The problem of correct choice of ferrite beads
A ferrite bead is a passive electrical element used to suppress high-frequency noise in electric circuits. This is one of the simplest and the cheapest type of filters. Thus, such filters are widely used in electric and electronic apparatus for both domestic and industrial purposes. It would seem t...
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Інститут технічних проблем магнетизму НАН України
2016
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| Назва видання: | Електротехніка і електромеханіка |
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| Цитувати: | The problem of correct choice of ferrite beads / V.I. Gurevich // Електротехніка і електромеханіка. — 2016. — № 2. — С. 71-73. — англ. |
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irk-123456789-1470932019-02-15T01:23:33Z The problem of correct choice of ferrite beads Gurevich, V.I. Дискусії A ferrite bead is a passive electrical element used to suppress high-frequency noise in electric circuits. This is one of the simplest and the cheapest type of filters. Thus, such filters are widely used in electric and electronic apparatus for both domestic and industrial purposes. It would seem that such a wide application of these elements suggests that methods for their correct selection and use are well-defined. However, this is not quite true Ферритовый фильтр – пассивный электрический компонент, использующийся для подавления высокочастотных помех в электрических цепях. Это один из самых простых и дешёвых типов фильтров. Очевидно, именно поэтому фильтры такого типа нашли самое широкое применение в электронной и электротехнической аппаратуре как бытового, так и промышленного назначения. Казалось бы, при такой широкой распространенности этих элементов методика их правильного выбора и применения должна быть хорошо всем известна. Увы, на самом деле все оказалось не так просто 2016 Article The problem of correct choice of ferrite beads / V.I. Gurevich // Електротехніка і електромеханіка. — 2016. — № 2. — С. 71-73. — англ. 2074-272X DOI: https://doi.org/10.20998/2074-272X.2016.2.13 http://dspace.nbuv.gov.ua/handle/123456789/147093 316 en Електротехніка і електромеханіка Інститут технічних проблем магнетизму НАН України |
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Дискусії Дискусії Gurevich, V.I. The problem of correct choice of ferrite beads Електротехніка і електромеханіка |
| description |
A ferrite bead is a passive electrical element used to suppress high-frequency noise in electric circuits. This is one of the simplest
and the cheapest type of filters. Thus, such filters are widely used in electric and electronic apparatus for both domestic and industrial purposes. It would seem that such a wide application of these elements suggests that methods for their correct selection
and use are well-defined. However, this is not quite true |
| format |
Article |
| author |
Gurevich, V.I. |
| author_facet |
Gurevich, V.I. |
| author_sort |
Gurevich, V.I. |
| title |
The problem of correct choice of ferrite beads |
| title_short |
The problem of correct choice of ferrite beads |
| title_full |
The problem of correct choice of ferrite beads |
| title_fullStr |
The problem of correct choice of ferrite beads |
| title_full_unstemmed |
The problem of correct choice of ferrite beads |
| title_sort |
problem of correct choice of ferrite beads |
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Інститут технічних проблем магнетизму НАН України |
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2016 |
| topic_facet |
Дискусії |
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http://dspace.nbuv.gov.ua/handle/123456789/147093 |
| citation_txt |
The problem of correct choice of ferrite beads / V.I. Gurevich // Електротехніка і електромеханіка. — 2016. — № 2. — С. 71-73. — англ. |
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Електротехніка і електромеханіка |
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AT gurevichvi theproblemofcorrectchoiceofferritebeads AT gurevichvi problemofcorrectchoiceofferritebeads |
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2025-07-11T01:20:27Z |
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2025-07-11T01:20:27Z |
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1837311552295796736 |
| fulltext |
Дискусії
ISSN 2074-272X. Електротехніка і Електромеханіка. 2016. №2 71
© V. Gurevich
UDC 316 doi: 10.20998/2074-272X.2016.2.13
V.I. Gurevich
THE PROBLEM OF CORRECT CHOICE OF FERRITE BEADS
A ferrite bead is a passive electrical element used to suppress high-frequency noise in electric circuits. This is one of the simplest
and the cheapest type of filters. Thus, such filters are widely used in electric and electronic apparatus for both domestic and in-
dustrial purposes. It would seem that such a wide application of these elements suggests that methods for their correct selection
and use are well-defined. However, this is not quite true. Table 1, figures 11.
