RF Filter Switch Stack Layout for Low Loss and Power Resistance
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Solution Overview
Problem
Conventional radio-frequency filters face challenges in improving power resistance while reducing insertion loss and size, particularly in multi-band systems, where scaling down the switch and maintaining low loss are conflicting requirements.
Innovation Solution
The design incorporates a series-arm circuit configuration with multiple switch elements, where the first switch element near the input terminal has a higher stack number and gate width than the second switch element near the output terminal, allowing for increased withstand voltage and current while reducing resistance and insertion loss, and includes additional series-arm and parallel-arm circuits for fine-tuned frequency adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the switch size is scaled down to reduce filter size, then the filter size is reduced, but the electric power resistance and insertion loss performance deteriorate
Solution Approach 1:
The patent applies local quality by differentiating the switch element configurations at different locations within the filter. The first switch element near the input terminal uses a first configuration optimized for withstanding high voltage, while the second switch element near the output terminal uses a second configuration optimized for low resistance. This localized optimization allows the filter to achieve both compact size and high electric power resistance without uniform scaling of all components.
2Volume of moving object
If the switch size is scaled down to reduce filter size, then the filter size is reduced, but the insertion loss within passband increases
Solution Approach 1:
The patent implements local quality by positioning switch elements with different configurations at specific locations. The second switch element closer to the output terminal uses a configuration with lower resistance characteristics, which directly reduces insertion loss in the passband. Meanwhile, the first switch element handles voltage withstand requirements, allowing the overall filter to be compact without sacrificing low-loss performance.
3Reliability
If the stack number of switch elements is increased to improve voltage withstand capability, then the electric power resistance is improved, but the resistance when conducting increases and insertion loss worsens
Solution Approach 1:
The patent applies segmentation by dividing the switching function into two separate switch elements with different configurations. The first switch element is designed with higher stack number for voltage withstand, while the second switch element is designed with lower stack number for low resistance. This segmentation allows each switch element to be optimized for its specific function, resolving the trade-off between voltage withstand capability and conduction resistance.
Solution Approach 2:
The patent implements local quality by placing switch elements with different stack numbers at different locations in the circuit. The first switch element with higher stack number is positioned where voltage withstand is critical, while the second switch element with lower stack number is positioned where low resistance is critical. This localized differentiation optimizes both voltage handling and loss performance.
Data Source
AI summary
A radio-frequency filter includes a first series-arm circuit and a second series-arm circuit that is on a circuit path closer to the output terminal than the first series-arm circuit. A first parallel-arm circuit is connected to a ground and a node on the path between the first series-arm circuit and the second series-arm circuit. The first series-arm circuit includes a first series-arm resonator, and a first switch element, the first switch element including first semiconductor elements arranged in series. The second series-arm circuit includes a second series-arm resonator, and a second switch element, the second switch element including at least one second semiconductor element. A first stack number being higher than a second stack number, the first stack number being a number of the first semiconductor elements and the second stack number being a number of the one or more second semiconductor elements.