DC Bias Determination in AC-Coupled EML Transmitters
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Solution Overview
Problem
Conventional methods for determining the DC level in AC-coupled circuitry, such as using DC probes or signal taps, often result in inaccurate measurements due to internal circuitry limitations and added complexity, leading to voltage imbalance issues, especially in high-frequency systems.
Innovation Solution
A method and circuit that disable the AC-coupled signal, sample the disabled signal to obtain DC values, and calculate the DC level using a microcontroller or microprocessor, allowing for precise determination of the DC component or offset without additional complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods (DC probes, signal taps) are used to measure DC level, then measurement capability is provided, but measurement precision deteriorates and device complexity increases
Solution Approach 1:
The patent extracts the DC measurement function from separate external measurement devices (DC probes, signal taps) and integrates it into the existing AC-coupled circuitry by utilizing the circuit's own off-state to measure the DC level. This eliminates the need for additional measurement equipment and reduces overall system complexity while maintaining measurement precision.
Solution Approach 2:
The AC-coupled circuitry measures its own DC level using its own off-state characteristics. The circuit serves itself by utilizing the natural off-state of the AC-coupled elements (such as photodetectors or amplifiers) to determine the DC component, eliminating the need for external measurement devices and reducing system complexity.
2Measurement precision
If DC probes or signal taps are used, then DC level can be measured, but measurement precision deteriorates due to internal circuitry limitations
Solution Approach 1:
The patent removes the dependency on external DC probes and signal taps that introduce measurement errors. By using the circuit's own off-state, the measurement becomes intrinsic and eliminates the internal circuitry limitations of external measurement devices, thereby improving both precision and reliability.
Solution Approach 2:
The off-state of the AC-coupled circuitry serves as an intermediary that enables accurate DC measurement. Instead of directly measuring the DC component with error-prone external devices, the patent uses the natural off-state as a mediator to indirectly and accurately determine the DC level.
3Adaptability or versatility
If additional circuitry is added to measure DC component, then measurement capability is provided, but device complexity increases
Solution Approach 1:
The patent makes the existing AC-coupled circuitry multi-functional by enabling it to perform both its original AC signal processing function and the additional function of DC level measurement. The same circuit elements (photodetectors, amplifiers) are used for both purposes, eliminating the need for separate dedicated measurement circuitry and reducing overall complexity.
Solution Approach 2:
The circuit performs self-measurement of its DC level using its own operational states. The AC-coupled elements measure their own DC component during their normal operation (specifically during the off-state), making the system self-sufficient and eliminating the need for external measurement apparatus.
Data Source
AI summary
Methods, circuits, architectures, apparatuses, and algorithms for determining a DC level in an AC or AC-coupled signal. The method generally includes disabling the AC or AC-coupled signal; sampling the disabled AC or AC-coupled signal to obtain sampled DC values of the AC or AC-coupled signal; and calculating the DC level using the sampled DC values of the AC or AC-coupled signal. The present transmitter generally includes an electro-absorption modulated laser (EML); a photodetector; a signal source configured to provide an AC or AC-coupled signal to the EML; and a microcontroller or microprocessor configured to (i) control the signal source, (ii) receive information from the photodetector, and (iii) deactivate the signal source for a predetermined length of time. The circuits, architectures, and apparatuses generally include those that embody one or more of the inventive concepts disclosed herein.