Acoustic Wave Filter Cancel Line Layout for Better Isolation
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Solution Overview
Problem
The attenuation and isolation characteristics of acoustic wave filters and multiplexers are insufficient due to capacitive coupling as they decrease in size, limiting the effectiveness of cancel circuits in improving these characteristics.
Innovation Solution
Incorporating a piezoelectric substrate with series resonators and a cancel line that cancels signals outside the passband, where at least one series resonator has a grounded reflector, and using a second piezoelectric substrate with non-overlapping passbands to enhance the attenuation and isolation characteristics by reducing signal leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the filter and multiplexer are decreased in size, then the device compactness is improved, but the attenuation characteristic and isolation characteristic deteriorate due to capacitive coupling
Solution Approach 1:
A ground electrode is introduced as an intermediary element between the series resonator and the cancel circuit. This ground electrode acts as a mediator to reduce the capacitive coupling between the series resonator and cancel circuit, thereby maintaining effective attenuation characteristics even when the device is miniaturized. The ground electrode provides a reference potential that isolates the capacitive interaction while allowing the cancel circuit to function properly.
Solution Approach 2:
The structure is segmented by introducing a separate ground electrode layer that is electrically connected to the substrate ground. This segmentation divides the coupling path into controlled segments, allowing the capacitive coupling to be managed and reduced while maintaining the cancel circuit's functionality. The ground electrode creates distinct electrical zones that reduce unwanted coupling effects.
2Volume of moving object
If the filter and multiplexer are decreased in size, then the device compactness is improved, but the isolation characteristic deteriorates due to capacitive coupling
Solution Approach 1:
The ground electrode serves as an intermediary that reduces capacitive coupling between the series resonator and cancel circuit, thereby improving isolation characteristics. By providing a grounded reference plane, it prevents signal leakage through capacitive paths while maintaining the compact device structure.
Solution Approach 2:
The ground electrode creates segmented electrical zones that isolate different functional areas of the filter. This segmentation reduces the capacitive coupling paths between the series resonator and cancel circuit, thereby improving isolation between different frequency channels in the multiplexer.
3Reliability
If a cancel circuit is used to improve attenuation characteristic, then the attenuation performance is improved, but capacitive coupling increases when device size is reduced
Solution Approach 1:
The ground electrode is positioned between the series resonator and the cancel circuit to act as a mediator that reduces capacitive coupling. This intermediary element provides a grounded reference that minimizes the harmful capacitive interaction while allowing the cancel circuit to effectively improve attenuation characteristics.
Solution Approach 2:
The harmful capacitive coupling effect is extracted and managed by introducing the ground electrode as a separate element. This extraction allows the capacitive coupling to be controlled and reduced independently from the main filter structure, enabling the cancel circuit to function effectively without excessive coupling.
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 proposed solution effectively improves the attenuation and isolation characteristics of acoustic wave filters and multiplexers by reducing signal leakage and capacitive coupling, leading to enhanced performance even in smaller device sizes.
Implementation Method 1
a piezoelectric substrate; one or more series resonators that are located on the piezoelectric substrate
Implementation Method 2
acoustic wave filters and multiplexers using surface acoustic wave resonators have been used
Data Source
AI summary
A filter includes: a piezoelectric substrate; one or more series resonators that are located on the piezoelectric substrate and are connected in series between an input terminal and an output terminal; at least one series resonator that is connected between a first node and a second node, is included in the one or more series resonators, and includes a reflector that is grounded, the first node and the second node being located between the input terminal and the output terminal; and a cancel line that is connected in parallel with the at least one series resonator between the first node and the second node, and cancels a signal outside a passband propagating through the at least one series resonator from the first node to the second node.