High-Frequency Filter Topology for Wide Stop Bands and Low Loss
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Solution Overview
Problem
Existing high-frequency filters with elastic wave resonators have narrow stop bands, making it difficult to sufficiently attenuate signals in the pass band of other filters, especially when handling carrier aggregation, and increasing the number of resonators leads to increased insertion loss within the pass band.
Innovation Solution
A high-frequency filter configuration that includes at least one elastic wave resonator and an LC resonant circuit, where the frequency of the first attenuation pole is closer to the pass band, allowing for a broader stop band while reducing insertion loss, by utilizing a combination of series and parallel resonators and capacitors to define low pass and high pass filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the number of elastic wave resonators is increased to broaden the stop band, then the stop band width is improved, but the insertion loss within the pass band increases
Solution Approach 1:
The patent combines elastic wave resonators with an LC resonant circuit to create a hybrid filter structure. The LC resonant circuit generates an attenuation pole that complements the elastic wave resonator's attenuation pole, allowing the stop band to be broadened through the combined effect of both circuits rather than relying solely on multiple elastic wave resonators.
Solution Approach 2:
The patent adjusts the resonant frequency of the LC resonant circuit so that its attenuation pole is positioned at a frequency higher than the elastic wave resonator's attenuation pole. This parameter optimization allows the two attenuation poles to work together effectively, broadening the stop band while maintaining low insertion loss in the pass band.
2Loss of energy
If a narrow stop band is used to reduce insertion loss, then the insertion loss is reduced, but the ability to attenuate signals in other filters' pass bands is insufficient
Solution Approach 1:
By merging the attenuation effects of the elastic wave resonator and the LC resonant circuit, the patent creates a filter with a broad stop band that can effectively attenuate signals from other filters' pass bands, while keeping the insertion loss low since the filter does not rely on multiple elastic wave resonators.
Solution Approach 2:
The patent creates a composite filter structure combining two different types of resonant circuits (elastic wave and LC) with different characteristics. This composite structure leverages the advantages of both circuits to achieve both broad stop band and low insertion loss simultaneously.
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 configuration achieves a broad pass band with a steep attenuation slope and a broad stop band, reducing insertion loss and enabling effective signal attenuation across multiple frequency bands, thus enhancing the performance in carrier aggregation scenarios.
Implementation Method 1
a first attenuation pole defined by a resonant frequency or an anti-resonant frequency of the at least one elastic wave resonator
Implementation Method 2
a second attenuation pole defined by a resonant frequency of the LC resonant circuit
Data Source
AI summary
A high-frequency filter coupled between an input-output terminal and another input-output terminal includes series arm resonators, parallel arm resonators, and an inductor defining an LC resonant circuit. Frequencies at a first attenuation pole defined by resonant frequencies or anti-resonant frequencies of the series arm resonators and the parallel arm resonators and a frequency at a second attenuation pole defined by a resonant frequency of the LC resonant circuit are included in one stop band of the high-frequency filter, and the frequencies at the first attenuation pole are located closer than the frequency at the second attenuation pole to a pass band of the high-frequency filter.