XBAR Matrix Filter Switching for Wideband 5G RF Passbands
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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, particularly for 5G NR standards, which demand improved performance in handling higher frequency bands such as n77, n79, and millimeter wave communications.
Innovation Solution
The development of Transversely-Excited Film Bulk Acoustic Resonator (XBAR) matrix filters with noncontiguous passbands, utilizing a thin film conductor pattern on a piezoelectric plate with an interdigital transducer (IDT) that excites a shear primary acoustic wave, providing high electromechanical coupling and suitable for frequencies above 3 GHz, enabling the design of band-reject 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 range is limited and bandwidth is insufficient for 5G NR standards
Solution Approach 1:
The patent employs reconfigurable filter architectures where resonator elements can be dynamically switched in and out of the signal path using electronic switches. This allows the filter to adapt its frequency response and bandwidth characteristics dynamically, enabling it to handle multiple 5G NR frequency bands and bandwidth configurations with a single device structure.
Solution Approach 2:
The invention changes the electrical parameters of the filter by switching different resonator combinations into and out of the passband. By controlling the state of switches connected to individual resonators, the filter can adjust its center frequency, bandwidth, and rejection characteristics to match different 5G NR operational requirements.
2Adaptability or versatility
If more resonators are added to increase bandwidth, then the frequency coverage improves, but the device complexity and size increase
Solution Approach 1:
The filter is divided into multiple independent resonator elements that can be individually controlled. Each resonator can be switched independently into or out of the passband, allowing the total bandwidth to be segmented and reconfigured based on the specific communication band requirements, rather than requiring all resonators to be active simultaneously.
Solution Approach 2:
The same resonator array serves multiple functions by being reconfigured for different frequency bands and bandwidths. The resonators are designed with universal characteristics that allow them to contribute to different passbands depending on their switching state, reducing the need for separate filter structures for each frequency band.
3Adaptability or versatility
If reconfigurable switches are added to enable band switching, then the adaptability to different 5G bands improves, but the insertion loss increases
Solution Approach 1:
The patent uses carefully designed switching elements that act as intermediaries between the resonators and the signal path. These switches are positioned and designed to minimize their impact on signal transmission when in the conducting state, and to provide proper isolation when in the off state, thereby reducing the insertion loss penalty associated with reconfigurability.
4Speed
If higher frequency operation is enabled, then the 5G NR band coverage improves, but the electromechanical coupling decreases
Solution Approach 1:
The filter employs resonators constructed from composite material structures, including piezoelectric films deposited on substrate materials. This composite approach allows optimization of the electromechanical coupling coefficient at higher frequencies by selecting and combining materials with complementary properties, thereby maintaining reliable signal transmission at 5G NR frequency bands.
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 better performance than existing SAW, FBAR, and BAW devices by offering high piezoelectric coupling, enabling the design of microwave and millimeter-wave filters with appreciable bandwidth, suitable for 5G NR frequency bands, and allowing for reconfigurable filters with low loss and high rejection, addressing the limitations of current technologies.
Implementation Method 1
an interdigital transducer (IDT) that excites a shear primary acoustic wave
Implementation Method 2
providing high electromechanical coupling
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. Each sub-filter further has a first switch in parallel with a first capacitor shunt element and a second switch in parallel with a last capacitor shunt element.