Acoustic Filter Parallel IDT Circuit for Wideband Attenuation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing acoustic wave filters and multiplexers face challenges in achieving sufficient attenuation and isolation characteristics, especially with wider frequency bands, as desired phase adjustment is difficult and often results in inadequate performance.
Innovation Solution
Incorporating an additional circuit with an interdigital transducer (IDT) electrode group and reflectors having different numbers of pairs of electrode fingers, which broadens the phase adjustment range and enables effective attenuation of out-of-band signal components, thereby improving filter and multiplexer performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional cancellation circuit with identical reflectors is used, then the filter structure is simple, but the phase adjustment range is limited and attenuation characteristics are insufficient
Solution Approach 1:
The patent applies asymmetry by configuring the two reflectors with different numbers of electrode finger pairs (first reflector: 5 pairs, second reflector: 3 pairs). This asymmetric configuration creates different reflection characteristics that broaden the phase adjustment range of the cancellation circuit, enabling effective attenuation across a wider frequency band while maintaining structural simplicity
Solution Approach 2:
The patent applies local quality by making each reflector have distinct properties (different electrode finger counts) tailored to specific frequency ranges. The first reflector with 5 pairs targets lower frequency components while the second reflector with 3 pairs addresses higher frequency components, optimizing attenuation performance across the entire operating band
2Adaptability or versatility
If the frequency band is widened, then the filter covers more channels, but phase adjustment becomes difficult and isolation characteristics deteriorate
Solution Approach 1:
The patent applies segmentation by dividing the frequency band coverage task between two reflectors with different electrode finger configurations. The first reflector (5 pairs) handles lower frequency segments while the second reflector (3 pairs) handles higher frequency segments, enabling broad frequency coverage while maintaining adequate phase adjustment capability and isolation characteristics across the entire band
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 allows for enhanced attenuation characteristics in filters and isolation characteristics in multiplexers, ensuring better signal management across broader frequency bands.
Implementation Method 1
an interdigital transducer (IDT) electrode group including a plurality of IDT electrodes arranged in an acoustic wave propagation direction
Implementation Method 2
two reflectors that sandwich the IDT electrode group and including different numbers of pairs of electrode fingers
Implementation Method 3
generates a cancellation signal opposite in phase to out-of-band signal components transmitted through the filter circuit
Data Source
AI summary
A transmission filter includes a transmission filter circuit and an additional circuit. The transmission filter circuit is provided between a first terminal and a second terminal. Between the first terminal and the second terminal, the additional circuit is connected in parallel with at least a portion of the transmission filter circuit. The additional circuit includes an IDT electrode group including a plurality of IDT electrodes located next to each other in an acoustic wave propagation direction and two reflectors that sandwich the IDT electrode group and having different numbers of pairs of electrode fingers.