Loaded Series Resonators for LBAW Filter Sideband Notches
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Solution Overview
Problem
Lateral Bulk Acoustic Wave (LBAW) filters used in radio-frequency applications suffer from unwanted sidebands, which affect their band pass filter characteristics and overall performance.
Innovation Solution
Incorporating one or more acoustic resonators in series with the LBAW filter, featuring impedance notches at specific frequencies within the sideband range, to suppress parasitic sidebands and enhance the filter's stop-band response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If LBAW filters are used for radio-frequency applications, then small size and mass-production capability are achieved, but unwanted sidebands appear affecting band pass filter characteristics
Solution Approach 1:
The filter is segmented into multiple functional components: the main LBAW filter element and additional series resonators. Each resonator is designed with specific impedance notches at predetermined frequencies to target and suppress particular sidebands. This segmentation allows the filter to maintain compact size while improving band pass characteristics through the combined action of multiple specialized components.
Solution Approach 2:
Series resonators are introduced as intermediary elements between the signal source and the LBAW filter element. These resonators act as mediators that selectively block unwanted sideband frequencies through their impedance notches while allowing the desired passband frequencies to pass through, thereby cleaning up the filter output without affecting the main filtering function.
2Reliability
If series resonators with impedance notches are added to suppress sidebands, then stop-band response is improved, but device complexity increases
Solution Approach 1:
Multiple resonators with different impedance notches are merged in series with the LBAW filter element. By combining these resonators, the filter achieves comprehensive sideband suppression across multiple frequency ranges. The merging of components in series allows each resonator to contribute its specific frequency-selective特性, creating a unified filter structure with enhanced stop-band response.
Solution Approach 2:
The resonators are designed with specific impedance notches at predetermined frequencies that correspond to the unwanted sidebands. By carefully selecting and adjusting the notch frequencies and Q-factors of the resonators, the filter achieves optimal sideband suppression. This parameter optimization allows effective stop-band performance while minimizing the number of additional components 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
The solution effectively suppresses sidebands, improving the wideband and stop-band response of LBAW filters, allowing for simpler fabrication, higher frequency operation, and wider bandwidth compared to traditional filters, while maintaining a smaller size and reduced complexity.
Implementation Method 1
By applying an alternating voltage across the piezoelectric layer at the input resonator, a mechanical resonance is formed in the piezoelectric layer below the input electrode
Implementation Method 2
The first resonator has a first notch in resonator impedance at a first frequency, wherein one of the top and the bottom electrodes of the first resonator is electrically connected to the acoustic wave filter element
Data Source
AI summary
An acoustic wave filter device is disclosed. The device includes an acoustic wave filter element, and a first resonator and a second resonator coupled to the acoustic wave filter element. The acoustic wave filter element includes interdigited input electrodes and output electrodes located on a top surface of a piezoelectric layer. Each of the first and the second resonators includes a top electrode on the top surface, and a bottom electrode on the bottom surface of the piezoelectric layer. At least one of each of the first and the second resonators' electrodes is electrically connected to the acoustic wave filter element. The first resonator has a first notch in resonator impedance at a first frequency. The second resonator includes a first mass loading layer on the second resonator electrode such that the second resonator has a second notch in resonator impedance at a second frequency different from the first frequency.