Piezoelectric Filter Element Layout for Power Handling and Low IMD
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Solution Overview
Problem
Existing filter structures using acoustic wave resonators face challenges in improving electric power handling capability and IMD characteristics, as described in Japanese Unexamined Patent Application Publication No. 2007-267405.
Innovation Solution
The filter element and device incorporate a piezoelectric layer with a polarization axis direction and a series-parallel division of acoustic wave resonators, featuring specific electrode orientations and relationships to enhance electric power handling and IMD characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a BAW resonator is divided in series to increase electric power handling capability, then the electric power handling capability is improved, but the IMD characteristics are not sufficiently improved
Solution Approach 1:
The acoustic wave resonator is divided into multiple division resonators (at least four) that are connected in series and parallel combinations. This segmentation allows the electric power to be distributed across multiple resonators, increasing the overall electric power handling capability while maintaining individual resonator performance within optimal ranges.
Solution Approach 2:
The invention introduces asymmetric electrode orientation relationships among the division resonators. Specifically, division resonators are configured with forward direction relationships and opposite direction relationships relative to the polarization axis direction. By balancing the number of division resonators with forward direction relationships against those with opposite direction relationships, IMD components are canceled out, thereby improving IMD characteristics beyond what simple series division achieves.
2Object-generated harmful factors
If division resonators are configured with specific electrode orientations to cancel IMD components, then IMD characteristics are improved, but the structural complexity increases
Solution Approach 1:
Each division resonator is configured with specific local electrode orientation characteristics relative to the polarization axis direction. Some division resonators have forward direction relationships while others have opposite direction relationships. This local differentiation in electrode orientation creates the necessary conditions for IMD cancellation while maintaining a relatively simple overall structure that can be manufactured using standard processes.
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 improves electric power handling capability and IMD characteristics without increasing ripple in the pass band, by balancing resonant frequencies and canceling out IMD components through strategic electrode orientations.
Implementation Method 1
a piezoelectric layer with a polarization axis direction, and a plurality of division resonators including at least four division resonators provided at the piezoelectric layer
Data Source
AI summary
A filter element includes a piezoelectric layer with a polarization axis direction, and division resonators provided at the piezoelectric layer. Each of the division resonators includes a functional electrode on the piezoelectric layer. Each of the functional electrodes includes high and low potential electrodes. When a direction parallel or substantially parallel to a direction in which the high and low potential electrodes face each other and oriented from the high-potential electrode toward the low-potential electrode is an inter-electrode direction, and a number of division resonators having the forward direction relationship is equal to a number of division resonators having the opposite direction relationship.