Dielectric Waveguide Filter Blind Via Coupling
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Solution Overview
Problem
Conventional waveguide-type dielectric filters face limitations in achieving wideband designs without compromising resonator Q and suffer from spurious band rejection due to high-order resonance modes, which restrict their application in microwave communications and other frequency-selective devices.
Innovation Solution
The introduction of metallized blind holes aligned with contact pads reduces the dielectric block thickness only in the vicinity of the pads, increasing coupling while maintaining resonator Q, and controls harmonic resonances by shifting the first harmonic frequency, thereby enhancing spurious response and achieving bandwidths of 10% or greater.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the size of the contact pad is increased to increase coupling, then the bandwidth is improved, but the contact pad size must remain smaller than the broad face of the resonator which limits the maximum achievable bandwidth
Solution Approach 1:
The patent introduces blind via holes that extend vertically through the dielectric block, adding a third-dimensional coupling path between contact pads and ground plane. This vertical dimension allows increased coupling without expanding the horizontal contact pad area, thereby achieving wider bandwidth while respecting the constraint that contact pads must remain smaller than the resonator broad face.
Solution Approach 2:
The blind via holes act as intermediary coupling elements between the contact pads and the ground plane. These metallized holes provide an additional coupling mechanism that mediates the electromagnetic field interaction, enabling enhanced bandwidth without directly increasing contact pad dimensions.
2Productivity
If the thickness of the dielectric block is reduced to increase coupling, then the bandwidth is improved, but the resonator Q is reduced which increases filter insertion loss
Solution Approach 1:
Instead of reducing the overall dielectric block thickness, the patent introduces vertical blind via holes that create localized coupling regions. This approach utilizes the thickness dimension selectively at specific locations (near contact pads) while maintaining sufficient overall thickness to preserve resonator Q and minimize insertion loss.
Solution Approach 2:
The blind via holes create localized regions of increased coupling density near the contact pads without affecting the overall dielectric block thickness. This local modification allows bandwidth enhancement while preserving the global structural integrity and resonator Q factor, thereby avoiding increased insertion loss.
3Productivity
If conventional filter structures are used to achieve wide bandwidth, then coupling is increased, but spurious band rejection deteriorates due to high-order resonance modes
Solution Approach 1:
The blind via holes introduce vertical electromagnetic coupling paths that differ from conventional horizontal coupling mechanisms. This dimensional change in the coupling structure modifies the resonance characteristics, allowing wide bandwidth achievement while better controlling spurious responses through the unique vertical field distribution pattern.
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 solution enables wideband dielectric waveguide filters with improved spurious response and reduced insertion loss, suitable for microwave communications and radar applications, offering miniaturization and weight reduction while maintaining high resonator Q, thus overcoming the limitations of conventional filters.
Implementation Method 1
metallized blind holes which are aligned with the contact pads are provided to increase the coupling to the desired level. These blind via holes start from, or open at the surface of the dielectric block that opposes the surface on which the contact pads are provided, and terminate at a position within the dielectric block, thus avoiding electrical connection to the contact pads. In this manner, the thickness of the dielectric block is reduced only in the target vicinity of the contact pads, which moves the ground plane closer to the contact pad, and thus increases the amount of coupling.
Implementation Method 2
a waveguide-type dielectric filter suitable for narrow to wideband filter applications which is made from one or more blocks of dielectric material, such as a ceramic material
Implementation Method 3
The resonators of the filters have high order resonance modes occurring at high frequencies which result in spurious (and normally undesired) pass-bands
Data Source
AI summary
A waveguide-type dielectric filter suitable for wideband filter applications made of a metallized dielectric material is provided. The filter includes two or more mutually coupled resonators disposed in a longitudinal manner. The coupling between adjacent resonators is provided and adjusted by slots or through holes. The dielectric block is covered with metal ground coating with the exception of an uncoated area at the input and output that creates two contact pads on one surface of the dielectric block that are electrically isolated from the metal ground coating. Metallized blind holes are formed on the opposing surface of the dielectric block with respect to the contact pads. These blind holes effectively move the ground plane closer to the contact pad, which, in turn increases the coupling between the input and output resonators and external circuitry, which is essential for building wide bandwidth band pass filters.