Multimode Acoustic Wave Filter Layout for Low-Loss Multi-Band Output
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Solution Overview
Problem
Existing acoustic wave filters for multi-band cellular phones face challenges in achieving low insertion loss while maintaining a compact size, as they require multiple filters connected in parallel, which increases insertion loss due to the need for series resonators.
Innovation Solution
The design incorporates two acoustic wave filters with multimode filters having different aperture lengths, allowing one filter to be in a high-impedance state within the pass band of the other, eliminating the need for series resonators and reducing insertion loss, while maintaining amplitude and phase balance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple acoustic wave filters are connected in parallel to cover multiple communication bands, then the filter can handle multiple bands, but insertion loss increases due to the need for series resonators
Solution Approach 1:
The patent merges multiple acoustic wave filters into a single integrated filter structure that can handle multiple communication bands simultaneously. The filter incorporates multiple resonance circuits with different resonance frequencies within a unified design, eliminating the need for separate parallel filter connections and their associated series resonators, thereby reducing insertion loss while maintaining multi-band capability.
Solution Approach 2:
The acoustic wave filter is designed with multi-functionality to cover multiple communication bands (e.g., FDD LTE bands 1, 3, 5, 8 and TDD LTE band 40) within a single device. The filter structure incorporates multiple resonance circuits that can selectively pass different frequency bands, making one filter perform the function of multiple filters without requiring additional series resonators for each band.
2Reliability
If series resonators are added to adjust impedance in parallel-connected acoustic wave filters, then one filter can be in high-impedance state in the pass band of the other, but device size increases
Solution Approach 1:
The patent combines the impedance matching function into the main filter structure by integrating resonance circuits directly within the acoustic wave filter. This eliminates the need for separate series resonators that would increase device size, while still achieving the required impedance matching and high-impedance states for proper filter operation across multiple bands.
Solution Approach 2:
The resonance circuits are nested within the acoustic wave filter structure itself, with multiple resonance circuits incorporated into a single integrated design. This nesting approach allows the filter to achieve proper impedance matching and high-impedance states without adding external series resonators, thereby maintaining a compact device size.
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 reduced insertion loss and downsized acoustic wave devices with improved amplitude and phase balance characteristics, allowing for efficient signal transmission across multiple communication bands.
Implementation Method 1
an acoustic wave filter having a first group of multimode filters connected in parallel to a first unbalanced input node In10 with a first balanced output nodes Out10, Out12
Implementation Method 2
a first multimode filter 10 among the first group of multimode filters 10, 12, 14 and 16 being connected to the two first balanced output nodes Out10 and Out12
Data Source
AI summary
An acoustic wave filter includes: a first acoustic wave filter having a first group of multimode filters connected, a first unbalanced input node and two first balanced output nodes, a first multimode filter among the first group of multimode filters being connected to the two first balanced output nodes; and a second acoustic wave filter having a second group of multimode filters, a second unbalanced input node and two second balanced output nodes, a second multimode filter among the second group of multimode filters having an aperture length different from that of the first multimode filter and a connection with the two second balanced output nodes, the first and second multimode filters having different pass bands. One of the two first balanced output nodes and one of the two second balanced output nodes are unified, and the other first balanced output node and the other second balanced output node are unified.