Series RF Switch Layout for Parasitic-Aware Voltage Division
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Solution Overview
Problem
Radio frequency switches in high-frequency environments are affected by parasitic effects, leading to an increase in equivalent capacitance and adverse performance due to varying voltage requirements across different applications.
Innovation Solution
A radio frequency switch design featuring N switch transistors connected in series, where each transistor has a different withstand voltage based on channel length and width, progressively increasing from input to output, using silicon-on-insulator MOS transistors to minimize parasitic effects without additional peripheral circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If N switch transistors are connected in series to increase withstand voltage, then the maximum withstand voltage of the radio frequency switch increases, but parasitic effects cause equivalent capacitance increase that adversely affects performance
Solution Approach 1:
The patent applies local quality by assigning different channel lengths (and thus different withstand voltages) to different transistors based on their position in the series chain. Transistors closer to the input end have longer channel lengths for higher withstand voltage, while those closer to the output end have shorter channel lengths. This localized differentiation optimizes the voltage distribution across the series-connected transistors, allowing the system to achieve high total withstand voltage while minimizing the parasitic capacitance effect that would otherwise limit performance.
2Reliability
If switch transistors with different withstand voltages are used, then voltage division capability is optimized, but device complexity increases
Solution Approach 1:
The patent implements parameter changes by systematically varying the channel length parameter across the series-connected transistors. Each transistor's channel length is adjusted to provide a specific withstand voltage rating, creating a gradient from input to output. This parameter differentiation enables optimized voltage division and matching of voltage stress across each device, improving reliability while the systematic approach keeps the design manageable.
Data Source
AI summary
Disclosed is a radio frequency switch and its radio frequency communication system. The RF switch comprises: N switch transistors Q1˜QN connected in series, wherein a first conducting terminal of Q1 serves as an output end, a second conducting terminal of QN serves as an input end a switch transistor located closer to the output end has a higher or equal withstand voltage than that of a switch transistor located closer to the input end, or a switch transistor located closer to the output end has a lower or equal withstand voltage than that of a switch transistor located closer to the input end, and Q1 and QN has different withstand voltages. The withstand voltages of the switch transistors match the voltage division situation of the switch transistors affected by parasitic effect in the RF switch, thus the voltage withstand capability is basically not affected by parasitic effect.