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Special Topic 1　Utilizing Amplitude Probability Distribution Mapping Measurements in the assessment and suppression of electromagnetic compatibility issues in digital wireless devices
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Utilizing Amplitude Probability Distribution Mapping
Measurements in the assessment and suppression of
electromagnetic compatibility issues in digital wireless devices
Recently, electromagnetic compatibility (EMC) issues have taken on growing importance, especially selfgenerated noise which represent interferes with reception in wireless handsets.
Until recently, there was no adequate method of measurement for this issue and subsequently effective suppression methods could not be developed.
In order to solve this noise measurement issue, Taiyo Yuden has developed methods by which the adjacent
electromagnetic field is measured through use of APD (Amplitude Probability Distribution).
These methods enable us to measure the noise causing electromagnetic compatibility issues that until now
had proven difficult to measure.
In this article, we will present the findings of our research on noise evaluation and counter measures derived by APD measurements in the adjacent electromagnetic fields.
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Special Topic 1　Utilizing Amplitude Probability Distribution Mapping Measurements in the assessment and suppression of electromagnetic compatibility issues in digital wireless devices
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Figure 1 Internal noise of cellular phones
Frequency spectrum
Time waveform
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Level [dBm]
LCD module
Level [dBm]
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877.49
877.51
Frequency [MHz]
877.53
877.55
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0.15
0.2
0.25
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877.47
877.49
877.51
Frequency [MHz]
877.53
877.55
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Level [dBm]
Level [dBm]
Special Topic 1　Utilizing Amplitude Probability Distribution Mapping Measurements in the assessment and suppression of electromagnetic compatibility issues in digital wireless devices
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0.1
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0
0.05
0.1
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0
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0.2
0.25
Time [sec]
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877.45
0.05
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877.45
0
Time [sec]
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Camera module
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877.47
Level [dBm]
Level [dBm]
Processor
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1
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877.45
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877.47
877.49
877.51
Frequency [MHz]
877.53
877.55
Time [sec]
from even low levels of noise, that previously
LCD module, processor IC and camera module
had not been an issue.
of a cellular phone by magnetic field probe.
In wireless handsets and mobile devices, such
Circuits of DC-DC converters, LCD modules,
In the most commonly used frequencies, con-
as cellular phones, electromagnetic compat-
CPUs etc. are often victims of this issue. The
spicuous spectrum peaks cannot be observed
ibility issues continue to grow in significance.
operating frequencies of these circuits usually
and is similar to the heat noise value. That
We are seeing more issue such as auto-jamming
ranges from several MHz to tens of MHz, but
means any obvious noise cannot be detected .
which is caused by self-gererated noise, recep-
the harmonic noise that may exist, is often up to
However, by measuring the time fluctuation
tion and sensitivity issues, among others, de-
ten orders greater than the frequency, even if it
of noise values in the same frequency range,
grading device performance-largely due to self-
is a faint one.
as indicated on the right, we can observe clear
generated noise from the device itself.
Until now this has not been an issue, but if and
fluctuations in the noise waveform.
Due to layout considerations, wireless handsets
when the frequencies overlap with those of the
In this way, the inner noise of the device can be
are forced to place multiple components [anten-
circuits there is a strong possibility of EMC is-
shown by hourly fluctuation, which cannot be
nas, tuners] and digital circuits which generate
sues occurring.
adequately measured by a spectrum analyzer.
noise unexpectedly in close proximity to one
Noise characteristics from actual cellular
But, by measuring the time fluctuation, noise of
another, which often come into conflict.
phones which could affect sensitivity are shown
this kind can be clearly measured.
This coupled with the greatly improving sensi-
in Figure 1.
One method of measuring and evaluating hour-
tivity of wireless circuits, such as tuners, often
The noise waveform on the left indicates data
ly noise fluctuation is through APD Mapping.
leads to electromagnetic compatibility issues
outputs measured by a spectrum analyzer of the
Noise causing EMC issues
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Figure 2 APD
P1 : Hourly probability exceeding threshold R1
Pk : Hourly probability exceeding threshold Rk
Rk :
Threshold
W（
: Term in which the value of noise exceeds threshold
n Rn）
R0 R1 Rk:Voltage
P1
Waveform of noise W
（t）
Probability
W1（R1）
W1（R2） W（
n Rn）
1
R0
(Formula 1) which is obtained by Wi(Rk); the
total amount of time of X(t) exceeding R(k) dividing by T0; whole amount of measuring time.
