Duplexer Circular Metal Layer Isolation Design
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Solution Overview
Problem
In duplexers, further downsizing leads to unnecessary signal leakage from the transmission side to the reception side due to the circular metal layer on the wiring substrate, degrading transmission-reception isolation characteristics.
Innovation Solution
A duplexer design with a reception filter and transmission filter mounted on a single substrate, where a circular metal layer surrounds the electrodes and is electrically connected to the ground, ensuring the shortest distance between the metal layer and the reception electrode is larger than the metal layer's width, reducing electromagnetic coupling and improving isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the circular metal layer is formed on the upper surface of the wiring substrate to fix sealing solder, then the acoustic wave filter is sealed and fixed, but a leakage electric field is generated that degrades transmission-reception isolation characteristics
Solution Approach 1:
An insulating layer is introduced between the circular metal layer and the acoustic wave filter to act as an intermediary that blocks the leakage electric field while maintaining the sealing function. This mediator prevents direct electromagnetic coupling between the metal layer and the filter, resolving the contradiction between sealing effectiveness and isolation characteristics.
Solution Approach 2:
The permittivity parameter of the insulating layer is specifically selected to be lower than that of the acoustic wave filter. By changing the electrical parameter (permittivity) of the intermediate material, the leakage electric field is suppressed while maintaining mechanical sealing, thus improving transmission-reception isolation characteristics without compromising sealing reliability.
2Volume of moving object
If further downsizing is performed in the duplexer, then the device size is reduced, but unnecessary signal leaks from transmission side to reception side through the circular metal layer, degrading transmission-reception isolation characteristics
Solution Approach 1:
The insulating layer serves as a mediator that prevents signal leakage through the circular metal layer even in downsized configurations. By placing this electromagnetic barrier between the metal layer and the acoustic wave filter, signal leakage is blocked while maintaining the compact form factor, thus resolving the contradiction between miniaturization and isolation performance.
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
This design enhances transmission-reception isolation characteristics by minimizing signal leakage, achieving better shielding effectiveness and maintaining high airtightness and reliability.
Implementation Method 1
a circular metal layer surrounding the reception electrode, the transmission electrode and the antenna electrode, and electrically connected to a ground
Data Source
AI summary
A duplexer includes: a reception filter connected between a reception terminal and an antenna terminal; a transmission filter connected between a transmission terminal and the antenna terminal; and a wiring substrate including the reception filter and the transmission filter on an upper surface, the reception terminal, the transmission terminal and the antenna terminal being formed on a lower surface, and a reception electrode electrically connected to the reception terminal, a transmission electrode electrically connected to the transmission terminal, an antenna electrode electrically connected to the antenna terminal, and a circular metal layer surrounding the reception, transmission and antenna electrodes, and electrically connected to a ground being formed on an upper surface, wherein a shortest distance between a side of the circular metal layer closest to the reception and transmission terminals and the reception electrode is larger than a width of the side of the circular metal layer.