Variable RF Band Filter Tuning Structures
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Solution Overview
Problem
Existing variable radio frequency band filters face challenges in achieving high Q-factor and robust, fault-tolerant tuning while minimizing dielectric losses and manufacturing costs, particularly in maintaining accuracy and robustness against tolerances.
Innovation Solution
A variable radio frequency band filter design featuring a housing with cavities and resonators, where tuning structures are mechanically connected to shift simultaneously, with a small gap between metallic surfaces and the cavity wall to achieve virtual grounding, and a plastic base member with metal plating for precise and cost-effective tuning, along with a field blocking element to suppress dielectric losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dielectric tuning rods are placed in very close proximity to the resonator to achieve a wide tuning range, then the tuning range is improved, but dielectric losses increase and Q-factor decreases
Solution Approach 1:
The patent removes the dielectric material from the tuning structure, extracting the harmful dielectric losses from the system. The tuning is achieved using only metallic surfaces (tuning plates) that can be shifted relative to the resonator without introducing dielectric losses, while still achieving the required tuning range through the capacitive coupling mechanism.
Solution Approach 2:
The patent introduces an air gap as an intermediary between the metallic tuning surfaces and the resonator, replacing the direct dielectric contact. This air gap acts as a lossless medium that allows capacitive coupling for tuning while preventing dielectric losses, effectively mediating between the tuning requirement and the loss minimization goal.
2Manufacturing precision
If complex tuning mechanisms are used to achieve precise simultaneous tuning of multiple cavities, then tuning precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges multiple individual tuning mechanisms into a single unified tuning plate structure that can simultaneously tune multiple cavities. The tuning plates are mechanically connected through a common support structure, allowing simultaneous adjustment of multiple resonators with a single tuning action, thereby reducing overall device complexity while maintaining precision.
Solution Approach 2:
The tuning plates serve multiple functions: they provide capacitive coupling for frequency tuning, act as mechanical supports for the resonators, and enable simultaneous tuning of multiple cavities. This multi-functionality reduces the need for separate dedicated tuning mechanisms for each cavity, simplifying the overall device while maintaining tuning precision.
3Loss of energy
If metallic surfaces are placed close to the cavity wall to achieve virtual grounding, then Q-factor is improved, but manufacturing precision requirements increase due to gap uniformity constraints
Solution Approach 1:
The patent segments the tuning structure into multiple discrete metallic tuning plates, each with its own gap to the cavity wall. This segmentation allows each plate to be independently positioned and adjusted, making it easier to achieve uniform gaps across multiple surfaces without requiring extremely tight overall manufacturing tolerances. The modular nature of segmented plates simplifies the manufacturing and assembly process.
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 design achieves a wide tuning range with high accuracy and robustness, minimizing dielectric losses and manufacturing costs, while being less susceptible to tolerances and maintaining a high Q-factor.
Implementation Method 1
the gap between the second surface and the wall should preferably be such that a capacitance formed between the second metallic surface and the wall is at least 3pF
Implementation Method 2
the tuning rods may be approached to the top surface of an essentially cylindrical resonator placed in the respective cavities. The proximity of the dielectric material influences the resonance frequency of the resonator
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A variable radio frequency band filter comprising: a housing (10) with a plurality of cavities (12a, 12b); a plurality of resonators (16a, 16b), wherein one resonator (16a, 16b) is arranged in each of the cavities (12a, 12b); a tuning arrangement (28) comprising a plurality of tuning structures (34a, 34b), wherein one of the tuning structures (34a, 34b) is arranged in each of the cavities (12a, 12b) and wherein the tuning structures (34a, 34b) of multiple cavities (12a, 12b) among the plurality of cavities (12a, 12b) are mechanically connected such that the tuning structures (34a, 34b) may be shifted simultaneously in order to simultaneously vary the resonance frequencies of the cavities (12a, 12b) and wherein each tuning structure (34a, 34b) includes at least one first metallic surface (42, 42') facing the resonator (16a, 16b) and at least one second metallic surface (44, 44') facing a wall (24) of the cavity (12a, 12b), the first and second metallic surfaces (42, 42' 44, 44') being conductively connected. It is proposed that the second metallic surface (44, 44') is arranged such that a small and essentially uniform gap (50) is formed between the second metallic surface (44, 44') and the wall in order to achieve a virtual grounding of the metallic surfaces (42, 42', 44, 44').