Acoustic Wave Multiplexer IDT Pitch Layout for Lower IMD
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Solution Overview
Problem
Existing multiplexers with acoustic wave filters suffer from deterioration in bandpass characteristics and intermodulation distortion due to nonlinearities, particularly when high-frequency signals are input, leading to increased size and power consumption, and insufficient IMD reduction.
Innovation Solution
A multiplexer configuration with serial and parallel arm resonators connected to a common terminal, where the electrode finger pitch of IDT electrodes is varied to maximize at the center and minimize at the ends, maintaining linearity and resonant frequency without increasing size, and ensuring uniformity in other resonators to maintain high Q values and reduce insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the acoustic wave resonator is divided into a plurality of pieces to reduce power consumption per unit area, then the electric power handling capability is improved, but the acoustic wave filter increases in size and the multiplexer increases in size
Solution Approach 1:
The patent applies local quality by varying the electrode finger pitch within the IDT electrode - the center portion has a maximum pitch while end portions have minimum pitch. This non-uniform local structure reduces intermodulation distortion in the high-power transmission band without requiring division of the resonator, thereby maintaining compact size while improving power handling capability.
2Reliability
If the electrode finger pitch is varied to reduce intermodulation distortion, then the linearity is improved, but the resonant frequency may change and the Q value may decrease
Solution Approach 1:
The patent changes the electrode finger pitch parameter non-uniformly across the IDT electrode - maximum at center, minimum at ends. This parameter variation reduces intermodulation distortion while the patent carefully controls the pitch values to maintain resonant frequency stability and high Q values, achieving both improved linearity and frequency stability.
3Reliability
If the acoustic wave filter is designed with high attenuation to improve noise performance, then the bandpass characteristics are improved, but the intermodulation distortion increases due to nonlinearity
Solution Approach 1:
The patent applies local quality by implementing different electrode finger pitches in different regions of the IDT electrode. The center portion with maximum pitch reduces intermodulation distortion, while end portions with minimum pitch maintain high Q values and low insertion loss, thereby simultaneously improving noise performance and reducing intermodulation distortion.
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
The configuration effectively reduces intermodulation distortion and maintains bandpass characteristics, allowing for a compact multiplexer design that handles high-frequency signals without deteriorating reception sensitivity or increasing size.
Implementation Method 1
an acoustic wave resonator including an IDT (InterDigital Transducer) electrode provided on a substrate having piezoelectricity
Implementation Method 2
one or more serial arm resonators provided on a path connecting the common terminal and the first input and output terminal, and one or more parallel arm resonators provided between the path and a ground, each of the one or more serial arm resonators and the one or more parallel arm resonators is an acoustic wave resonator
Data Source
AI summary
A multiplexer includes a transmission-side filter connected to a common terminal and a transmission input terminal, and a reception-side filter connected to the common terminal and a reception output terminal, in which the transmission-side filter includes serial arm resonators, parallel arm resonators, and a parallel arm circuit. In an interdigital transducer electrode included in the serial arm resonator connected closest to the common terminal, an electrode finger pitch at a center portion in an arrangement direction of electrode fingers is maximum among electrode finger pitches of the interdigital transducer electrode, and electrode finger pitches at end portions in the arrangement direction are minimum among the electrode finger pitches of the interdigital transducer electrode.