Common-Mode Rejection Circuit for Accurate LOS Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional loss of signal (LOS) detectors in optical data transmission networks are vulnerable to common mode voltage levels, affecting the accuracy of signal detection and leading to incorrect alerts due to differences in common mode voltages between received and threshold signals.
Innovation Solution
An improved LOS detector system with a cross-coupled common mode rejection circuit and programmable threshold and hysteresis control, using a rectifier arrangement that sets the threshold voltage based on signal amplitude and generates differential threshold voltages independent of common mode, along with a high output impedance configuration that filters noise without needing capacitors, allowing for adjustable detection thresholds and reduced power dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional LOS detectors are used to detect signal loss, then signal detection function is provided, but common mode voltage differences cause detection inaccuracy and false alerts
Solution Approach 1:
The patent introduces a common mode rejection circuit as an intermediary between the received signal and the comparison operation. This circuit actively measures the common mode voltage of the received signal and generates a compensated threshold signal by adjusting the reference threshold with the measured common mode voltage, thereby eliminating the harmful effect of common mode voltage differences on detection accuracy
Solution Approach 2:
The patent dynamically changes the threshold parameter based on the common mode voltage of the received signal. By measuring the common mode voltage and adjusting the threshold signal accordingly (threshold_compensated = threshold_reference - common_mode_received), the system adapts to varying common mode conditions and maintains accurate detection despite common mode interference
2Device complexity
If traditional threshold comparison methods are used, then simple detection is achieved, but false alerts occur due to common mode voltage differences
Solution Approach 1:
The common mode rejection circuit serves as an intermediary that processes the received signal to extract common mode voltage information and generates a compensated threshold. This additional intermediary stage increases circuit complexity but eliminates false alerts by ensuring the comparison is made between properly compensated signals, thereby improving detection reliability
Solution Approach 2:
The system implements feedback by measuring the common mode voltage of the received signal and using this measurement to adjust the threshold signal. The common mode rejection circuit continuously monitors the common mode voltage and feeds this information back to the threshold generation stage, creating a closed-loop system that maintains accurate detection under varying conditions
3Use of energy by moving object
If fixed threshold detection is used, then power consumption is low, but detection accuracy deteriorates under varying common mode conditions
Solution Approach 1:
The patent changes the threshold parameter dynamically based on the common mode voltage of the received signal. Instead of using a fixed threshold, the system adjusts the threshold voltage to compensate for common mode variations, maintaining detection precision while consuming additional power only for the common mode measurement and compensation circuitry
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 system provides improved common mode immunity and precise signal detection, reducing false alerts and power consumption while maintaining stability against temperature and device mismatches, enabling effective detection of signal presence or absence in noisy conditions.
Implementation Method 1
a rectifier arrangement that sets the threshold voltage corresponding directly to the amplitude of the signal itself and that generates differential threshold voltages from a common mode voltage
Implementation Method 2
a high output impedance configuration that filters noise without needing capacitors
Data Source
AI summary
A loss of signal (LOS) detector may include a comparator including a first input, a second input and an output indicating a LOS status. The LOS detector further includes circuitry to compare a first signal on the first input generated by differential input signals and a threshold signal common mode with a second signal on the second input generated by differential threshold signals at a first level and an input signal common mode. The circuit further configured to generate a LOS indicator on the output based on the compare.