R1
Rk
Level of interference
2. APD as an indicator of interference
in digital communication
APD allows study of issues related to interfer-
Noise measurement technology referred to as
ence values of digital communication.
“APD” is an effective method of analyzing the
For example, a strong correlation can be shown
time fluctuation of noise, which can cause elec-
to exist between the APD noise in the band
tromagnetic compatibility issues.
frequency of a digital communication system
APD correlates the value of interference to the
like GSM and the influence of that noise on the
digital transmission, like “One-Segment” a
system.[*2,3]
Japanese digital terrestrial broadcasting service
APD is the data graphed from the relation be-
That is why measurements by ADP are a reli-
tween the Rk (horizontal axis) and variable of
able indicator of interference for wireless hand-
Since APD also provides hourly statistical val-
provability P(rk) (Verticalaxis).
sets using digital communications.
ues, it can be used to effectively measure time
This data indicate the probability the noise
This is strongly supported by the reception
fluctuation of noise, which is close to heat noise
would emerge, how frequently and how strongly
sensitivity data of "One-Segment TV" and the
(Figure 2) by measuring the time fluctuation
interference values measured by APD.
of noise.
In "One-Segment TV", an OFDM (Orthogonal
1. APD
In order to more accurately measure and evalu-
Frequency Division Multiplexing) modulation is
APD or "Amplitude Probability Distribution", is
ate EMC, Taiyo Yuden has developed its own
adopted for the wireless communication system.
a tool for statistical analysis.
measuring device to better apply APD.
Our experimental result shows a strong (positive)
Now recognized by CISPR16-1-1, APD pro-
In high-frequencies commonly used in wireless
correlation between the deteriorating value in re-
cesses are now increasingly being applied to
communications, this instrument allows mea-
ception sensitivity and noise measured by APD.
accurately measure electromagnetic noise.
surement of the time fluctuation of noise and
The spectrum band of 473 to 767 MHz was ap-
APD stands for the relation, in case that a
calculates the APD at an arbitrary amplitude
plided, as in digital TV broadcasting channels
for mobile TV.
in level.
[*2]
[*1]
An APD overview follows below.
threshold Rk is set to an amplitude waveform
X(t), between Rk and a variable of provability P
and time.
[*1]
13-62.
The spectrum band is so broad that the fre-
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Special Topic 1　Utilizing Amplitude Probability Distribution Mapping Measurements in the assessment and suppression of electromagnetic compatibility issues in digital wireless devices
Time
T0：Total measurement time
APD Noise Measuring
Technology
APD Curve
Pk
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Special Topic1
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quency from which the noise comes from is
"One-segment TV" through hybrid electric cir-
converter operates at 1MHz) by wide-range
different for each channel.
cuits, which can add high-frequency signals.
antenna and adding it to the signal through the
By measuring the relation between the value of
In this situation, if the output of the signal
hybrid-circuits.
noise in each channel and the sensitivity of re-
generator is turned down, the tuner could not
The measurement systems was connected,
ception, we observed a correlation between the
provide a picture at a certain level.
noise was measured and APD determined.
sensitivity of reception in OFDM modulation
We set the level of each channel to the tuner's
From the APD method, a certain value of
communication systems and the measurement
sensitivity level of reception without noise.
probability was derived (for example 10-2), and
of noise by APD.
The receptions deterioration due to noise was
a correspoinding threshold was obtained.
The measurement system is shown in Figure 3.
provided by measuring the reception sensitiv-
By comparing the thresholds which have the
A signal generator produces digital TV broad-
ity of the tuner to the generated noise received
same value of provability, we can see the rela-
cast signals, was connected to the tuner of
from the source of the black box (DC-DC
tion between the two in the quantity of noise.
