Coupled Acoustic Resonator Notch Filters for Low-Loss Multi-Band RF
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Solution Overview
Problem
Current RF filters for wireless communication, particularly in LTE standards, face challenges with high insertion loss, increased area consumption, and complexity due to the need to support multiple frequency bands, leading to higher power requirements and interference issues.
Innovation Solution
The development of acoustically coupled resonator notch filters using Bulk Acoustic Wave (BAW) technology, which replaces capacitive elements in all-pass lumped element networks with the natural capacitances of BAW resonators, such as Stacked Crystal Filters (SCF) or Coupled Resonator Filters (CRF), to create compact, tunable, and highly selective RF notch filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional RF filters are used to support multiple frequency bands, then frequency band coverage is improved, but insertion loss increases and area consumption increases
Solution Approach 1:
The patent implements a universal filter design using coupled acoustic resonators that can operate across multiple frequency bands through a single device structure. The resonators are designed with specific coupling coefficients and impedance transformations that enable the same filter topology to provide frequency-selective filtering for different bands, eliminating the need for multiple separate filters and reducing overall insertion loss.
Solution Approach 2:
The patent replaces conventional electrical lumped-element components with acoustic resonator-based filtering mechanisms. By using acoustic waves and resonant structures instead of traditional electrical circuits, the system achieves frequency selectivity through acoustic impedance transformations and coupling, resulting in lower insertion loss and reduced area consumption while maintaining multi-band capability.
2Adaptability or versatility
If conventional RF filters are used to support multiple frequency bands, then frequency band coverage is improved, but area consumption increases
Solution Approach 1:
The patent merges multiple filtering functions into a single integrated acoustic resonator structure. By combining multiple resonators with specific coupling arrangements in one compact device, the filter provides multi-band frequency selectivity without requiring separate filter components for each band, thereby significantly reducing the total area consumption while maintaining versatility.
Solution Approach 2:
The patent transitions from planar two-dimensional filter layouts to three-dimensional acoustic resonator structures with vertical stacking and layered coupling. This dimensional change allows multiple filtering functions to be integrated in the vertical dimension rather than requiring extensive horizontal space, achieving compact area consumption while supporting multiple frequency bands.
3Reliability
If conventional RF filters are used, then filtering function is provided, but device complexity increases
Solution Approach 1:
The patent segments the filtering function into multiple independent acoustic resonators with defined coupling relationships. Each resonator handles a specific frequency range or function, and their combined response provides the overall multi-band filtering capability. This segmentation simplifies the design and analysis compared to complex electrical circuits while maintaining reliable filtering performance.
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 approach reduces the complexity and size of RF frontends, improves reference sensitivity, and enhances attenuation capabilities, making them suitable for future mobile communication standards by minimizing the number of components and form factor while maintaining high selectivity and flexibility.
Implementation Method 1
acoustically coupled resonator notch filters using Bulk Acoustic Wave (BAW) technology
Implementation Method 2
acoustically coupled resonator notch filters using Bulk Acoustic Wave (BAW) technology
Data Source
Figure 1(a)~1(c)
Figure 1(d)~2(a)
Figure 2(b)~3(a)
AI summary
A notch filter includes a first inductor coupled between an input node and an output node, a dual-resonator structure coupled between the input node and the output node, and a second inductor coupled between the dual-resonator structure and ground.