Cavity Filter Notch Layout for Thin PCB Antenna Integration
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Solution Overview
Problem
Conventional radio frequency filters face challenges in reducing size and weight due to the extension of resonators within cavities and the need for additional conductor materials, and dielectric ceramic filters restrict the use of printed circuit boards, limiting their application in slim antenna designs.
Innovation Solution
A filter design using a folding method to construct a hexahedral cavity with notch-forming parts, including L-notch and C-notch components, which are formed within the cavity to secure frequency characteristics while minimizing thickness and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resonators are extended within cavities in the thickness direction, then bandpass characteristics can be achieved, but the size of the filter in the thickness direction increases
Solution Approach 1:
The patent transitions from extending resonators in the thickness direction to arranging multiple resonators side-by-side in the horizontal plane within a single cavity. This dimensional change allows achieving the required bandpass characteristics through lateral arrangement rather than vertical stacking, thereby reducing the filter's thickness while maintaining filtering performance.
Solution Approach 2:
The patent divides the filtering function into multiple independent resonators (first resonator, second resonator, etc.) that are arranged side-by-side within a single cavity. Each resonator handles a specific frequency component, and their combined arrangement achieves the overall bandpass characteristic without requiring vertical extension, thus reducing thickness.
2Reliability
If additional conductor materials are installed for inductive or capacitive coupling, then coupling between resonators is improved, but the weight of the filter increases
Solution Approach 1:
The patent combines the coupling function with the existing cavity structure by using the cavity walls themselves as coupling elements. The first and second resonators are positioned within the same cavity, and their coupling is achieved through the cavity's conductive walls, eliminating the need for separate inductive or capacitive coupling components and thereby reducing overall weight.
Solution Approach 2:
The cavity structure serves multiple functions simultaneously: it provides the resonating environment for the resonators and also acts as the coupling medium between them. This multi-functionality eliminates the need for additional dedicated coupling components, reducing the total amount of conductor material required and thus reducing weight.
3Reliability
If dielectric ceramic filters are used, then filter characteristics are achieved, but the use of both sides of printed circuit board is restricted
Solution Approach 1:
The patent employs a thin, planar cavity structure that can be integrated onto a printed circuit board without requiring thick dielectric ceramic materials. This thin-film approach allows the filter to be mounted on one side of the PCB while leaving the other side accessible for additional circuitry, thereby maintaining PCB versatility while achieving required filter characteristics.
Solution Approach 2:
The patent replaces traditional mechanical dielectric ceramic filter structures with an electromagnetic cavity resonance structure that can be implemented using PCB trace patterns and air-filled or dielectric-filled cavities. This substitution allows for more flexible mounting options that do not restrict PCB usage on both sides, while maintaining the necessary filtering performance.
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 design allows for easy formation of notches on both sides of the passband, securing various frequency characteristics with a smaller size and simpler form, facilitating the use of printed circuit boards in slim antenna designs.
Implementation Method 1
L-notch part through inductive coupling
Implementation Method 2
C-notch part through capacitive coupling
Implementation Method 3
a resonance stage that is a portion in which electric coupling is dominant, compared to other portion in which magnetic coupling is relatively dominant
Data Source
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Figure 5
AI summary
The present invention relates to a filter for a communication device, and in particular, can simplify the complexity of the filter and achieve the performance of various filters due to comprising a notch forming unit that restricts a filtering frequency area by forming prescribed notches at the left end and right end of a passband, wherein the notches are disposed closer than the separation distance between adjacent resonance elements at a portion in which magnetic field coupling between the resonance elements is dominant or a portion in which electrical field coupling between the resonance elements is dominant among at least three adjacent resonance elements sequentially selected along the longitudinal direction of a cavity for multipath coupling.