RF Multiplexer Filter Layout for Lower Intermodulation Distortion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Multiplexers with acoustic wave filters experience deterioration in reception sensitivity due to intermodulation distortion (IMD) caused by the non-linear elastic constant of acoustic wave resonators, particularly when transmitting signals in multiple frequency bands, leading to reduced performance in reception sensitivity.
Innovation Solution
The multiplexer design incorporates a configuration with a common terminal and three filters, where the first filter has a serial and parallel arm resonance circuit, and the fractional bandwidth of the parallel arm resonance circuit is set to be smaller than that of the serial arm resonance circuits, reducing current density and thereby minimizing IMD and preserving reception sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If acoustic wave resonators are used in parallel arm resonance circuits to achieve filtering functionality, then the multiplexer can transmit signals in multiple frequency bands, but intermodulation distortion occurs due to non-linear elastic constant causing deterioration of reception sensitivity
Solution Approach 1:
The patent changes the key parameter of fractional bandwidth for the parallel arm resonance circuit. By setting the fractional bandwidth to be smaller than that of serial arm resonance circuits, the patent reduces current density in the parallel arm circuit, thereby suppressing intermodulation distortion while maintaining multi-frequency band transmission capability
Solution Approach 2:
The patent applies different quality characteristics to different parts of the resonance circuit. Specifically, the parallel arm resonance circuit is designed with smaller fractional bandwidth compared to serial arm resonance circuits, creating local quality differentiation that reduces non-linear effects in critical areas while maintaining overall system functionality
2Adaptability or versatility
If the number of frequency bands is increased to improve versatility, then the multiplexer can handle more communication standards, but insertion loss increases and reception sensitivity deteriorates
Solution Approach 1:
The patent optimizes the fractional bandwidth parameter of the parallel arm resonance circuit to reduce current density, which suppresses intermodulation distortion and reduces energy loss in the form of distortion, thereby maintaining lower insertion loss even when handling multiple frequency bands
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 effectively suppresses the deterioration of reception sensitivity by reducing intermodulation distortion, ensuring better performance in multiplexers handling multiple frequency bands.
Implementation Method 1
an acoustic wave resonator included in the parallel arm resonance circuit is smaller in fractional bandwidth than a maximum value of a fractional bandwidth of each of the at least one serial arm resonance circuit
Implementation Method 2
The first parallel arm resonance circuit is connected between the common terminal and a grounding point and includes at least one acoustic wave resonator
Data Source
AI summary
A multiplexer includes a common terminal, a first terminal, a second terminal, and a third terminal, a first filter, a second filter, and a third filter. With a frequency f3 being defined as M×f1±N×f2 or M×f2±N×f1, M and N being natural numbers, f1 being a frequency included in a first passband of the first filter and f2 being a frequency included in a second passband of the second filter, at least a part of a range of frequency f3 overlaps a third passband of the third filter. No acoustic wave resonator is connected between the common terminal and a first parallel arm resonance circuit. A fractional bandwidth of the first parallel arm resonance circuit is smaller than a maximum value of a fractional bandwidth of each of at least one serial arm resonance circuit.