XBAR Matrix Filter Layout for Noncontiguous 5G Passbands
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current RF filters using acoustic wave resonators are not well-suited for higher frequencies and wider bandwidths required in future communication networks, such as those defined in the 5G NR standard, particularly for bands n77, n79, and millimeter wave frequencies.
Innovation Solution
The development of transversely-excited film bulk acoustic resonators (XBARs) and matrix XBAR filters, which utilize a thin film conductor pattern on a piezoelectric plate with an interdigital transducer to achieve high electromechanical coupling and frequency capability, enabling the design of band-reject, band-pass filters, duplexers, and multiplexers suitable for frequencies above 3 GHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional SAW, BAW, or FBAR resonators are used, then the filter structure is well-established and manufacturable, but the frequency capability and bandwidth are insufficient for 5G NR and millimeter wave applications
Solution Approach 1:
The patent changes the fundamental operating parameters of the resonator by transitioning from longitudinal wave modes (BAW, FBAR) to shear horizontal wave modes in a transversely-excited configuration. This parameter change enables operation at higher frequencies (5G NR and millimeter wave bands) while maintaining the bulk acoustic wave mechanism that provides superior performance compared to surface acoustic wave (SAW) devices.
2Adaptability or versatility
If the filter bandwidth is increased to support wider communication channels, then the frequency range expands, but the selectivity and rejection performance deteriorate
Solution Approach 1:
The patent segments the filter into multiple independent resonator circuits, each tuned to specific frequency ranges. By combining multiple segmented resonators with different center frequencies and bandwidths, the filter achieves both wide overall bandwidth and sharp selectivity within each passband. This segmentation allows independent optimization of each resonator for its specific frequency range while maintaining overall filter performance.
3Speed
If more resonators are added to increase bandwidth and frequency coverage, then the frequency capability improves, but the device complexity and size increase
Solution Approach 1:
The patent designs universal resonator circuits that can be configured for different frequency ranges by adjusting the resonator parameters rather than requiring completely different resonator types. The same basic resonator structure can serve multiple frequency bands (sub-6 GHz, 5G NR, millimeter wave) by changing the piezoelectric material and geometric parameters, reducing overall device complexity.
Solution Approach 2:
The patent employs a nested architecture where multiple resonator circuits are integrated within a compact filter structure. The resonators are arranged and coupled in a nested configuration that allows frequency multiplication and harmonic utilization, enabling wide frequency coverage without proportionally increasing the physical size of the filter.
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 provide improved performance compared to existing SAW, FBAR, and BAW devices, enabling the design of filters with appreciable bandwidth and high piezoelectric coupling, suitable for next-generation communication systems, including 5G NR and millimeter wave frequencies.
Implementation Method 1
a piezoelectric plate with an interdigital transducer to achieve high electromechanical coupling
Implementation Method 2
acoustic wave resonators including surface acoustic wave (SAW) resonators, bulk acoustic wave (BAW) resonators, film bulk acoustic wave resonators (FBAR)
Data Source
AI summary
There are disclosed matrix filters having an input port and sub-filters connected between the input port and respective output ports. Each of the sub-filters includes a ladder circuit with n transversely-excited film bulk acoustic resonator (XBAR) series elements and n−1 capacitor shunt elements, where n, the order of the sub-filter, is an integer greater than 2. The sub-filters having noncontiguous passbands.