RF Filter Resonator Layout for Narrowband Steep Attenuation
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Solution Overview
Problem
Conventional band-stop filters used in radio-frequency circuits face challenges in achieving steep attenuation characteristics in a narrower bandwidth, which is necessary for applications like dual band-type antennas in small-sized mobile terminals. Increasing the number of resonator electrodes to achieve steeper attenuation results in a larger device size.
Innovation Solution
The filter device incorporates a dielectric substrate with a main line and resonators, including a first and second resonator intersecting the main line, and an intermediate resonator disposed between them. This configuration generates cross-coupling between the resonators, allowing for improved attenuation characteristics with a smaller number of stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the number of resonator electrodes is increased to achieve steeper attenuation characteristics in a narrower bandwidth, then the filter characteristics are improved, but the substrate area and device size increase
Solution Approach 1:
An intermediate resonator is introduced between the first and second resonators that intersect the main line. This intermediate resonator acts as a mediator to generate cross-coupling, which produces additional attenuation poles and improves filter characteristics without requiring an increase in the total number of resonator stages, thereby avoiding substrate area expansion
Solution Approach 2:
The resonators are arranged in a multi-dimensional configuration where the first and second resonators intersect the main line at different positions, and the intermediate resonator is disposed between them. This spatial arrangement in multiple dimensions enables cross-coupling effects that improve attenuation characteristics without simply adding more resonators in a linear sequence, thus controlling substrate area
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 filter device achieves enhanced filter characteristics with steeper attenuation in a narrower bandwidth, while maintaining a compact size, thus addressing the limitations of conventional filters.
Implementation Method 1
cross-coupling is generated between a resonator at a first stage and a resonator at a last stage with the main line and/or the intermediate resonator. Since a new pole is generated due to the cross-coupling, an attenuation amount in the stop band can be ensured
Data Source
AI summary
A filter device applied to a radio-frequency circuit includes a dielectric substrate on which a ground electrode is disposed and a main line which has an input end and an output end. The filter device also includes first and second resonators and an intermediate resonator. The main line is disposed to face the ground electrode and extends in a first direction. The first resonator intersects the main line and extends in a second direction. The second resonator intersects the main line and extends in the second direction in a region further to an output end side than the first resonator. At least part of the intermediate resonator is disposed between the first resonator and the second resonator.