Folded Resonator RF Filter for Compact Negative Coupling
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Solution Overview
Problem
Existing small size metal filters face challenges in achieving desired resonator coupling, leading to increased size, cost, and performance issues due to the need for extra negative coupling pieces and spurious parasitic zeros.
Innovation Solution
The design incorporates resonators with body parts, enlarged portions, and folded portions made of metal strip lines or metallized surfaces, allowing for easy negative coupling by adjusting the orientation and placement of folded portions, eliminating the need for extra coupling pieces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If normal air-strip line metal filters use extra negative coupling pieces to achieve transmission zero, then transmission zero performance is improved, but filter size and cost increase
Solution Approach 1:
The patent merges the negative coupling function into the resonator structure itself by adding folded portions to the resonator body. This integration eliminates the need for separate negative coupling pieces, achieving both transmission zero performance and compact filter size simultaneously.
Solution Approach 2:
The folded portions are nested within the resonator structure, with the coupling function embedded in the resonator body. This nesting approach allows the filter to achieve negative coupling without adding external components, thereby reducing overall filter size.
2Adaptability or versatility
If resonators are changed in direction to achieve negative coupling, then coupling capability is improved, but spurious parasitic zeros increase and tuning difficulty increases
Solution Approach 1:
The patent applies local quality by adding folded portions only to specific resonators where negative coupling is needed. This localized modification allows precise control over coupling characteristics while minimizing the generation of spurious parasitic zeros in other parts of the filter.
Solution Approach 2:
The folded portions provide dynamic coupling adjustment capability, allowing the filter to achieve desired coupling characteristics without rigid structural changes. This flexibility enables better control over parasitic zeros while maintaining coupling capability.
3Adaptability or versatility
If resonators are produced separately and assembled, then manufacturing flexibility is improved, but assembly complexity and production difficulty increase
Solution Approach 1:
The patent combines the resonator body and coupling structure into a single integrated component. This merging simplifies the assembly process by reducing the number of separate parts that need to be assembled, while still maintaining manufacturing flexibility through standardized resonator designs.
Data Source
AI summary
An RF filter, comprising a chassis (1) that defines a cavity, and a plurality of resonators (2a, 2b) that are disposed in the cavity, wherein at least one resonator (2) comprises a body part (21) that extends in a first plane from a first end to an opposite second end along a first direction, an enlarged portion (22) that is provided at the second end and extends in the first plane along a second direction substantially perpendicular to the first direction so as to have a larger width in the second direction than the body part (21), and a folded portion (23) that is formed by bending along a lateral edge of the enlarged portion (22) at an angle of about 90° so as to extend in a second plane substantially perpendicular to the the second direction. The folded portion (23) plays a role in forming a coupling of the resonator with an adjacent resonator. The body part (21), the enlarged portion (22) and the folded portion (23) are made of a metal strip line, or a strip-line made of non-metal base with a metallized surface. The folded positions of two adjacent resonators can achieve desired coupling polarity.