Acoustic Wave Duplexer IDT Duty Layout for Lower IMD
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Solution Overview
Problem
Acoustic wave duplexers and filters face challenges with intermodulation distortion (IMD) and miniaturization due to the nonlinear nature of acoustic wave filters, where existing solutions require additional capacitors to reduce IMD, complicating further miniaturization.
Innovation Solution
The design incorporates a piezoelectric substrate with series arm resonators, where the duty of the IDT electrode closest to the antenna terminal is minimized, and other resonators have varying duties and sizes to reduce IMD and facilitate miniaturization without additional capacitors, using a combination of series and parallel arm resonators and longitudinally coupled filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a capacitor is connected in parallel with the parallel arm resonator to increase resonant frequency and reduce IMD, then intermodulation distortion is suppressed, but device complexity increases due to additional capacitor configuration
Solution Approach 1:
The patent extracts the harmful capacitance effect from a separate capacitor component and integrates it directly into the parallel arm resonator structure. By forming the capacitance using the resonator's own electrode configuration and piezoelectric substrate properties, the design eliminates the need for discrete capacitor components while maintaining the IMD suppression function.
Solution Approach 2:
The patent merges the function of the parallel arm resonator with the capacitance element into a single integrated structure. The parallel arm resonator simultaneously performs resonance filtering and provides the necessary capacitive effect through its electrode arrangement and substrate properties, combining multiple functions into one component.
2Object-generated harmful factors
If additional capacitors are configured to reduce IMD, then intermodulation distortion is suppressed, but miniaturization becomes difficult due to increased component count
Solution Approach 1:
The patent extracts the capacitance function from external capacitor components and embeds it within the resonator structure itself. This integration removes the need for separate capacitor elements that would occupy additional space, enabling miniaturization while maintaining IMD suppression capabilities.
Solution Approach 2:
The patent nests the capacitance function within the parallel arm resonator structure. The电容ive effect is embedded in the resonator's electrode configuration and substrate integration, creating a nested functional arrangement where the resonator contains both resonance and capacitance functions, thereby reducing overall device volume.
3Object-generated harmful factors
If the resonant frequency of the parallel arm resonator is increased by adding capacitors, then return loss is reduced and IMD is suppressed, but manufacturing complexity increases
Solution Approach 1:
The patent extracts the capacitance requirement from external capacitor components and satisfies it through the resonator's inherent structure. By using the piezoelectric substrate and electrode arrangement to provide the necessary capacitance, the design simplifies manufacturing by reducing the number of discrete components that need to be assembled and configured.
Solution Approach 2:
The patent merges the resonator fabrication process with the capacitance formation into a single manufacturing workflow. The parallel arm resonator is fabricated using standard piezoelectric device processes, and the capacitance is simultaneously established through the electrode pattern and substrate properties, eliminating separate capacitor assembly steps.
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 approach significantly reduces IMD and allows for further miniaturization of acoustic wave devices and duplexers, maintaining filter steepness and reducing insertion loss, while eliminating the need for additional capacitors, thus simplifying manufacturing and enhancing performance for carrier aggregation applications.
Implementation Method 1
an acoustic wave device includes a piezoelectric substrate, an antenna terminal that is provided on the piezoelectric substrate
Implementation Method 2
a plurality of resonators that are provided on the piezoelectric substrate and that include an IDT electrode
Data Source
AI summary
An acoustic wave device includes an antenna terminal, a signal terminal, and a plurality of resonators that are provided on a piezoelectric substrate. The plurality of resonators include a plurality of series arm resonators on a series arm, and the duty of an IDT electrode of the series arm resonator closest to the antenna terminal among the plurality of series arm resonators is smaller than the duty of an IDT electrode of at least one series arm resonator among the other series arm resonators.