Acoustic Wave Filter Layout for Compact Tx-Rx Isolation
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Solution Overview
Problem
Existing acoustic wave devices require additional circuits to improve isolation characteristics, making them difficult to miniaturize while maintaining effective performance.
Innovation Solution
An acoustic wave device design featuring a substrate with a transmission filter and reception filter, where a specific parallel resonator is electrically connected to the reception ground pad but not the transmission ground pad, and is positioned farthest from the input terminal, with a smaller capacitance and resonant frequency aligned with the highest frequency of the passband, allowing for improved isolation characteristics without additional circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an additional circuit is provided in the acoustic wave device to improve isolation characteristics, then the isolation characteristics are improved, but the device size cannot be miniaturized
Solution Approach 1:
The patent merges the isolation function with the existing filter structure by electrically connecting a specific parallel resonator (P3b) to the reception ground pad. This integration eliminates the need for separate isolation circuits while achieving improved isolation characteristics between transmission and reception paths.
Solution Approach 2:
The parallel resonator P3b serves multiple functions simultaneously: it acts as part of the filter structure and provides isolation between transmission and reception paths. By making this single component multi-functional, the patent avoids adding extra circuits that would increase device size.
2Volume of moving object
If the device is miniaturized, then the device size is reduced, but it becomes impossible to maintain effective isolation characteristics without additional circuits
Solution Approach 1:
The patent applies local quality by making the parallel resonator P3b electrically connected to the reception ground pad while other parallel resonators remain connected to the transmission ground pad. This localized differentiation in electrical connection creates effective isolation in the reception path without affecting the overall filter performance or requiring additional components.
3Reliability
If a parallel resonator is electrically connected to both transmission and reception ground pads, then the filter functionality is maintained, but isolation characteristics are degraded
Solution Approach 1:
The patent introduces asymmetry in the electrical connection configuration where parallel resonator P3b is connected only to the reception ground pad, while other parallel resonators are connected to the transmission ground pad. This asymmetric arrangement creates directional isolation properties that improve transmission-reception separation without requiring complex additional circuitry.
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 design achieves a smaller form factor with enhanced isolation characteristics and reduced insertion loss, while maintaining effective signal passing and durability, and is suitable for use in modules requiring improved acoustic wave performance.
Implementation Method 1
the substrate is a substrate in which a piezoelectric substrate and a substrate made of sapphire, silicon, alumina, spinel, quartz, or glass are bonded to each other
Implementation Method 2
the transmission filter includes a plurality of series resonators and a plurality of parallel resonators
Data Source
AI summary
An acoustic wave device includes a substrate, a transmission filter formed on the substrate, a reception filter formed on the substrate, a transmission ground pad of the transmission filter, the transmission ground pad is formed on the substrate, and a reception ground pad of the reception filter, the reception ground pad is formed on the substrate. The transmission filter includes a plurality of series resonators and a plurality of parallel resonators. The plurality of parallel resonators includes a first parallel resonator electrically connected to the reception ground pad.