Ladder Filter Third Parallel Resonator Layout for Lower Insertion Loss
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Solution Overview
Problem
Ladder filters face issues with impedance matching and increased insertion loss due to capacitive frequency range widening and impedance degradation, particularly when the anti-resonant frequency of parallel arm resonators is low and the electrostatic capacitance of capacitive-type resonators is high.
Innovation Solution
Incorporating a third parallel arm resonator with a smaller electrostatic capacitance and strategically positioning its anti-resonant frequency outside the pass band, along with optimizing the connection of parallel arm resonators to reduce capacitive frequency range and improve impedance matching, while using surface acoustic wave resonators for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the second parallel arm resonator is connected in parallel to a parallel arm resonator with low anti-resonant frequency, then the capacitive frequency range is widened in the pass band, but impedance matching is degraded and insertion loss is increased
Solution Approach 1:
The patent changes the resonant frequency parameter of the third parallel arm resonator to be positioned outside the pass band (higher than the anti-resonant frequency of the second parallel arm resonator). This parameter change reduces the capacitive frequency range within the pass band, thereby improving impedance matching and reducing insertion loss while maintaining out-of-band attenuation performance.
2Reliability
If the anti-resonant frequency of parallel arm resonators is positioned low, then the capacitive frequency range is widened, but impedance matching is degraded
Solution Approach 1:
The patent positions the resonant frequency of the third parallel arm resonator outside the pass band, specifically higher than the anti-resonant frequency of the second parallel arm resonator. This parameter optimization narrows the capacitive frequency range within the pass band, significantly improving impedance matching characteristics.
3Loss of energy
If the electrostatic capacitance of the second parallel arm resonator is decreased, then insertion loss is reduced, but the capacitive frequency range is widened when anti-resonant frequency is low
Solution Approach 1:
The patent introduces a third parallel arm resonator with resonant frequency positioned outside the pass band. This allows the second parallel arm resonator to have optimized electrostatic capacitance for reduced insertion loss, while the third resonator compensates by narrowing the overall capacitive frequency range through its strategic frequency positioning.
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 configuration significantly improves impedance matching, reduces insertion loss, and enhances out-of-band attenuation, leading to better harmonic characteristics and reduced size of the ladder filter.
Implementation Method 1
the ladder filter includes at least one serial arm resonator and first and second parallel arm resonators... using surface acoustic wave resonators for enhanced performance
Implementation Method 2
The resonant frequency of the serial arm resonator and the anti-resonant frequencies of the first and second parallel arm resonators are positioned in the certain pass band
Data Source
AI summary
A ladder filter in which the pass band is defined by serial arm resonators and first and second parallel arm resonators includes the serial arm resonators, the first and second parallel arm resonators, and a third parallel arm resonator. The third parallel arm resonator is connected in parallel to the first parallel arm resonator, the electrostatic capacitance of the third parallel arm resonator is smaller than that of the first parallel arm resonator, and the anti-resonant frequency of the third parallel arm resonator is positioned outside the pass band of the ladder filter. The anti-resonant frequency of the first parallel arm resonator is positioned at the high frequency side of the anti-resonant frequencies of the second parallel arm resonators.