Key words: ferrite, filters, electromagnetic pulse.
Ферритовый фильтр – пассивный электрический компонент, использующийся для подавления высокочастотных
помех в электрических цепях. Это один из самых простых и дешёвых типов фильтров. Очевидно, именно поэтому
фильтры такого типа нашли самое широкое применение в электронной и электротехнической аппаратуре как бы-
тового, так и промышленного назначения. Казалось бы, при такой широкой распространенности этих элементов
методика их правильного выбора и применения должна быть хорошо всем известна. Увы, на самом деле все оказалось
не так просто. Табл. 1, рис. 11.
Ключевые слова: ферриты, фильтры, электромагнитный импульс.
The ferrite bead is the simplest type of the filter: it is
characterized by low cost and significant attenuation of
short electromagnetic pulses (similar to high-frequency
signal) in conductors connected to electronic apparatus. It
is shaped as a ring (cylinder) filter put on the conductor
(see Fig. 1).
Fig. 1. Ferrite Elements (FE) of Ferrite Bead Filters
The impedance of the winding consists of one or
several turns of a control cable run through the ferrite ring
and is too low both for low-frequency operating signals
and for commercial frequency alternating current At the
same time it is too high for high-frequency (short pulse)
signals within the selected frequency range which de-
pends on the number of turns, material and size of the ring
itself. This results in significant attenuation of pulse and
high-frequency noise penetrating such cables. Attenuation
provided by such filters is in the range of 10-15 dB.
Numerous companies manufacture dozens of such
filter types both miniature, designed to be installed on the
printed circuit boards inside the apparatus (see Fig. 2),
and those suitable for the installation on the conductor
(cable) itself. For the sake of installation convenience
such filters are often made as two matching semi-rings
(semi-cylinders) located in snap-in plastic covers. This
provides fast and convenient installation of the filters on
the conductors (see Fig. 3).
Fig. 2. Miniature Filters Built Based on Ferrite Elements (FE)
and Designed for Installation on a Printed Circuit Board
Fig. 3. Design of Ferrite Beads Providing Fast and Convenient
Installation on Conductors
Such filters can be widely used in electronic
equipment: in control circuits, in circuits of logical and
pulse signal transmission, and in communication cir-
cuits (see Fig. 4).
Fig. 4. Ferrite Ring Filter Installed on a Control Cable Entering
the Electronic Equipment
72 ISSN 2074-272X. Електротехніка і Електромеханіка. 2016. №2
FE-based filters are manufactured by numerous
companies as given in Table 1.
Frequency ranges shown in Table 1 do not corre-
spond to the certain filter type, but describe the frequency
area provided by certain companies. Actual frequency
ranges of certain filter types are much lower than shown
in Table 1. Fig. 5 shows examples of frequency ranges of
different types of materials used in FE manufactured by
Fire-Rite Products Corp.
Table 1
Frequency Response of FE-based Filters Manufactured
by Different Companies
Company name Frequencies intervals for filters produced
by companies, MHz
Fire-Rite Products
Corp.
1 – 1000
Ferrishield 30 – 2450
Ferroxcube 0.2 – 200
Murata Miniature filters for PCB mounting
NEC/Tokin 0.1 – 300
Parker Chomerics 30 – 200
Laird 30 – 2000
TDK 10 –500
Leader Tech, Inc 1 – 2450
Wurth Elektronik Miniature filters for PCB mounting
Fig. 5. Frequency Ranges of Different Material Types
(designated by numbers) used in FE Manufactured
by Fire-Rite Products Corp.
Despite the apparent simplicity and cheapness (1-10
USD) ferrite filters are not as simple as they seem. Their
effectiveness depends on the numerous parameters, such
as: material type, equivalent frequency of current pulse to
be attenuated, size of FE, number of turns of the conduc-
tor passed-through the FE, the value of the DC-
component in the conductor, temperature, etc.
The frequency response of the filter depends on sev-
eral parameters, primarily on the FE material type. Man-
ganese-zinc ferrites (Mn-Zn) with relative magnetic per-
meability (magnetic inductive capacity) µ = 600 – 20.000
are usually used for frequency range of 0.1 MHz – 2
MHz, and for 1MHz – 2.45 GHz – nickel zinc ferrites (Ni
– Zn) with relative magnetic permeability µ = 15 – 2000
are used. Different ferrite mixes are also used during the
manufacture.
