Dual-IDT Acoustic Wave Resonator Layout for IMD Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Acoustic wave devices used in multiplexers experience degradation of receive sensitivity due to intermodulation distortion (IMD) caused by interference wave signals, particularly in specific communication bands like Band 25.
Innovation Solution
The acoustic wave device incorporates a piezoelectric substrate with a first and second interdigital transducer (IDT) electrode, where the second IDT electrode is designed to resonate at interference wave frequencies, and its busbars are configured to overlap with the first IDT electrode, with one busbar connected to signal potential and the other to ground, reducing IMD by canceling out interference signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional acoustic wave resonator with a single IDT electrode is used in filters of a multiplexer, then the device complexity is low, but intermodulation distortion (IMD) occurs in the receive band when interference wave signals are inputted from the antenna, resulting in degradation of receive sensitivity
Solution Approach 1:
The single IDT electrode is segmented into two separate IDT electrodes (first IDT electrode and second IDT electrode) with different resonant frequencies. The first IDT electrode operates at the communication band frequency while the second IDT electrode operates at the interference wave frequency, allowing independent optimization of each electrode's function to eliminate IMD while maintaining receive sensitivity.
Solution Approach 2:
Each IDT electrode is designed with specific local characteristics: the first IDT electrode has electrode fingers and busbars configured for the communication band, while the second IDT electrode has different electrode finger configurations optimized for the interference wave frequency. This local differentiation allows each electrode to perform its specific function without interfering with the other.
2Object-generated harmful factors
If additional elements are added to hinder interference waves, then intermodulation distortion is reduced, but the device complexity increases and insertion loss may increase
Solution Approach 1:
The acoustic wave resonator structure is made multi-functional by incorporating two IDT electrodes that simultaneously handle both the communication band signal and the interference wave signal. This eliminates the need for separate interference suppression elements, maintaining device simplicity while achieving both signal transmission and interference rejection functions.
Solution Approach 2:
The interference wave suppression function is merged into the main resonator structure by integrating the second IDT electrode directly into the acoustic wave resonator. This combines the signal processing and interference suppression functions into a single unified structure, avoiding additional separate elements and reducing overall device complexity.
3Object-generated harmful factors
If the busbars of the second IDT electrode are positioned to overlap with the first IDT electrode, then the intersecting area increases improving interference wave handling, but the area occupied by electrodes increases
Solution Approach 1:
The second IDT electrode is positioned in a different spatial arrangement relative to the first IDT electrode, with busbars that overlap in the planar view but are separated in the vertical dimension by the piezoelectric substrate thickness. This dimensional separation allows the electrodes to share the same footprint area while maintaining electrical independence and achieving the desired intersecting area for effective interference wave resonance.
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 configuration significantly reduces intermodulation distortion, thereby preventing degradation of receive sensitivity in multiplexers, as demonstrated by lower IMD3 levels compared to comparative examples, without the need for additional elements to hinder interference waves, maintaining design flexibility and avoiding increased insertion loss.
Implementation Method 1
a piezoelectric substrate including a piezoelectric layer
Implementation Method 2
an interdigital transducer (IDT) electrode on the piezoelectric substrate
Implementation Method 3
a pair of reflectors are disposed on both sides with respect to the IDT electrode in the propagation direction of acoustic wave
Data Source
AI summary
An acoustic wave device includes a piezoelectric substrate, a first interdigital transducer (IDT) electrode, reflectors on both sides of the first IDT electrode in a propagation direction of an acoustic wave, and a second IDT electrode facing the first IDT electrode with a reflector interposed therebetween. The first and second IDT electrodes include first and second intersecting areas in which electrode fingers overlap in the propagation direction. The first and second intersecting areas overlap in the propagation direction. A third busbar of the second IDT electrode is coupled to a first busbar of the first IDT electrode. A fourth busbar of the second IDT electrode is coupled to a ground potential. A resonant frequency of the second IDT electrode is in a frequency band of an interference wave signal.