Electro Acoustic RF Filter With Damped Inactive Impedance Element
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Solution Overview
Problem
Conventional RF filters experience performance degradation due to unwanted acoustic activity in capacitance elements intended to be acoustically inactive, leading to increased electrode finger resistance loss and manufacturing complexities.
Innovation Solution
An electro acoustic RF filter design that includes an acoustically inactive impedance element electrically coupled to an electro acoustic resonator, with a damping and/or dissipation element to remove acoustic energy and suppress unwanted acoustic effects, thereby reducing acoustic activity and resonance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional capacitance elements are used in RF filters, then fabrication efforts are reduced, but unwanted acoustic activity occurs resulting in performance degradation
Solution Approach 1:
A damping layer is introduced as an intermediary element between the capacitance element and the acoustic field. This damping layer absorbs acoustic energy and prevents it from coupling into the piezoelectric substrate, thereby eliminating unwanted acoustic activity while preserving the electrical functionality of the capacitance element.
Solution Approach 2:
The patent converts the harmful acoustic energy generated by capacitance elements into a beneficial dissipation mechanism. By placing damping material adjacent to the capacitance element, the acoustic energy that would otherwise cause performance degradation is absorbed and converted into heat, transforming a harmful effect into a controlled energy dissipation process.
2Object-generated harmful factors
If interdigitated structures are rotated to reduce electro acoustic coupling, then acoustic activity is reduced, but electrode finger resistance loss increases
Solution Approach 1:
Instead of rotating the interdigitated structures, a damping layer is placed as an intermediary between the capacitance element and the piezoelectric substrate. This approach reduces acoustic coupling without altering the electrical geometry, thereby avoiding increased electrode finger resistance loss while still achieving the goal of reducing acoustic activity.
Solution Approach 2:
The patent changes the acoustic parameter (acoustic coupling) by introducing a damping layer with specific acoustic absorption properties, rather than changing the electrical parameter (interdigitated structure orientation). This allows independent optimization of both acoustic performance and electrical performance.
3Object-generated harmful factors
If acoustic resonance frequencies are shifted away from working frequencies, then acoustic interference is reduced, but manufacturing tolerances become more critical
Solution Approach 1:
A damping layer is introduced as an intermediary that broadly absorbs acoustic energy across multiple frequencies. This approach reduces acoustic resonance interference without requiring precise frequency matching or critical dimensional tolerances, as the damping layer's acoustic absorption property is less sensitive to manufacturing variations compared to resonant frequency tuning.
Solution Approach 2:
The patent changes the approach from frequency-based acoustic control (which requires precise resonance frequency matching) to material-based acoustic control (using damping layers with specific loss tangents). This parameter change from frequency-domain to material-domain control reduces sensitivity to manufacturing tolerances.
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 unwanted acoustic resonances and improves filter performance by preventing acoustic energy accumulation, enhancing the filter's electric performance and compatibility with miniaturization trends without significant manufacturing complexity increases.
Implementation Method 1
The damping and/or dissipation element is provided and configured to remove acoustic energy from the inactive impedance element by either dissipation of acoustic energy
Implementation Method 2
The electro acoustic resonators can use the piezoelectric effect to convert between electromagnetic RF signals and acoustic waves
Data Source
AI summary
An improved electro acoustic RF filter (FC) is provided . The RF filter comprises an electro acoustic resonator (EAR) connected between an input port and an output port, an impedance element and a damping and/or dissipation element (DE) in mechanical contact to the impedance element. The damping and/or dissipation element is provided and configured to remove acoustic energy from the impedance element which has a similar construction as the resonator on the same substrate. With such a construction an acoustically inactive impedance element (AIIE) is obtained.