Apart from the frequency response the impedance –
is another very important parameter of FE-based filter. It
defines the level of noise suppression.
To a large extent the impedance of FE-based filter is
also determined by the type of material used and by the
operating frequency (see Fig. 6).
Fig. 6. Dependency of the Impedance of FE-based Filter
on the Material Type and Frequency
As FE-filter has inductance, capacitance and active
resistance (see Fig. 7), it is apparent that filter frequency
response and impedance also depend on FE size (particu-
larly on its length, see Fig. 8).
Fig. 7. Equivalent Circuit of FE-based Filter
Fig. 8. Dependence of Filter Impedance Z on the Ferrite
Element Length L made of two types of material (43 and 61)
manufactured by the Fire-Rite Products Corp.
ISSN 2074-272X. Електротехніка і Електромеханіка. 2016. №2 73
As shown in Fig. 8, the filters having longer FE al-
ways have higher impedance with all other parameters
being equal. This results from higher inductance of filters
with long FE.
To a large extent the impedance of FE-based filters
also depends on the number of wire turns passed through
the FE (see Fig. 9). As shown in Fig. 9 the starting im-
pedance of the filter with several wire turns is great com-
pared to the one-turn filter. However, the further increase
in noise frequency makes filters with several turns less
effective compared to filters with one turn which can re-
sult from the higher capacitance of the filter with several
turns.
Also, FE-based filters have another unpleasant char-
acteristic: their properties depend on the value of the DC-
component of the passing current (see Fig. 10). This re-
sults from the change of FE magnetic properties under the
existence of the DC-component of the current.
Fig. 9. Typical Dependency of Filter Impedance on the Number
of Turns (designated as 1-3) Passed through the FE
Fig. 10. Influence of the DC-component on Filter Characteristics
The presence of inductance and capacitance in the
filter equivalent circuit (see Fig. 7) provokes the hazard of
resonance under the certain frequencies. This can lead to
another problem of such filters – such as amplification of
noise instead of its attenuation.
So, if there are so many factors influencing the filter
parameters, what are the basics to correctly select the fil-
ter ensuring effective protection against electromagnetic
noise under a wide frequency range? It is tricky. This is
especially due to 1) unavailability of standards unifying
the procedure for measuring the parameters of such fil-
ters, and 2) different methods of measurement used by
different manufacturers. Due to all these problems it is
almost impossible to compare the parameters of filters
produced by different manufacturers.
According to the above analysis the following
method for the correct selection of FE-based filter can be
recommended:
1. In order to ensure the effective noise suppression
within the maximum frequency range it is required using
at least three in-series filters installed on the same con-
ductor (cable). Such filters should be made of different
materials providing maximum filter impedance within
low- (0.1 MHz), medium- (300 to 500 MHz) and high-
frequency range (2 to 2.45 GHz). Three filters installed
in-series on the same conductor also allows for eliminat-
ing the resonance, as they have different characteristics
and thus significantly different resonant frequencies.
2. Manufacturer data can be used only for preliminary
filter selection. Afterwards it is required to test the noise
suppression effectiveness within the full frequency and
current range needed for the customer.
This test can be done on the unit consisting of the
high-frequency pulse generator simulating the noise sig-
nal within the actual frequency range, and of the receiving
unit, such as oscilloscope, spectral analyzer or electronic
voltmeter with the extended frequency range. The genera-
tor should be connected to the input of the receiver using
the cable equipped with the filters (see Fig. 11). The
measured generator output voltage within the required
frequency spectrum (with and without filters installed on
the cable) characterizes the value of signal attenuation on
the filters and enables selecting the proper set of filters
providing necessary attenuation of high-frequency signal,
as well as ensuring that there is no resonance within the
full frequency operating range.
Fig. 11. Test Unit Designed to Check the FE-based filter
effectiveness
Received 19.10.2015
Vladimir I. Gurevich, Ph.D, Senior specialist,
Central Electric Laboratory of Israel Electric Corp.
31000, Israel, Haifa, POB 10,
e-mail: vladimir.gurevich@gmx.net
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