For this measurement, the thresholds of
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34ch
（599.142857MHz）
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30
37
41
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57
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probability were 10 -2, 10 -3, 10 -4 and 10 -5 and
graphed for each channel.
Receive sensitivity [dBm]
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-80
Noise Level [dBm]
Special Topic 1　Utilizing Amplitude Probability Distribution Mapping Measurements in the assessment and suppression of electromagnetic compatibility issues in digital wireless devices
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Figure 4 Measurement of interference by receiver sensitivity and APD
Moreover, this graph made without adding the
noise shows the noise of the measurement sysNoise from
DUT
（10-2~10-5）
System noise
on APD
measurement
（10-2~10-5）
RS with noise
RS without noise
RS:Receive sensitivity
tem (thermal noise).
Figure 4 shows the comparisons of those
graphs at each channel. This figure demonstrates that the reception of high channel
whose noise level is evaluated by APD as high
deteriorates significantly. In contrast, the re-
CHANNEL [CH]
ception at low channel is less deteriorated.
Figure 3 Receiver sensitivity in "One-seg" and APD
LEADER ISDB-T LG3802
Digital TV signal generator
Tuner for One-seg TV broadcasting
PC
Hybrid circuit
Shield box
DUT
Antenna
APD measurement machine
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can be used as a tool to evaluate EMC from the
taneously map the electric and magnetic noise
by APD can be an index of influence which has
device itself.
of DC-DC converters that previously proved
an impact on reception of one-segment tuner.
To do this Taiyo Yuden has developed an APD
too difficult due to large time fluctuation in the
mapping measurement system.
electric and magnetic fields (as shown in Fig-
3. Mapping Measurement of adjacent
By use of this system we can now accurately
ure 6).
electromagnetic field by use of APD
and simultaneously determine the APDs in
Differences in mapping results between the
EMC issues are caused by adjacent electro-
both electric and magnetic fields. This is ac-
spectrum analyzer and APD approaches may
magnetical field interference as the source of
complished by use of a special sensor, designed
occur.
the noise.
by Taiyo Yuden, featuring two outputs, thereby
A distribution of a digital IC magnetic field, as
For this reason the mapping of the electromag-
enabling detection of both electric and magnetic
in Figure 7, appears in the lower region of the
netic field in devices is an effective predictor of
fields and then segregating the data. (Figure 5)
IC when using a spectrum analyzer, but in the
issues or validation of countermeasures.
After the sensor automatically scans the fields
upper region when using APD.
”Conventional mapping is accomplished by us-
APDs are calculated and mapped in both electric
This difference is attributable to the fact that
ing a spectrum analyzer to obtain values.
and magnetic fields, color-coded and displayed.
several signals have different time fluctuations,
However, in digital communication systems the
This system is capable of analyzing spaces from
but the same frequency in the IC.
correlation between the spectrum analyzer val-
approximately 0.5mm-1.0mm, can analyze
We confirmed this by measuring indistinct sig-
ues and the interference is too weak to be used
electric components; multilayer ceramic capaci-
nals in a spectrum with a large time fluctuation
as an effective predictor of EMC issues.
tors, ferrite beads, and can also analyze traces
flow to the upper region of the IC terminals,
While mapping of the adjacent electromagnetic
on the electronic substrates to determine EMC
while distinct signals in a spectrum with a small
field by using ADP related to an value could
issues.
hourly fluctuation flow to the lower regions of
effect the digital communication systems, this
This powerful new system enables us to simul-
the IC.
