5.5 GHz Wi-Fi Front-End Module Using Single-Crystal BAW Filtering
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Solution Overview
Problem
Conventional bulk acoustic wave resonators using polycrystalline piezoelectric thin films face degradation at frequencies above 5 GHz due to poor crystalline quality, limiting their performance in high-frequency applications, while single crystalline films maintain quality but are challenging to manufacture and integrate effectively.
Innovation Solution
The development of a method and structure for bulk acoustic wave resonator devices using single crystal piezoelectric films, integrated into a front-end module with a power amplifier, diversity switch, and low noise amplifier, which includes a 5.5 GHz resonator and a single pole two throw switch, enabling efficient high-frequency operation with a compact form factor and reduced size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polycrystalline piezoelectric thin films are used in bulk acoustic wave resonators, then manufacturing is easier and cost is lower, but crystalline quality degrades at frequencies above 5 GHz
Solution Approach 1:
The patent changes the fundamental material parameter from polycrystalline to single crystalline structure. This parameter change enables the resonator to maintain high crystalline quality at 5.5 GHz frequencies while still allowing for manufacturing through epitaxial growth techniques on compatible substrates.
Solution Approach 2:
The patent employs a composite structure combining single crystalline piezoelectric films with compatible crystalline substrates. This composite approach leverages the advantages of both the single crystal material (high quality factor at 5.5 GHz) and the substrate (manufacturability through established epitaxial growth processes).
2Reliability
If single crystal piezoelectric films are used to maintain crystalline quality at high frequencies, then performance improves, but manufacturing complexity and integration challenges increase
Solution Approach 1:
The patent segments the manufacturing process into distinct stages: growing single crystalline films on compatible substrates using epitaxial techniques, then transferring these pre-grown films to the final resonator structure. This segmentation reduces integration complexity by decoupling the film growth requirements from the final device assembly.
Solution Approach 2:
The patent uses compatible crystalline substrates as intermediaries during the manufacturing process. These substrates serve as temporary carriers that enable the growth of high-quality single crystalline films, which can then be transferred to the final resonator structure, simplifying the overall manufacturing complexity.
3Speed
If resonator thickness is reduced to increase operating frequency to 5.5 GHz, then frequency performance improves, but polycrystalline film quality degrades quickly below 0.5 um thickness
Solution Approach 1:
The patent changes the material structure parameter from polycrystalline to single crystalline, which fundamentally alters the thickness-frequency relationship. This enables the use of thinner films (below 0.5 um) at 5.5 GHz frequencies while maintaining high film quality, as single crystalline structures do not suffer from the same degradation mechanisms as polycrystalline films when thinned.
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 solution provides a cost-effective, high-performance RF filter with improved quality factor and electro-mechanical coupling, enabling efficient operation at 5.5 GHz frequencies with reduced size and power consumption, allowing coexistence with adjacent frequency bands in tri-band router configurations.
Implementation Method 1
Bulk acoustic wave resonators (BAWR) using crystalline piezoelectric thin films
Data Source
AI summary
A front end module (FEM) for a 5.5 GHz Wi-Fi acoustic wave resonator RF filter circuit. The device can include a power amplifier (PA), a 5.5 GHz resonator, and a diversity switch. The device can further include a low noise amplifier (LNA). The PA is electrically coupled to an input node and can be configured to a DC power detector or an RF power detector. The resonator can be configured between the PA and the diversity switch, or between the diversity switch and an antenna. The LNA may be configured to the diversity switch or be electrically isolated from the switch. Another 5.5 GHZ resonator may be configured between the diversity switch and the LNA. In a specific example, this device integrates a 5.5 GHz PA, a 5.5 GHZ bulk acoustic wave (BAW) RF filter, a single pole two throw (SP2T) switch, and a bypassable LNA into a single device.