Optical Receiver Balancing via Adjustable Transimpedance Gain
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Solution Overview
Problem
Optical receivers face challenges in balancing the responsivity and frequency response differences between photodetectors, leading to suboptimal common-mode rejection ratio (CMRR) performance due to varying photocurrent paths and detector interfaces.
Innovation Solution
A transimpedance amplifier circuit with adjustable gain controllers and frequency response controllers, utilizing variable resistors and capacitors, is implemented to match the amplifier gain and frequency response between photodetectors, thereby reducing responsivity and frequency response differences, and improving CMRR performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If fixed amplifier gain is used in transimpedance amplifier circuit, then circuit design is simple, but photodetector responsivity differences cannot be compensated
Solution Approach 1:
The patent implements adjustable amplifier gain through variable resistors (e.g., R1a, R1b, R1c, R1d) that allow dynamic compensation of photodetector responsivity differences. The gain can be tuned to match the specific characteristics of each photodetector, transforming a static circuit into a dynamically adjustable one that adapts to component variations.
Solution Approach 2:
The patent changes the electrical parameters (resistance values, capacitance values) of the transimpedance amplifier circuit to compensate for photodetector responsivity differences. By adjusting parameters such as the feedback resistance and capacitance, the amplifier gain is optimized for each photodetector's specific characteristics.
2Reliability
If identical interface design is used for both photodetectors, then manufacturing is easier, but frequency response differences cause poor CMRR performance
Solution Approach 1:
The patent applies different frequency response compensation to each photodetector's signal path. By introducing separate adjustable capacitors (e.g., C1a, C1b, C1c, C1d) in each photocurrent path, the circuit allows individual optimization of frequency response for each detector, accounting for their specific interface characteristics and parasitic elements.
Solution Approach 2:
The frequency response of each photocurrent path is made dynamically adjustable through variable capacitors that can be tuned to match the specific frequency characteristics of each photodetector interface. This dynamic adjustment enables optimal CMRR performance by compensating for frequency response differences.
3Ease of operation
If manual balancing of photodetector responsivity is performed, then adjustment precision can be achieved, but time consumption and operational complexity increase
Solution Approach 1:
The patent implements automatic gain balancing through a feedback mechanism that measures the output signals from both photodetectors and adjusts the amplifier gain accordingly. The controller uses the measured power levels to automatically tune the variable resistors and capacitors, eliminating the need for manual balancing while achieving precise responsivity matching.
Solution Approach 2:
The system performs self-balancing by automatically adjusting its own parameters (amplifier gain, frequency response) based on measured output signals. The transimpedance amplifier circuit includes built-in control mechanisms that autonomously compensate for photodetector variations without requiring external manual intervention.
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 solution effectively balances photodetector responsivity and frequency responses, enhancing the CMRR performance of optical receivers by automatically adjusting amplifier gain and frequency characteristics, resulting in improved signal processing and noise rejection.
Implementation Method 1
a first photodetector and a second photodetector respectively obtain a first optical signal and a second optical signal to generate a first photocurrent and a second photocurrent
Data Source
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AI summary
A method. The method may include transmitting an optical noise signal to a first photodetector and a second photodetector within an optical receiver circuit that includes a transimpedance amplifier circuit. The method may further include measuring, in response to transmitting the optical noise signal, a power output from the optical receiver circuit. The method may further include determining, using the power output, a difference in photodetector responsivity between the first photodetector and the second photodetector. The method may further include adjusting, using a transimpedance gain controller, an amplifier gain within the optical receiver circuit to decrease a difference in photodetector responsivity between the first photodetector and the second photodetector.