Acoustic Filter Additional Circuit for Wideband Isolation
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Solution Overview
Problem
Existing filters and multiplexers with additional circuits face challenges in achieving adequate attenuation and isolation characteristics, particularly with wider frequency bands, as they struggle to effectively control signal amplitudes and phase adjustments.
Innovation Solution
Incorporating an additional circuit with a resonator group and capacitive elements, including a second capacitive element connected between the resonator group and ground, which generates a cancellation signal of opposite phase and similar amplitude to the cancellation target signal, thereby improving attenuation and isolation characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an additional circuit is added to improve attenuation and isolation characteristics, then the attenuation and isolation characteristics are improved, but the device complexity increases
Solution Approach 1:
The additional circuit is nested within the existing filter structure by connecting it in parallel with specific portions of the filter circuit. This integration allows the cancellation signal generation functionality to be embedded within the existing circuit architecture, improving attenuation characteristics while minimizing the increase in overall device complexity.
Solution Approach 2:
The additional circuit acts as an intermediary element that generates cancellation signals to counteract harmful signals in the filter. By introducing this intermediate cancellation mechanism, the system achieves improved attenuation and isolation characteristics without requiring complete redesign of the entire filter system.
2Adaptability or versatility
If the frequency band of the filter is widened, then the frequency band coverage is improved, but the ability of the additional circuit to improve attenuation and isolation characteristics deteriorates
Solution Approach 1:
The additional circuit is configured to provide localized cancellation functionality at specific points within the filter circuit where harmful signals are most problematic. By targeting specific locations rather than attempting uniform cancellation across the entire widened frequency band, the circuit maintains effective attenuation characteristics even as frequency band coverage expands.
Solution Approach 2:
The additional circuit utilizes capacitive elements with specific capacitance values to adjust its cancellation characteristics. By optimizing these electrical parameters, the circuit can effectively counteract signals across a wider frequency band while maintaining the required attenuation performance.
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 significantly enhances the attenuation and isolation characteristics of filters and multiplexers by effectively controlling the amplitude of cancellation signals, leading to improved performance across a wider frequency range.
Implementation Method 1
a second capacitive element electrically connected between a ground and a signal path electrically connecting the resonator group and the first capacitive element
Implementation Method 2
a resonator group including a plurality of interdigital transducer (IDT) electrodes provided adjacent to or in a vicinity of each other in an acoustic wave propagation direction
Data Source
AI summary
A filter includes a transmission filter circuit and an additional circuit that is electrically connected in parallel with at least a portion of the transmission filter circuit. The additional circuit includes a resonator group including a plurality of interdigital transducer electrodes provided adjacent to or in a vicinity of each other in an acoustic wave propagation direction, a first capacitive element electrically connected between the resonator group and one end of the additional circuit, and a second capacitive element connected between a ground and a signal path electrically connecting the resonator group and the first capacitive element. A capacitance of the second capacitive element is greater than about 0 pF and less than or substantially equal to about 2.0 pF.