Multiplexer Filter Circuit Using Multi-Pitch IDT Resonators
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Solution Overview
Problem
Existing filter devices in multiplexers face challenges in improving attenuation characteristics across multiple frequency bands due to difficulties in adjusting phases for various frequency bands, leading to insufficient isolation between filters.
Innovation Solution
The implementation of a filter device with an additional circuit comprising at least two IDT electrode groups and a capacitance element, where the IDT electrode groups have different average pitches and electrode finger counts, allowing for the generation of cancel signals with opposite phases and amplitudes in multiple frequency bands, effectively improving attenuation characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single additional circuit is used to improve attenuation characteristics, then isolation between filters is improved in one frequency band, but sufficient attenuation cannot be achieved across multiple frequency bands
Solution Approach 1:
The additional circuit is divided into multiple IDT electrode groups (first IDT electrode group and second IDT electrode group), where each group targets a specific frequency band. The first IDT electrode group generates cancel signals for one frequency band while the second IDT electrode group generates cancel signals for another frequency band, allowing simultaneous improvement of attenuation characteristics across multiple bands.
Solution Approach 2:
Each IDT electrode group is designed with specific electrode finger counts and pitch values optimized for its target frequency band. The first IDT electrode group has a first number of electrode fingers and first pitch, while the second IDT electrode group has a second number of electrode fingers and second pitch, enabling each group to provide locally optimized attenuation for its designated frequency range.
2Adaptability or versatility
If multiple IDT electrode groups with different configurations are used to achieve multi-band attenuation, then phase adjustment for multiple frequency bands becomes possible, but device complexity increases
Solution Approach 1:
Multiple IDT electrode groups are merged into a single additional circuit that is connected in parallel with the filter. This integration allows the circuit to simultaneously generate cancel signals for multiple frequency bands without requiring separate additional circuits for each band, thereby providing phase adjustment capability across multiple bands while controlling overall device complexity.
Solution Approach 2:
The additional circuit is designed with multi-functional IDT electrode groups that can operate across different frequency bands. Each IDT electrode group serves multiple purposes: generating cancel signals, providing phase adjustment, and achieving attenuation for its target frequency band, thereby reducing the need for separate dedicated circuits for each function.
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 enables enhanced attenuation characteristics across multiple frequency bands, improving signal isolation between filters and supporting multiband and wideband communication requirements.
Implementation Method 1
IDT (Interdigital Transducer) electrodes that are arranged in an acoustic wave propagation direction
Data Source
AI summary
A filter device includes a filter between an input terminal and an output terminal, and an additional circuit connected in parallel with the filter between the input terminal and the output terminal. The additional circuit includes at least two longitudinally coupled resonators connected in parallel with each other and including longitudinally coupled resonators, and at least one capacitance element between the input terminal and the at least two longitudinally coupled resonators or between the output terminal and the at least two longitudinally coupled resonators. The average pitch of a plurality of electrode fingers of IDT electrodes of the longitudinally coupled resonator and the average pitch of a plurality of electrode fingers of IDT electrodes of the longitudinally coupled resonator are different from each other.