RF Transistor Stack Capacitor Balancing for Off-State Voltage Sharing
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Solution Overview
Problem
Conventional RF switches with stacks of field effect transistors (FETs) face issues with non-uniform RF voltage distribution, leading to low power handling capability and high off-state leakage currents, resulting in signal losses.
Innovation Solution
Incorporating a capacitor network across multiple transistors in the stack to balance RF voltages, reducing off-state leakage currents and enhancing the switch's ability to handle high power signals with minimal signal loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional FET stacks are used in RF switches, then the power handling capability is improved, but non-uniform RF voltage distribution causes high off-state leakage currents and signal losses
Solution Approach 1:
The patent introduces capacitor networks that modify the electrical parameters of the FET stack by adding capacitive elements in parallel with individual FETs. This changes the voltage distribution characteristics across the stack, balancing the RF voltage across each FET to reduce off-state leakage currents while maintaining high power handling capability.
Solution Approach 2:
Capacitor networks are introduced as intermediary elements between the FETs in the stack. These capacitors act as mediators that redistribute the RF voltage across the FETs, preventing non-uniform voltage distribution and the associated leakage currents without requiring changes to the FETs themselves.
2Power
If FET stacks are used to achieve higher power handling capability, then power handling is improved, but non-uniform RF voltage distribution across FETs reduces the effective power handling capability
Solution Approach 1:
The capacitor networks modify the electrical parameters of the FET stack by introducing capacitive reactance in parallel with each FET. This changes the impedance characteristics and voltage distribution across the stack, ensuring more uniform voltage sharing and maximizing the effective power handling capability of the entire stack.
Solution Approach 2:
The capacitor networks work to create equipotential conditions across the FETs in the stack by balancing the voltage distribution. This ensures that each FET operates at similar voltage levels, preventing any single FET from being over-stressed and thereby improving the overall reliability and effective power handling capability.
3Reliability
If conventional balancing techniques are used, then RF voltage distribution is improved, but off-state leakage currents increase leading to signal losses
Solution Approach 1:
The patent employs capacitor networks that specifically target the capacitive reactance parameter to achieve voltage balancing. By carefully selecting capacitor values, the system achieves uniform voltage distribution across FETs while maintaining low off-state leakage currents, thereby avoiding signal losses that would result from conventional resistive balancing techniques.
Solution Approach 2:
The patent replaces conventional resistive balancing mechanisms with capacitive balancing mechanisms. This substitution eliminates the need for resistive elements that would generate heat and cause signal losses, while achieving the same voltage balancing effect through reactive capacitive elements that do not dissipate power.
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 capacitor network balances RF voltages across the transistors, improving the RF switch's power handling capability while maintaining low off-state leakage currents, thereby reducing signal losses.
Implementation Method 1
a capacitor network coupled between terminals of the transistors, wherein the capacitor network balances AC voltages across the transistors
Data Source
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AI summary
A switch circuit includes a transistor stack coupled between first and second ports. The transistor stack includes a group of multiple, adjacent, series-coupled transistors, and at least one additional transistor coupled in series with the group between the first and second ports to provide a first variably-conductive path between the first and second ports. The switch circuit also includes a balancing capacitor with a first terminal coupled to an input of the group of multiple, adjacent, series-coupled transistors, and a second terminal coupled to an output of the group of multiple, adjacent, series-coupled transistors.