RF Series-Shunt Switch Acceleration for Faster Switching
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Solution Overview
Problem
Existing RF series switches face a tradeoff between switching speed and RF performance due to the RC time constant, which cannot be easily reduced without degrading power losses and voltage division in high-stacked antenna tuning switches.
Innovation Solution
The implementation of a shunt-series switch arrangement with a switching time acceleration circuit, which includes a positive and negative acceleration path input, allows for the establishment of a conductive path during switching transients and OFF-state operations, and breaks the conductive path during ON-state operations, thereby accelerating switching times without compromising RF performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the RC time constant is reduced to decrease switching time, then switching speed is improved, but power losses increase and voltage division is distorted
Solution Approach 1:
The acceleration control circuit proactively charges the gate-source capacitance before the main switching event occurs. By pre-charging the capacitance through a dedicated acceleration path, the switch is prepared to transition faster when the main control signal is applied, reducing the effective switching time without requiring a reduction in the RC time constant of the biasing network.
Solution Approach 2:
The gate control is divided into two independent paths: a main control path through the high-ohmic biasing resistor that maintains proper DC biasing and voltage division, and a separate acceleration path that provides additional charge to the gate capacitance during switching transients. This segmentation allows each path to be optimized for its specific function without compromising the other.
2Stability of the object's composition
If the gate-source capacitance is increased to keep drains/sources well-defined, then switching stability is improved, but switching time increases due to larger RC time constant
Solution Approach 1:
The acceleration control circuit acts as an intermediary that provides additional charge to the gate-source capacitance during switching transitions. This intermediary path compensates for the larger capacitance value by supplying extra charge quickly, enabling fast switching despite the increased capacitance that provides stability during RF operation.
Data Source
AI summary
An RF switch arrangement includes a shunt switch having a first RF terminal, a second RF terminal coupled to ground, a main control input, and an acceleration control input; a series switch having a first RF terminal coupled to the first RF terminal of the shunt switch, a second RF terminal, a main control input, and an acceleration control input; and a switching time acceleration circuit having a positive acceleration path input, a negative acceleration path input, and a first output coupled to the main control input of the series switch.