Figure 5 APD measurement system in Electric field/Magnetic field
Divider
Lo. oscillator
CH1
Electric wave form in time domain=CH1+CH2
Magnetic wave form in time domain =CH1-CH2
Down-converter
30MHz – 2.7GHz
70MHz IF
CH2
30MHz – 2.7GHz
70MHz IF
A/D converter
PC
A/D converter
Electric APD
Magnetic APD
Synchronize
Loop (sensing part)
Output A
H
E
Output B
A=Ie-Im
Ie = (A+B)/2
Im = -(A-B)/2
B=Ie+Im
Ie
Ie
Ie : Electric field current output
Im Im : Magnetic field current output
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Special Topic 1　Utilizing Amplitude Probability Distribution Mapping Measurements in the assessment and suppression of electromagnetic compatibility issues in digital wireless devices
This verifies that noise level which is evaluated
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Figure6 Case sample of measuring DC-DC converter
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Measurement by APD
Hourly waveform
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CH1-CH2 Time [dBm]
CH1-CH2 Time [dBm]
Hourly waveform
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0
10
20
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40
0
10
20
0-44 [msec]
30
40
0-44 [msec]
Measurement by spectrum
Spectrum waveform
Spectrum waveform
0
CH1-CH2 FFT [dBm]
0
CH1-CH2 FFT [dBm]
Special Topic 1　Utilizing Amplitude Probability Distribution Mapping Measurements in the assessment and suppression of electromagnetic compatibility issues in digital wireless devices
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Figure7 Difference of the distribution measurement between APD and Spectrum
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580.8
580.9
581.0
581.1
478.85-479.43 [MHz]
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580.8
580.9
581.0
581.1
581.2
478.85-479.43 [MHz]
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Figure8 Substrates of the DC-DC converter used for the experiment
TPS62040(1.25 MHz Step-Down converter: Texas Instruments)
150 mm
Ground
4.7μH
2.8 ohm
50 mm
22μF
22μF
Input
Vin:5V
200 k-ohm
610 k-ohm
Output
Vout:2.02 V
1
22μF
Without slits
▼The magnetic field distribution
Without slit
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The magnetic
The electric
field distribution field distribution
Noise Level [dBm]
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-95
▼The electric field distribution
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737.142857MHz (57 CH)
CHANNEL [CH]
▼The magnetic field distribution
With slit
With slits
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The magnetic
The electric
field distribution field distribution
Noise Level [dBm]
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-95
▼The electric field distribution
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737.142857MHz (57 CH)
CHANNEL [CH]
Countermeasures for noise
deteriorating One seg TV's
reception
tained an electronic circuit composed of a DC/
Our comparison therefore included both a
DC converter operated at 1.25MHz and pas-
conventional substrate, without slits, and a
sive components; a wound inductor, two ce-
substrate with slits at the ground of the substrate
A test was conducted for evaluation of coun-
ramic capacitors, and for voltage control. used
and power supply pattern as in Figure 9.
termeasures using the APD measuring system
two resistors.
By setting antennas adjacent to each substrate,
in the One seg TV frequency range.
Operating test conditions of the circuit: input
noise of each the channels was received and
We chose a DC/DC converter as our example
voltage of 5V, output voltage-2v, and current of
measured by the APD system, so its values
since it is a commonly used component and
about 700mA flowing in a load-resistor of 2.8Ω.
could then be evaluated the interference value
source of noise in One seg TV.
Noise causing EMC issues is greatly influ-
to the One seg TVs.
The experimental substrate, Figure 8, con-
enced by the circuit design on the substrate.
In the first half of the channel there is little dif-
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Special Topic 1　Utilizing Amplitude Probability Distribution Mapping Measurements in the assessment and suppression of electromagnetic compatibility issues in digital wireless devices
Figure9, Figure10 Noise and its distribution with slits and without slits
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Special Topic1
Special Topic 1　Utilizing Amplitude Probability Distribution Mapping Measurements in the assessment and suppression of electromagnetic compatibility issues in digital wireless devices
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From this we can determine substrates with slits
For each of the channels, the comparison results
half noise generated from the substrate contain-
enable capacitors for input and output to oper-
showed noise generated in each substrate in
ing slits was lower.
ate more effectively as decoupling elements in
APD of probability 10-2 as shown in Figure 12.
In the frequency of channel 57, the noise value
higher frequency ranges.
On the whole, the value of noise received by
difference is great, about 8 db, and the resulting
By evaluating the substrate with slits, we were
the antenna adjacent to low ESL capacitor was
mapping distribution of noise in the electro-
able to evaluate the variation of results and ef-
lower than that of the conventional capacitor,
magnetic field over the top surface of the entire
fectiveness of countermeasures attributable to
while the values for the “Capacitive Filter” were
substrate by APD measurement is shown in
different decoupling elements.
even lower.
