Planar Microstrip Filter with Movable Dielectric Components
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Solution Overview
Problem
Planar filters with metal cases suffer from cavity mode resonance, leading to unintended passbands and degraded frequency characteristics, especially at higher frequencies, due to the propagation of electromagnetic waves and resonance issues within the metal casing.
Innovation Solution
Incorporating dielectric structural components at specific intervals within the metal case, arranged in the traveling direction of electromagnetic waves or perpendicular to the wavefront of standing waves, to suppress wave propagation and resonance, thereby maintaining the original filter characteristics without adverse effects on the passband or stopband attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a planar filter is sealed in a metal case to eliminate electromagnetic wave propagation, then electromagnetic wave shielding is improved, but cavity mode resonance occurs causing unintended passbands and degraded frequency characteristics
Solution Approach 1:
The patent introduces dielectric members as intermediary elements positioned between the input line and output line within the metal case. These dielectric members serve as mediators that suppress cavity mode resonance by disrupting the electromagnetic field distribution, thereby preventing unintended passbands while maintaining the shielding effect of the metal case. The dielectric members are positioned at specific intervals corresponding to standing wave patterns to maximize their resonance-suppressing effect.
2Reliability
If unnecessary higher-order mode shield plates are used to solve resonance problems, then cavity mode resonance is suppressed, but device complexity increases
Solution Approach 1:
The patent divides the resonance suppression function into multiple discrete dielectric members positioned at different locations within the metal case. Instead of using a single complex shield plate, the solution segments the suppression function across several simpler dielectric elements spaced at intervals corresponding to standing wave antinodes. This segmentation approach achieves effective resonance suppression while maintaining simpler individual components and easier adjustability.
Solution Approach 2:
The patent incorporates adjustable mechanisms that allow the dielectric members to be moved along the input and output lines. This dynamic positioning capability enables optimization of the resonance suppression effect by adjusting the dielectric members to precise locations corresponding to standing wave patterns, while also allowing for adaptability to different frequency requirements and ease of manufacturing tolerances.
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 effectively reduces transmission coefficients near the center frequency, minimizes resonance interference, and allows for precise frequency adjustment of resonators, maintaining the original filter characteristics while suppressing electromagnetic wave propagation in the metal case.
Implementation Method 1
This problem is caused by cavity mode resonance of the metal case. For example, input power into a planar filter induces cavity mode resonance
Implementation Method 2
input power into a planar filter induces cavity mode resonance, and the cavity mode resonance is picked up by the output line of the planar filter
Data Source
AI summary
A filter of an embodiment includes: a microstrip-line planar filter that includes an input line, resonators, and an output line, and has a passband with a center frequency f0; a metal case housing the planar filter; and structural components that include dielectric components, the structural components arranged in the metal case at an interval in the traveling direction of electromagnetic waves from the input line to the output line or in a direction perpendicular to the wavefront of the standing waves generated by the electromagnetic waves resonating in the metal case, the interval being ⅕ to ½ wavelength in terms of the electrical length of the center frequency f0.