Optical Signal Generator with Dynamic Harmonic Selection
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Solution Overview
Problem
Conventional signal generators face limitations in achieving high spectral purity, frequency stability, large frequency tuning range, high frequency tuning resolution, and rapid tuning speed.
Innovation Solution
A signal generator comprising an optical pulse source, a photosensitive element, a frequency selector, a direct digital synthesizer (DDS), and a frequency converter, which dynamically selects and shifts harmonics to produce a second output, enabling high spectral purity and frequency stability, with a frequency extender for further output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional signal generators use traditional electronic oscillators and frequency synthesis methods, then device complexity is reduced, but spectral purity and frequency stability deteriorate
Solution Approach 1:
The patent replaces traditional electronic oscillators and frequency synthesis circuits with an optical-based system. An optical oscillator generates optical pulses that are detected by a photodetector to produce electrical signals with superior spectral purity. This substitution of electronic mechanisms with optical mechanisms resolves the contradiction by achieving higher measurement precision (spectral purity) while accepting increased device complexity as a necessary trade-off for the performance improvement.
Solution Approach 2:
The patent introduces an optical field as an intermediary between the oscillator and the electrical signal output. The optical oscillator generates optical pulses, which are then converted to electrical signals through photodetection. This intermediary optical domain enables the system to achieve frequency stability and spectral purity unattainable by direct electronic methods, resolving the technical contradiction.
2Adaptability or versatility
If conventional signal generators use fixed frequency oscillators, then device complexity is reduced, but frequency tuning range and tuning resolution deteriorate
Solution Approach 1:
The patent implements dynamic frequency tuning by allowing the optical oscillator's repetition rate to be varied over a wide range. The frequency of the generated electrical signals is directly tied to the optical pulse repetition rate, enabling continuous frequency adjustment. This dynamic capability provides large frequency tuning range and high tuning resolution, resolving the contradiction between adaptability and device complexity.
3Reliability
If conventional signal generators use traditional frequency synthesis, then device complexity is reduced, but frequency stability and spectral purity deteriorate
Solution Approach 1:
The patent replaces traditional electronic frequency synthesis with an optical oscillator-based approach. The optical oscillator inherently provides superior frequency stability due to the stability of optical resonators, and the direct photodetection process preserves this stability in the electrical output. This substitution resolves the contradiction by achieving high reliability (frequency stability) at the cost of increased device complexity.
4Measurement precision
If conventional signal generators use electronic oscillators, then device complexity is reduced, but spectral purity and phase noise performance deteriorate
Solution Approach 1:
The patent substitutes electronic oscillation with optical oscillation. The optical oscillator generates pulses with extremely low phase noise due to the high Q-factor of optical resonators. The photodetector converts these optical pulses to electrical signals, preserving the low phase noise characteristics. This substitution resolves the contradiction by achieving superior measurement precision (phase noise performance) while accepting increased device complexity.
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 solution achieves exceptionally high spectral purity, frequency stability, large frequency tuning range, high frequency tuning resolution, and rapid tuning speed, with phase noise below −100 dBc/Hz and frequency instability of 2×10−15 at 1 second averaging time.
Implementation Method 1
a photosensitive element configured to receive optical pulses and to produce an electrical signal from optical pulses
Implementation Method 2
a frequency converter to receive the harmonic from the frequency selector and the first output from the DDS, wherein the frequency converter shifts a frequency of the harmonic by an amount substantially equal to a frequency of the first output from the DDS
Data Source
AI summary
A signal generator includes an optical pulse source to provide a plurality of optical pulses; a photosensitive element configured to receive optical pulses and to produce an electrical signal from optical pulses 6, electrical signal 10 including a spectrum that includes a plurality of discrete frequencies that occur at a repetition rate corresponding to that of the optical pulses or a harmonic thereof; a frequency selector to receive the electrical signal from the photosensitive element, to select dynamically the harmonic from the electrical signal and to communicate the dynamically selected harmonic; a direct digital synthesizer (DDS) to receive the harmonic of the electrical signal from the frequency selector and to produce a first output; and a frequency converter to receive the harmonic from the frequency selector and the first output from the DDS, wherein the frequency converter shifts a frequency of the harmonic by an amount substantially equal to a frequency of the first output from the DDS to produce a second output.