Optical Modulator Transmission Line Layout for Broad Frequency Response
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Solution Overview
Problem
Existing semiconductor optical modulation devices have limited frequency response characteristic improvement, particularly below 5 GHz, and are ineffective in addressing multiple reflection issues between the semiconductor optical element and the metal stem.
Innovation Solution
A semiconductor optical modulation device is designed with a second transmission line of lower impedance between the first and third transmission lines, and a series circuit of a second resistor and capacitor connected to the third transmission line, which compensates for group delay characteristic deviations, thereby improving frequency response across a broad frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lower impedance transmission line is added to limit multiple reflection, then frequency response characteristic is improved in high-frequency region, but improvement effect is low at frequencies equal to or lower than 5 GHz
Solution Approach 1:
The patent introduces a series circuit of resistor and capacitor connected to the third transmission line, which changes the impedance parameters across different frequency ranges. This RC circuit creates frequency-dependent impedance transformation that compensates for group delay deviations at lower frequencies (≤5 GHz), while the lower impedance second transmission line continues to suppress multiple reflections at higher frequencies (>10 GHz), thus achieving broad frequency range improvement
Solution Approach 2:
The series circuit of resistor and capacitor acts as an intermediary element connected to the third transmission line. This intermediary circuit compensates for group delay characteristic deviations generated by the lower impedance second transmission line, enabling the system to achieve both multiple reflection suppression and broad frequency response improvement across different frequency bands
2Reliability
If a series circuit of resistor and capacitor is connected to improve frequency response, then group delay characteristic deviation is compensated, but device complexity increases
Solution Approach 1:
The series circuit of resistor and capacitor connected to the third transmission line serves multiple functions simultaneously: it compensates for group delay characteristic deviations, improves frequency response across broad frequency ranges, and works in conjunction with the lower impedance second transmission line to suppress multiple reflections. This multi-functional design achieves complex performance goals without proportionally increasing device complexity
Data Source
AI summary
A first resistor connected in parallel to a semiconductor optical modulator having first ends, the first resistor and first ends connected to a reference potential. A first end of a first transmission line is connected to second ends of the semiconductor optical modulator and the first resistor. A second transmission line is connected in series to the first transmission line and has an impedance lower than that of the first resistor. A first end of the second transmission line is connected to a second end of the first transmission line. A third transmission line is connected in series to the first and second transmission lines and has an end connected to a second end of the second transmission line, and has an impedance equal to that of the first transmission line. A second resistor and a capacitor are connected in series between the third transmission line and the reference potential.