Dual-DDS Frequency Conversion for Low-Jitter Laser Pulse Synchronization
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Solution Overview
Problem
Existing technologies face challenges in synchronizing the repetition frequencies of optical pulses from two lasers, leading to jitter issues when these frequencies are differentiated by a predetermined frequency.
Innovation Solution
A signal output device comprising a first and second direct digital synthesizer, along with crystal oscillators and phase difference detectors, is used to stabilize and synchronize the frequencies of optical pulses from two lasers, ensuring that the difference between the predetermined frequency and the internal signal is greater than the difference between the predetermined frequency and the output signal, thereby reducing jitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the repetition frequencies of optical pulses from two lasers are differentiated by a predetermined frequency, then the frequency resolution is improved, but the jitter of optical pulses increases
Solution Approach 1:
The patent introduces an intermediary signal processing system consisting of a first DDS generating an internal signal at frequency (Q-P) and a second DDS generating the output signal at frequency (Q-Δ). This intermediary dual-DDS architecture acts as a mediator between the reference frequency Q and the desired differentiated frequency Q-Δ, enabling precise frequency control while maintaining phase coherence to reduce jitter.
Solution Approach 2:
The patent changes the frequency parameters of the optical pulses by using DDS devices to generate signals at specifically controlled frequencies. The first DDS changes the reference frequency Q to (Q-P) by subtracting P, and the second DDS further changes it to (Q-Δ) by subtracting Δ. This parameter transformation approach allows precise control of frequency differentiation while maintaining stability.
2Reliability
If the repetition frequencies are made coincident, then the jitter is reduced, but the frequency differentiation capability is lost
Solution Approach 1:
The patent implements a dynamic frequency control system where the output frequency can be adjusted by changing the parameter Δ while maintaining the relationship with the reference frequency Q. The system dynamically adapts the frequency differentiation while preserving phase coherence, allowing both jitter reduction and frequency differentiation capability to coexist through controlled dynamic adjustment.
Solution Approach 2:
The dual-DDS system performs multiple functions simultaneously: it maintains phase coherence for jitter reduction while enabling frequency differentiation for spectral analysis. The same signal processing architecture serves both purposes, making the system universal in handling both synchronization and frequency differentiation requirements.
3Device complexity
If a single DDS is used to generate the output signal, then the device complexity is reduced, but the frequency stability and jitter control are insufficient
Solution Approach 1:
The patent segments the frequency synthesis function into two separate DDS devices: the first DDS handles the coarse frequency adjustment by generating (Q-P), and the second DDS handles the fine frequency adjustment by generating (Q-Δ). This segmentation allows each DDS to operate within optimized parameters, improving overall frequency stability and jitter control while maintaining manageable system complexity.
Data Source
AI summary
A frequency converter includes a first direct digital synthesizer that receives a signal having a predetermined frequency f_master as a clock signal and further an internal frequency setting signal, and outputs an internal signal having a frequency based on the internal frequency setting signal, and a second direct digital synthesizer that receives the internal signal as a clock signal, and further an output frequency setting signal, and outputs an output signal having a frequency f_slave (=f_master−Δ) based on the output frequency setting signal. A difference between the predetermined frequency f_master and the frequency of the internal signal is larger than a difference between the predetermined frequency f_master and the frequency f_slave of the output signal.