RF Switch Voltage Equalization Using Progressive Gate Resistors
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Solution Overview
Problem
Radio-frequency (RF) switches with stacked field-effect transistors (FETs) face challenges in evenly distributing input voltage across multiple FETs, leading to increased insertion loss and vulnerability to electrostatic discharge due to the use of passive elements like capacitors for voltage equalization.
Innovation Solution
A radio-frequency switch design incorporating a series of FETs with progressively increasing gate and body resistor values, arranged in a series-shunt configuration, to ensure uniform voltage distribution and reduce electrostatic discharge risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If passive elements (capacitors or resistors) are connected between bodies of stacked FETs to evenly distribute input voltage, then voltage distribution is improved, but device complexity increases and electrostatic discharge vulnerability increases
Solution Approach 1:
The patent removes the capacitor elements from the voltage equalization circuit, keeping only the resistor elements. This extraction eliminates the electrostatic discharge vulnerability associated with capacitors while maintaining the voltage distribution function through the resistor network connected to gate and body terminals of stacked FETs
Solution Approach 2:
The patent uses simple resistor elements instead of complex capacitor-resistor combinations. Resistors are more robust, simpler to manufacture, and do not store energy that could be damaged by electrostatic discharge, making them a more reliable choice for voltage equalization in stacked FET configurations
2Power
If the number of stacked FETs is increased to handle high power, then power handling capability is improved, but insertion loss increases
Solution Approach 1:
The patent optimizes the resistance values in the voltage equalization network to achieve uniform voltage distribution across stacked FETs. By carefully selecting resistor values, the system maintains efficient power handling while minimizing voltage drops that would cause insertion loss, thus optimizing the trade-off between power capability and signal loss
3Loss of energy
If a single FET with high breakdown voltage is used to reduce insertion loss, then insertion loss is improved, but isolation performance deteriorates due to large parasitic capacitance
Solution Approach 1:
The patent divides the single high-voltage FET into multiple stacked FETs with lower individual breakdown voltages. This segmentation reduces the parasitic capacitance of each individual FET, thereby improving isolation performance while maintaining the overall high voltage handling capability through the series connection and voltage equalization network
4Manufacturing precision
If gate resistors are added to evenly distribute voltage across shunt FETs, then voltage distribution is improved, but device complexity increases
Solution Approach 1:
The patent applies gate resistors specifically to the shunt FETs in the stacked configuration where voltage distribution needs equalization. By placing resistors only where necessary (at gate terminals of specific FETs) rather than throughout the entire circuit, the solution achieves uniform voltage distribution with minimal additional complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed design effectively distributes voltage across FETs, reducing insertion loss and enhancing the RF switch's isolation while minimizing the risk of electrostatic discharge, thereby improving the overall performance and reliability of the RF switch.
Implementation Method 1
a first shunt gate resistor circuit including a plurality of gate resistors respectively connected to gates of the plurality of shunt FETs of the first shunt switch, wherein respective resistance values of the plurality of gate resistors of the first shunt gate resistor circuit successively increase
Data Source
AI summary
A radio-frequency switch includes a first series switch including a plurality of series field-effect transistors (FETs) connected in series between a first terminal and a second terminal, a first shunt switch including a plurality of shunt FETs connected in series between the first terminal and a first ground terminal, and a first shunt gate resistor circuit including a plurality of gate resistors respectively connected to gates of the plurality of shunt FETs of the first shunt switch. Respective resistance values of the plurality of gate resistors of the first shunt gate resistor circuit successively increase in a direction away from the first ground terminal toward the first terminal.