Phase-Compensated Acoustic Wave Filter for Stopband Isolation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional ladder-type filters in antenna duplexers face challenges in achieving high isolation characteristics due to the need for reduced component count in modern communications devices, requiring improved attenuation in stopbands without impacting passbands.
Innovation Solution
Incorporating a phase shift circuit with slanted-finger interdigitated transducer electrodes and capacitor elements, connected in parallel with the main filter circuit, to provide an auxiliary signal with opposite phase and similar amplitude, enhancing signal attenuation in the stopband and improving isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the number of components in the antenna duplexer is reduced to make devices smaller, then device size is reduced, but isolation characteristic deteriorates
Solution Approach 1:
The patent combines the main filter circuit and phase shift circuit into a single integrated filter device. The phase shift circuit is connected in parallel with the main filter circuit, merging multiple functional components into one unified structure that provides both filtering and phase compensation functions, thereby reducing overall device size while maintaining isolation characteristics.
Solution Approach 2:
The phase shift circuit acts as an intermediary element that compensates for the deterioration of isolation characteristic. By introducing this intermediate component with opposite phase characteristic, the system achieves improved isolation without requiring additional separate components, thus resolving the contradiction between size reduction and isolation maintenance.
2Device complexity
If conventional ladder-type filters are used, then device structure is simple, but stopband attenuation is insufficient
Solution Approach 1:
The filter device is segmented into two distinct functional circuits: the main filter circuit for basic filtering and the phase shift circuit for stopband enhancement. This segmentation allows each circuit to be optimized for its specific function, with the phase shift circuit specifically designed to provide additional attenuation in the stopband region without complicating the overall structure.
Solution Approach 2:
The filter device uses a composite circuit structure combining different types of circuits (main filter circuit and phase shift circuit) with different characteristics. This composite approach allows the system to leverage the advantages of both circuit types, achieving superior stopband attenuation while maintaining reasonable structural complexity.
3Reliability
If phase-influencing circuit is added to improve isolation, then isolation characteristic is improved, but device complexity increases
Solution Approach 1:
The phase shift circuit is designed to perform multiple functions simultaneously: it provides phase compensation in the stopband to improve isolation characteristic, while also maintaining a relatively simple structure that does not significantly increase device complexity. The circuit achieves multi-functionality by using acoustic wave elements that can be integrated into the existing filter architecture.
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 phase shift circuit effectively cancels the main signal in the attenuation band, significantly improving the isolation characteristic of the antenna duplexer without negatively affecting the transmission band, thus meeting modern design requirements.
Implementation Method 1
a pair of acoustic wave elements connected in series between the first capacitor element and the second capacitor element, the pair of acoustic wave elements including a pair of slanted-finger interdigitated transducer electrodes
Implementation Method 2
The phase shift circuit has a second phase characteristic that is opposite to the first phase characteristic in an attenuation band that corresponds to at least a portion of the first stopband
Data Source
AI summary
Phase shift circuits including two or more slanted-finger IDT electrodes, and filters, duplexers, or other electronic devices incorporating same. In one example a filter includes a main filter circuit connected between an input and an output and having a first phase characteristic, and a phase shift circuit connected in parallel with the main filter circuit, the phase shift circuit including first and second capacitor elements and a pair of acoustic wave elements connected in series between the first and second capacitor elements, the pair of acoustic wave elements including a pair of slanted-finger IDT electrodes disposed apart from each other on a single acoustic wave path along which acoustic waves propagate through the acoustic wave elements, the phase shift circuit having a second phase characteristic opposite to the first phase characteristic in an attenuation band that corresponds to at least a portion of a stopband of the main filter circuit.