Monolithic FBAR Duplexer Layout for Signal Isolation
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Solution Overview
Problem
Existing duplexer designs for FDD communication systems are bulky and suffer from signal interference due to separate components and wire bonding, which is unsuitable for small-sized, high-performance devices like mobile phones.
Innovation Solution
A monolithic duplexer is fabricated with transmitting and receiving filters formed on a single substrate, integrated with a phase shifter on a packaging substrate to prevent signal interference, using a 90-degree phase difference LC parallel circuit and connection electrodes to reduce size and signal loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If separate elements are formed, packaged and combined into one using wire bonding method, then the duplexer can be fabricated with traditional processes, but the size becomes larger and signal loss occurs due to parasitic components
Solution Approach 1:
The patent merges the filters and phase shifter into a single integrated structure formed on one substrate. The phase shifter is formed in a groove of the substrate while filters are formed on the surface, eliminating the need for separate packaging and wire bonding. This integration directly reduces the overall size and eliminates parasitic components from wire connections.
Solution Approach 2:
The phase shifter is formed within a groove etched into the substrate, creating a nested structure where the phase shifter is embedded within the substrate volume rather than occupying external space. This nesting approach reduces the overall footprint of the duplexer while maintaining all necessary functional elements.
2Ease of manufacture
If separate elements are connected by wire bonding method, then traditional fabrication can be used, but signal loss occurs due to parasitic components in wire parts
Solution Approach 1:
The patent combines all signal paths into a single integrated structure where filters and phase shifter are directly connected through the substrate. This eliminates wire bonds entirely, removing the parasitic inductance and resistance that cause signal loss in traditional wire-bonded designs.
Solution Approach 2:
The patent replaces the mechanical wire bonding system with an integrated planar structure where electrical connections are made through conductive traces and direct substrate integration. This substitution eliminates the mechanical wire components that introduce parasitic effects and signal loss.
3Volume of moving object
If filters are formed on a single substrate with integrated phase shifter, then size is reduced and signal interference is prevented, but fabrication process becomes more complex
Solution Approach 1:
The patent segments the substrate into distinct functional regions: a groove area for the phase shifter and surface areas for the filters. This segmentation allows each component to be optimized independently while maintaining overall integration, reducing fabrication complexity compared to fully monolithic designs.
Solution Approach 2:
The patent utilizes the third dimension by etching a groove into the substrate to accommodate the phase shifter, while filters are formed on the two-dimensional surface. This dimensional approach allows integration of multiple components without increasing planar footprint, managing complexity through spatial organization.
4Reliability
If phase shifter is formed on packaging substrate to prevent signal interference, then filtering performance is improved, but overall structure becomes more complex
Solution Approach 1:
The patent merges the phase shifter with the substrate structure itself by forming it in a groove, rather than placing it on a separate packaging substrate. This integration maintains the signal interference prevention function while eliminating the additional packaging layer, thereby reducing structural complexity.
Solution Approach 2:
The phase shifter is nested within the substrate groove, utilizing the substrate's own structure to house the interference-prevention component. This nesting eliminates the need for a separate packaging substrate, reducing overall structural complexity while maintaining the phase shifting function for signal isolation.
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 solution results in a compact, high-performance duplexer with reduced signal interference and size, suitable for small-sized devices by integrating filters and phase shifters on a single substrate, eliminating the need for wire bonding and minimizing signal loss.
Implementation Method 1
The phase shifter is typically implemented by a combination of a capacitor and an inductor that generates a frequency phase difference between the transmitted signal and the received signal of 90 degrees to prevent the mutual influence exerted between them.
Implementation Method 2
a resonator and a trimming inductor formed on a substrate
Implementation Method 3
a resonator and a trimming inductor formed on a substrate
Data Source
AI summary
A method for fabricating subminiature, high-performance monolithic duplexer is disclosed. The method comprises depositing and patterning a lower electrode on an upper surface of an insulation layer on a substrate, so as to expose a first part of the insulation layer; depositing a piezoelectric layer on an upper surface of the exposed insulation layer and the lower electrode; depositing a metal on the upper part of the piezoelectric layer and patterning the metal to form a resonance part and a trimming inductor, wherein the lower electrode electrically couples the resonance part and the trimming inductor; fabricating air gap type FBARs (film bulk acoustic resonances) by forming a cavity by etching the substrate under the resonance part; and bonding a packaging substrate on the substrate, the packaging substrate having a phase shifting part which substantially prevents inflow of signal between the air gap type FBARs.