Level-Shifter Driver Circuit for High-Swing Ring Modulators
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Solution Overview
Problem
State-of-the-art silicon ring modulators face limitations in voltage swing due to supply voltage constraints, which restrict the achievable extinction ratio and optical modulated amplitude, leading to higher transmitter penalties.
Innovation Solution
A driver circuit with a level shifter circuit and voltage distribution circuit using capacitors to generate output voltages beyond the supply voltage limits, without additional electrical supplies or control voltages, allowing increased voltage swing for improved extinction ratio and optical modulated amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If supply voltage is increased to increase voltage swing, then extinction ratio and optical modulated amplitude improve, but device complexity and power consumption increase due to additional electrical supplies
Solution Approach 1:
The patent changes the voltage levels by using a level shifter circuit that transforms the input voltage range (0 to VDD) to an expanded output voltage range (0 to 2×VDD). This parameter transformation allows achieving higher voltage swing without increasing the physical supply voltage, thereby improving extinction ratio and optical modulated amplitude while avoiding additional power supplies
Solution Approach 2:
The patent introduces a level shifter circuit as an intermediary component between the standard CMOS logic and the ring modulator. This intermediary circuit uses capacitors and transistors to generate the elevated voltage levels needed for high-performance modulation without requiring the main system to operate at higher supply voltages, thus maintaining simplicity while achieving enhanced performance
2Strength
If supply voltage is increased to increase voltage swing, then optical modulated amplitude improves, but power consumption increases
Solution Approach 1:
The level shifter circuit transforms the voltage parameter locally at the modulator interface, allowing high voltage swing (0 to 2×VDD) only where needed for optical modulation. The rest of the digital logic continues to operate at the standard lower supply voltage VDD, thus achieving high optical modulated amplitude while keeping overall power consumption low
3Measurement precision
If voltage swing is increased to improve extinction ratio, then optical signal quality improves, but device complexity increases due to additional control voltages
Solution Approach 1:
The level shifter circuit automatically transforms the standard logic voltage levels to the elevated levels required for high extinction ratio modulation. This parameter transformation is achieved through the inherent capacitance and switching action of the level shifter, without requiring separate control voltage generators or additional complex control logic
Solution Approach 2:
The level shifter circuit uses the input signal itself and the available supply voltage VDD to generate the elevated output voltages. The circuit is self-contained and uses internal capacitors and transistors to create the voltage multiplication effect, eliminating the need for external voltage references or additional control signals
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 driver circuit enhances the voltage swing across the ring modulator, reducing transmitter penalties and increasing the optical modulated amplitude, thereby improving the efficiency of optical signal transmission.
Implementation Method 1
The level shifter circuit is configured to generate, based on the input voltage and using a first capacitor of the two capacitors, a first voltage varying between the positive supply voltage level and a positive first level that is greater than the positive supply voltage level. In addition, the level shifter circuit is configured to generate, based on the input voltage and using the second capacitor of the two capacitors, a second voltage varying between ground and a negative second level.
Data Source
AI summary
Examples include a driver circuit for driving a voltage controlled electro-optical modulator. The driver circuit includes a supply input and an input for receiving the input voltage. The driving circuit further includes a level shifter circuit, which includes first and second capacitors and is electrically connected to the input, and a voltage distribution circuit, which is electrically connected between the level shifter circuit and an output of the driver circuit for providing the output voltage. The level shifter circuit is configured to generate, based on the input voltage and using the first capacitor, a first voltage varying between the positive supply voltage level and a positive first level that is greater than the positive supply voltage level. The level shifter circuit is also configured to generate, based on the input voltage and using the second capacitor, a second voltage varying between ground and a negative second level.