Miniaturized Radio Filter Resonator Coupling Stability
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Solution Overview
Problem
Existing miniaturized bandpass filters in radio communication apparatuses face challenges in maintaining consistent coupling coefficients due to dimensional accuracy deviations, leading to fluctuating filter characteristics and limited miniaturization potential.
Innovation Solution
The filter design incorporates adjacent resonators with specific microstrip line configurations, where the first resonator has a pair of broad lines and a narrower line connected between them, while the second resonator has a narrower line on a separate region, with a shorter distance between the broad lines for capacitive coupling and a longer distance for inductive coupling, optimizing the coupling coefficient and reducing size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the filter uses a pair of broad lines and narrow lines for miniaturization, then the filter size is reduced, but the full length of the filter in the arrangement direction increases
Solution Approach 1:
The patent transitions from a planar arrangement where broad and narrow lines are arranged side-by-side in the same direction to a multi-dimensional structure where the narrow line is positioned on an opposite surface of the substrate. This spatial reconfiguration reduces the filter's footprint in the arrangement direction while maintaining the necessary coupling characteristics, effectively resolving the contradiction between miniaturization and length extension.
2Volume of moving object
If adjacent resonators are closed to each other for miniaturization, then the filter size is reduced, but the capacitive coupling and inductive coupling are cancelled to each other
Solution Approach 1:
The patent applies different coupling mechanisms to different spatial locations: capacitive coupling is established through the narrow line on the opposite surface where voltage is maximum, while inductive coupling occurs through the broad lines where current is maximum. By optimizing the distance and configuration in each local region, the patent ensures that both coupling types contribute constructively to the overall coupling coefficient, preventing cancellation and maintaining stability despite miniaturization.
3Device complexity
If the filter uses conventional microstrip line configuration, then the structure is simple, but the deviation of coupling coefficient due to dimensional accuracy increases
Solution Approach 1:
The patent utilizes the third dimension (opposite surface of the substrate) to position the narrow line, creating a vertical separation that reduces sensitivity to lateral dimensional variations. This spatial arrangement in multiple dimensions provides a more stable coupling coefficient that is less affected by manufacturing tolerances in the planar directions, thereby improving manufacturing precision without significantly increasing structural complexity.
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 configuration stabilizes the coupling coefficient, reduces size, shortens adjustment time, and improves yield by prioritizing capacitive coupling and minimizing the impact of dimensional accuracy deviations, enabling more efficient miniaturization and production consistency.
Implementation Method 1
the capacitive coupling occurring between the adjacent resonators due to a pair of broad lines
Implementation Method 2
the inductive coupling occurring due to the narrow lines
Implementation Method 3
a bandpass filter in a radio communication apparatus comprises a plurality of resonators arranged in cascade
Data Source
AI summary
A filter contains first and second resonators adjacent to each other in a first direction, each of the first resonator and the second resonator comprising a pair of first microstrip lines formed on a first region in a second direction perpendicular to the first direction and each having an open end and other end and a first width, and a second microstrip line arranged on a second region in the second direction, and connected between other ends of the pair of first microstrip lines, and having a second width smaller than the first width, wherein a minimum distance between the first microstrip lines adjacent to the first resonator and the second resonator is set at a value smaller than a minimum distance between the second microstrip lines adjacent to the first resonator and the second resonator.