RF Switch and Duplexer Layout to Cut Parasitic Capacitance
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Solution Overview
Problem
In existing radio frequency circuits, the increased number of switch terminals for connecting multiple filters leads to degraded pass characteristics due to parasitic capacitance from unconnected switch terminals.
Innovation Solution
A radio frequency module is designed with a specific configuration of switches and filters, where a first switch connects an antenna to filters for different communication bands, and a second switch connects these filters to additional filters, reducing the number of unconnected switch terminals and minimizing parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of filters for multiple communication bands is increased to enable simultaneous communication, then the communication capability is improved, but the number of switch terminals increases and parasitic capacitance degrades pass characteristics
Solution Approach 1:
The patent divides the filter connection system into two separate switches: a first switch connecting the antenna to first/second filters, and a second switch connecting third/fourth filters to the antenna. This segmentation allows each switch to have fewer terminals, reducing off-capacitance and improving pass characteristics while maintaining support for multiple communication bands through coordinated operation of both switches.
2Device complexity
If more filters are connected to a single switch to support multiple bands, then the device complexity is reduced, but the off-capacitance increases and degrades switch performance
Solution Approach 1:
Instead of using one switch with many terminals to connect all filters, the patent segments the switching function across two switches with fewer terminals each. The first switch handles antenna connections to first/second filters, while the second switch handles third/fourth filter connections, thereby reducing off-capacitance per switch and improving overall switch performance.
3Reliability
If the number of unconnected switch terminals is reduced to minimize parasitic capacitance, then the pass characteristics are improved, but the configuration complexity increases
Solution Approach 1:
The patent segments the filter connection architecture into two independent switching stages, where each switch connects the antenna to a subset of filters. This segmentation naturally reduces the number of unconnected terminals on each switch, minimizing parasitic capacitance and improving pass characteristics, while the modular configuration actually simplifies the overall design compared to a single complex switch.
Data Source
AI summary
A radio frequency circuit includes a switch that includes a terminal connected to an antenna connection terminal and terminals, a duplexer that is connected to the terminal and has a pass band including a communication band A, a duplexer that is connected to the terminal and has a pass band including a communication band B which is available for simultaneous communication with the communication band A, a switch that includes a terminal connected to the terminal and terminals, a duplexer that is connected to the terminal and has a pass band including a communication band C, and a transmit/receive filter that is connected to the terminal and has a pass band including a communication band D.