Hybrid TM-TE-TM Ceramic Air Cavity Filter for Compact Macro Base Stations
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Solution Overview
Problem
Macro base station radio filters require high-quality factor resonators with large power handling and sharp filter selectivity, leading to large filter sizes, and existing technologies struggle to achieve compact designs while maintaining high Q factors and selectivity.
Innovation Solution
A ceramic-loaded hybrid triple-mode air-cavity filter is designed with a ceramic block having removed portions and slots that support multiple fundamental TM modes and one fundamental TE mode, allowing for compact size and high Q factors, along with tuning screws and coupling structures for independent mode tuning and flexible coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If multiple modes per resonating cavity are exploited, then the filter size is reduced, but the manufacturing precision and mode coupling control become more difficult
Solution Approach 1:
The ceramic resonating cavity is segmented by introducing radial and axial slots that divide the cavity into distinct regions. This segmentation allows independent control of different resonant modes (TE and TM modes) within the same cavity volume, enabling size reduction while maintaining manufacturability and mode coupling control through the slot geometry
Solution Approach 2:
Different regions of the ceramic cavity are given different properties through the slot structure. The radial slots and axial slots create localized field distributions that support specific modes, allowing precise control over mode coupling and resonance characteristics while maintaining a compact overall filter size
2Reliability
If high quality factor resonators are used, then the filter selectivity is improved, but the filter size increases
Solution Approach 1:
Multiple resonant modes (TE011 and TM modes) are merged into a single ceramic cavity structure. This allows the filter to achieve high selectivity through multiple transmission zeros provided by different modes while maintaining a compact size, as all modes coexist in one integrated cavity rather than requiring separate large resonators
Solution Approach 2:
The invention utilizes three-dimensional mode structures within the ceramic cavity, exploiting both radial and axial dimensions through the slot configurations. This enables high-Q factor performance and sharp selectivity by creating multiple transmission zeros in different dimensional spaces, achieving high performance without increasing the overall filter footprint
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 solution achieves compact, high-Q factor filters with low insertion loss, high power handling, and sharp selectivity, suitable for macro base stations, by utilizing a ceramic-loaded hybrid triple-mode air-cavity structure that supports multiple resonant modes and allows for precise tuning and coupling control.
Implementation Method 1
a combined structure of the ceramic block, cavity, and metal structure supports multiple fundamental TM modes and one fundamental TE mode
Data Source
AI summary
An apparatus includes a filter. The filter includes a metal structure forming a cavity and includes a ceramic block, which is suspended in the cavity. The ceramic block has two removed portions, the removed portions removed from two opposing sides of the ceramic block. The ceramic block further has one or more slots that that span a region of ceramic between the two removed portions and connects chambers formed by the two regions with chambers formed by the one or more slots, wherein a combined structure of the ceramic block, cavity, and metal structure supports multiple fundamental TM modes and one fundamental TE mode. The filter comprises multiple coupling structures to couple radio frequency signals into and out of the filter. The apparatus may include multi-cavity filters including one and typically multiple ones of the filters.