Acoustic Filter Resonator Layout for Steep Upper Passband Edges
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current RF filters struggle to achieve a steep upper passband edge without requiring large-scale circuitry, which is necessary to effectively reject neighboring operating frequencies, such as transitioning from Wi-Fi 5 to Wi-Fi 6.
Innovation Solution
The implementation of a filter device with at least three series resonators and two shunt resonators, where the series resonator with the lowest anti-resonance frequency has the largest capacitance value, and the IDT area and pitch are adjusted to increase the steepness of the upper passband edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional implementations are used to obtain a steep upper passband edge, then the steepness of the upper passband edge is improved, but large-scale circuitry is required which increases device complexity and area
Solution Approach 1:
The patent changes the operating frequency parameter of the lowest operating series resonator from a higher frequency to a lower frequency. This parameter change allows the resonator to provide the necessary steepness at the upper passband edge without requiring additional circuitry elements, thereby resolving the contradiction between achieving steepness and maintaining simple circuitry.
Solution Approach 2:
Instead of adding more circuitry elements in the horizontal dimension to achieve steepness, the patent moves to the frequency dimension by lowering the operating frequency of the existing lowest series resonator. This dimensional shift allows the same circuitry to achieve the desired steepness through frequency tuning rather than through adding components.
2Manufacturing precision
If the area of the lowest operating series resonator is increased to achieve steepness, then the steepness of the upper passband edge is improved, but the overall filter area increases
Solution Approach 1:
The patent changes the operating frequency parameter rather than increasing the physical area of the resonator. By lowering the operating frequency of the lowest series resonator, the patent achieves the desired steepness effect without expanding the physical footprint of the filter, thus resolving the contradiction between steepness and area.
3Manufacturing precision
If the pitch of the electrodes is adjusted to increase capacitance, then the steepness of the upper passband edge is improved, but the resonator area increases
Solution Approach 1:
The patent primarily relies on changing the operating frequency parameter to achieve steepness. While electrode pitch adjustment is mentioned as a possible method to increase capacitance, the patent's main approach is frequency tuning, which avoids the area increase that would result from changing physical dimensions like pitch.
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 a steep upper passband edge without the need for large-scale circuitry, enhancing the filter's ability to reject neighboring frequencies and improve overall system performance.
Implementation Method 1
The IDT includes a first set of parallel fingers, extending from a first busbar and a second set of parallel fingers extending from a second busbar. The first and second sets of parallel fingers are interleaved. A microwave signal applied to the IDT excites a shear primary acoustic wave in the piezoelectric diaphragm.
Implementation Method 2
The transversely-excited film bulk acoustic resonator (XBAR) is an acoustic resonator structure for use in microwave filters. XBAR resonators provide very high electromechanical coupling and high frequency capability.
Data Source
AI summary
A filter device is provided that includes a first and second series resonator connected between a pair of ports. The device may include at least one shunt resonator connected between a ground connection and a node between the first series resonator and the second series resonator or between one of the pair of ports and one of the first and second series resonators, wherein the first and second series resonators include a first and second capacitance value, respectively, that are different from each other, and wherein the first and second series resonator and the at least one shunt resonator includes: a substrate, at least one piezoelectric layer attached either directly or via one or more intermediate layers to the substrate, and an interdigital transducer (IDT) at a surface of the at least one piezoelectric layer and including a plurality of interleaved IDT fingers.