Arbitrary Pulse Generation via Optical Frequency Comb
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Solution Overview
Problem
Current methods are inadequate for generating electromagnetic signals with defined pulse shapes and narrow bandwidths between 18 GHz and 1 THz in a simple and cost-effective manner, particularly for ultra-wideband and radar systems.
Innovation Solution
The method involves generating a frequency comb with equidistant frequency lines, adjusting the amplitude and time interval of sinc pulses, and summing them to create pulses with specific shapes within the desired bandwidth range using standard optical components like couplers, splitters, and modulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If electrical AWGs are used to shape signals, then pulse shape control is achieved, but the bandwidth is limited to below 18 GHz
Solution Approach 1:
The patent replaces electrical AWG systems with an optical-based system using frequency combs and photodetectors. This substitution enables the system to overcome the bandwidth limitations of electrical components and achieve operation in the 18 GHz to 1 THz range while maintaining precise pulse shape control through optical frequency domain processing.
Solution Approach 2:
The patent transforms the signal processing approach by changing from direct electrical time-domain shaping to optical frequency-domain processing. By generating a frequency comb and selectively adjusting amplitude and phase of individual frequency lines, then transforming back to time domain, the system achieves both wide bandwidth and precise pulse shaping that electrical AWGs cannot provide.
2Adaptability or versatility
If optical pulse conversion methods are used for broadband pulses, then pulse shape flexibility is improved, but the system complexity and cost increase
Solution Approach 1:
The patent segments the broadband pulse generation task into discrete frequency components using a frequency comb. Each frequency line of the comb can be independently adjusted in amplitude and phase, allowing flexible pulse shaping. This segmentation approach provides control flexibility while using standard optical components rather than complex custom devices.
Solution Approach 2:
The patent employs universal optical components (frequency comb generator, photodetectors, standard optical elements) that can generate various pulse shapes across a wide bandwidth range. This multi-functional approach replaces the need for specialized equipment for each pulse type, reducing overall system complexity and cost while maintaining versatility.
3Adaptability or versatility
If a frequency comb with many equidistant frequency lines is generated, then the bandwidth coverage is improved, but the number of components required increases
Solution Approach 1:
The patent merges multiple frequency components into a unified frequency comb structure with equidistant lines. By using a single frequency comb generator to produce all necessary frequency components simultaneously, the system covers a wide bandwidth without requiring separate components for each frequency, thus reducing the total component count while maintaining broad bandwidth coverage.
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 allows for the generation of pulses with any shape within the 18 GHz to 1 THz range, enabling efficient signal transmission with minimal distortion, suitable for microwave photonics, radar applications, and THz communication.
Implementation Method 1
The pulse train is incident on a photodetector with which it can be converted into an electromagnetic signal in the microwave or terahertz range
Data Source
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Figure 3a~3b
AI summary
A method for generating an electromagnetic signal s(t) of defined pulse shape and a maximum cutoff frequency (flimit) by summing sinc pulses of different amplitudes and defined time intervals, wherein samples are taken along the pulse shape at the defined time intervals, generating a frequency comb with a number N equidistant frequency lines with a spacing Δf, which corresponds to the Fourier transform of a first sequence of sinc pulses of equal amplitude and the same or linearly different phase, wherein these sinc pulses have a first time interval of 1/Δf, which is greater than the defined time interval, wherein the first time interval 1/Δf of the sinc pulses is delayed to the time interval n/(N*Δf), with n=1,2,3,...the sampled values are increased, whereby the amplitude of the individual sinc pulses is adjusted to the height of the respective assigned sampled value, and whereby the individual sinc pulses are summed to form the pulse to be generated.