Defected Ground Structure Shielding for Compact RF Filters
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Solution Overview
Problem
Current wireless communication systems face challenges in designing filters with small size, low cost, high selectivity, and high performance due to the large area occupied by passive devices, and the difficulty in integrating these devices into silicon substrates.
Innovation Solution
A defected ground structure with a shielding effect is introduced, comprising a dielectric layer, a defected metal layer, a grounded metal layer, and conductive mushroom-like structures that reduce transmission line characteristic impedance and generate a slow wave effect, thereby minimizing filter size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional planar micro strip filter structures are used, then the filter can be fabricated with small size and low cost, but the filter occupies large area and has limited integration capability
Solution Approach 1:
The patent embeds the defected ground structure within the ground plane of the microstrip filter, nesting the DGS pattern (such as U-shaped, E-shaped, or F-shaped defects) inside the existing ground layer. This nesting approach allows the filter to maintain its compact form while the embedded DGS structures provide additional electromagnetic control, effectively reducing the overall filter area without compromising integration capability
Solution Approach 2:
The patent transitions from conventional two-dimensional planar filter designs to three-dimensional structures by incorporating vertical ground vias and multi-layer DGS patterns. The ground vias extend perpendicular to the ground plane, creating vertical electromagnetic coupling that reduces the horizontal footprint of the filter while maintaining its filtering function, thus solving the area-integration contradiction
2Ease of manufacture
If passive devices are designed with traditional structures, then the devices can be manufactured with simple processes, but the devices occupy 65% of the total area of RF front-end circuit
Solution Approach 1:
The patent merges the ground plane with the filtering function by introducing defected ground structures directly into the ground layer of the microstrip filter. Instead of treating the ground plane as a separate supporting structure, the DGS patterns are integrated into the ground layer itself, combining mechanical support and electromagnetic filtering functions into a single structure, thereby reducing overall device area while maintaining manufacturing simplicity
Solution Approach 2:
The defected ground structure serves multiple functions simultaneously: it acts as the reference ground plane for the microstrip transmission line, provides electromagnetic shielding, creates resonant cavities for filtering, and controls impedance. This multi-functionality eliminates the need for separate components, reducing the total area occupied by passive devices in the RF front-end circuit
3Area of stationary object
If defected ground structure is used to reduce filter size, then the filter area is reduced, but the selectivity and performance may be compromised
Solution Approach 1:
The patent applies different DGS patterns (U-shaped, E-shaped, F-shaped, etc.) at different locations within the ground plane, with each pattern specifically designed to address local electromagnetic requirements. The ground vias are strategically positioned at specific points to enhance shielding at critical frequencies. This localized optimization ensures that filter selectivity is maintained or improved even as the overall filter area is reduced
Solution Approach 2:
The patent systematically varies key parameters of the DGS structures, including the size, shape, position, and distribution of ground vias, as well as the dimensions and configurations of DGS patterns. By optimizing these parameters, the patent achieves precise control over the filter's frequency response, maintaining high selectivity and performance metrics while minimizing the filter footprint
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 proposed structure effectively reduces filter size by creating a slow wave effect, enhances shielding to isolate interference, and suppresses radiation effects, while maintaining high performance and selectivity.
Implementation Method 1
conductive mushroom-like structures that reduce transmission line characteristic impedance and generate a slow wave effect
Implementation Method 2
defected ground structure with a shielding effect
Implementation Method 3
When an electromagnetic wave propagates on the DGS with periodic obstacles, energy (or frequency) thereof only appears at some specific wave vectors
Data Source
AI summary
A defected ground structure with shielding effect is provided. The structure includes a dielectric layer, a defected metal layer, a grounded metal layer and at least a conductive mushroom-like structure. The defected metal layer has a line-shaped opening and is disposed in the dielectric layer. The conductive mushroom-like structure is disposed between the defected metal layer and the grounded metal layer and is arranged along an extending direction of the line-shaped opening periodically. The conductive mushroom-like structure includes a laterally extending member and a vertically extending member. The laterally extending member is parallel to the defected metal layer and a distance is maintained away from the defected metal layer. The projection area of the laterally extending member on the defected metal layer covers a length of the line-shaped opening corresponding to the laterally extending member. The vertically extending member connects the laterally extending member and the grounded metal layer.