Non-Uniform Optical Sampling for Frequency Disambiguation
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Solution Overview
Problem
Conventional analog-to-digital conversion (ADC) systems face limitations at higher frequencies due to poor performance, timing jitter, and frequency ambiguity in sub-sampling, especially with electronic samplers, and are restricted by the limited optical bandwidth of electronically-generated optical pulse sources.
Innovation Solution
The use of a non-uniform optical sampling system with a pulsed laser and an acousto-optic delay modulator to modulate the time between pulses, enabling wider optical bandwidth and lower timing jitter, allowing for the determination of all input signal frequencies by adding modulation sidebands that uniquely identify the input signal frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If uniform sub-sampling is used to extend the sampling rate beyond the Nyquist limit, then the sampling rate can exceed twice the maximum signal frequency, but frequency ambiguity occurs where signals at frequencies separated by multiples of the sampling frequency fold onto one another
Solution Approach 1:
The patent applies dynamics by transitioning from uniform to non-uniform sampling intervals. The sampling interval is dynamically varied according to a known pattern (e.g., alternating short and long intervals), which encodes additional information about the signal frequency and resolves the frequency ambiguity that plagues uniform sub-sampling systems.
Solution Approach 2:
The patent changes the sampling interval parameter from constant to variable. By modulating the sampling interval according to a known waveform (such as a square wave or alternating pattern), the system introduces known variations that allow disambiguation of folded frequencies while maintaining the ability to sample at rates exceeding the Nyquist limit.
2Measurement precision
If electronic samplers are used for non-uniform sub-sampling to resolve frequency ambiguity, then additional information can be obtained to determine signal frequency, but timing jitter limits the performance
Solution Approach 1:
The patent replaces the electronic sampling mechanism with an optical sampling mechanism. A mode-locked laser generates optical pulses with extremely low timing jitter (on the order of femtoseconds), which serves as the sampling clock. This optical clock replaces the electronic timing mechanism, thereby eliminating the timing jitter limitation while maintaining the non-uniform sampling pattern needed for frequency disambiguation.
Solution Approach 2:
The patent changes the physical domain of the sampling clock from electronic to optical. By using optical pulses from a mode-locked laser, the system achieves timing precision orders of magnitude better than electronic systems, while the non-uniform interval pattern is maintained through optical modulation techniques.
3Adaptability or versatility
If electronically-generated optical pulse sources are used, then optical sampling can be implemented, but the limited optical bandwidth restricts the applicable signal frequency range
Solution Approach 1:
The patent replaces electronically-generated optical pulses with pulses from a mode-locked laser. The laser's intrinsic optical bandwidth is much wider than what can be achieved with electronic generation and modulation, enabling sampling of signals at ultra-high and terahertz frequencies while maintaining the non-uniform sampling capability through optical modulation.
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 high-performance analog-to-digital conversion across ultra-high to terahertz frequency bands, effectively aliasing microwave frequencies into a single zone and disambiguating signal frequencies, providing wideband spectral folding and frequency disambiguation with a single sampler.
Implementation Method 1
an acousto-optic delay modulator to modulate the time between pulses
Data Source
AI summary
Systems and methods are provided for non-uniform optical sampling with wider optical bandwidth and lower timing jitter than conventional systems, which can make non-uniform optical sampling more feasible. Embodiments of the present disclosure further provide systems and methods for determining all input signal frequencies, including those left ambiguous by prior methods.