Pulse-Mode Miniature Atomic Clock with Single-Microcell Frequency Control
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Solution Overview
Problem
Existing CPT miniature atomic clocks with pulse mode operation face challenges in achieving a balance between size, cost, and performance, with the current architecture being costly and large due to the need for multiple components in the feedback control loop for optical frequency control, and lacking flexibility in implementing the pulsing mechanism.
Innovation Solution
The proposed solution simplifies the feedback control loop by using a single alkaline vapour microcell for both microwave and optical frequency control, eliminating the need for a second microcell and photodiode, and allowing for a pulsed control block that generates correction signals during specific periods, thereby reducing component count and size while maintaining performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a second microcell and photodiode are used for optical frequency control, then the clock can maintain accurate optical frequency, but the size, cost, and device complexity increase significantly
Solution Approach 1:
The patent combines the optical frequency control function with the existing single alkaline vapour microcell and photodiode that are already used for microwave frequency control. The single photodiode detects both microwave and optical frequency signals, and the single microcell serves both frequency control purposes, thereby eliminating the need for duplicate components while maintaining control accuracy.
Solution Approach 2:
The patent makes the existing microcell and photodiode perform multiple functions: they simultaneously control both microwave and optical frequencies. The photodiode detects both microwave and optical signals, and the control system processes both frequency types through the same hardware path, achieving multi-functionality without additional components.
2Reliability
If continuous mode operation is used, then the clock maintains stable frequency, but pulse mode operation is needed to improve performance while reducing power consumption
Solution Approach 1:
The patent implements pulse mode operation where the laser source and microcell are activated periodically rather than continuously. The system uses periodic pulsed interrogation sequences that switch between different operational states, achieving both power savings during idle periods and maintaining frequency stability during active measurement intervals through controlled periodic operation.
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 results in a more cost-effective, compact, and simpler miniature atomic clock with improved manufacturing ease and flexibility in implementing pulsing mechanisms, achieving a better size/cost/performance compromise without significant degradation in performance.
Implementation Method 1
a dual-frequency laser source receiving an output signal from the local oscillator and having an optical frequency. The frequency deviation between the spectral components of the output signal (laser beam) of the dual-frequency laser source is equal to the frequency of the local oscillator
Implementation Method 2
an alkaline vapour microcell receiving the output signal from the dual-frequency laser source and using coherent population trapping
Implementation Method 3
a photodiode receiving an output signal from the alkaline vapour microcell. The photodiode transforms the pulsed light intensity into an electrical signal that also carries the comparison information
Data Source
AI summary
A miniature atomic clock with pulse mode operation. The clock includes: a local oscillator; a dual-frequency laser source; a pulsing element to pulse the output signal from the source according to a Ramsey-type interrogation sequence having pulses with duration T1 separated by intervals with duration T2; an alkaline vapour microcell; a photodiode; a feedback control loop for controlling the microwave frequency of the local oscillator; and a feedback control loop for controlling the optical frequency of the source by using a pulse control block receiving the output signal from the photodiode and the interrogation sequence, and providing a correction signal to the source. During the period T1, the block extracts an error signal from the output signal received from the photodiode and generates the correction signal from the error signal. During the period T2, the block resets the error signal to zero and generates the correction signal by extrapolation.