Acoustic Wave Multiplexer Using BAW-SAW Resonators for Harmonic Suppression
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Solution Overview
Problem
Acoustic wave filters in radio frequency systems face challenges with second-order distortion and harmonic characteristics due to asymmetry, particularly when using only bulk acoustic wave (BAW) or surface acoustic wave (SAW) resonators, leading to deteriorated antenna matching and harmonics issues in duplexers.
Innovation Solution
Incorporating a series surface acoustic wave (SAW) resonator between bulk acoustic wave (BAW) resonators and an antenna node in the transmit filter, along with a loop circuit that includes SAW elements, to suppress second-order harmonics and improve antenna matching, while also implementing SAW resonators in the receive filter to output a single-ended radio frequency signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If only bulk acoustic wave (BAW) or surface acoustic wave (SAW) resonators are used in the transmit filter, then the filter structure is simple, but second-order distortion increases and antenna matching deteriorates
Solution Approach 1:
The patent introduces asymmetry by combining two different types of acoustic wave resonators (BAW and SAW) with different characteristics in the transmit filter. The BAW resonators provide bulk acoustic wave filtering while SAW resonators provide surface acoustic wave filtering, creating an asymmetric resonator configuration that suppresses second-order distortion and improves antenna matching performance
Solution Approach 2:
The patent uses a composite approach by integrating both BAW and SAW resonators in the same transmit filter circuit. This composite resonator system combines the advantages of both resonator types to achieve better harmonic suppression and distortion reduction while maintaining filter functionality
2Ease of manufacture
If only BAW or SAW resonators are used in the transmit filter, then the manufacturing process is simple, but harmonic suppression deteriorates
Solution Approach 1:
The asymmetric combination of BAW and SAW resonators creates different propagation paths and resonance characteristics that interfere with harmonic signals. The BAW resonators handle fundamental frequency filtering while SAW resonators specifically target harmonic suppression, creating an asymmetric filtering effect that reduces second-order distortion
Solution Approach 2:
The composite resonator system integrates BAW and SAW technologies in a single filter assembly, combining their complementary strengths. The BAW portion provides robust fundamental frequency rejection while the SAW portion delivers superior harmonic suppression, achieving comprehensive distortion reduction
3Reliability
If a series surface acoustic wave (SAW) resonator is added between BAW resonators and the antenna node, then second-order distortion is reduced, but the filter structure becomes more complex
Solution Approach 1:
The transmit filter is segmented into distinct functional sections: BAW resonators for primary filtering, a series SAW resonator specifically positioned between the BAW resonators and antenna node for targeted harmonic suppression, and additional circuit elements. This segmentation allows each component to address specific distortion mechanisms independently
Solution Approach 2:
The series SAW resonator acts as an intermediary element between the BAW resonators and the antenna node. It mediates the signal path by providing additional filtering specifically for second-order harmonics that the BAW resonators alone cannot adequately suppress, thereby reducing distortion without requiring complete redesign of the entire filter
4Object-generated harmful factors
If loop circuit with SAW elements is added to suppress second-order harmonics, then harmonic suppression improves, but device complexity increases
Solution Approach 1:
The loop circuit incorporates feedback mechanisms where SAW elements detect and process harmonic signals, generating corrective signals that are fed back to suppress second-order harmonics. This feedback loop continuously monitors and adjusts the filtering action to maintain optimal harmonic suppression performance
Solution Approach 2:
The SAW elements in the loop circuit utilize mechanical vibration principles to generate acoustic waves that interfere with and suppress harmonic signals. The piezoelectric properties of SAW resonators convert electrical signals to mechanical vibrations and back, creating destructive interference patterns that reduce second-order distortion
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 solution effectively reduces second-order distortion, enhances antenna matching, and improves harmonic suppression, leading to more stable and efficient radio frequency signal processing in duplexers.
Implementation Method 1
An acoustic wave filter can include a plurality of resonators arranged to filter a radio frequency signal. Example acoustic wave filters include surface acoustic wave (SAW) filters and bulk acoustic wave (BAW) filters.
Implementation Method 2
surface acoustic wave (SAW) filters and bulk acoustic wave (BAW) filters
Implementation Method 3
The loop circuit can be configured to generate an anti-phase signal to a target signal at a particular frequency
Data Source
AI summary
Multiplexers are disclosed. A multiplexer can include a first filter and a second filter that are coupled to a common node. The second filter can include a first type of acoustic wave resonators (e.g., bulk acoustic wave resonators) and a series acoustic wave resonator of a second type (e.g., a surface acoustic wave resonator) that is coupled between the acoustic wave resonators of the first type and the common node. The first filter can provide a single-ended radio frequency signal. In certain embodiments, the first filter can be a receive filter and the second filter can be a transmit filter.