Dual Notch RF Filter Skirt Feature Optimization
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Solution Overview
Problem
Existing radio frequency filters face a trade-off between skirt feature and insertion loss, where improving skirt feature without increasing filter stages is challenging, and creating multiple notches at both ends of the processing band is difficult without additional structures.
Innovation Solution
The implementation of a dual notch structure using C-type and L-type notch configurations, where C-type notches are formed through capacitance coupling and L-type notches through inductance coupling, allowing for the creation of notches at both ends of the processing band in multi-stage filters without increasing the number of stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the stages of the filter are increased to improve the skirt feature, then the skirt feature becomes better, but the insertion loss becomes worse
Solution Approach 1:
The filter is divided into multiple resonators (first resonator, second resonator, third resonator) that are selectively coupled through coupling structures. This segmentation allows the filter to achieve complex frequency response characteristics with a limited number of stages, improving the skirt feature without proportionally increasing insertion loss.
Solution Approach 2:
Coupling structures (including capacitance coupling structures and inductance coupling structures) are introduced as intermediaries between resonators to control the frequency response. These coupling structures enable precise adjustment of the skirt feature by modifying the interaction between resonators, achieving better frequency selectivity without simply adding more filter stages.
2Manufacturing precision
If a single notch structure is used to improve the skirt feature, then the skirt feature is enhanced at one frequency band, but it is difficult to provide notch features at multiple frequency bands simultaneously
Solution Approach 1:
The filter incorporates multiple resonators (first, second, and third resonators) that can be independently coupled to create multiple notch features at different frequency bands. Each resonator-coupling combination can contribute to a specific notch, enabling the filter to provide multiple notches simultaneously without requiring separate filter sections.
Solution Approach 2:
The coupling structures serve multiple functions: they enable energy transfer between resonators, create notch features at specific frequency bands, and allow adjustment of both the skirt feature and insertion loss characteristics. This multi-functionality allows a single filter structure to achieve multiple notch features across different 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
This approach enhances the skirt feature of radio frequency filters by creating multiple notches, particularly in four-stage filters, while maintaining efficient insertion loss characteristics, and can be applied to various stage filters, including those beyond six stages.
Implementation Method 1
C-type notches are formed through capacitance coupling
Implementation Method 2
L-type notches through inductance coupling
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The present invention relates to a radio frequency filter employing a notch structure, wherein the notch structure is a dual notch structure which comprises: a C notch structure formed in a predetermined region at a partition between two cavities to be cross-coupled; and an L notch structure formed together with the C notch structure in a predetermined region at a partition between two cavities.