Acoustic Wave Duplexer Layout for Lower IMD Without Capacitors
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Solution Overview
Problem
Existing acoustic wave duplexers and filters face challenges with intermodulation distortion (IMD) and miniaturization, as they often require additional capacitors to adjust resonant frequencies, which complicates manufacturing and limits size reduction.
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, eliminating the need for additional capacitors.
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, then IMD is suppressed, but device complexity and size increase
Solution Approach 1:
The patent extracts and eliminates the capacitor component from the circuit configuration. Instead of adding a capacitor in parallel with the resonator to adjust resonant frequency, the invention uses a simplified series arm resonator configuration where the resonant frequency is determined by the series resonators themselves, removing the need for additional capacitive components and reducing overall device complexity.
Solution Approach 2:
The series arm resonators serve multiple functions simultaneously: they provide frequency selection, impedance matching, and resonant frequency adjustment without requiring separate capacitive components. The IDT electrode duty cycle modification enables the resonators to perform both filtering and frequency tuning functions that were previously required separate components.
2Object-generated harmful factors
If a capacitor is connected in parallel with the parallel arm resonator to increase resonant frequency, then IMD is suppressed, but device size increases
Solution Approach 1:
The patent removes the capacitor component entirely from the design, eliminating the space it would occupy. The resonant frequency adjustment is achieved through modifications to the series arm resonators' IDT electrodes rather than adding external capacitive elements, thereby reducing the overall device footprint.
Solution Approach 2:
The frequency adjustment function previously requiring a separate capacitor is merged into the series arm resonator structure itself. By modifying the IDT electrode duty cycle of the series resonators, the resonant frequency is adjusted without requiring additional discrete components, achieving compact integration.
3Object-generated harmful factors
If additional capacitors are configured to adjust resonant frequency, then IMD is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent eliminates the need for capacitor assembly and configuration from the manufacturing process. By using series arm resonators with modified IDT electrode duty cycles to achieve the desired resonant frequency adjustment, the invention removes the step of configuring and assembling additional capacitive components, simplifying manufacturing.
Solution Approach 2:
The invention changes the physical parameter of the IDT electrode duty cycle during fabrication to achieve resonant frequency adjustment. This parameter change is integrated into the standard photolithography and electrode deposition processes, avoiding the need for separate capacitor assembly and configuration steps that would complicate manufacturing.
4Object-generated harmful factors
If IDT electrode duty of series arm resonator closest to antenna terminal is reduced, then IMD is suppressed, but resonant frequency changes
Solution Approach 1:
The patent systematically changes the IDT electrode duty cycle parameter of the series arm resonators to achieve both IMD suppression and resonant frequency control. By carefully selecting and controlling the duty cycle values during fabrication, the invention simultaneously optimizes both the harmful factor suppression and frequency precision requirements.
Solution Approach 2:
The invention applies different IDT electrode duty cycle values to different series arm resonators based on their specific positions and functions in the circuit. The resonator closest to the antenna terminal has a reduced duty cycle for IMD suppression, while other resonators have duty cycles optimized for their respective frequency control requirements, achieving local optimization throughout the device.
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 occurrences and allows for further miniaturization of acoustic wave devices, maintaining filter steepness and reducing insertion loss, while simplifying the manufacturing process.
Implementation Method 1
an acoustic wave device includes a piezoelectric substrate, an antenna terminal that is provided on the piezoelectric substrate and that is electrically connected to an antenna
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.