Band Pass Filter with Parallel Microstrip Lines
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Solution Overview
Problem
Existing band pass filters require impedance transformers for matching, which increase in size with lower frequencies, making it difficult to miniaturize the filters and the associated electronic devices.
Innovation Solution
A band pass filter design utilizing a microstrip transmission line with multiple signal transmission lines in parallel between the input and output ports, eliminating the need for an impedance transformer and allowing for adjustable bandwidth and central frequency without changing the impedance value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an impedance transformer is used for impedance matching, then the impedance matching is achieved, but the size of the band pass filter increases
Solution Approach 1:
The patent extracts and eliminates the impedance transformer component from the traditional band pass filter structure. By using multiple signal transmission lines with specific impedance values (e.g., 25Ω, 50Ω, 75Ω) connected in parallel between input and output ports, the design achieves impedance matching directly without requiring a separate impedance transformer, thereby reducing the overall filter size while maintaining reliable impedance matching
Solution Approach 2:
The patent merges the impedance matching function with the signal transmission function by integrating multiple signal transmission lines that serve dual purposes: transmitting signals and providing impedance matching. This combination eliminates the need for a separate impedance transformer component, resolving the contradiction between achieving reliable impedance matching and minimizing filter size
2Reliability
If the frequency is lowered, then the signal transmission is improved, but the size of the impedance transformer increases
Solution Approach 1:
The patent changes the impedance parameters of the signal transmission lines to achieve frequency-independent impedance matching. By using multiple transmission lines with different characteristic impedances (25Ω, 50Ω, 75Ω) connected in parallel, the system maintains effective impedance matching across different frequencies without requiring larger transformer dimensions, thus resolving the contradiction between low-frequency signal transmission and compact size
3Area of stationary object
If multiple signal transmission lines are used, then the impedance transformer is eliminated, but the structure becomes more complex
Solution Approach 1:
The patent segments the impedance matching function into multiple parallel signal transmission lines, each with a specific impedance value. This segmentation allows the system to achieve impedance matching through the combined effect of multiple simple transmission lines rather than a single complex transformer, reducing overall filter size while keeping individual line structures simple and manageable
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 miniaturizes the band pass filter, reduces the size of electronic devices, and allows for flexible frequency adjustment by varying the number of signal transmission lines, while maintaining accurate signal filtering across desired frequency bands.
Implementation Method 1
a microstrip transmission line including: an input port formed on a top surface of the substrate to receive a transmission signal, an output port formed on the top surface of the substrate to output a filtered transmission signal, and a plurality of signal transmission lines disposed in parallel
Data Source
AI summary
A band pass filter including a microstrip transmission line comprises: a substrate having a grounding surface formed on a rear surface thereof; an input port which is formed on an upper surface of the substrate and receives a transmission signal; an output port which is formed on the upper surface of the substrate and outputs a filtered transmission signal; and a plurality of signal transmission lines spaced at predetermined distance from one another in parallel, each of the plurality of signal transmission lines having one end connected to and in contact with the input port, and having the other end connected to and in contact with the output port.