Stacked RF Switch Voltage Sensing for Equal Cell Distribution
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Solution Overview
Problem
RF switches with stacked transistors experience unequal voltage distribution due to parasitic elements, leading to degraded linearity and performance, particularly in high voltage applications like antenna switches, where each transistor should ideally share an equal fraction of the high voltage for optimal operation.
Innovation Solution
An RF switch and method that embeds a voltage sensing circuit within the stacked transistors to measure internal voltages across each transistor, allowing for a DC readout of the RF voltage swing without affecting the switch's operation, and providing insights into voltage distribution for improved linearity and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multiple RF cells are coupled together to handle high voltage, then the voltage breakdown limit is exceeded, but unequal voltage distribution occurs due to parasitic elements
Solution Approach 1:
The patent divides the high voltage handling into multiple stacked RF cells, where each cell handles a portion of the total voltage. This segmentation allows the system to withstand high voltages that exceed the breakdown limit of a single transistor while distributing the voltage across multiple lower-voltage components.
Solution Approach 2:
The patent incorporates voltage sensing circuits that measure the actual voltage across each RF cell and provide feedback information. This feedback enables detection of unequal voltage distribution caused by parasitic elements, allowing for system adjustment or compensation to improve voltage distribution uniformity.
2Manufacturing precision
If voltage sensing circuits are added to measure internal voltages, then voltage distribution uniformity can be improved, but device complexity increases
Solution Approach 1:
The voltage sensing circuits are integrated within the existing RF switch structure, nesting the measurement functionality inside the stacked transistor configuration. This allows voltage monitoring without adding external components, thereby reducing the increase in device complexity.
Solution Approach 2:
The sensing circuits serve multiple functions: they measure voltage for monitoring purposes, provide feedback for adjusting voltage distribution, and enable optimization of linearity and performance. This multi-functionality justifies the added complexity by delivering multiple benefits from a single addition.
Data Source
Figure 1~3(b)
Figure 4(a)~5(b)
Figure 6~7
AI summary
An RF switch includes series-coupled RF switch cells coupled between an RF input and ground, a transistor including a first current node coupled to a first load resistor, a second current node coupled to ground, and a control node coupled to an internal switch node, and a filter having an input coupled to the first current node of the first transistor and an output for providing a DC voltage corresponding to the RF power present at the internal switch node.