Inductor Guide

Basic Facts about Inductors [Lesson 2] Roles of Inductors 1- "Inductors for high-frequency range"

Inductors have many different uses, and a variety of product types are available according to the application.
Murata Manufacturing offers a diverse lineup of chip inductors classified by application into the three types of inductors: high-frequency circuits; power supply line inductors (power inductors); inductors for general circuits.
This article describes inductors for high-frequency circuits.

As the name implies, inductors for high-frequency circuits are used in the high-frequency band from 10 MHz to several GHz. As these products require a high Q (Quality factor) value, most have a non-magnetic core structure, and they are mainly used in the high-frequency circuits of mobile communications equipment, such as mobile phones, wireless LAN, and others.
 

Application Location Purpose 
Matching Lines between components in
antenna and IF blocks, etc.
Eliminating impedance mismatch and
minimizing reflection and loss
Resonance Synthesizers and oscillation
circuits
Securing the required frequencies
Choke Power supply lines of functional
components used in RF an
IF blocks
Cutting AC currents such as high-
frequency components

Table 1 Examples of inductor applications in each circuit block of a mobile phone

Murata Manufacturing offers a diverse lineup of inductor products for high-frequency circuits with three different structures: wire wound, multilayer and film.
The features and suitable applications of each structure are briefly described below.

◆ Features of the wire wound structure

The wire wound structure is formed by winding copper wire in a spiral shape around an alumina core. The coil can be formed using thicker wire than the multilayer and film structures, which provides the following features:

1) Low DC resistance is possible
2) Extremely high Q (Quality factor) value
3) Large currents can be supported

These features make the wire wound structure suitable for matching applications in antenna and PA circuits that require an extremely highQ factor, and resonance applications in IF circuits.

Applicable Murata products: LQW04AN/15AN/18AN series
 

◆Features of the multilayer structure

The multilayer structure is formed by layering ceramic materials and a coil conductor to create an integrated multilayer-type inductor. This enables a smaller size and lower cost compared to the wire wound structure.
While the Q factor is lower than that of the wire wound structure, the multilayer structure provides good overall balance between the L value deviation, rated current, size, price, and other characteristics, enabling use in a wide range of applications.
The multilayer structure is suitable for various applications such as RF circuit matching, choke, and resonance for mobile communication equipment.

Applicable Murata products: LQG15HN/15HS/LQG18HN series
 

◆ Features of the film structure

Film structure chip inductors have a multilayer structure, but the coil is formed with high accuracy over ceramic materials using Murata's original micro-processing technology.
Extremely accurate cores can be formed, providing the following features:

1) High-performance electrical characteristics can be realized even for compact chips such as 0603 size
2) Stable inductance and small inductance value steps are supported
3) High Q and high SRF

This makes film structure chip inductors suitable for RF circuit matching and resonance applications that require narrow deviation and a high Q factor to support trends toward smaller and more lightweight mobile communication equipment.

Applicable Murata products: LQP03TN/LQP02TN series

As described above, inductors for high-frequency circuits are used in various RF circuits by making effective use of the features of each type. The next article will introduce the structures and suitable applications of inductors for power circuits.

 

person in charge: Murata Manufacturing Co., Ltd.  N.H

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