Reflectionless Acoustic Filter Layout for Improved Return Loss
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Solution Overview
Problem
Traditional acoustic filters suffer from high reflection coefficients in their stopbands and require quarter wavelength lines or inductor-capacitor circuits, which are undesirable due to size and loss, and do not maximize the steepness of passband transition regions.
Innovation Solution
The development of reflectionless acoustic filters using bulk acoustic wave (BAW) or surface acoustic wave (SAW) resonators, eliminating the need for quarter wavelength lines and inductors, and incorporating impedance matching components to achieve reduced reflections and improved return loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional acoustic filters use quarter wavelength lines or inductor-capacitor circuits, then the filter structure is established, but the device size increases and energy loss occurs
Solution Approach 1:
The patent extracts and eliminates the quarter wavelength lines and inductor-capacitor circuits from the traditional acoustic filter structure. By removing these unnecessary components, the filter achieves the desired functionality without the associated size increase and energy loss, directly resolving the technical contradiction between reliability and device volume.
2Device complexity
If traditional acoustic filters are designed without impedance matching, then the structure is simpler, but reflection coefficients are high in stopbands
Solution Approach 1:
The patent introduces impedance matching components as intermediary elements between the acoustic filter and the transmission line. These matching components act as mediators that transform the impedance levels, thereby reducing reflection coefficients in the stopband without significantly increasing the overall device complexity.
3Device complexity
If traditional acoustic filters lack impedance matching components, then the design is simpler, but return loss is poor across frequency range
Solution Approach 1:
The patent applies parameter changes by introducing impedance matching components that optimize the impedance parameters across the frequency range. This allows the filter to achieve improved return loss characteristics by transforming the impedance parameters at critical frequencies, resolving the contradiction between design simplicity and reliability.
4Ease of manufacture
If acoustic filters use conventional designs, then the implementation is straightforward, but passband transition region steepness is not maximized
Solution Approach 1:
The patent employs dynamic design elements in the acoustic filter structure, such as variable impedance transformations and frequency-dependent matching networks. These dynamic characteristics enable the filter to achieve steeper passband transition regions while maintaining straightforward implementation through standardized acoustic wave components.
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 filters achieve smaller size, reduced insertion loss, and improved return loss across a frequency range, maintaining steep passband transition regions and minimizing reflections down to DC and up to harmonic frequencies.
Implementation Method 1
The development of reflectionless acoustic filters using bulk acoustic wave (BAW) or surface acoustic wave (SAW) resonators
Implementation Method 2
The development of reflectionless acoustic filters using bulk acoustic wave (BAW) or surface acoustic wave (SAW) resonators
Implementation Method 3
The filters achieve smaller size, reduced insertion loss, and improved return loss across a frequency range, maintaining steep passband transition regions and minimizing reflections down to DC and up to harmonic frequencies
Data Source
AI summary
Embodiments of an acoustic filter are disclosed. In some embodiments, a bandpass filter is included in a passband signal path, the passband signal path is connected between a first terminal and a second terminal. A first bandstop filter is located in a first stopband signal path, the first stopband signal path connected at the first terminal. Additionally, a second bandstop filter is located in a second stopband signal path, the second stopband signal path is connected at the second terminal.