EMI (Conducted and Radiated Emissions) Suppression and Evaluation Service

Wave Technology Inc. (WTI) offers superior services to help clients with conductive noise and radiation noise issues.

EMI(conducted / radiated emission) suppression and evaluation service


As electrical equipment operates increasingly faster, the proportion of EMC (Electro-Magnetic Compatibility) evaluations in the product development process tends to increase.

EMC = EMI (Electro-Magnetic Interference)
  + EMS (Electro-Magnetic Susceptibility)

Are you sure you aren’t having any trouble securing an anechoic chamber or equipment for evaluating conducted and radiated emissions?
WTI is here to solve such product development challenges. We use our technology to your advantage, offering EMI solution services with our 3-meter range semi-anechoic chamber, and our evaluation equipment, all which fully comply with various international standards (IEC, FCC, CISPR, VCCI).

Allow our specialized technical experts to perform all the EMI pre-compliance conducted and radiated emission measurements, and investigate solutions, on your behalf.

WTI offers EMI solutions for the following products:
Consumer equipment, medical equipment, marine equipment, power supplies (maximum 4.5 KVA single-phase*1), wireless communication equipment, etc.*2

*1 Radiated emission (up to 20 A, 310 VAC (40 to 550 Hz), 440 VDC),
     Conducted emission (up to 16 A, 250 VAC (50/60 Hz), 400 VDC)
*2 WTI facilities are currently unable to accommodate automotive equipment.


Features of our EMI suppression and evaluation service

(1) At WTI, design and development services are our primary business, and so our technical team is well-versed in analog, digital, high frequency, power supply and housing design, and various technical fields.

WTI engineers verify EMI countermeasures against problems such as conducted and radiated emission from a designer’s point of view.

Features of the EMI Suppression and Evaluation Service


(2) After measuring conducted and radiated emission, we determine what countermeasures (if any) are necessary. Then, should you need to revise the hardware, WTI provides one-stop service— from board design to trial production, re-evaluation to certification test proxy agency services.

By using our one-stop service, clients are freed from laborious work such as reprototype setup, anechoic chamber re-reservation and verification preparation, and can concentrate on other value-added development operations.

Features of the EMI Suppression and Evaluation Service


Features of EMI countermeasure verification equipment

We have installed specialized EMI equipment which allows us to efficiently review EMI countermeasures for conducted noise and radiated noise.

◆Electromagnetic wave visualization system

By using the electromagnetic wave visualization system ,you can easily identify points which would benefit from countermeasures. Measured electromagnetic field intensity levels can be displayed in color on the heat map on the PC monitor, superimposed on the actual image of the measurement object. This can be customized according to specifications such as measurement frequency and object size. Therefore, this system can visualize and confirm not only the noise distribution on the board, but also the state of noise conducted and radiated to cables.

Features of EMI Countermeasure Verification Equipment

Example of using this system for conduction noise countermeasures

Below is an example of how to use the electromagnetic wave visualization system for countermeasures against conducted noise.

When the board of a product that doesn’t meet conduction noise standards is observed by the electromagnetic wave visualization system, the result is as shown in the figure below. (The redder the area is, the higher the noise level is. The blue area is not affected by the noise.)

Features of EMI Countermeasure Verification Equipment

This figure shows that the noise source is confined to a small area, which is an ideal design. However, this conduction noise was found to leak into the power cable.

As described below, what caused the problem was the way this board was built into the case.

Features of EMI Countermeasure Verification Equipment

When installing it in the case as shown in this figure, the power cable is pulled into the case and connected to the power connector on the board. However, in this case, the surplus part of the cable passed directly above the noise source. And so, although the noise on the board was wonderfully confined in an ideal state, the power cable becomes contaminated with noise and propagates it to the outside as conducted noise. Not only that, this power cable also acts as an antenna and emits radiated noise to the outside.

In such a situation, the noise level can be drastically improved simply by changing the internal cable routing so it does not interfere with the noise source.

