Low-Noise Laser Driver and Receiver for Self-Mix Modules
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing audio and acoustic signal processing technologies face challenges in reducing noise and enhancing signal quality, particularly in environments with multiple sources of noise and interference, which affects the performance of optical and laser microphones.
Innovation Solution
The use of a laser-based microphone system that incorporates a low-noise laser driver and receiver, with a drive current composed of a Direct Current component and an attenuated Alternating Current component, and hardware-based demodulation to remove the Direct Current component before digitization, along with a hybrid photo-diode configuration to reduce noise and improve signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional laser driver is used to drive the laser diode, then the device can operate, but it generates significant amplitude and frequency noise that degrades signal quality
Solution Approach 1:
The drive current is segmented into two separate components: a DC component with limited bandwidth and an AC component with a different bandwidth. This segmentation allows each component to be optimized independently, with the DC component providing stable bias and the AC component carrying the modulated signal, thereby reducing overall noise while maintaining signal quality.
Solution Approach 2:
The invention changes the bandwidth parameter of the DC component by limiting it to be less than the AC component's bandwidth. This parameter change reduces low-frequency noise (1/f noise) in the DC component while preserving the signal-carrying AC component, directly addressing the noise degradation problem.
2Measurement precision
If the full bandwidth AC component is applied to the laser diode, then the signal bandwidth is preserved, but noise is amplified along with the signal
Solution Approach 1:
The total bandwidth requirement is segmented between two components: the DC component handles low-frequency stabilization with limited bandwidth, while the AC component handles high-frequency signal modulation. This segmentation allows the signal bandwidth to be preserved in the AC component without amplifying unnecessary noise across the entire frequency spectrum.
Solution Approach 2:
The DC component applies only partial action with limited bandwidth, providing just enough bias current for stable operation without excessive current that would amplify noise. The AC component then provides the necessary signal modulation with appropriate bandwidth, achieving signal preservation without full-bandwidth noise amplification.
3Stability of the object's composition
If the DC component bandwidth is not limited, then the laser operates stably, but low-frequency noise (1/f noise) degrades the signal
Solution Approach 1:
The bandwidth parameter of the DC component is explicitly changed and limited to be less than the AC component bandwidth. This parameter change reduces the 1/f noise in the DC component while maintaining laser stability through the combined action of both components, directly resolving the contradiction between stability and noise reduction.
4Measurement precision
If hardware-based demodulation is implemented in the receiver, then the Signal-to-Noise Ratio is improved, but the device complexity increases
Solution Approach 1:
The hardware-based demodulation performs preliminary action by removing the DC component from the receiver output signal before digitization. This preliminary processing improves the Signal-to-Noise Ratio by eliminating low-frequency noise early in the signal chain, reducing the burden on subsequent digital processing stages and effectively managing overall system complexity.
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 significantly reduces noise and enhances signal quality by minimizing amplitude and frequency noise, thereby improving the Signal-to-Noise Ratio and enabling effective noise reduction and source separation in audio and acoustic signal processing.
Implementation Method 1
a photo-diode associated with a low-noise photo-diode receiver RX
Implementation Method 2
a laser-diode associated with a low-noise laser driver TX
Data Source
AI summary
Optical microphone, laser-based microphone, and laser microphone having reduced-noise components of low-noise components. A laser microphone comprises a laser-diode associated with a low-noise laser driver TX; and a photo-diode associated with a low-noise photo-diode receiver RX. The low-noise laser driver TX supplies a drive current which is a combination of a Direct Current component having a first bandwidth, and an attenuated version of an Alternating Current component having a second, different, bandwidth. Additionally or alternatively, the low-noise photo-diode receiver RX utilizes hardware-based demodulation of the analog signal, and operates to remove a Direct Current component of its output signal prior to digitization.