XBAR Resonator Package With Cavity Structure for RF Filters Above 3 GHz
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Solution Overview
Problem
Current RF filters using acoustic wave resonators, such as SAW and BAW resonators, are not well-suited for higher frequency communications bands above 3 GHz, limiting their effectiveness in future wireless communication systems.
Innovation Solution
The development of transversely-excited film bulk acoustic resonators (XBARs) with a thin film conductor pattern on a piezoelectric plate, specifically designed for frequencies above 3 GHz, which includes an interdigital transducer and a cavity structure to enhance acoustic wave propagation, and a packaging method that provides mechanical protection and electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional SAW and BAW resonators are used, then the filter structure is well-established and manufacturable, but the resonators cannot operate effectively at frequencies above 3 GHz
Solution Approach 1:
The patent changes the fundamental operating parameters of the resonator by transitioning from surface acoustic wave propagation to bulk acoustic wave propagation through a thin film. This parameter change enables the resonator to operate at frequencies above 3 GHz, resolving the frequency limitation of conventional SAW and BAW resonators while maintaining manufacturability through established thin film deposition techniques
2Adaptability or versatility
If the resonator structure is modified to achieve higher frequency operation, then frequency applicability improves, but the device complexity increases
Solution Approach 1:
The resonator is segmented into distinct functional layers: a piezoelectric substrate, a thin film layer, and electrode structures. This segmentation allows each layer to be optimized independently for its specific function while maintaining overall simplicity. The thin film is deposited as a separate layer rather than requiring complex monolithic structure modifications
Solution Approach 2:
The thin film acts as an intermediary layer between the piezoelectric substrate and the electrodes. This intermediary enables bulk acoustic wave propagation at high frequencies without requiring direct modification of the substrate structure, thus achieving frequency applicability above 3 GHz while keeping the overall device structure relatively simple
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
XBARs offer improved performance for RF filters in higher frequency bands, enabling wider communication channel bandwidths and better suited for future wireless communication systems, with enhanced mechanical protection and electrical connectivity.
Implementation Method 1
a piezoelectric plate, upon which a thin film conductor pattern is formed
Implementation Method 2
an interdigital transducer and a cavity structure to enhance acoustic wave propagation
Data Source
AI summary
Acoustic resonator devices and filters are disclosed. A piezoelectric plate is attached to a substrate, a portion of the piezoelectric plate forming a diaphragm spanning a cavity in the substrate. A first conductor pattern is formed on a surface of the piezoelectric plate. The first conductor pattern includes interleaved fingers of an interdigital transducer disposed on the diaphragm, and a first plurality of contact pads. A second conductor pattern is formed on a surface of a base, the second conductor pattern including a second plurality of contact pads. Each pad of the first plurality of contact pads is connected to a respective pad of the second plurality of contact pads. A seal is formed between a perimeter of the piezoelectric plate and a perimeter of the base.