Low-Q Inductive-Peaking Optical Receiver Bandwidth
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Solution Overview
Problem
Conventional optical front-end inductive-peaking techniques require high-quality-factor inductors, leading to thick on-chip wires that increase capacitance, reducing the effectiveness of bandwidth enhancement.
Innovation Solution
An integrated circuit with a low-Q inductive-peaking optical receiver design, featuring an inductor with resistance greater than 40 mΩ/μm and negligible parasitic capacitance, which is dispersion-less and modeled as a series-peaking topology to enhance bandwidth without the need for high-Q inductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-quality-factor inductors with thick on-chip wires are used for inductive peaking, then the inductor quality factor is improved, but the capacitance increases and bandwidth enhancement effectiveness is reduced
Solution Approach 1:
The patent changes the key parameter from high-Q factor to low-Q factor inductors. By using thin on-chip wires instead of thick wires, the inductor resistance per unit length is increased to greater than 40 mΩ/μm, which reduces the Q factor to less than 5. This parameter change simultaneously reduces the parasitic capacitance while maintaining effective bandwidth enhancement through the resistive analog front-end stage.
2Reliability
If thick on-chip wires are used for inductor design, then the inductor quality factor is improved, but the implementation complexity and on-chip area increase
Solution Approach 1:
The patent inverts the conventional approach by using low-Q factor inductors instead of high-Q factor inductors. This inversion allows the use of thin on-chip wires with higher resistance per unit length, which reduces parasitic capacitance and simplifies on-chip implementation while achieving bandwidth enhancement through the resistive analog front-end stage with gain.
3Speed
If conventional inductive peaking techniques are used, then bandwidth enhancement is achieved, but the requirement for high-Q inductors makes on-chip implementation impractical
Solution Approach 1:
The patent changes the Q factor parameter from high to low, enabling practical on-chip implementation. The low-Q inductor with resistance per unit length greater than 40 mΩ/μm and Q factor less than 5 can be easily fabricated on-chip using thin wires, while the resistive analog front-end stage provides the necessary bandwidth enhancement without requiring complex high-Q inductor designs.
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 design increases bandwidth by more than 50% compared to conventional techniques, enabling improved communication performance in optical links by reducing the dominant pole's impact and eliminating the need for trans-impedance amplifiers, thus enhancing data rates and reducing non-linearity.
Implementation Method 1
a photodiode that receives an optical signal and that outputs a corresponding current
Implementation Method 2
an inductor that is electrically coupled to the photodiode... Some optical front-end circuits use inductive peaking techniques to enhance the bandwidth
Data Source
AI summary
An integrated circuit that includes an optical receiver is described. This integrated circuit may include an optical receiver. The optical receiver may include a photodiode that receives an optical signal and that outputs a corresponding current. Moreover, the optical receiver may include an inductor that is electrically coupled to the photodiode. Furthermore, the optical receiver may include a resistive analog front-end stage that is electrically coupled to the inductor. Note that the inductor may have a resistance per unit length that is greater than a first threshold value (such as 40 mΩ/μm), and the inductor may be approximately dispersion-less. For example, a Q factor for inductive peaking associated with the inductor is less than a second threshold value (such as 5).