator signal to produce the output signal
Data Source
AI summary
Techniques and devices for measuring phase noise in radio frequency (RF), microwave, or millimeter signals based on photonic delay.