Features of EMI Countermeasure Verification Equipment
Example of reassessed internal cable wiring

You may find conducted noise countermeasures surprisingly simple, once you get to the solutions. Designers often assume they may have taken insufficient countermeasures for the board they designed. They even try to examine those measures one by one. This method would lead to an answer, eventually, but it clearly takes much time and effort.

Wave Technology Inc. (WTI) employs the latest equipment such as electromagnetic wave visualization system and Δ type LISN (Delta LISN) in order to efficiently take measures against conducted noise and radiated noise.

Wave Technology Inc. (WTI) makes full use of these facilities to efficiently support customers’ EMI countermeasures.

◆Mains terminal interference voltage* 3 measurement system

Measuring mains terminal interference voltage (conducted noise)? Clients are welcome to use our power supply impedance stabilization network (Δ type LISN: Line Impedance Stabilizing Network), which can distinguish between differential mode and common mode noise. This makes it possible to study effective conduction noise countermeasures.

Noise terminal voltage * 3 measurement system

* 3 The term mains terminal interference voltage refers to conducted noise level on mains terminals.

Example of mains terminal interference voltage (conduction noise) measurement

Figure 1 shows the mains terminal interference voltage (conducted noise) measurement results using a normal V-type LISN.
These measurement results contain a mixture of differential mode noise and common mode noise. Because it is difficult to separate these noise components, the trial and error approach, which relies on experience and intuition, used to be the primary method used in noise countermeasures.
Because of this, it took vast amounts of time to take and examine measures against the conduction noise.

Figure 1: Normal noise terminal voltage (conduction noise) measurement results

Our Δ-type LISN can measure differential mode noise and common mode noise separately, as shown in Figure 2.

Figure 2: Measurement results with our Δ type LISN


The Δ-type LISN is an indispensable device in analyzing the cause of conduction noise and carrying out efficient countermeasure study.

Of course, WTI also has a regular V type LISN available.

Equipment details
◆Our semi-anechoic chamber specifications
This is a semi-anechoic chamber which supports various international standards such as IEC, FCC, CISPR, and VCCI. Radiated emissions can be measured in the frequency range of 150 kHz to 6 GHz, and mains terminal interference voltage in the frequency range of 9 kHz to 30 MHz.

Main Specifications

  • 3 x 7 x 2.6 (H) m
Measurable distance
  • 3 m
Measurable frequency
  • 150 kHz to 6 GHz
Shield characteristics
  • 150 kHz to 1 GHz 100 dB or more, 1 GHz to 10 GHz
         80 dB or more (MIL Std285)
Measuring device
  • System controller (Microwave Factory Co., Ltd.)
  • EMI test receiver (Rohde & Schwarz)
  • Loop antenna (9 kHz to 30 MHz)
  • BiLog antenna (biconical/log hybrid antenna) (30 to 1000 MHz)
  • Horn antenna (1 to 6 GHz)
Power supply
impedance stabilization
network (Δ type
LISN)(V type LISN)
  • 9 kHz to 30 MHz
  • Single-phase 2-wire (L / N / PE), 16A (250V AC)
Power supply
  • Power filter AC500V 30A
  • AC stabilized power supply DP045S single-phase 4.5 KVA
Measurement support system
(Automatic control)
  • Turntable φ1.2 m embedded type, load capacity 100 kg
  • Antenna elevator lift range 1-1.6m (from ground plane)
Ancillary equipment
  • ITV camera system
  • Intercom


Visit the WTI blog for more information:
What to do if the anechoic chamber is fully booked (EMI measures)
Fully operational, at last! WTI anechoic chamber rental & EMI countermeasure verification services
You can’t wave a wand and magically cure conduction noise… But you can find the cause and countermeasures! (Part 1)
You can’t wave a wand and magically cure conduction noise… But you can find the cause and countermeasures! (Part 2)

Electronic circuit design “Hint PLUS”


Click here for WTI video link

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