FM Tuner Ground Isolation Using Ferrite Beads

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Solution Overview

Problem

The use of a car lighter adapter (CLA) ground signal line as an antenna for FM tuners in portable electronic systems requires a large and bulky inductive component for isolation, posing design constraints due to significant current flow, which is undesirable in portable systems.

Innovation Solution

Implementing ferrite beads as isolation elements between the FM tuner ground and the device ground to provide ground isolation, allowing the ground signal line to be used as an FM antenna without the need for a large isolation inductor, and enabling the use of printed circuit board signal lines as antennas when the CLA is detached.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a car lighter adapter ground signal line is used as an antenna for FM tuner, then FM signal reception is enabled, but a large and bulky inductive component is required for isolation

Engineering Contradiction:

ImproveFM signal reception capabilityVSAvoidisolation inductor size

Core Design Contradiction:

Adaptability or versatilityVSVolume of moving object

Solution Approach 1:

The patent changes the isolation mechanism from a large inductive component to ferrite beads, which are significantly smaller. This parameter change in the isolation element type resolves the contradiction by maintaining the necessary electromagnetic isolation while dramatically reducing the volume required for the isolation component.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the large, bulky inductor with small ferrite beads that are inexpensive and compact. These ferrite beads provide sufficient isolation for the application without requiring the large inductive component, thus resolving the volume constraint while maintaining functionality.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Reliability

If a large isolation inductor is used to isolate CLA ground from device ground, then ground isolation is achieved, but the design becomes bulky and constrained

Engineering Contradiction:

Improveground isolation effectivenessVSAvoidisolation component size

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the physical and electrical parameters of the isolation element from a large inductor to small ferrite beads. This parameter change maintains the ground isolation effectiveness while reducing the component size and simplifying the overall design, thus resolving the contradiction between isolation reliability and device complexity.

Inventive Principle:

Principle #35Parameter changes

3Volume of moving object

If ferrite beads are used for ground isolation, then component size is reduced, but isolation effectiveness must be maintained

Engineering Contradiction:

Improveisolation component sizeVSAvoidground isolation effectiveness

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent introduces ferrite beads as an intermediary element between the device ground and the FM tuner ground. These ferrite beads act as a mediator that provides sufficient electromagnetic isolation while being compact in size, thus resolving the contradiction between component size reduction and isolation effectiveness.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution allows for a compact design by eliminating the need for large inductive components, enabling effective FM signal reception using the ground signal line as an antenna, even when the CLA is not attached, and maintaining functionality as an electrically small antenna.

Implementation Method 1

The ground isolation can be implemented, for example, using one or more isolation elements, such as ferrite beads, coupled between the FM tuner ground and the device ground

Methodology Applied

Scientific EffectFerrite bead electromagnetic isolation: Ferromagnetism

Implementation Method 2

the RF input (RF IN) 205 for the FM tuner IC 206 is coupled to the CLA ground (CLAGND) signal line 220 through capacitor (C1) 214

Methodology Applied

Scientific EffectElectromagnetic radiation reception: Electromagnetic Induction

Data Source

PatentUS8208884B2Method and system for FM tuner ground isolation when using ground signal line as FM antenna

Publication Date: 2012.06.26 SKYWORKS SOLUTIONS INC

AI summary

Methods and systems are disclosed that utilize FM tuner ground isolation when using a ground signal line as an FM antenna for an FM tuner integrated circuit (IC) within a portable electronic system. The ground isolation can be implemented, for example, using one or more isolation elements, such as ferrite beads, coupled between the FM tuner ground and the device ground. The ferrite beads can also be coupled between other pins for the FM tuner and the device circuitry. A car lighter adapter (CLA) coupled to the device circuitry can be configured to provide a ground signal line for use as an antenna for the FM tuner IC. Further, signal lines on a printed circuit board (PCB) can also provide a ground signal line for use as an antenna for the FM tuner IC. The device can also be as a personal navigation device.