Stripline Filter Bandwidth Expansion via 3D Resonator Coupling
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Solution Overview
Problem
Existing stripline filters face limitations in expanding their bandwidth due to constraints on element size and coupling between resonators, making it difficult to achieve wide-band frequency characteristics and optionally set attenuation poles, especially on the high-frequency side.
Innovation Solution
A stripline filter design featuring ¼ wavelength resonators with bent parts that face each other, allowing for jump coupling and adjustable coupling amounts, enabling the placement of an attenuation pole on the high-frequency side by varying the line lengths and widths of parallel and bent parts, and using side surface lines to stabilize frequency characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If interdigital coupling between resonators is used to expand bandwidth, then bandwidth is improved, but element size constraints limit further expansion
Solution Approach 1:
The patent utilizes the thickness dimension of the substrate by providing resonant lines that extend from the front surface to the rear surface of the substrate. This three-dimensional configuration allows for increased coupling between resonators without increasing the planar area, thereby expanding bandwidth while respecting element size constraints.
Solution Approach 2:
The resonant lines are embedded within the substrate thickness, with conductive patterns formed on both front and rear surfaces that connect through the substrate volume. This nesting approach maximizes the use of available space within the element dimensions to achieve stronger coupling and wider bandwidth.
2Force
If line lengths are increased to improve coupling, then coupling strength is improved, but element size constraints prevent further increases
Solution Approach 1:
Instead of increasing line length in the planar direction, the patent increases coupling strength by utilizing the thickness dimension. Resonant lines extend through the substrate thickness and connect via conductive patterns on the rear surface, creating a three-dimensional coupling path that achieves stronger interaction without exceeding planar size limits.
3Adaptability or versatility
If attenuation poles are added to achieve wide-band characteristics, then frequency selectivity is improved, but device complexity increases
Solution Approach 1:
The resonant lines serve multiple functions simultaneously: they provide the primary resonant coupling for bandwidth expansion and also create attenuation poles for frequency selectivity. The same conductive patterns that extend through the substrate thickness for coupling purposes also generate the necessary attenuation characteristics, eliminating the need for separate attenuation pole structures.
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 design enhances the flexibility in setting resonator coupling and allows for a wide range of attenuation pole placement on the high-frequency side, expanding the filter's passband while maintaining stable frequency characteristics, even with positional errors during manufacturing.
Implementation Method 1
by causing the bent parts of the second resonant line and the third resonant line to face each other, jump coupling occurs between the ends of these electrodes. Due to this jump coupling between the ends, the second resonant line and the third resonant line are capacitively coupled to each other
Data Source
AI summary
A stripline filter with wide-band filter characteristics having an attenuation pole on a high frequency side of frequency characteristics. The stripline filter includes at least three resonant lines, and two of the resonant lines include parallel line parts and bent parts. The third resonant line has a U shape in which both ends thereof are open and interdigitally coupled to the two resonant lines located on both sides thereof. The parallel line parts extend from base ends connected to a ground electrode via side surface lines that are parallel to respective line parts of the third resonant line. The bent parts extend so as to be bent from ends of the parallel line parts, and face each other at an interval.