Multiplexer Circuit Topology for Low-Loss Antenna Impedance Matching
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Solution Overview
Problem
Existing multiplexers experience increased insertion loss in the pass band due to the use of inductance elements with low Q factors, particularly when connected in series with antenna terminals, which degrades the performance of filters like the Band 25 reception filter.
Innovation Solution
The implementation of a multiplexer design that includes a plurality of elastic wave filters with a common terminal connected via a connection path, featuring a first inductance element between the connection path and a reference terminal, and a second inductance element interposed between the common terminal and the antenna element, allowing for impedance matching without series connection, thereby reducing the influence of the Q factor on insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an inductance element is connected in series between the antenna terminal and the filter, then impedance matching is achieved, but insertion loss degrades due to the Q factor of the inductance element
Solution Approach 1:
A capacitor is introduced as an intermediary element between the inductance element and the filter. This capacitor transforms the series connection configuration into a parallel connection configuration, allowing the inductance element to provide impedance matching without directly affecting the signal path through the filter, thereby reducing insertion loss while maintaining impedance matching capability
Solution Approach 2:
The patent inverts the conventional impedance matching approach by connecting the inductance element in parallel rather than in series with the filter. This inversion changes the topology from a direct series connection that degrades insertion loss to a parallel connection that maintains low insertion loss while achieving impedance matching through the combined effect of the inductance element and capacitor
2Device complexity
If an inductance element with low Q factor is used, then device complexity is reduced, but insertion loss in the pass band increases
Solution Approach 1:
The capacitor acts as a mediator that decouples the Q factor requirements of the inductance element from the filter performance. By introducing this intermediary capacitive element, the system can use simple, low-Q inductance elements without sacrificing filter insertion loss characteristics, as the capacitor compensates for the inductance element's limitations in the signal path
3Reliability
If an inductance element is connected in series with the antenna terminal, then impedance matching is achieved, but the Q factor of the inductance element greatly influences insertion loss
Solution Approach 1:
The capacitor serves as an intermediary that isolates the filter from the Q factor variations of the inductance element. This configuration makes the system more adaptable and less sensitive to changes in inductance element quality, as the capacitor compensates for Q factor variations and maintains consistent filter performance across different inductance element specifications
Solution Approach 2:
The patent changes the connection parameter of the inductance element from series to parallel configuration. This parameter change fundamentally alters how the inductance element interacts with the filter, making the system's insertion loss characteristics independent of the inductance element's Q factor while maintaining impedance matching capability
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 design significantly reduces insertion loss in the pass band of each filter, even when using inductance elements with low Q factors, while maintaining effective impedance matching and minimizing the area occupied by inductance elements on the mounting substrate.
Implementation Method 1
Elastic wave filters that characteristically have low loss in a pass band and sharp band pass characteristics around the pass band are used as a plurality of band pass filters included in such a multiplexer
Implementation Method 2
an inductance element is connected in series between an antenna element and a connection path of an antenna terminal and reception and transmission SAW filters to achieve impedance matching between the antenna element and the antenna terminal
Data Source
AI summary
A multiplexer includes filters and a common terminal connected to an antenna element by a connection path, a first inductance element being connected between the connection path and a reference terminal. A terminal closer to the antenna element among an input terminal and an output terminal of one filter among the filters is connected to a parallel resonator and is connected to the common terminal with a second inductance element interposed therebetween. A terminal closer to the antenna element among an input terminal and an output terminal of each of other filters other than the one filter among the filters is connected to the common terminal and a series resonator.