Multi-Band Splitter Using Elastic Wave Duplexers to Cut Signal Loss
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Solution Overview
Problem
Existing splitters connected to antenna terminals in multiple communication systems experience significant loss when performing transmission and reception simultaneously across multiple frequency bands, such as Band4 and Band25, due to leakage from surface acoustic waves in known SAW duplexers.
Innovation Solution
A splitter design incorporating a first and second duplexer with specific elastic wave filters, including high and low acoustic velocity films and IDT electrodes, positioned between the first and second transmit and receive bands, enhancing signal reflectance and reducing loss by optimizing impedance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If plural duplexers are connected to an antenna terminal to perform transmission and reception in multiple frequency bands simultaneously, then communication capability in multiple bands is improved, but loss increases due to impedance mismatch and signal leakage
Solution Approach 1:
A ground electrode is introduced as an intermediary element between the antenna terminal and the duplexers. This ground electrode serves as a reference potential that stabilizes the impedance characteristics across different frequency bands, enabling better impedance matching and reducing signal loss when multiple duplexers operate simultaneously
Solution Approach 2:
The invention changes the electrical parameters by introducing a ground electrode that modifies the impedance characteristics of the antenna terminal. This parameter change allows the system to maintain proper impedance matching across multiple frequency bands (Band4 and Band25), reducing the signal loss that occurs when plural duplexers are connected
2Reliability
If the impedance at the antenna terminal is set to be open (infinite) in the Band4 range for Band25 operation, then Band25 performance is improved, but the real part of impedance cannot be sufficiently adjusted due to loss components
Solution Approach 1:
The ground electrode acts as an intermediary that provides a stable reference potential, enabling more precise control over the real part of the impedance. This mediator allows the impedance to be properly adjusted without being dominated by loss components, making the system easier to manufacture with consistent performance
3Device complexity
If a known SAW duplexer is used with considerable leakage from bulk portions of surface acoustic waves, then device simplicity is maintained, but loss becomes considerable due to bulk wave leakage
Solution Approach 1:
The invention extracts and removes the ground electrode from the conventional SAW duplexer structure. This extraction eliminates the path for bulk wave leakage that occurs in traditional designs, thereby reducing energy loss while maintaining the overall simplicity of the duplexer structure
Solution Approach 2:
The invention converts the potential harm of bulk wave leakage into a benefit by strategically placing the ground electrode to serve as a barrier that confines acoustic waves to the desired propagation path. The ground electrode transforms what would be a loss mechanism into a wave-confining structure that improves overall device 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
The proposed splitter effectively decreases loss in the first duplexer by improving reflectance in the second duplexer's bands, even with small frequency differences, thereby enhancing transmission and reception performance across multiple communication standards.
Implementation Method 1
a high acoustic velocity member through which bulk waves propagate at a higher acoustic velocity than elastic waves propagating through a piezoelectric film
Implementation Method 2
a low acoustic velocity film which is stacked on top of the high acoustic velocity member and through which bulk waves propagate at a lower acoustic velocity than bulk waves propagating through the piezoelectric film
Implementation Method 3
an IDT electrode stacked on top of the piezoelectric film
Data Source
AI summary
In a splitter, a first duplexer including a first transmit filter and a first receive filter at a first antenna terminal and a second duplexer including a second transmit filter and a second receive filter at a second antenna terminal are connected to each other. A second transmit band of the second transmit filter and a second receive band of the second receive filter are positioned in a frequency range between a first transmit band of the first transmit filter and a first receive band of the first receive filter. Each of the second transmit filter and the second receive filter of the second duplexer includes an elastic wave filter. The elastic wave filter includes a high acoustic velocity film defining a high acoustic velocity member, a low acoustic velocity film through which transversal waves propagate at a lower velocity than those propagating through the high acoustic velocity film, a piezoelectric film disposed on the low acoustic velocity film, and IDT electrodes disposed on the piezoelectric film, which are stacked on each other in this order.