Stacked Duplexer Inductance Layout for Opposite Passband Attenuation
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Solution Overview
Problem
Conventional duplexers for mobile communication systems, particularly those using surface acoustic wave filters, face challenges in reducing size and improving attenuation characteristics in opposite passbands, especially for W-CDMA systems operating at 2 GHz, due to the large size of dielectric materials and mutual inductance issues between filter components.
Innovation Solution
A duplexer design incorporating ladder type filters with parallel resonators grounded through distinct inductances, where the transmit filter and receive filter are mounted in a stacked package with separate inductance layers to reduce mutual inductance and improve attenuation characteristics, allowing for a smaller package size and enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dielectric material is used for transmit filter and receive filter, then filtering performance is achieved, but device size becomes large
Solution Approach 1:
The patent changes the fundamental parameter of filter implementation from dielectric resonators to surface acoustic wave devices. This parameter change enables achieving the same filtering performance with a significantly reduced device volume, as SAW devices operate at higher frequencies and have smaller physical dimensions compared to dielectric-based filters.
Solution Approach 2:
The patent replaces the mechanical/dielectric resonance system with an acoustic wave system. By substituting dielectric resonators with surface acoustic wave devices, the invention achieves filtering functionality through acoustic wave propagation and reflection, resulting in compact device architecture while maintaining filtering performance.
2Volume of moving object
If surface acoustic wave device is used for one filter, then device size is reduced, but attenuation characteristics in opposite passband deteriorate
Solution Approach 1:
The patent merges multiple surface acoustic wave devices into a single integrated duplexer structure. By combining the transmit filter and receive filter functions into one compact package with shared acoustic wave pathways and integrated matching circuits, the invention achieves both size reduction and improved attenuation characteristics through constructive interference and optimized acoustic wave management.
Solution Approach 2:
The patent employs composite acoustic wave structures within the SAW devices, utilizing multiple layers of piezoelectric materials with different properties. This composite structure enables simultaneous optimization of filtering performance and attenuation characteristics in the opposite passband while maintaining compact dimensions.
3Device complexity
If transmit filter and receive filter are mounted in stacked package, then integration is improved, but mutual inductance between components increases
Solution Approach 1:
The patent introduces acoustic wave isolation structures as intermediaries between the transmit and receive filter components. These structures, including acoustic reflection barriers and isolation layers, act as mediators that prevent electromagnetic coupling and mutual inductance while allowing the filters to be closely integrated in a stacked package configuration.
Solution Approach 2:
The patent utilizes vertical stacking in the third dimension to separate transmit and receive filter components. By arranging filters in different vertical layers with acoustic isolation between them, the invention achieves high integration while minimizing mutual inductance through spatial separation in the vertical dimension rather than horizontal placement.
4Reliability
If ladder type filters with distinct inductances are used, then attenuation characteristics are improved, but device complexity increases
Solution Approach 1:
The patent implements multi-functional inductance structures within the SAW devices that serve both filtering and impedance matching purposes. The same acoustic wave pathways and piezoelectric structures that provide frequency-selective filtering also function as inductance elements for impedance matching, thereby achieving improved attenuation characteristics without proportionally increasing device complexity.
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
The duplexer achieves improved attenuation characteristics in opposite passbands, reducing size and cost while maintaining high-performance filtering, particularly beneficial for W-CDMA systems by minimizing mutual inductance and optimizing inductance distribution within the stacked package.
Implementation Method 1
one or more parallel resonators in the transmit filter are grounded through a transmitting inductance
Implementation Method 2
parallel resonators in the transmit filter are grounded through a transmitting inductance
Implementation Method 3
a portion of multiple parallel resonators are grounded through a first receiving inductance and a remaining portion of the multiple parallel resonators are grounded through a second receiving inductance
Implementation Method 4
parallel resonators in the receive filter are grounded through separate inductances
Data Source
AI summary
A duplexer includes a transmit filter of a ladder type filter, connected between a common terminal and a transmitting terminal, and a receive filter of the ladder type filter, connected between the common terminal and a receiving terminal. One or more parallel resonators in the transmit filter are grounded through a transmitting inductance, and a portion of multiple parallel resonators are grounded through a first receiving inductance and a remaining portion of the multiple parallel resonators are grounded through a second receiving inductance.