Filter Multiplexer Circuit With a Low-Q Attenuation Pole
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing filters with attenuation poles struggle to increase the steepness of the attenuation pole (Q factor) effectively, as it is difficult to enhance the Q factors of capacitors and inductors.
Innovation Solution
A filter design that includes capacitors connected in series with a capacitive element, such as an acoustic wave resonator, and an inductor, where the Q factor of the capacitive element is less than or equal to 0.6 times the Q factors of the other capacitors, forming a steep attenuation pole at a frequency lower than the passband.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the Q factors of the capacitor and inductor are increased to improve the steepness of the attenuation pole, then the steepness of the attenuation pole is improved, but it is difficult to increase the Q factors of the capacitor and inductor
Solution Approach 1:
The patent changes the Q factor parameter of the capacitive element to be smaller than those of the series capacitors, which is opposite to the conventional approach. This parameter change enables the formation of a steep attenuation pole without requiring high Q factors for all capacitors and inductors, thus resolving the manufacturing difficulty while achieving the desired steepness.
2Manufacturing precision
If a capacitive element with a small Q factor is used to form the attenuation pole, then the steepness of the attenuation pole is improved, but the capacitive element needs to be carefully selected or designed
Solution Approach 1:
The patent applies local quality by assigning different Q factor characteristics to different capacitive elements in the circuit. Specifically, the capacitive element forming the attenuation pole has a smaller Q factor, while the series capacitors have larger Q factors. This localized differentiation of properties allows the attenuation pole to achieve steepness without requiring complex design for all elements.
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 filter achieves a steeper attenuation pole by reducing the Q factor of the capacitive element, improving the steepness of the attenuation pole without increasing the Q factors of the capacitors and inductors, contrary to conventional methods.
Implementation Method 1
the capacitive element may be an acoustic wave resonator, and the acoustic wave resonator may form a second minimum of a second attenuation pole between the first minimum and the passband
Data Source
AI summary
A filter includes an input terminal, an output terminal, a ground terminal, a first capacitor and a second capacitor that are connected in series between the input terminal and the output terminal, a capacitive element that is connected in parallel to the first capacitor and the second capacitor between the input terminal and the output terminal, and has a Q factor that is smaller than a Q factor of the first capacitor and is smaller than a Q factor of the second capacitor, and an inductor that has a first end and a second end, the first end being coupled to a node that is provided between the first capacitor and the second capacitor and that is coupled to the capacitive element through the first capacitor and the second capacitor, the second end being coupled to the ground terminal.