Ladder Duplexer Layout for Strong Coupling and Smaller SAW Filters
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Solution Overview
Problem
The miniaturization of duplexers with ladder elastic wave filters is hindered by the need for large spaces to accommodate electromagnetic coupling devices, which limits their application in compact devices like cellular phones.
Innovation Solution
The duplexer design includes an inductance component positioned outside the piezoelectric substrate, with specific orientations and spacings that enhance electromagnetic coupling between the inductance component and the transmitting-side shunt-arm resonator, improving isolation characteristics and allowing for miniaturization by eliminating the need for large inductance values and additional electronic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromagnetic coupling devices are provided within the piezoelectric substrate to achieve electromagnetic coupling with the antenna terminal, then electromagnetic coupling is achieved, but a large space is required in the piezoelectric substrate making miniaturization difficult
Solution Approach 1:
The electromagnetic coupling device is extracted from the piezoelectric substrate and placed on the module substrate. This separation removes the space constraint from the piezoelectric substrate, allowing miniaturization while maintaining electromagnetic coupling functionality through the inductance component positioned on the module substrate.
Solution Approach 2:
The electromagnetic coupling is achieved by moving from a planar layout within the piezoelectric substrate to a three-dimensional arrangement where the inductance component is positioned vertically above the transmitting-side shunt-arm resonator on the module substrate, utilizing the Z-axis dimension for coupling.
2Area of stationary object
If the inductance component is disposed outside the piezoelectric substrate to enable miniaturization, then miniaturization is achieved, but electromagnetic coupling strength may be reduced
Solution Approach 1:
The inductance component is specifically positioned to be adjacent to the transmitting-side shunt-arm resonator, creating a localized region of strong electromagnetic coupling. This targeted placement ensures strong coupling at the critical interface while allowing the overall device to be miniaturized.
Solution Approach 2:
The inductance component is pre-positioned on the module substrate in a location that optimizes electromagnetic coupling with the transmitting-side shunt-arm resonator before final assembly. This preliminary positioning ensures strong coupling is achieved without requiring additional space during operation.
3Reliability
If conventional electromagnetic coupling devices with multiple coiled patterns are used, then electromagnetic coupling is achieved, but device complexity and manufacturing complexity increase
Solution Approach 1:
The complex multi-pattern electromagnetic coupling device is replaced by a single inductance component positioned on the module substrate. This extraction simplifies the device structure while maintaining coupling functionality through the strategic placement adjacent to the transmitting-side shunt-arm resonator.
Solution Approach 2:
Instead of creating complex planar coiled patterns within the piezoelectric substrate, the solution inverts the approach by using a simple inductance component positioned vertically on the module substrate, achieving coupling through three-dimensional positioning rather than complex two-dimensional patterns.
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 configuration effectively improves isolation in the pass band of the receiving filter while enabling the miniaturization of the duplexer, maintaining performance without increasing the physical size of the module substrate.
Implementation Method 1
electromagnetic coupling between the inductance component and the transmitting-side shunt-arm resonator
Implementation Method 2
elastic wave resonator provided on the piezoelectric substrate
Data Source
AI summary
A duplexer includes elastic wave resonators disposed on a piezoelectric substrate to define a ladder elastic wave filter including shunt-arm resonators and series-arm resonators. The duplexer includes an inductance component connected between an antenna terminal and a ground potential. A transmitting filter includes the ladder elastic wave filter. The inductance component is disposed outside a short side of the piezoelectric substrate such that the electromagnetic coupling between the shunt-arm resonator located closest to a transmitting terminal in the ladder circuit configuration, and the inductance component is stronger than the electromagnetic coupling between the inductance component and the remaining shunt-arm resonators.