Sandwiched XBAR Layout for Third-Harmonic Coupling and Spurious Mode Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current RF filters using acoustic wave resonators are not well-suited for higher frequencies and bandwidths required in future communication networks, particularly for 5G NR standards, as they face challenges in achieving broad band filters due to insufficient resonator coupling into higher harmonic modes.
Innovation Solution
The development of sandwiched XBAR devices with IDT electrodes embedded in a dielectric layer between two thin piezoelectric plates, which suppresses spurious modes and provides high coupling into a third harmonic mode, enabling the creation of 15 GHz bandpass filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional acoustic wave resonators are used for higher frequency operations, then frequency capability is improved, but resonator coupling into higher harmonic modes becomes insufficient
Solution Approach 1:
The resonator structure is segmented into multiple layers including a piezoelectric layer, a sacrificial layer, and a cladding layer. This segmentation allows independent optimization of each layer's properties to enhance coupling into higher harmonic modes while maintaining high frequency operation capability.
Solution Approach 2:
The patent modifies physical parameters of the resonator structure, specifically the thickness ratios of different layers (piezoelectric layer thickness to cladding layer thickness), material properties, and geometric configurations to optimize coupling into third and higher harmonic modes for frequencies above 3 GHz.
2Adaptability or versatility
If broader bandwidth filters are designed for 5G NR standards, then communication capacity is improved, but spurious modes increase
Solution Approach 1:
The patent converts the potentially harmful spurious modes into beneficial higher harmonic modes by designing the resonator structure to intentionally excite and control third harmonic and higher order modes. This allows broader bandwidth operation while maintaining signal purity through controlled harmonic generation rather than uncontrolled spurious responses.
Solution Approach 2:
The resonator employs composite material structures combining piezoelectric materials with specific dielectric cladding layers and sacrificial materials. This composite approach enables precise control over mode propagation characteristics, suppressing unwanted spurious modes while enhancing desired higher harmonic modes for wideband 5G NR filter applications.
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 allows for the design of high-frequency bandpass filters with improved resonator coupling and reduced spurious modes, effectively addressing the limitations of existing technologies in handling higher frequency ranges.
Implementation Method 1
An XBAR resonator comprises an interdigital transducer (IDT) formed on a thin floating layer, or diaphragm, of a single-crystal piezoelectric material. A microwave signal applied to the IDT excites a shear primary acoustic wave in the piezoelectric diaphragm.
Implementation Method 2
XBAR resonators provide very high electromechanical coupling and high frequency capability. XBAR resonators may be used in a variety of RF filters including band-reject filters, band-pass filters, duplexers, and multiplexers.
Data Source
AI summary
A filter device has a first piezoelectric plate spanning a first and second cavity of a substrate. A first and second interdigital transducer (IDT) are on a front surface of the first piezoelectric plate over the first and second cavity. A dielectric layer is formed on the first piezoelectric plate and covers the first IDT and second IDT. A second piezoelectric plate is bonded to a front surface of the dielectric layer over the first cavity and the second cavity. A second dielectric layer is formed on a front surface of the second piezoelectric plate over the first cavity but not over the second cavity. The thickness of the dielectric layer, the first piezoelectric plate and the second piezoelectric plate can be selected to tune a shunt resonator over the first cavity and a series resonator over the second cavity.