XBAR Matrix Filter Layout for Wideband RF Above 3 GHz
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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 the 5G NR standard, which necessitates the development of more effective filtering solutions for frequencies above 3 GHz.
Innovation Solution
The use of Transversely-Excited Film Bulk Acoustic Resonator (XBAR) matrix filters, which incorporate a thin film conductor pattern on a piezoelectric plate with an interdigital transducer that excites a shear primary acoustic wave, providing high electromechanical coupling and frequency capability, suitable for frequencies above 3 GHz and enabling the design of band-reject, band-pass filters, duplexers, and multiplexers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional acoustic wave resonators (SAW, BAW, FBAR) are used, then the filter structure is well-established and manufacturable, but the frequency capability and bandwidth are insufficient for future communication networks above 3 GHz
Solution Approach 1:
The patent changes the fundamental operating parameters of the resonator by switching from longitudinal acoustic wave modes to shear horizontal acoustic wave modes. This parameter change enables the resonator to operate at higher frequencies (above 3 GHz) with wider bandwidth while maintaining the established FBAR structural framework, thus resolving the contradiction between frequency capability and performance adequacy
2Productivity
If the communication bandwidth is widened to support future networks, then the data rate and network capacity improve, but the required frequency increases above 3 GHz where existing resonator technologies fail
Solution Approach 1:
The patent introduces dynamic control capabilities through varactor diodes connected to the resonator electrodes, enabling electronic tuning of the resonator's operating frequency and bandwidth. This dynamic adjustment allows the filter to adapt to different communication standards and bandwidth requirements while operating at the required high frequencies above 3 GHz, resolving the contradiction between bandwidth and frequency
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
XBAR matrix filters achieve improved performance by offering high piezoelectric coupling, enabling the design of microwave and millimeter-wave filters with appreciable bandwidth, effectively addressing the limitations of existing technologies in handling higher frequencies and wider bandwidths.
Implementation Method 1
an interdigital transducer that excites a shear primary acoustic wave
Implementation Method 2
Transversely-Excited Film Bulk Acoustic Resonator (XBAR) matrix filters
Data Source
AI summary
Radio frequency filters. A radio frequency filter includes a substrate attached to a piezoelectric plate, portions of the piezoelectric plate forming a plurality of diaphragms spanning respective cavities in the substrate. A conductor pattern formed on the piezoelectric plate includes a plurality of interdigital transducers (IDTs) of a respective plurality of resonators, interleaved fingers of each IDT disposed on a respective diaphragm of the plurality of diaphragms. The conductor pattern connects the plurality of resonators in a matrix filter circuit including a first sub-filter and a second sub-filter, each sub-filter comprising two or more resonators from the plurality of resonators.