Balanced Photodetector Responsivity Compensation
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Solution Overview
Problem
Balanced photodetectors face degradation in Common Mode Rejection Ratio (CMRR) due to differences in photodiode responsivities and optical path imbalances, which is not effectively addressed by conventional methods that rely on inline optical attenuators or amplifiers.
Innovation Solution
The balanced photodetector employs an adaptive operation by tuning operating parameters such as bias voltage and temperature to adjust the responsivities of the photodiodes, ensuring they operate under the same conditions and compensating for responsivity differences and optical imbalances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods using inline optical attenuators or amplifiers are used to compensate for photodiode responsivity differences, then the CMRR can be maintained, but the device complexity and chip space requirements increase
Solution Approach 1:
The patent extracts and eliminates the need for inline optical attenuators or amplifiers by implementing a different compensation mechanism. The control circuit compensates for photodiode responsivity differences through electrical signal processing rather than optical components, thereby removing unnecessary device complexity while maintaining CMRR
Solution Approach 2:
The control circuit serves multiple functions: it not only compensates for photodiode responsivity differences but also balances optical path imbalances and maintains CMRR. This multi-functionality eliminates the need for separate compensating components, reducing overall device complexity
2Reliability
If conventional methods using inline optical attenuators or amplifiers are used to compensate for photodiode responsivity differences, then the CMRR can be maintained, but the chip space utilization deteriorates
Solution Approach 1:
The patent merges the functions of CMRR maintenance and photodiode balancing into a single control circuit. By combining these functions electronically rather than using separate optical components, the chip space required is significantly reduced while maintaining the necessary CMRR performance
3Ease of manufacture
If photodiodes operate under different conditions due to manufacturing variations, then the manufacturing process is simpler, but the CMRR degrades
Solution Approach 1:
The control circuit performs preliminary compensation for photodiode responsivity differences and optical path imbalances. By pre-balancing the photodiodes through electrical adjustment before signal processing, the system maintains high CMRR despite manufacturing variations, allowing simpler manufacturing processes without sacrificing performance
Solution Approach 2:
The control circuit changes electrical parameters (gain, offset, bias) to compensate for photodiode variations. By adjusting these parameters dynamically, the system maintains optimal CMRR performance despite differences in photodiode manufacturing characteristics
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 CMRR and signal-to-noise ratio (SNR) of the balanced photodetector, allowing for efficient chip space utilization and a simple control strategy, while improving detection sensitivity in long-range LIDAR systems.
Implementation Method 1
a first photodiode and a second photodiode coupled with one another at a common node, wherein the first photodiode has a first effective responsivity and the second photodiode has as second effective responsivity
Data Source
AI summary
A balanced photodetector may include: a balanced photodetector including a first photodiode and a second photodiode coupled with one another at a common node, wherein the first photodiode has a first effective responsivity and the second photodiode has as second effective responsivity; and a control circuit configured to set an operating parameter of the balanced photodetector to compensate for a difference between the first effective responsivity and the second effective responsivity.