Microstrip Line Filter With Defected Ground Structure
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Solution Overview
Problem
Conventional filters, such as those using lumped elements, occupy larger circuit areas and increase manufacturing costs, limiting their applications in wireless communication products, while also requiring more elements to achieve effective attenuation of high-frequency components.
Innovation Solution
A microstrip line filter with a defected ground structure is used, which includes specific patterns etched into the ground plane of a printed circuit board to form equivalent inductors and capacitors, allowing for better frequency characteristics and reduced circuit area by aligning the defected ground structure with the microstrip line circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional filters using lumped elements are used, then the filtering function is achieved, but the circuit area occupied is large and manufacturing cost increases
Solution Approach 1:
The patent replaces conventional lumped element filters with a microstrip line filter implemented directly on the PCB circuit board. The filtering function is achieved through distributed LC elements formed by the microstrip transmission lines and defected ground structures, eliminating the need for separate mechanical lumped elements and reducing both circuit area and manufacturing complexity
Solution Approach 2:
The patent utilizes the third dimension by creating defected ground structures on the ground plane layer beneath the microstrip lines. This vertical stacking approach allows the filter components to occupy board space in the Z-direction rather than spreading out in the XY-plane, significantly reducing the circuit footprint while maintaining filtering performance
2Reliability
If conventional filters are used, then the filtering function is achieved, but more elements are required to attenuate high-frequency components
Solution Approach 1:
The defected ground structures serve multiple functions simultaneously: they provide the necessary capacitance for the filtering function, create equivalent inductance when aligned with microstrip lines, and attenuate high-frequency components through their defective ground plane configuration. This multi-functionality reduces the total number of elements needed compared to conventional filters
Solution Approach 2:
The patent merges the ground plane with the filtering function by creating defected ground structures that are integral parts of the filter circuit. The ground plane is no longer just a reference plane but actively participates in the filtering mechanism by providing capacitive and inductive effects, thereby reducing the number of separate components required
3Area of stationary object
If the defected ground structure is aligned with the microstrip line circuit, then equivalent inductance is increased and circuit area is reduced, but the structure complexity increases
Solution Approach 1:
The defected ground structure is segmented into multiple discrete defective regions positioned at specific locations beneath the microstrip lines. This segmentation allows precise control over the equivalent inductance and capacitance values while maintaining a systematic layout that does not excessively increase fabrication complexity
Solution Approach 2:
The patent controls the equivalent inductance by adjusting the geometry parameters of the defected ground structures, such as the size, shape, and spacing of the defective regions. By changing these parameters, the desired inductance value is achieved without requiring complex structural arrangements, keeping the fabrication process relatively simple
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 microstrip line filter achieves improved frequency characteristics, particularly in the high-frequency range, with increased attenuation at stop-bands, reducing the need for additional elements and manufacturing costs, while maintaining consistent frequency performance and smaller circuit size.
Implementation Method 1
equivalent inductance can be increased and hence the same filtering function can be accomplished with a smaller circuit area
Implementation Method 2
A filter is an important component in wireless communication products because the filter is capable of removing unwanted frequency components from signals
Data Source
AI summary
Disclosed herein is a microstrip line filter including a dielectric substrate, a first hairpin resonator, and a metal ground layer. The first hairpin resonator is disposed on a first layer of the dielectric substrate. The metal ground layer is disposed on a second layer of the dielectric substrate. The metal ground layer includes a first defected ground structure. The first defected ground structure includes a first defected area, a second defected area, and a third defected area. The projection of the first defected area on the first layer is located inside the hairpin structure of the first hairpin resonator. The projection of the second defected area on the first layer is located in a direction opposite to an opening direction of the first hairpin resonator. The third defected area connects the first defected area and the second defected area.