Multiplexer Filter Layout for Lower IMD in Carrier Aggregation
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Solution Overview
Problem
Existing multiplexers experience intermodulation distortion (IMD) during 2-uplink carrier aggregation, leading to degradation of receive filter sensitivity.
Innovation Solution
A multiplexer design with specific center frequency relationships and electrode finger pitch ratios between transmit and receive filters, including a series arm resonator in the first receive filter, reduces IMD and maintains receiving sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple transmit filters and receive filters are connected to a common terminal for carrier aggregation, then communication functionality is improved, but intermodulation distortion occurs causing degradation of receive filter sensitivity
Solution Approach 1:
The patent applies local quality by making the series arm resonator in the first receive filter have a different electrode finger pitch than other resonators in the multiplexer. This localized differentiation in pitch creates a specific impedance characteristic that suppresses intermodulation distortion products falling within the receive filter's pass band, thereby protecting receive filter sensitivity while maintaining carrier aggregation functionality.
Solution Approach 2:
The patent changes the physical parameter of electrode finger pitch for the series arm resonator in the first receive filter. By setting this pitch to be different from other resonators, the resonator presents a different impedance to intermodulation distortion products, causing these products to be reflected or attenuated rather than passed through to the receive filter output, thus reducing IMD impact.
2Ease of manufacture
If filters are designed with standard electrode finger pitch for manufacturing simplicity, then manufacturing precision is improved, but intermodulation distortion increases
Solution Approach 1:
Instead of changing all resonators, the patent applies local quality by modifying only the series arm resonator in the first receive filter with a different electrode finger pitch. This localized modification creates the necessary impedance mismatch to suppress IMD while keeping the rest of the multiplexer manufactured with standard pitch processes, balancing manufacturing ease with IMD suppression.
Solution Approach 2:
The patent applies partial action by modifying only one specific resonator (the series arm resonator in the first receive filter) rather than all resonators in the multiplexer. This partial modification is sufficient to suppress the harmful IMD products affecting receive sensitivity while minimizing the complexity of manufacturing changes required.
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
Reduces IMD and prevents degradation of receive filter sensitivity by optimizing electrode finger pitch ratios and phase alignment of signals.
Implementation Method 1
The one or more parallel arm resonators and the one or more series arm resonators are each formed by an acoustic wave resonator
Data Source
AI summary
A multiplexer includes a common terminal, first and second transmit filters, and a first receive filter connected to the common terminal and each including resonators, a relationship Tx1c<Rx1c<Tx2c is satisfied, where Tx1c, Tx2c, and Rx1c denote center frequencies of pass bands Tx1, Tx2, and Tx3 of the first and second transmit filters and the first receive filter, respectively, a resonator closest to the common terminal in the first receive filter is a series arm resonator, and a pitch ratio denoted by pS1 (Rx1)/p(Tx2) is more than about 1 and less than or equal to about 1.035, where p(Tx2) denotes an electrode finger pitch of an IDT electrode in a resonator closest to the common terminal in the second transmit filter and pS1 (Rx1) denotes an electrode finger pitch of an IDT electrode of the series arm resonator closest to the common terminal in the first receive filter.