Multiplexer Impedance Matching for Low Passband Insertion Loss
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Solution Overview
Problem
Existing multiplexers face increased insertion loss due to impedance mismatch between the transmission/reception terminal side of surface acoustic wave filters and the antenna terminal side, especially when the characteristic impedance differs, which is not adequately addressed by current impedance matching methods.
Innovation Solution
A multiplexer configuration with multiple elastic wave filters, each connected to a common terminal via a series or parallel resonator, and an inductance element, allowing for flexible impedance matching through the use of first and second circuit elements, such as inductance and capacitance elements, to adjust complex impedance and match characteristic impedance, thereby reducing insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the characteristic impedance of transmission/reception terminal is matched to PA/LNA to reduce matching elements, then device complexity is reduced, but insertion loss increases due to impedance mismatch with antenna terminal
Solution Approach 1:
The multiplexer is divided into multiple independent filter units, each with its own inductance element for impedance matching. This segmentation allows each filter to be optimized independently for impedance matching with the antenna terminal, reducing insertion loss without requiring additional matching elements between filters and amplifiers.
Solution Approach 2:
Each filter unit is provided with a specific inductance element tailored to its characteristic impedance requirements. This local optimization ensures that each filter maintains proper impedance matching with the antenna terminal (50Ω) while connected to amplifiers with different characteristic impedances, thereby minimizing insertion loss at each stage.
2Device complexity
If multiple elastic wave filters are connected to a common terminal without additional matching elements, then device complexity is reduced, but insertion loss increases due to impedance mismatch
Solution Approach 1:
The inductance element serves multiple functions: it acts as an impedance matching element between the filter and antenna terminal, and simultaneously functions as part of the filter's resonant circuit. This multi-functionality reduces the need for separate matching elements while maintaining low insertion loss in the passband.
Solution Approach 2:
The inductance value of each inductance element is specifically designed and adjusted according to the characteristic impedance of its associated filter unit. By changing the inductance parameter to match each filter's requirements, proper impedance matching is achieved without adding complex matching networks, thereby reducing insertion loss.
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 enables effective impedance matching across different terminal sides, reducing insertion loss in the passband of each elastic wave filter even when characteristic impedance differs, eliminating the need for additional matching elements between filters and amplifiers, and maintaining low loss within the passband.
Implementation Method 1
an elastic wave filter having low loss in the passband, and steep passband characteristics around the passband, is used as the multiple passband filters defining the multiplexer
Implementation Method 2
the characteristic impedance of the antenna-side terminal of the transmission-side surface acoustic wave filter and the reception-side surface acoustic wave filter is 50Ω, and therefore, the characteristic impedance may be different between the transmission terminal or the reception terminal side of the surface acoustic wave filter and the antenna terminal side
Data Source
AI summary
A multiplexer includes filters, a common terminal with which an inductance element is connected to a connection path of the common terminal and an antenna element and a capacitance element is connected in series to the connection path, and another inductance element. An input terminal of one of the filters is connected to the common terminal via the another inductance element, and is connected to a parallel resonator. In each of the filters other than the one filter, one of the input terminal and the output terminal, which is a terminal closer to the antenna element, is connected to the common terminal, and is connected to the series resonator.