Multilayer Band Pass Filter With Attenuation Pole for Crosstalk Suppression
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Solution Overview
Problem
Existing band pass filters in high-frequency devices suffer from mutual interference due to low attenuation outside the passband, leading to degradation in reception sensitivity, as they fail to meet market requirements for high-frequency applications.
Innovation Solution
A band pass filter circuit with a plurality of main LC parallel resonators electromagnetically coupled and a sub LC parallel resonator inserted between the ground and the connected ends of the main resonators, which defines an attenuation pole outside the passband, improving high-frequency attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an LC parallel resonant circuit is used as the band pass filter configuration, then the filter allows signals in a predetermined frequency band to pass, but the attenuation outside the passband is insufficient, causing mutual interference between high-frequency devices
Solution Approach 1:
The filter is divided into multiple LC parallel resonant circuits (first, second, and third resonant circuits) with different resonant frequencies. Each resonant circuit segment handles a specific frequency range, with the third resonant circuit specifically targeting high-frequency attenuation. This segmentation allows the filter to achieve both passband signal transmission and stopband attenuation simultaneously by distributing functions across multiple segments.
Solution Approach 2:
A series connecting inductor is introduced as an intermediary element between the resonant circuits. This inductor acts as a mediator that enhances the attenuation effect in the stopband while maintaining signal transmission in the passband. The inductor's reactance frequency is set higher than the resonant frequencies of the resonant circuits, allowing it to provide additional attenuation without interfering with the primary filtering function.
2Object-affected harmful factors
If the attenuation outside the passband is increased to suppress interference, then reception sensitivity is improved, but the device complexity increases due to additional components
Solution Approach 1:
Multiple resonant circuits are merged into a single filter structure where they work together to achieve both attenuation and signal transmission functions. The first, second, and third LC parallel resonant circuits are connected in parallel between the input and output terminals, with their combined effect providing superior attenuation characteristics while maintaining a unified filter configuration rather than separate stages.
Solution Approach 2:
The third LC parallel resonant circuit serves multiple functions: it acts as a standard resonant circuit for signal transmission in its passband while simultaneously functioning as an attenuation mechanism for high-frequency signals in the stopband. This multi-functionality reduces the need for separate attenuation circuits, thereby limiting the increase in device complexity while achieving the desired interference suppression.
3Reliability
If a sub LC parallel resonator is added to define an attenuation pole, then the attenuation characteristics outside the passband are improved, but the manufacturing complexity increases
Solution Approach 1:
The resonant frequencies and reactance frequencies of the resonant circuits and inductor are strategically parameterized to achieve the desired attenuation characteristics. By setting the reactance frequency of the series connecting inductor higher than the resonant frequencies of the resonant circuits, and by configuring the third resonant circuit with specific parameters, the filter achieves superior attenuation without requiring complex additional components or assembly steps.
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 solution enhances attenuation characteristics outside the passband, reducing crosstalk and maintaining high reception sensitivity by effectively isolating nearby high-frequency devices.
Implementation Method 1
The plurality of main LC parallel resonators are configured to be electromagnetically coupled with one another in a predetermined manner
Implementation Method 2
At least one sub LC parallel resonator, including an inductor and a capacitor, which defines an attenuation pole is inserted between a ground and the connected second ends of the plurality of main LC parallel resonators
Data Source
AI summary
A band pass filter circuit includes an input terminal, an output terminal, a signal line, and a plurality of main LC parallel resonators. First ends of the plurality of main LC parallel resonators are connected to the signal line, and second ends of the plurality of main LC parallel resonators are connected to one another. At least one attenuation-pole-defining sub LC parallel resonator including an inductor and a capacitor is inserted between a ground and the connected second ends of the plurality of main LC parallel resonators.