RF Multiplexer Switching Layout for Adjacent-Band Matching

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Solution Overview

Problem

In multiplexers for communication devices supporting multi-band and multi-mode communication, the increasing number of filters leads to larger losses and mismatching due to parasitic capacitances, making impedance adjustment complex and inefficient.

Innovation Solution

A multiplexer configuration with adjacent frequency band filters connected to a common terminal, using switches and a reactance element to reduce the number of signal paths and minimize mismatching, thereby simplifying the circuit and improving performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the number of filters increases to support more frequency bands, then the adaptability of the multiplexer improves, but the loss in switches and return loss due to parasitic capacitances increase

Engineering Contradiction:

Improvesupport for multiple frequency bandsVSAvoidswitch loss and return loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent combines multiple filters (first filter and second filter) to share a common connection point (second connection point), reducing the total number of separate signal paths. This merging approach decreases the number of switches required and reduces parasitic capacitances at connection points, thereby lowering switch loss and return loss while maintaining support for multiple frequency bands.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The common connection point (second connection point) serves multiple functions by connecting both the first filter and second filter, allowing a single connection point to handle multiple frequency bands. This multi-functional design reduces the overall complexity and number of components needed, improving adaptability without proportionally increasing losses.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If the number of filters increases to support more frequency bands, then the adaptability of the multiplexer improves, but the mismatching at the common connection point increases

Engineering Contradiction:

Improvesupport for multiple frequency bandsVSAvoidimpedance matching

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent segments the connection structure into two distinct connection points: a first connection point for individual filter connections and a second connection point for common connections. This segmentation allows for better impedance control and reduced mismatching by separating the connection paths, enabling precise impedance matching for each filter while maintaining multi-band support.

Inventive Principle:

Principle #1Segmentation

3Adaptability or versatility

If the number of variable parameters increases to accommodate more filters, then the adaptability improves, but the complexity of adjustment increases

Engineering Contradiction:

Improvefilter combination flexibilityVSAvoidmatching circuit adjustment

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent creates equipotential connection points (first and second connection points) that provide stable reference impedances for filter connections. By establishing these equipotential points, the circuit reduces the number of variable parameters that need adjustment, as the connection points maintain consistent impedance characteristics across different filter combinations, simplifying the matching adjustment process.

Inventive Principle:

Principle #12Equipotentiality

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 reduces switch losses and parasitic capacitance-related issues, achieving better matching and simpler adjustment across multiple frequency bands, resulting in a more efficient and effective multiplexer design.

Implementation Method 1

a return loss due to parasitic capacitances become larger

Methodology Applied

Scientific EffectParasitic capacitance: Parasitic Capacitance

Implementation Method 2

Therefore, as more signal paths are connected to the common connection point, mismatching at the common connection point increases. To achieve matching, the impedance need to be more largely adjusted

Methodology Applied

Scientific EffectImpedance matching:

Data Source

PatentUS12040822B2Multiplexer, radio frequency front-end circuit, and communication device

Publication Date: 2024.07.16 MURATA MFG CO LTD

AI summary

A multiplexer includes first, second, and third filters with first, second, and third frequency bands different from each other, a first connection point connected to a common terminal, a second connection point connected to one end of the first filter and one end of the second filter, a first switch that switches connection and disconnection between the first and second connection points, a reactance element whose one end is connected to a signal path connecting the second connection point and the first switch, a second switch that switches connection and disconnection between the other end of the reactance element and the first connection point, and a third switch that switches connection and disconnection between one end of the third filter and the first connection point. The first and second frequency bands are adjacent to each other among the first, second, and third frequency bands.