Figure 10.
As shown in Figure 11, the measured APDs
From this, we can confirm the results of coun-
In the substrate without slits, we can see that
act as an indicator of the value of influence upon
termeasures used to the value of the noise mea-
the distribution of electric and magnetic fields
the sensitivity of reception in One segment TV.
sured with the APD system.
are dispersed widely throughout the ground and
We measured three different types of capacitors
As demonstrated above, we now have methods
power supply. There is one particular concen-
utilized as decoupling capacitors; a convention-
to effectively evaluate EMC issues and counter-
trated field on the input side of 5V.
al multilayer ceramic capacitor, a LW reversal
measures, making it possible to tailor solutions
In the substrate with slits, we can see the dis-
capacitor with low ESL, and a “Capacitive filter”
to effectively counteract these issues.
tribution occurs mainly around the IC, and less
functioning as a low-pass filter that has a feature
diffusion across the substrate can be seen.
of four terminal geometry.
Figure11,Figure12 Decoupling elements and noise
Noise level（APD 10-2）
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Noise floor
A）JMK212:Conventional type
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B）AWK107:Low ESL type
A) Conventional multilayer ceramic capacitor
JMK212
C）
Decoupling filter
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Noise Level [dBm]
1
ference in noise demonstrated, but in the latter
B) Low ESL type multilayer ceramic capacitor
AWK212
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CHANNEL [CH]
C) Decoupling filter
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develop even more effective solutions and
Taiyo Yuden has developed an accurate and
measurement methods for electromagnetic
effective system to evaluate electromagnetic
noise, which will leads Taiyo Yuden to
noise through innovative use of APD and
advance and develop techniques to further
mapping systems.
utilization of APD.
Based on the findings presented herein, it
The reference list
has been demonstrated that APD can be
[*1] Kazama, Hori & Tsutagaya, “Suggestion for new
measurement method of electromagnetic noise for
EMC countermeasure of wireless applications”,
Nikkei electronics no.919 pp.115-122
[*2] K. Gotoh, Y. Matsumoto, and S. Ishigami, “Performance evaluation of multicarrier wireless systems
affected by a disturbance using amplitude probability distribution,” in Proc. EMC Europe Workshop, Paris, June, 2007.
[*3] S, Kazama and H. Tsutagaya, “ADJACENT ELECTROMAGNETIC FIELD APD MEASUREMENT FOR ANALYZING AUTOJAMMING
ISSUE ON WIRELESS COMMUNICATION
SYSTEM“, 2007 IEEE Int. Symp. On EMC Recordings (CD-rom)
[*4] Kazama; “Break with try and error, suggestion for
new method of measurement technology of high
frequency EMI”, Nikkei electronics no.809 pp.105114
effectively used in evaluation and analysis of
EMC issues and countermeasures as in our
tests illustrating the deteriorating sensitivity
of reception in a One seg TV signal.
Going forward, Taiyo Yuden confidently
supports the use of APD systems as an
effective method through which noise issues
can be quantified and solved by prposing
proper countermeasues and components.
By collaborating with customers through
ADP evaluation technologies, we can
1
Special Topic 1　Utilizing Amplitude Probability Distribution Mapping Measurements in the assessment and suppression of electromagnetic compatibility issues in digital wireless devices
Coming Trends in the Years Ahead
Reference: Taiyo Yuden's products for suppressing noise Line up
Products for
suppressing noise
SMD type
Serial connection type
Ferrite beads
Parallel connection
type Capacitors
Common mode
choke coils
Leaded type
For DC
For AC
Ferrite beads BK series, FBM series
Applicable to noise in any type of
equipment because of affluent lineup
Multilayer ceramic capacitors,
three-terminal type, LWDC series
For power supplies with
low impedance and PCs with low ESL
Common mode Choke coil CM01series
For high-speed differential signal [Mbps -Gbps],
suppressing noise in MHz to GHz band
Common mode
Choke coils for DC line
Common mode Choke coils
for AC line TLF series
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