Opto-Electronic Receiver Assembly With Adaptive MOS Feedback
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Solution Overview
Problem
High-speed optical communication systems face issues with amplitude non-linearity and transient response stability due to the simplicity of transimpedance amplifier (TIA) circuits, leading to errors in data decision functions.
Innovation Solution
The proposed solution involves an assembly of electronic components including a photodiode, a first amplifier, feedback resistors, and a configuration of MOS transistors of the same channel polarity, where the MOS transistors are arranged in parallel or series, and a system that adjusts bias voltage based on the input signal level to control resistance and improve signal fidelity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If simple circuits are used for TIA to handle high bandwidth range, then bandwidth performance is improved, but amplitude linearity deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the output signal is fed back through a capacitor to the gate of the MOS transistor. This feedback loop dynamically adjusts the transistor's conductance to compensate for amplitude non-linearity, allowing the simple circuit to maintain both high bandwidth and improved amplitude linearity simultaneously
Solution Approach 2:
The patent changes the operating parameters of the MOS transistor by applying a time-varying voltage to the gate through the feedback capacitor. This dynamic parameter adjustment allows the transistor's resistance to vary in response to signal amplitude, correcting non-linearity while preserving the simple circuit architecture and high bandwidth characteristics
2Speed
If simple circuits are used for TIA to handle high bandwidth range, then bandwidth performance is improved, but transient response stability deteriorates
Solution Approach 1:
The feedback capacitor connects the output to the gate, creating a dynamic compensation mechanism that stabilizes the transient response. This feedback action counteracts the instability caused by large signal swings, allowing the simple high-bandwidth circuit to achieve improved transient response stability without sacrificing bandwidth performance
3Adaptability or versatility
If AGC system is used to adjust TIA gain, then adaptability to different signal strengths is improved, but circuit complexity increases
Solution Approach 1:
The patent merges the gain control function with the existing feedback structure by using the same feedback capacitor to simultaneously provide transient stabilization and gain adaptation. This integration allows the circuit to adapt to different signal strengths through the natural operation of the feedback mechanism, achieving AGC functionality without adding separate complex control circuits
Solution Approach 2:
The circuit uses its own output signal to automatically adjust its gain through the feedback capacitor. The feedback mechanism self-regulates the transistor's conductance based on the instantaneous output amplitude, providing automatic gain control without requiring external AGC circuitry, thereby maintaining circuit simplicity while achieving signal strength adaptability
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 configuration enhances amplitude linearity and time domain stability, reducing errors and improving the fidelity of the signal waveform in optical communication systems.
Implementation Method 1
The conversion from the optical signals received from the fibre into electrical signals is typically performed using a photodiode
Implementation Method 2
said system is configured to apply a bias voltage to gates of said at least two MOS transistors, said bias voltage being varied by said system according to said received input signal level in a manner to control a resistance apparent through a configuration of said at least two MOS transistors
Data Source
AI summary
Assemblies of electronic components for reception of data using optical fibre and methods for providing same. Assemblies comprise a photodiode; an amplifier coupled to the photodiode; at least one feedback resistor coupled between the input and output of the amplifier; an arrangement of at least two MOS transistors of same channel polarity and configured in parallel with the feedback resistor(s); a system for sensing received input signal level and applying a bias voltage to gates of the MOS transistors, the bias voltage varied according to the received input signal level to control a resistance apparent through the arrangement of MOS transistors; at least one capacitor configured to couple signals from the amplifier output to a gate of at least one of the MOS transistors; and at least one bias resistor configured to couple the bias voltage to a gate of at least one of the MOS transistors.