Capacitive Reflector Structure for Steeper SAW Resonator Skirts
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Solution Overview
Problem
Existing acoustic wave elements, such as SAW resonators, face challenges in achieving steep skirt characteristics without increasing the device area, especially with the demand for miniaturization in 5G front-end modules.
Innovation Solution
The implementation of a capacitive reflector structure using a slit reflector in acoustic wave elements, which shifts the parallel resonance frequency toward the series resonance frequency without additional capacitors, thereby improving skirt characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional capacitors are connected to the acoustic wave element to improve skirt characteristics, then the parallel resonance frequency shifts toward the series resonance frequency, but the device area increases
Solution Approach 1:
The patent merges the capacitor function into the reflector structure by forming capacitive electrodes that are electrically connected to the IDT electrodes through conductive layers. This integration eliminates the need for separate discrete capacitors while achieving the desired frequency shift and improved skirt characteristics, thereby resolving the contradiction between performance improvement and area increase
Solution Approach 2:
The reflector structure is given dual functionality: it serves both as an acoustic wave reflector (through its grating structure) and as a capacitor (through the capacitive electrodes formed between IDT electrodes and reflector electrodes). This multi-functionality allows the same structure to achieve both frequency shift and area efficiency, resolving the technical contradiction
2Adaptability or versatility
If more filters and RF devices are added to limited space for 5G front-end modules, then the number of acoustic wave elements increases, but mutual interference between frequencies increases
Solution Approach 1:
The patent uses acoustic field management through carefully designed reflector structures that control acoustic wave propagation. The capacitive reflectors create specific acoustic impedance patterns that redirect waves constructively, allowing multiple filters to operate in close proximity without mutual interference by managing the acoustic field environment
Solution Approach 2:
The patent changes the electrical and acoustic parameters of the reflector structure by forming capacitive electrodes with specific capacitance values. This parameter modification allows precise control over resonance frequencies and impedance matching, enabling multiple filters to operate at different frequencies without interference while maintaining compact spacing
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
This configuration allows for enhanced skirt characteristics, achieving a steeper response curve and improved frequency selectivity without increasing the device area, thus supporting the miniaturization needs of 5G technology.
Implementation Method 1
an acoustic wave element with a capacitive reflector structure by implementing a capacitor function to move a parallel resonance frequency toward a series resonance frequency in the acoustic wave element used in a resonator or a filter that converts an electrical signal into an acoustic wave of a piezoelectric material using a piezoelectric effect of the piezoelectric material and converts the converted acoustic wave back into an electrical signal
Implementation Method 2
a slit reflector that is placed in the propagation direction of the acoustic wave generated from the IDT electrode to reflect the acoustic wave to the IDT electrode
Implementation Method 3
forms slit capacitance, a slit structure that functions as capacitance
Data Source
AI summary
An acoustic wave element having reflectors providing capacitance according to the present invention further improves skirt characteristics of the acoustic wave element steeply by configuring the reflector structure of the acoustic wave element such as a SAW resonator, a composite resonator, and DMS as a capacitive reflector structure so that the parallel resonance frequency can be shifted toward the series resonance frequency without additional capacitors connected to the acoustic wave element while maintaining the area.