XBAR Package Structure for Low-Loss RF Filtering Above 3 GHz
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current RF filters using acoustic wave resonators are not well-suited for higher frequency communications bands above 3 GHz, such as those proposed for future wireless communication systems, as they fail to provide optimal performance in terms of insertion loss, rejection, isolation, power handling, linearity, size, and cost.
Innovation Solution
The development of transversely-excited film bulk acoustic resonators (XBARs) utilizing 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 packaged with an interposer and cap to provide mechanical protection and electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional acoustic wave resonators are used for RF filters, then the filters can operate at lower frequencies, but they fail to provide optimal performance at higher frequency bands above 3 GHz
Solution Approach 1:
The patent changes the fundamental operating parameters of the resonator by transitioning from surface acoustic wave (SAW) or bulk acoustic wave (BAW) modes to transversely-excited film bulk acoustic resonator (XBAR) mode. This involves changing the excitation direction, resonator geometry, and acoustic wave propagation characteristics to enable optimal performance at frequency bands above 3 GHz while maintaining reliability
Solution Approach 2:
The invention introduces a transverse excitation dimension by placing interdigital transducers on opposite sides of the piezoelectric substrate, exciting acoustic waves that propagate perpendicular to the substrate surface. This dimensional change in wave propagation enables the resonator to achieve the necessary quality factors and frequency responses for high-band RF filtering
2Device complexity
If existing RF filter designs are used, then the structure is relatively simple, but they exhibit high transmission loss and poor filter characteristics at higher frequencies
Solution Approach 1:
The patent implements a nested structure where the piezoelectric substrate contains embedded cavities that hold dielectric materials, which in turn support the interdigital transducers. This nested arrangement creates acoustic mirrors and resonant cavities that trap and enhance acoustic energy, reducing transmission loss through the filter while maintaining a compact overall structure
Solution Approach 2:
The invention uses composite material structures combining piezoelectric substrates with high-dielectric-constant materials in the cavities. This composite approach creates acoustic impedance mismatches that reflect acoustic waves back into the resonator, enhancing the quality factor and reducing energy loss at high frequencies
3Ease of manufacture
If traditional acoustic wave resonators are used, then manufacturing is straightforward, but they cannot support wider communication channel bandwidths required for future wireless standards
Solution Approach 1:
The XBAR resonator design provides a universal platform that can be configured for different frequency bands and filter responses by adjusting the interdigital transducer geometry, cavity dimensions, and dielectric material properties. This multi-functionality allows the same basic structure to support wider communication channel bandwidths while maintaining compatibility with existing semiconductor manufacturing processes
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 in RF filters for higher frequency bands by reducing transmission loss and enhancing filter characteristics, enabling wider communication channel bandwidths and supporting future wireless communication standards.
Implementation Method 1
a piezoelectric plate, upon which is formed a thin film conductor pattern
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.