Balanced Acoustic Wave Filter Layout for Phase Matching and Low Loss
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Solution Overview
Problem
Existing acoustic wave filter devices with balanced-unbalanced conversion functions face challenges in enhancing out-of-band attenuation and balancing between signals transmitted to balanced terminals, while also struggling with miniaturization and increased insertion loss due to complex wiring configurations and added reactance components.
Innovation Solution
The proposed acoustic wave filter device incorporates a longitudinally-coupled resonator type acoustic wave filter unit with divided IDT electrodes and a surface acoustic wave resonator connected between signal lines, featuring different electrode sections and configurations to improve phase and amplitude balancing, and prevent insertion loss deterioration by maintaining an induction property within the passband.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-port acoustic wave resonator is connected to the unbalanced terminal with both bus bars extending to signal lines, then out-of-band attenuation is increased, but the wiring configuration becomes complicated and miniaturization is difficult
Solution Approach 1:
The bus bar of the acoustic wave resonator is divided into a first bus bar and a second bus bar. The first bus bar connects to the first signal line while the second bus bar connects to the second signal line, separating the wiring paths and simplifying the overall configuration while maintaining out-of-band attenuation performance
Solution Approach 2:
The patent utilizes the spatial arrangement by connecting the divided bus bars to different signal lines in a balanced configuration, transforming the wiring from a complex single-path arrangement to a structured multi-dimensional layout that achieves miniaturization
2Stability of the object's composition
If the same influence of resonator connection is applied to both balanced terminals, then balancing is not considerably deteriorated, but phase balancing is not positively improved
Solution Approach 1:
The patent introduces asymmetry by making the first and second divided electrode sections different from each other. This asymmetric configuration allows positive improvement of phase balancing between the balanced terminals while maintaining overall stability through the controlled asymmetric design
3Measurement precision
If comb-shaped electrodes are added to one balanced terminal to improve phase balancing, then phase balancing is improved, but insertion loss increases due to increased parasitic capacitance
Solution Approach 1:
The patent extracts the phase balancing function from a separate reactance component (comb-shaped electrodes) and integrates it into the acoustic wave resonator's electrode structure itself. This eliminates the need for additional parasitic capacitance while achieving phase balancing
4Measurement precision
If reactance component is added to improve phase balancing, then phase balancing is improved, but device area increases making the filter chip larger
Solution Approach 1:
The patent merges the phase balancing function with the acoustic wave resonator's electrode structure by making the divided electrode sections different from each other. This integration eliminates the need for separate reactance components, thereby reducing the overall device area while achieving phase balancing
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 effectively enhances out-of-band attenuation and balancing between signals, while allowing for miniaturization and reducing insertion loss, by ensuring equal phase shifts and distinct electrode configurations that control signal phases and amplitudes efficiently.
Implementation Method 1
IDT (interdigital transducer) electrodes which include a plurality of electrode fingers alternately arranged in a propagation direction of surface acoustic waves and connected to bus bars
Implementation Method 2
a single-port surface acoustic wave resonator 1012 has a first bus bar connected to the first signal line 1010 and a second bus bar connected to the second signal line 1011
Implementation Method 3
A resonant frequency of the single-port surface acoustic wave resonator 1012 is set in a lower side of pass bands of the surface acoustic wave filters 1006 and 1007
Data Source
AI summary
An acoustic wave filter device including a balanced-unbalanced conversion function in which balancing between signals transmitted to first and second balanced terminals is improved includes a longitudinally-coupled resonator type acoustic wave filter unit including an unbalanced end and first and second balanced ends and an acoustic wave resonator. First and second divided electrode sections included in an IDT are respectively connected to first and second signal lines which are connected to the first and second balanced ends of the acoustic wave filter unit. A length of a line which connects the first divided electrode section to the first balanced end is equal or substantially equal to a length of a line which connects the second divided electrode section to the second balanced end, and the first divided electrode section is different from the second divided electrode section.