Single Pole Multi Throw Switch Parasitic Capacitance Matching
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Solution Overview
Problem
Single pole N-throw RF switches face issues with high insertion loss due to on-resistance and parasitic capacitance, and often require a large number of discrete elements or external components for impedance matching.
Innovation Solution
A single pole multi throw switch design featuring two switching units and a matching unit, where the parasitic off-state capacitance of one switching unit is used for impedance matching, reducing the need for external components and improving impedance matching by configuring the matching unit to contribute with the capacitance when the other switching unit is inactive.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the size of shunts is increased to reduce resistance, then insertion loss is reduced, but device complexity increases
Solution Approach 1:
The patent converts the harmful parasitic capacitance of the inactive switching unit into a beneficial matching element. The parasitic capacitance is intentionally utilized as part of the impedance matching network, eliminating the need for separate matching components and reducing overall device complexity while maintaining low insertion loss.
Solution Approach 2:
The parasitic capacitance of the inactive switching unit serves dual purposes: it maintains port isolation while simultaneously functioning as part of the impedance matching network. This multi-functionality reduces the number of discrete components needed in the circuit.
2Manufacturing precision
If external LC matching networks are added to match parasitic capacitance, then impedance matching is improved, but device complexity increases
Solution Approach 1:
The inactive switching unit's parasitic capacitance serves itself by functioning as part of the matching network. This self-service approach eliminates the need for external matching components, reducing device complexity while maintaining impedance matching performance.
Solution Approach 2:
The parasitic capacitance performs multiple functions: maintaining port isolation when the switching unit is inactive and providing impedance matching. This multi-functionality eliminates the need for separate matching networks and reduces overall device complexity.
3Reliability
If multiple discrete elements are used for ESD protection and frequency band compensation, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple functions (ESD protection, frequency band compensation, impedance matching, and port isolation) into a unified circuit architecture. The matching unit and parasitic capacitance work together to provide multiple benefits simultaneously, reducing the number of discrete elements while maintaining reliability.
4Reliability
If the number of shunts is increased to improve port to port isolation, then isolation is improved, but insertion loss increases
Solution Approach 1:
The parasitic capacitance of the inactive switching unit, which would normally degrade isolation, is converted into a beneficial element by using it as part of the matching network. This approach maintains port isolation without requiring additional shunts that would increase insertion loss.
Data Source
AI summary
A single pole multi throw switch comprises a first switching unit, a second switching unit coupled to a common port and comprising a parasitic off state capacitance, and a matching unit. The matching unit may be coupled between the first switching unit and the common port, wherein the matching unit is configured to contribute, in conjunction with the parasitic off state capacitance of the second switching unit, to an impedance match if the first switching unit is active and the second switching unit is inactive.