Surface Acoustic Wave Filter Layout for Wide Passband Signals
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Solution Overview
Problem
Existing acoustic wave devices struggle to pass signals with wide pass bandwidths, particularly those exceeding 5% fractional bandwidth, which is necessary for modern communication devices due to the variety of frequency bands used in communication systems.
Innovation Solution
A surface acoustic wave device comprising two acoustic wave elements with overlapping frequency bands, where the first element has a pass band at a lower frequency and the second element at a higher frequency, sharing a common input and output terminal, and designed to satisfy specific reflection coefficient conditions to achieve a wide pass bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single acoustic wave element is used, then the device structure is simple, but the pass bandwidth is limited and cannot exceed 5% fractional bandwidth
Solution Approach 1:
The patent combines multiple acoustic wave elements (first and second acoustic wave elements) into a single device with common input and output terminals. The elements are merged such that their pass bands overlap, creating a composite frequency response that achieves wide bandwidth (exceeding 5% fractional bandwidth) while maintaining a relatively simple overall structure.
Solution Approach 2:
The patent divides the wide bandwidth requirement into multiple narrower pass bands, each handled by a separate acoustic wave element. The first acoustic wave element handles a lower frequency pass band while the second element handles a higher frequency pass band, and their combination through overlapping frequencies achieves the total wide bandwidth requirement.
2Adaptability or versatility
If multiple acoustic wave elements are used to achieve wide pass bandwidth, then the bandwidth requirement is met, but the device complexity increases
Solution Approach 1:
Multiple acoustic wave elements are merged into a unified structure with common input and output terminals. The elements are configured to operate simultaneously with overlapping frequency ranges, achieving wide pass bandwidth while minimizing the increase in device complexity through integrated design.
Solution Approach 2:
The patent adjusts key parameters of the acoustic wave elements including their pass band frequencies, bandwidths, and reflection coefficients. By optimizing these parameters so that the pass bands overlap and satisfy specific reflection coefficient conditions, the device achieves wide bandwidth (exceeding 5% fractional bandwidth) with only two elements rather than requiring more complex multi-element configurations.
3Adaptability or versatility
If the pass bandwidth is increased to cover various frequency bands, then compatibility with communication devices is improved, but the signal integrity may be degraded
Solution Approach 1:
The patent optimizes the reflection coefficients of the acoustic wave elements within the pass band to satisfy specific conditions that maintain signal integrity. By carefully controlling these parameters while achieving wide bandwidth coverage, the device maintains consistent signal quality across different frequency bands, ensuring both compatibility with various communication devices and preservation of signal integrity.
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 device effectively passes signals with a wide pass bandwidth, ensuring compatibility with various frequency bands, thereby enhancing the performance of communication devices by maintaining signal integrity across a broader range of frequencies.
Implementation Method 1
A communication device such as a portable terminal or the like mounts an acoustic wave device using a Surface Acoustic Wave (SAW), a Bulk Acoustic Wave (BAW) or the like to extract only a signal of a specific frequency band.
Data Source
AI summary
In order to pass a signal having a wide pass bandwidth with respect to a center frequency of a pass band, a surface acoustic wave device includes a first surface acoustic wave element provided with a first pass band; and a second surface acoustic wave element having a second pass band in a high frequency band compared with the first pass band of the first surface acoustic wave element, in which the first surface acoustic wave element and the second surface acoustic wave element have a common input terminal and a common output terminal, and a frequency of a high frequency side of the first pass band of the first surface acoustic wave element is partially overlapped with a frequency of a low frequency side of the second pass band of the second surface acoustic wave element.