Acoustic Wave Filter Balun Integration for Low-Noise RF Front Ends
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Solution Overview
Problem
Existing acoustic wave filters in wireless devices face challenges in efficiently filtering radio frequency signals, particularly in reducing intermodulation and harmonic interference, which can mask desired signals and desensitize receivers.
Innovation Solution
The implementation of a front-end module that includes an acoustic wave filter with a single-ended and differential interdigital transducer electrode configuration, coupled with a low noise amplifier and a matching circuit, provides balun functionality without the need for a separate balun circuit element, thereby reducing additional loss and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a separate balun circuit element is added to convert single-ended to differential signals, then signal conversion functionality is improved, but device complexity and additional loss increase
Solution Approach 1:
The patent merges the balun functionality into the acoustic wave filter structure itself. The interdigital transducer (IDT) electrodes are configured such that the input IDT receives single-ended signals while the output IDTs generate differential signals with 180-degree phase difference, eliminating the need for a separate balun circuit element.
Solution Approach 2:
The acoustic wave filter is designed to perform multiple functions simultaneously: signal filtering and balun conversion. By configuring the IDT electrodes with specific grounding arrangements and phase relationships, the filter structure itself provides both frequency selection and single-ended to differential signal conversion capabilities.
2Adaptability or versatility
If a separate balun circuit element is added for signal conversion, then signal conversion is improved, but additional loss and noise are introduced
Solution Approach 1:
The balun conversion is integrated directly into the acoustic wave filter's IDT electrode configuration, eliminating the separate balun circuit element that would introduce additional insertion loss and noise. The electromagnetic coupling between IDT fingers inherently provides the phase splitting without additional energy loss.
3Adaptability or versatility
If the front-end module uses traditional separate components for filtering and signal conversion, then functionality is complete, but module size and complexity increase
Solution Approach 1:
The patent combines multiple signal processing functions (filtering, single-ended to differential conversion) into a single acoustic wave filter structure. This integration reduces the overall front-end module size by eliminating the need for separate balun circuits and reducing the number of discrete components required.
Solution Approach 2:
The acoustic wave filter structure is designed to perform multiple functions simultaneously - frequency filtering and balun conversion - thereby reducing the total component count and module size while maintaining complete signal processing functionality.
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 effectively reduces intermodulation and harmonic interference, improving signal rejection and sensitivity in wireless devices, while also minimizing the size and complexity of the front-end module by eliminating the need for additional circuit elements.
Implementation Method 1
A surface acoustic wave resonator of a surface acoustic wave filter typically includes an interdigital transductor electrode on a piezoelectric substrate. A surface acoustic wave resonator is arranged to generate a surface acoustic wave.
Implementation Method 2
an interdigital transductor electrode on a piezoelectric substrate
Data Source
AI summary
A front-end module may include an acoustic wave filter with a first and second interdigital transducer electrode, and a low noise amplifier (LNA) that converts a differential input to a single-ended output with respect to ground. The first interdigital transducer electrode may be single-ended with a first input bus bar configured to receive an input signal and a second input bus bar connected to ground. The second interdigital transducer electrode may be differential with a first output bus bar connected to a first output terminal and a second output bus bar connected to a second output terminal. The LNA may have a differential input connected to the acoustic wave filter, a first input transistor that receives a first signal from the first output terminal of the acoustic wave filter, and a second input transistor that receives a second signal from the second output terminal of the acoustic wave filter.