Signal Path Modulation for Spectrometer Noise Reduction
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Solution Overview
Problem
Conventional spectrometry systems face challenges with phase stability due to spurious thermal and mechanical disturbances that modulate the received electromagnetic field intensity, and conventional lock-in amplifier technology is costly and complex, making it difficult to achieve high demodulation signal-to-noise ratio and stability.
Innovation Solution
A system and method that modulates the path length of electromagnetic signals by altering the length of propagation paths using a spool and actuator, combined with Discrete Fourier Transformation processing, to improve signal demodulation and stability, and uses a modulator to elevate the signal carrier above 1/f noise regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional lock-in amplifier technology is used for signal demodulation, then demodulation accuracy can be achieved, but device complexity and cost increase significantly
Solution Approach 1:
The patent replaces the conventional lock-in amplifier (an electronic instrument system) with a digital signal processing approach using a field-programmable gate array (FPGA). The FPGA implements digital lock-in detection algorithms, substituting complex electronic demodulation hardware with programmable digital logic, thereby reducing device complexity and cost while maintaining demodulation accuracy.
Solution Approach 2:
The patent implements a virtual copy of the lock-in amplifier functionality through software algorithms running on the FPGA. Instead of using physical lock-in amplifier hardware, the system creates a digital replica of its demodulation functions through programmed signal processing operations, achieving the same measurement precision with simpler hardware.
2Reliability
If path length is kept constant for stable transmission, then signal transmission stability improves, but ability to mitigate thermal and mechanical disturbances decreases
Solution Approach 1:
The patent applies periodic modulation to the optical path length using a piezoelectric actuator that oscillates the mirror position at a specific frequency. This periodic action creates a time-varying path length that allows the system to distinguish the modulated signal from static or low-frequency thermal and mechanical disturbances, thereby mitigating their harmful effects while maintaining transmission stability.
Solution Approach 2:
The patent converts the potential harm of path length variations caused by thermal and mechanical disturbances into a benefit by using intentional periodic modulation. The modulation frequency is chosen to be above the 1/f noise region, transforming what would be harmful low-frequency fluctuations into a useful high-frequency carrier that can be easily filtered and detected, improving signal-to-noise ratio.
3Ease of operation
If modulation frequency is kept low for ease of processing, then signal processing simplicity improves, but signal-to-noise ratio deteriorates due to 1/f noise
Solution Approach 1:
The patent changes the modulation frequency parameter from low frequency to high frequency (above the 1/f noise region). This parameter change moves the signal carrier to a frequency range where white noise dominates over 1/f noise, significantly improving the signal-to-noise ratio. The FPGA-based digital processing maintains simplicity despite the higher frequency by using efficient digital signal processing algorithms.
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 enhances the signal-to-noise ratio and stability of demodulated signals by mitigating path length variations and reducing noise, allowing for accurate measurement of absorption losses and characterization of samples.
Implementation Method 1
The arrangement may comprise a spool and actuator. In such instances, an optical fiber propagation path may be wound about the spool, and the actuator may be configured to alter the diameter of the spool, and thereby alter the length of the respective propagation path.
Implementation Method 2
the modulator is configured to modulate the electromagnetic signal at a frequency (e.g., ω m ), which may be above the 1/f noise region of the receiver.
Implementation Method 3
the processor is configured to receive a sequence of samples of the received electromagnetic signal, and Discrete Fourier Transformation process the sequence of samples.
Implementation Method 4
the receiver is configured to receive the electromagnetic signal and another electromagnetic signal for mixing therewith
Data Source
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AI summary
A system includes a transmitter is configured to transmit an electromagnetic signal to a receiver, which is configured to receive the electromagnetic signal and another electromagnetic signal for mixing therewith. Propagation paths of the signals to the transmitter and receiver include a first propagation path of the electromagnetic signal to the transmitter, and a second propagation path of the other electromagnetic signal to the receiver. The arrangement, which is located along either or each of the propagation paths of signals to the transmitter and receiver, is configured to alter the length of a respective propagation path. And the processor configured to recover an amplitude and phase of the transmitted electromagnetic signal, including being configured to receive a sequence of samples of the received electromagnetic signal, and Discrete Fourier Transformation process the sequence of samples.