Semiconductor Light Modulator Matching Circuit for Wideband Stability
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Solution Overview
Problem
Conventional semiconductor light modulating apparatuses face challenges in achieving favorable frequency characteristics and maintaining a desired band due to impedance mismatching and parasitic effects at high frequencies.
Innovation Solution
A semiconductor light modulating apparatus with a terminal matching circuit connected in parallel to the semiconductor light modulator, comprising a resistor and a capacitor of 0.1 pF or lower, which reduces gain variation and band degradation by improving frequency characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional terminal matching circuit is connected in parallel to the semiconductor light modulator, then impedance matching is improved, but gain variation occurs at low frequencies and band degradation occurs at high frequencies
Solution Approach 1:
The patent changes the electrical parameters of the matching circuit by introducing a capacitor with specifically controlled capacitance (0.01 pF or less) in parallel with the resistor. This parameter modification allows the circuit to maintain impedance matching while extending the usable frequency band and reducing gain variation, effectively resolving the frequency characteristic degradation problem.
2Speed
If the frequency of the input signal is increased to achieve high-speed communication, then communication speed is improved, but impedance matching becomes impossible and band degradation occurs due to parasitic effects
Solution Approach 1:
The patent converts the harmful parasitic capacitance and resistance of the semiconductor light modulator into a beneficial matching condition by introducing a compensating capacitor in the terminal matching circuit. This capacitor, with capacitance of 0.01 pF or less, counteracts the parasitic effects and enables impedance matching to be maintained even at high frequencies up to 10 GHz or higher.
3Reliability
If a terminal matching circuit is designed to maintain impedance matching, then matching performance is improved, but gain decrease and band degradation occur at higher frequencies
Solution Approach 1:
The patent modifies the matching circuit parameters by adding a capacitor with precisely controlled small capacitance (0.01 pF or less). This parameter change transforms the circuit's frequency response, enabling it to maintain both impedance matching and wide bandwidth simultaneously, thereby resolving the contradiction between matching performance and bandwidth.
Data Source
AI summary
A semiconductor light modulator (5) modulates light in accordance with a high-frequency wave signal (11). A terminal matching circuit (12) is connected in parallel to the semiconductor light modulator (5). The terminal matching circuit (12) has a resistor (8) and a capacitor (9) of 0.1 pF or lower connected in parallel to the resistor (8).