RF Filter Module Layout for Temperature Stability in Smaller Footprints
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Solution Overview
Problem
Conventional RF filters face challenges in maintaining temperature ruggedness while minimizing size, as adding temperature compensating layers to all resonators degrades contour size and increases complexity, and omitting them can impact frequency stability and skirt steepness.
Innovation Solution
A filter module design that selectively uses temperature compensating layers for specific resonators, allowing for tailored temperature coefficient of frequency and resonator thickness variations to enhance temperature ruggedness and reduce contour size, by combining resonators with and without TC layers in a single module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If temperature compensating layers are added to all resonators, then temperature stability is improved, but contour size increases and device complexity increases
Solution Approach 1:
The patent applies temperature compensating layers selectively to specific resonators based on their individual temperature coefficients of frequency (TCF). Resonators with higher TCF values receive compensating layers, while those with lower TCF values do not. This localized approach maintains temperature stability for critical resonators while avoiding unnecessary size increases from universal application.
Solution Approach 2:
Instead of applying temperature compensating layers to all resonators (excessive action), the patent applies them only to the extent necessary - specifically to resonators whose TCF values require compensation. This partial action achieves the required temperature stability while minimizing the added contour size.
2Stability of the object's composition
If temperature compensating layers are added to all resonators, then temperature stability is improved, but device complexity increases
Solution Approach 1:
The patent differentiates between resonators based on their individual TCF characteristics, applying compensating layers only where needed. This creates a differentiated structure that reduces complexity compared to a uniform approach applied to all resonators.
Solution Approach 2:
The patent changes the parameter of temperature compensating layer presence based on the TCF value of each resonator. By adjusting this parameter selectively, the system achieves temperature stability without the complexity overhead of universal application.
3Area of stationary object
If temperature compensating layers are omitted from resonators, then contour size is reduced, but frequency stability deteriorates
Solution Approach 1:
The patent applies compensating layers locally to resonators that require frequency stability, while omitting them from resonators where stability is less critical. This selective approach maintains overall filter performance while minimizing contour size.
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 improves temperature stability and filter performance by allowing degrees of freedom in design, reducing contour size, and optimizing resonator performance for critical characteristics, while maintaining efficient frequency handling and rejection.
Implementation Method 1
at least one resonator among the plurality of series resonators and the plurality of shunt resonators being a first type of resonator with a temperature compensating layer for better temperature coefficient of frequency
Implementation Method 2
An acoustic wave filter, which is used widely in the wireless communication field, can include a plurality of resonators arranged to filter a radio frequency signal. Example acoustic wave filters include surface acoustic wave (SAW) filters and/or bulk acoustic wave (BAW) filters.
Data Source
AI summary
A filter module comprises a first terminal, a second terminal, and a filter disposed along each signal path extending from the first terminal to the second terminal, the filter including a plurality of series resonators and a plurality of shunt resonators disposed between the series resonators and a ground, at least one resonator among the plurality of series resonators and the plurality of shunt resonators being a first type of resonator with a temperature compensating layer for better temperature coefficient of frequency, at least one resonator among the plurality of series resonators and the plurality of shunt resonators being a second type of resonator without a temperature compensating layer.