Acoustic Wave Filter Layout for High-Power H2 Suppression
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Solution Overview
Problem
Bulk acoustic wave (BAW) filters generate second harmonic emissions (H2) due to non-linearity at high power levels, which is undesirable and challenging to fully suppress with existing techniques.
Innovation Solution
The implementation of a bulk acoustic wave filter design that includes a pair of BAW resonators in anti-series with reverse electrode polarization and a balancing capacitor to compensate for parasitic capacitance mismatches, reducing H2 emissions by arranging anti-series pairs in parallel and using passive impedance elements to balance resonant frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If BAW resonators are used to filter radio frequency signals, then filtering function is achieved, but second harmonic emissions are generated at high power levels
Solution Approach 1:
The patent divides a single BAW resonator into multiple BAW resonators (at least two) and connects them in parallel. Each resonator processes a portion of the signal, which reduces the non-linear distortion and second harmonic emissions generated by individual resonators operating at high power levels.
Solution Approach 2:
The patent combines multiple BAW resonators in parallel configuration to achieve better linearity and reduce second harmonic emissions. The combined operation of multiple resonators provides improved filtering performance with reduced harmful emissions compared to a single resonator.
2Object-generated harmful factors
If multiple BAW resonators are connected in parallel to reduce H2 emissions, then second harmonic suppression is improved, but device complexity increases
Solution Approach 1:
The patent segments the filtering function across multiple resonators connected in parallel, where each resonator contributes to the overall filtering performance while collectively reducing second harmonic emissions. This segmentation approach achieves emission suppression without requiring complex circuit topologies.
Solution Approach 2:
The patent optimizes parameters such as the number of parallel resonators, their individual capacitances, and operating characteristics to achieve effective second harmonic suppression. By carefully selecting and tuning these parameters, the patent reduces emissions while maintaining reasonable device complexity.
3Ease of manufacture
If parasitic capacitance mismatch exists between resonators, then manufacturing tolerances are accommodated, but second harmonic suppression performance deteriorates
Solution Approach 1:
The patent addresses parasitic capacitance mismatch by introducing compensating capacitances or adjusting resonator parameters during design and manufacturing. This allows the system to accommodate normal manufacturing variations while maintaining effective second harmonic suppression performance.
Solution Approach 2:
The patent employs design approaches that account for and compensate parasitic capacitance effects, effectively creating a feedback mechanism where the system design anticipates and corrects for manufacturing variations. This ensures consistent second harmonic suppression across production batches.
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
This design achieves higher rejection of second harmonic emissions compared to previous methods, providing effective H2 suppression and improving filter linearity, especially in high-power applications.
Implementation Method 1
In BAW resonators, acoustic waves propagate in a bulk of a piezoelectric layer
Implementation Method 2
The capacitor is configured to compensate for a mismatch in parasitic capacitance between the first pair of bulk acoustic wave resonators and the second pair of bulk acoustic wave resonators
Data Source
AI summary
Aspects of this disclosure relate to acoustic wave filters with second harmonic emission suppression. In an embodiment, an acoustic wave filter includes a first pair of bulk acoustic wave resonators in anti-series with each other, a second pair of bulk acoustic wave resonators in anti-series with each other and having reverse electrode polarization relative to the first pair of bulk acoustic wave resonators, and a capacitor connected to a common electrode of a first bulk acoustic wave resonator and a second bulk acoustic wave resonator of the first pair of bulk acoustic wave resonators. Such an acoustic wave filter can provide second harmonic emission suppression. Other embodiments of acoustic wave filters with second harmonic emission suppression are disclosed. Related multiplexers, radio frequency modules, wireless communication devices, and methods are disclosed.