Parallel Coupled Line Filter Miniaturization With Grounded Lumped Capacitors
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Solution Overview
Problem
Current miniaturized radio communication filters face structural limitations, complex design challenges, and poor harmonic and skirt characteristics, particularly in high-frequency applications, making them difficult to design and fabricate efficiently.
Innovation Solution
A miniaturized parallel coupled line filter is developed using lumped capacitors and grounding, which reduces the size of the filter by adjusting the length of the parallel coupled lines and determining capacitances based on even-mode and odd-mode characteristic impedances, allowing for simpler design and improved filtering characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If miniaturized filters are developed using conventional structures (ladder filter, combine filter, hairpin filter), then the filter size is reduced, but the structure becomes extremely complicated and design calculation becomes extremely difficult
Solution Approach 1:
The patent transforms the conventional distributed parameter transmission line structure into a lumped parameter equivalent circuit model. By changing the parameter representation from distributed to lumped, the design equations become algebraic rather than differential, dramatically simplifying the design calculation while maintaining the same filtering function and achieving miniaturization.
Solution Approach 2:
The patent replaces the physical transmission line structure with an equivalent circuit model using lumped elements (capacitors and inductors). This substitution allows the filter to be designed and analyzed using simple circuit theory instead of complex electromagnetic field analysis, reducing both design complexity and physical size.
2Volume of moving object
If miniaturized filters are developed using conventional structures, then the filter size is reduced, but the harmonic characteristics and skirt characteristics on the high frequency side become very poor
Solution Approach 1:
The patent introduces lumped capacitors at specific locations in the equivalent circuit to control harmonic impedances. By carefully selecting capacitor values, the filter achieves high impedance at harmonic frequencies, effectively suppressing harmonics and improving skirt characteristics while maintaining miniaturized dimensions.
3Volume of moving object
If conventional transmission lines are bent to miniaturize the hairpin filter, then the filter size is reduced, but the transmission lines can be bent only to a certain extent creating fabrication limitations
Solution Approach 1:
The patent replaces the bent transmission line structure with a planar equivalent circuit layout using lumped elements. This substitution eliminates the need for complex bending and folding of transmission lines, allowing the filter to be fabricated using simple planar processes while achieving the same miniaturized footprint.
4Volume of moving object
If miniaturized filters are developed using self capacitors and mutual capacitors, then the filter size is reduced, but extremely complicated calculation in the self capacitor and mutual capacitor makes design more difficult
Solution Approach 1:
The patent simplifies the capacitor model by considering only self-capacitance effects and neglecting mutual capacitance between adjacent lines. This parameter simplification transforms the design equations from complex coupled differential equations into simple algebraic equations, making the design process tractable while maintaining accurate filtering performance.
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 solution achieves a miniaturized filter with superior frequency selectivity, improved harmonic characteristics, and sharp skirt characteristics on the high-frequency side, while maintaining equivalent performance to full-size filters, and simplifies the design process using relatively simple theoretical knowledge.
Implementation Method 1
capacitances of the first and second capacitors may be determined based on an even-mode characteristic impedance and an odd-mode characteristic impedance of the parallel coupled line
Implementation Method 2
A miniaturized parallel coupled line filter is developed using lumped capacitors and grounding
Implementation Method 3
At least one of the other input port and the other output port may be grounded
Data Source
AI summary
A parallel coupled line filter is miniaturized by using lumped capacitors and grounding the capacitors. The parallel coupled line filter includes a parallel coupled line, a first capacitor connected to one of two input ports of the parallel coupled line, and a second capacitor connected to one of two output ports of the parallel coupled line. The parallel coupled filter can be miniaturized to a desirable size, on the basis of relatively simple theoretical knowledge. The parallel coupled line filter exhibits excellent frequency selectivity and improved harmonic characteristics.