Tunable BAW Resonator Filter for Wideband RF Selectivity
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Solution Overview
Problem
Conventional RF filters for communication devices require a large number of discrete components due to fixed resonance frequencies, leading to increased circuit complexity, radio frequency losses, and limited space in mobile devices, necessitating the development of tunable filters with improved tuning range and selectivity.
Innovation Solution
The integration of acoustically coupled BAW resonators with a tuning circuit, utilizing different piezoelectric materials for the resonators to achieve a wide tuning range while maintaining a small bandwidth, and using a variable capacitor and inductor in the tuning circuit to shift resonance frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional fixed-frequency BAW resonators are used, then high selectivity is achieved, but a large number of discrete filters are required increasing device complexity and space
Solution Approach 1:
The patent implements a universal filter structure where a single BAW resonator can operate across multiple frequency bands by dynamically adjusting its resonance frequency through voltage-controlled capacitance. The filter is designed to support both FDD and TDD modes, as well as multiple LTE bands, replacing what would traditionally require multiple discrete fixed-frequency filters.
Solution Approach 2:
The patent introduces dynamic frequency tuning capability by replacing fixed capacitors with voltage-controlled variable capacitors. This allows the resonance frequency of the BAW resonator to be dynamically adjusted during operation, enabling the filter to adapt to different frequency bands and communication modes without requiring physical reconfiguration or multiple separate filters.
2Reliability
If multiple discrete filters are used for different frequency bands, then frequency selectivity is maintained, but radio frequency losses increase due to multiple components
Solution Approach 1:
The patent merges multiple filter functions into a single integrated BAW resonator structure. By combining the filtering functionality for multiple frequency bands into one resonator with dynamic tuning capability, the number of discrete components is reduced, thereby minimizing the cumulative RF losses that would occur through multiple separate filter components and interconnections.
3Ease of manufacture
If fixed-frequency filters are implemented, then manufacturing simplicity is maintained, but space requirements increase due to the need for multiple filters
Solution Approach 1:
The patent designs a universal filter structure that can serve multiple frequency bands and communication modes (FDD/TDD, multiple LTE bands) through a single BAW resonator. This multi-functional approach significantly reduces the number of discrete filters needed, thereby reducing the space required for the RF front end while maintaining the ability to manufacture using standard BAW processes.
4Adaptability or versatility
If conventional tuning techniques are applied to BAW filters, then some tuning capability is achieved, but tuning range and selectivity are limited with increased losses
Solution Approach 1:
The patent changes the capacitance parameter of the tuning circuit by using voltage-controlled variable capacitors instead of fixed capacitors. This parameter change enables continuous frequency tuning across a wide range while maintaining high selectivity. The BAW resonator is designed with optimized coupling and capacitance values that allow for extensive tuning range without introducing significant losses, overcoming the limitations of conventional tuning techniques.
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 number of filters required, minimizes circuit complexity, and enhances the tuning range, allowing for more efficient use of space in communication devices while maintaining high selectivity and reducing radio frequency losses.
Implementation Method 1
a piezoelectric material provided between the first and second electrodes
Implementation Method 2
acoustically coupled BAW resonators
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A resonator element for use in a filter (1800) is provided. The resonator element (1812,1814,1816) includes a first resonator (1812A,1814A,1816A) acoustically coupled to a second (1812B,1814B,1816B) or third resonator or both. The first resonator has terminals for incorporation in a filter structure. A tuning circuit (1812C,1814C,1816C) is coupled to the second or third resonator or both to enable tuning of the resonator element. The tuning circuit includes a variable capacitor and an inductor.