RF Switch Shunt Path Impedance Matching Against Signal Reflection
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Solution Overview
Problem
RF switches in existing technologies reflect RF signals when turned off, leading to damage to the signal source and abnormal operation.
Innovation Solution
A radio frequency switch with a shunt path comprising stacked transistors that provide impedance matching when turned off, preventing signal reflection by equating the equivalent resistance to the load resistance, thereby protecting the signal source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the RF switch is turned off to block RF signals, then the signal transmission is blocked, but signal reflection occurs causing damage to the signal source
Solution Approach 1:
The patent introduces a shunt path as an intermediary component connected to the switch node. This shunt path includes impedance matching components (resistors and capacitors) that act as a mediator to absorb and dissipate reflected RF signals safely to ground, preventing them from damaging the signal source while maintaining the switch's primary function
2Reliability
If a shunt path is added to prevent signal reflection, then signal source protection is improved, but circuit area increases
Solution Approach 1:
The patent optimizes the impedance values and component parameters of the shunt path to achieve effective signal reflection prevention with minimized component sizes. By carefully selecting resistance and capacitance values that match the RF signal characteristics, the circuit achieves protection functionality while keeping the physical footprint small
3Reliability
If impedance matching is implemented to prevent signal reflection, then signal source protection is improved, but device complexity increases
Solution Approach 1:
The patent implements preliminary impedance matching design in the shunt path configuration. The impedance matching components are pre-configured with specific values that automatically match the RF signal impedance characteristics, eliminating the need for complex dynamic adjustment mechanisms and reducing overall device complexity while maintaining effective protection
Data Source
AI summary
A radio frequency switch includes a signal terminal, a reference voltage terminal, and a shunt switch path. The shunt switch path includes a first transistor and a second transistor. The first transistor includes a first terminal coupled to the signal terminal, a second terminal, and a control terminal. The second transistor includes a first terminal coupled to the second terminal of the first transistor, a second terminal coupled to the reference terminal, and a control terminal. When the shunt switch path is switched to a first state, the shunt switch path has a first impedance. When the shunt switch path is switched to a second state, the shunt switch path has a second impedance, the first impedance and the second impedance being different. The first impedance is between 40 ohms to 85 ohms.