Mixer-Based Microwave Generation With Optoelectronic Phase Locking
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Solution Overview
Problem
Conventional microwave signal sources face challenges in achieving large bandwidth and high center frequency due to bandwidth bottlenecks in electronic means, and existing microwave photonic methods suffer from poor phase noise characteristics and instability in multi-mode signals.
Innovation Solution
A mixer-based microwave signal generation device that utilizes a local oscillator, mixer, filters, electro-optic modulator, optical signal delayer, photodetector, and amplifier to generate and stabilize single-mode or multi-mode oscillator signals through a closed optoelectronic feedback loop, ensuring phase locking and frequency conversion to produce stable microwave signals with adjustable center frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a dual-wavelength laser heterodyne method is used to generate microwave signals, then broadband and high center frequency are achieved, but phase noise characteristics deteriorate due to poor coherence of the two emission wavelengths
Solution Approach 1:
The patent segments the microwave signal generation into multiple discrete frequency modes (first mode and second mode) that are systematically related through the optical feedback loop, rather than relying on two independent laser wavelengths. This segmentation allows each mode to be stabilized independently while maintaining phase coherence through the feedback mechanism.
Solution Approach 2:
The patent implements an optical feedback loop where the optical signal is delayed and fed back to the electro-optic modulator, creating a self-excited oscillation system. The mixer compares the original and delayed signals to generate error signals that stabilize the phase and frequency of the microwave modes, directly addressing the phase noise issue while maintaining broadband capability.
2Speed
If the frequency-time mapping method is used to generate microwave signals, then broadband signals are achieved, but time-bandwidth product is limited due to small signal duration
Solution Approach 1:
The patent creates a continuous self-excited oscillation in the optoelectronic feedback loop, where the microwave signal is continuously generated and sustained rather than being a transient pulse. The feedback mechanism ensures continuous energy replenishment to the oscillating modes, enabling long-duration stable operation while maintaining broadband coverage through multiple frequency modes.
3Reliability
If an optoelectronic oscillator operates in multi-mode state to generate single-frequency signals, then ultra-low phase noise is achieved, but stability deteriorates due to mode competition and mode hopping
Solution Approach 1:
The patent introduces the mixer as an intermediary device that mediates between the multiple oscillating modes and the feedback control mechanism. The mixer converts the multi-mode signals into difference frequency signals that serve as error signals for phase stabilization, enabling the system to maintain stable multi-mode operation without mode hopping while achieving ultra-low phase noise through the feedback loop.
4Device complexity
If purely electronic means are used for microwave signal generation, then device simplicity is maintained, but bandwidth is limited due to bandwidth bottleneck
Solution Approach 1:
The patent substitutes electronic frequency multiplication and filtering mechanisms with an optoelectronic system that uses optical feedback and electro-optic modulation. This substitution leverages the vast bandwidth of optical carriers to generate microwave signals with bandwidths far exceeding conventional electronic limits, while the integrated feedback loop maintains system simplicity through self-excited oscillation.
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 device achieves stable multi-mode oscillator signals with improved phase noise characteristics and adjustable frequency range, overcoming the limitations of conventional methods by locking the phase sum during frequency conversion and utilizing a closed optoelectronic feedback loop.
Implementation Method 1
an electro-optic modulator configured to load the single-mode or multi-mode self-excited oscillator signal onto the optical carrier
Implementation Method 2
a photodetector configured to perform a beat frequency restoration on the optical signal delayed
Data Source
AI summary
A mixer-based microwave signal generation device is provided, and the mixer-based microwave signal generation device includes a microwave local oscillator source, a mixer, a first filter, a laser, an electro-optic modulator, an optical signal delayer, a photodetector, a second filter, an amplifier and a passive power divider.