Composite Filter Layout Using LiNbO3 and LiTaO3 to Cut Insertion Loss
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Solution Overview
Problem
Existing composite filter devices in cellular phones face high insertion loss due to conductance components, and using LiNbO3 substrates to reduce loss is costly.
Innovation Solution
A composite filter device with a first filter using a rotated Y-cut LiNbO3 substrate and an IDT electrode made of dense metals, connected to multiple second filters with specific passbands that satisfy certain frequency conditions to reduce bulk wave emission and insertion loss, while utilizing LiTaO3 substrates for the second filters to lower costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If LiNbO3 substrates are used for all bandpass filters to reduce insertion loss, then insertion loss is reduced, but manufacturing cost increases
Solution Approach 1:
The patent applies different substrate materials to different filter positions based on their specific requirements. The first bandpass filter uses LiNbO3 substrate for low loss performance, while the second and third bandpass filters use LiTaO3 substrates. This local differentiation optimizes overall system performance while controlling costs by not uniformly applying the expensive material throughout.
Solution Approach 2:
The patent employs a composite material strategy by combining LiNbO3 and LiTaO3 substrates within the same multiplexer device. Each substrate type is selected for its specific properties: LiNbO3 for the first filter's low loss characteristics and LiTaO3 for the other filters' cost-effectiveness and adequate performance, creating a hybrid structure that balances performance and cost.
2Device complexity
If multiple bandpass filters share a common antenna terminal connection, then device integration is improved, but insertion loss increases due to conductance components
Solution Approach 1:
The patent changes the substrate material parameter of the first bandpass filter to LiNbO3, which has superior low-loss characteristics compared to conventional materials. This parameter change specifically targets and reduces the conductance component effects in the common connection path, thereby reducing insertion loss while maintaining the integrated multi-filter structure.
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 effectively reduces insertion loss and costs by optimizing the frequency bands of the second filters relative to the first filter's Rayleigh waves, minimizing bulk wave emission and maintaining low costs through the use of LiTaO3 substrates for the second filters.
Implementation Method 1
the first filter includes a piezoelectric substrate made of LiNbO3, an IDT electrode provided on the piezoelectric substrate
Implementation Method 2
the first filter generates a fundamental wave of Rayleigh waves
Data Source
AI summary
A composite filter device includes a first filter and a plurality of second filters with different passbands. End portions of the first filter and the plurality of second filters are connected to a common connection. The first filter includes a piezoelectric substrate made of LiNbO3, an IDT electrode provided on the piezoelectric substrate, and a dielectric layer provided on the piezoelectric substrate so as to cover the IDT electrode. The first filter utilizes a fundamental wave of Rayleigh waves. The passband of the first filter is arranged in a frequency band that is lower than any of the passbands of the plurality of second filters.