Modular Cavity Filters With Planar Resonators for Easier Tuning
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Solution Overview
Problem
Cavity filters at low frequencies, such as microwaves, are typically expensive, heavy, and bulky due to the complexity of resonator geometries and the need for multiple resonators, which complicates design and tuning, especially in high-order filters used in base stations and mobile communications.
Innovation Solution
A modular cavity filter design with planar resonators and magnetic coupling between filtering modules, allowing for a reduced number of resonators and easier tuning, while using a hybrid approach of new resonator geometries and materials to achieve high Q-values and compact size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional cavity filter design with multiple resonators is used, then filtering performance is achieved, but weight and volume increase
Solution Approach 1:
The filter is divided into multiple modular filter sections, each containing a specific number of resonators (e.g., three resonators per section). These sections can be independently designed, manufactured, and assembled. By segmenting the filter, the overall weight is distributed across multiple lighter modules, and the design can be optimized for each section rather than treating the entire filter as a monolithic structure.
Solution Approach 2:
The patent transitions from traditional three-dimensional cavity resonators to planar (two-dimensional) resonator structures. This dimensional reduction allows resonators to be arranged in a compact planar configuration within each filter section, significantly reducing the overall volume and weight of the filter while maintaining the required filtering performance through careful design of the planar resonator geometries and their coupling structures.
2Reliability
If multiple resonators are used to achieve high-order filtering, then filtering performance improves, but device complexity increases
Solution Approach 1:
High-order filters are divided into multiple identical or similar filter sections, each containing a small number of resonators (e.g., three resonators per section). Each section can be designed and tuned independently using standardized procedures, avoiding the need to design and tune a large number of resonators as a single complex unit. This segmentation dramatically reduces design and tuning complexity while achieving high-order filtering through the cascaded connection of multiple sections.
Solution Approach 2:
The patent creates universal filter sections that can be reused multiple times to build different high-order filters. Each filter section is designed with standardized resonator configurations and coupling structures that can be replicated and combined in series to achieve various filtering orders and specifications. This universality allows engineers to leverage the same design templates and tuning procedures across different filter applications, significantly reducing overall design complexity.
3Reliability
If cross-coupling between non-adjacent resonators is implemented, then transmission zeros are created, but geometrical complexity increases
Solution Approach 1:
Cross-coupling between non-adjacent resonators is achieved by introducing coupling structures at the interfaces between adjacent filter sections rather than creating direct geometric couplings within each resonator. The segmentation into modular sections allows coupling structures to be placed at standardized interface locations, simplifying the geometric design compared to creating complex direct couplings between individual non-adjacent resonators within a monolithic structure.
Solution Approach 2:
The patent introduces coupling structures as intermediary elements that facilitate cross-coupling between non-adjacent resonators across filter section boundaries. These coupling structures act as mediators, enabling the required electromagnetic coupling without requiring complex direct geometric arrangements between the resonators themselves. The coupling structures can be independently optimized and integrated into the modular filter sections, simplifying the overall geometric design.
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
The modular design enables the synthesis of high-order filters with lower weight and volume, improved accuracy, and reduced production complexity, making them suitable for a broad range of applications, especially sub-6 GHz solutions, with the ability to customize filter performance by adding or removing modules.
Implementation Method 1
a plurality of resonators arranged within the cavity, at least one of the resonators being movable so as to vary an electromagnetic coupling between the resonator and other resonators
Implementation Method 2
Each of the filtering modules is coupled to at least one other filtering module of the plurality of filtering modules via a magnetic coupling
Implementation Method 3
at least one of the resonators being movable so as to vary an electromagnetic coupling between the resonator and other resonators
Data Source
AI summary
The disclosure provides a filtering module for a cavity filter having a housing defining an enclosed cavity, wherein a surface of the cavity is electromagnetically conductive; and a plurality of planar resonators arranged within the cavity, one or more of the resonators being rotatable about an axis of rotation so as to vary an electric-field coupling between the resonator and other resonators of the plurality of resonators. The disclosure also provides a cavity filter having an input for receiving a signal to be filtered; a plurality of filtering modules, each filtering module comprising: a cavity, wherein a surface of the cavity is electromagnetically conductive; and a plurality of resonators arranged within the cavity, at least one of the resonators being movable so as to vary an electromagnetic coupling between the resonator and other resonators of the plurality of resonators; and an output for outputting a filtered signal.