BAW Filter Anti-Series Resonator Layout for H2 Suppression
Find Innovative SolutionsGenerate Solutions
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
1Reliability
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 connected in anti-series configuration. This segmentation creates multiple resonating elements that work together to suppress second harmonic emissions while maintaining the filtering function, directly addressing the contradiction between reliable filtering and harmful harmonic generation.
Solution Approach 2:
The patent employs anti-series connection configuration where resonators are connected with reversed polarity. This asymmetric arrangement causes the second harmonic emissions from individual resonators to cancel each other out, while the fundamental filtering function is preserved through the combined resonant response.
2Object-generated harmful factors
If anti-series BAW resonator configuration is used to suppress H2 emissions, then second harmonic rejection is improved, but parasitic capacitance mismatch occurs between resonators
Solution Approach 1:
The patent introduces a balancing capacitor as an intermediary element connected to the anti-series BAW resonators. This capacitor compensates for parasitic capacitance mismatches between the resonators, ensuring that the anti-series configuration functions optimally for H2 suppression without being degraded by manufacturing variations in parasitic capacitance.
Solution Approach 2:
The patent adjusts the capacitance value of the balancing capacitor to match and compensate for the parasitic capacitance differences between resonators. By changing the electrical parameter (capacitance) of the balancing capacitor, the overall parasitic capacitance balance is achieved, enabling effective H2 suppression despite manufacturing tolerances.
3Object-generated harmful factors
If multiple BAW resonators are arranged in anti-series pairs with reverse polarization, then H2 suppression is enhanced, but device complexity increases
Solution Approach 1:
The patent merges multiple BAW resonators into an anti-series pair configuration with reverse polarization. By combining these resonators in a specific topological arrangement, the patent achieves enhanced H2 suppression through constructive and destructive interference of harmonic emissions, while the merged structure shares common electrodes to reduce overall device complexity.
Solution Approach 2:
The anti-series BAW resonator configuration serves multiple functions simultaneously: it provides the primary radio frequency filtering function while also suppressing second harmonic emissions. The reverse polarization arrangement enables both functions to be achieved with a single resonator structure, avoiding the need for separate suppression circuits and reducing overall device complexity.
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 bulk acoustic wave resonator, a second bulk acoustic wave resonator in anti-parallel with the first bulk acoustic wave resonator, and a passive impedance element in series with the first bulk acoustic wave resonator. The passive impedance element can reduce an imbalance in resonant frequency between the first and second bulk acoustic wave resonators. 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.