Acoustic Wave Filter Canceling Circuit for Compact Attenuation
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Solution Overview
Problem
Existing acoustic wave filters face challenges in achieving reduced size while maintaining improved attenuation characteristics, as additional circuits for improving attenuation are often separate from the transmission-side filter, leading to increased size.
Innovation Solution
The acoustic wave filter incorporates a canceling circuit with longitudinally coupled acoustic wave resonators connected in parallel to a portion of the first path, which includes series-arm and parallel-arm resonators, allowing the resonators to function as parallel-arm resonators within the pass band, thereby reducing the number of parallel-arm resonators needed and improving attenuation characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an additional circuit is disposed independently from the transmission-side filter to improve attenuation characteristics, then the attenuation characteristics are improved, but the size of the transmission-side filter and the multiplexer is increased
Solution Approach 1:
The patent combines the additional circuit (canceling circuit) with the transmission-side filter into a single integrated structure. The canceling circuit includes acoustic wave resonators that are electrically connected to the transmission-side filter, merging two previously separate functions into one unified component, thereby improving attenuation characteristics without increasing the overall size of the multiplexer
Solution Approach 2:
The acoustic wave resonators in the canceling circuit serve multiple functions: they are part of the transmission-side filter structure and simultaneously provide attenuation enhancement by canceling unwanted signals. This multi-functionality allows a single component to fulfill both filtering and attenuation improvement roles, resolving the size contradiction
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 achieves a smaller filter size with enhanced attenuation characteristics by utilizing the canceling circuit to generate a signal in an opposite phase, reducing unnecessary signals and allowing for a more compact design without compromising performance.
Implementation Method 1
an acoustic wave filter according to a preferred embodiment of the present invention includes a first circuit connected to a first terminal and a second terminal, and a second circuit connected in parallel to at least a portion of a first path connecting the first terminal and the second terminal. The first circuit includes one or more series-arm resonators on the first path and one or more parallel-arm resonators between the first path and a ground. The second circuit includes a plurality of first acoustic wave resonators in parallel or substantially in parallel in a propagation direction of an acoustic wave.
Implementation Method 2
An anti-resonant frequency of the at least one of the plurality of first acoustic wave resonators is in a pass band of the first circuit
Data Source
AI summary
An acoustic wave filter includes a filter circuit connected to input-and-output terminals, and a canceling circuit connected in parallel to at least a portion of a first path connecting the input-and-output terminals. The filter circuit includes one or more series-arm resonators on the first path, and one or more parallel-arm resonators between the first path and a ground. The canceling circuit includes acoustic wave resonators in parallel or substantially in parallel in a propagation direction of an acoustic wave. At least one of the acoustic wave resonators is connected to the ground, and an anti-resonant frequency of the at least one of the acoustic wave resonators is in a pass band of the filter circuit.