Switch Circuit Inductor Layout for Impedance-Matched Signal Paths

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Solution Overview

Problem

The variation in the quantity of switches on different signal paths in switch circuits leads to degradation of transmission characteristics due to differences in parasitic capacitance, known as off-capacitance.

Innovation Solution

A switch circuit design with an inductor connected between nodes of signal paths with higher switch quantities, balancing the parasitic capacitance and reducing impedance mismatching.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the quantity of switches varies depending on signal paths to enable selective signal transmission, then signal routing flexibility is improved, but transmission characteristics are degraded due to differences in parasitic capacitance

Engineering Contradiction:

Improvesignal routing flexibilityVSAvoidtransmission characteristics

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent changes the electrical parameters of the circuit by adding inductors with specific inductance values to signal paths with more switches. This compensates for the increased parasitic capacitance in those paths, balancing the total impedance across all signal paths and maintaining consistent transmission characteristics while preserving routing flexibility

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the harmful effect of increased parasitic capacitance in paths with more switches into a beneficial outcome by adding inductors that provide inductive reactance to counterbalance the capacitive effect. This transforms the impedance mismatch problem into a balanced transmission system

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Adaptability or versatility

If more switches are added to certain signal paths to increase routing options, then signal path versatility is improved, but transmission loss increases due to higher parasitic capacitance

Engineering Contradiction:

Improverouting optionsVSAvoidtransmission loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent modifies the impedance parameters of signal paths with more switches by adding inductors, which changes the overall electrical characteristics to compensate for increased capacitive losses from additional switches, thereby reducing transmission loss while maintaining routing versatility

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If switches are added to increase signal path flexibility, then routing adaptability is improved, but impedance matching deteriorates due to parasitic capacitance differences

Engineering Contradiction:

Improverouting adaptabilityVSAvoidimpedance matching

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent adjusts the impedance parameters of affected signal paths by adding inductors with calculated inductance values that specifically compensate for the parasitic capacitance introduced by additional switches, restoring impedance matching across all paths while preserving routing adaptability

Inventive Principle:

Principle #35Parameter changes

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 design reduces transmission loss and maintains consistent impedance across signal paths with varying switch counts, enhancing overall transmission characteristics.

Implementation Method 1

the quantity of switches on a signal path passing through a multiplexer is greater than the quantity of switches on a signal path bypassing the multiplexer. If the quantity of switches varies depending on multiple signal paths, the transmission characteristics of the multiple signal paths may be degraded due to the difference in parasitic capacitance resulting from the off-capacitance of the switches.

Methodology Applied

Scientific EffectParasitic capacitance: Capacitance

Implementation Method 2

a first inductor connected between the first node and a ground and is connected between the second node and the ground

Methodology Applied

Scientific EffectInductance: Inductor

Data Source

PatentUS20260081599A1Switch circuit

Publication Date: 2026.03.19 MURATA MFG CO LTD

AI summary

A switch circuit includes a first switch that connects and disconnects a first signal path between a common terminal and a first selection terminal; a second switch that connects and disconnects a second signal path between the common terminal and a first node; a third switch that connects and disconnects a third signal path between the first node and a selection terminal; a fourth switch that connects and disconnects a fourth signal path between the common terminal and a second node; a fifth switch that connects and disconnects a fifth signal path between the second node and a third selection terminal; an inductor connected between the first and second nodes and a ground. Each of the quantity of switches on the second and third signal paths and the quantity of switches on the fourth and fifth signal paths is greater than the quantity of switches on the first signal path.