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 pure electric capacitance elements, which are intended to be acoustically inactive, leading to increased electrode finger resistance loss and manufacturing complexity.
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 connected to remove acoustic energy, either by dissipation, reduced coupling, or suppressing acoustic modes, thereby eliminating unwanted acoustic effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional capacitance elements with interdigitated structures 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 interdigitated capacitance structure and the piezoelectric substrate. This damping layer absorbs acoustic energy and prevents unwanted acoustic activity while maintaining the electrical capacitance function, thus resolving the contradiction between ease of manufacture and filter performance
Solution Approach 2:
The harmful acoustic activity is extracted and isolated from the capacitance element by introducing a separate damping layer. This allows the capacitance element to maintain its simple interdigitated structure for easy fabrication while the damping layer independently handles the acoustic energy dissipation
2Object-generated harmful factors
If interdigitated structures are rotated relative to the piezoelectric axis to reduce electro acoustic coupling, then acoustic activity is reduced, but electrode finger resistance loss increases
Solution Approach 1:
The damping layer serves as a mediator that allows the interdigitated structure to maintain its optimal orientation for electrical performance while absorbing the acoustic energy that would otherwise cause harmful acoustic activity. This eliminates the need to rotate the structure and accept increased resistance loss
3Object-generated harmful factors
If acoustic resonance frequencies are shifted away from working frequency ranges, then acoustic activity is reduced, but manufacturing complexity increases due to smaller tolerances
Solution Approach 1:
The damping layer provides a straightforward manufacturing approach by simply adding a dissipative material layer, avoiding the need for complex frequency shifting techniques that would require precise control of acoustic resonance frequencies and smaller tolerances
Solution Approach 2:
Instead of changing the geometric parameters of the interdigitated structure to shift acoustic frequencies, the solution changes the material parameter by introducing a damping layer with specific loss characteristics, which is easier to manufacture with standard 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 in RF filters, enhancing filter performance by suppressing acoustic energy in inactive impedance elements, which improves the filter's electric performance without increasing manufacturing complexity or chip space requirements, and is compatible with miniaturization trends.
Implementation Method 1
a damping and/or dissipation element connected to the acoustically inactive impedance element, where 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, or by reducing the coupling or by suppressing an acoustic mode
Implementation Method 2
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 3
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.