Developing an EMC Desktop Evaluation System Using a New Measurement Technique

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"Today, we can perform EMI evaluation in the electronic equipment design phase using the advanced, low-cost, small-scale EMI evaluation instrument we developed."

- Naoki Hoshino, PERITEC Inc.

The Challenge:
Reducing the cost and complexity involved in measuring electromagnetic interference and noise when designing electronic equipment.

The Solution:
Developing an instrument using NI PXI hardware to replace anechoic chambers that measures electromagnetic noise and adjacent electromagnetic fields, including phase information.

Author(s):
Naoki Hoshino - PERITEC Inc.

Reducing Electronic Component Noise and Malfunction

Automobile part and medical equipment manufacturers rely on electronic components to help them comply with environmental and safety measures and offer cutting-edge technology. Noise protection is critical for these essential electronic components. Electronic product miniaturization, high-density integration, and high functionality increase background noise and malfunction susceptibility. Domestic electronic equipment manufacturers have a particularly strong need for a low-cost, small-footprint adjacent electromagnetic field measurement system with a long-range prediction function.

PERITEC Inc., received requests from electronic and automobile parts manufacturers and research facilities through TAIYO YUDEN Co., Ltd., to develop a system that addresses these concerns.

Figure 1. Traditional and New Technology Comparison

Creating an Electromagnetic Simulation Model

To measure long-range electromagnetic noise and determine radiation standards, companies often use a large-scale, expensive anechoic chamber. One room of equipment costs approximately ¥200 million to ¥2 billion (approximately $2 million USD to $20 million USD) and is difficult to maintain, so companies rarely implement their own chambers. This means engineers use anechoic chambers at authorized sites and public examination facilities, but these chambers have a long waiting period (usually a month) and high price tag.

Recently, researchers began performing experiments using simulation to analyze radiated electromagnetic noise, including predictions taken from adjacent to long range. However, producing a correct model for an actual electronic product is difficult. When creating an electromagnetic simulation model, researchers must consider component composition and detailed wiring.

Figure 2. Adjacent and Long-Range Electromagnetic Field Measurement

Many researchers are working to predict long-range electromagnetic fields without using anechoic chambers. They measure adjacent electric and magnetic field distribution (including phase information) and apply the field-equivalence theorem. This eliminates the need for a large-scale facility such as an anechoic chamber, and greatly simplifies noise measurement. Although there are several patents for this method, it is not yet used in practical cases.

This method to predict long-range electromagnetic fields requires an instrument that can measure adjacent electric and magnetic field distribution, including phase information. A spectrum analyzer can only measure the noise frequency and magnitude—not phase information. For this reason, it cannot predict long-range electromagnetic fields from the measured adjacent electromagnetic fields. Currently, there is no instrument that can measure adjacent electric and magnetic field distribution, as well as phase information. Additionally, there is no equipment that can display the information in a way that the engineer can easily understand.

Configuring the System

We configured our system based on patented TAIYO YUDEN technology that can measure phase noise frequency up to 14 GHz. To effectively calculate the electric and magnetic field based on the phase difference between the two conductor current signal outputs, it is essential that we synchronize current measurements (Figure 3). We needed hardware that could make high-precision phase measurements up to 14 GHz and use a software algorithm.

Figure 3. Two Current Signals and Phase Difference

To implement this, we used an NI PXIe-5665 high-performance RF vector signal analyzer (VSA). An NI PXIe-5665 consists of an NI PXIe-5603 downconverter, an NI PXIe-5653 local oscillator synthesizer, and a 150 MS/s NI PXIe-5622 intermediate frequency digitizer. For phase measurements, we created a system to take two channels of synchronized RF measurements using the baseband sample clock and local oscillator.

  

Figure 4. NI PXIe-5665 High-Performance RF VSA Amplitude, Phase, and Correlation

Acquiring Adjacent Electromagnetic Noise

Using an NI PXIe-5665 RF VSA, we acquired the Adjacent electromagnetic noise, including phase information, magnitude, direction, and unit-under-test position. According to the Schelkunoff equivalence theorem of electromagnetism, we can calculate long-range electromagnetic fields from this electromagnetic noise phase distribution (Figure 5).

Figure 5. Long-Range Prediction Algorithm and Software Development

Figure 6. Dipole Antenna Electric and Magnetic Fields

Figure 6 shows electromagnetic field distribution measurement close to the dipole antenna. From the top down, the graph shows electric field magnitude and phase, and magnetic field magnitude and phase.

There is strong electric field distribution on both ends of the dipole antenna. There is also strong magnetic field distribution in the center of the dipole antenna. We can better understand antenna operating conditions using an animated display to show step-by-step phase changes.

For example, the upper part of Figure 7 indicates the electromagnetic field distribution of a 50 Ω microstrip line with open termination. A standing wave at a specific point on the microstrip line gets stronger and weaker with sinusoidal distribution. The lower part of Figure 7 demonstrates the electromagnetic field distribution of a 50 Ω microstrip line with a 50 Ω termination. A traveling wave (sine wave) transmits along the microstrip line. This demonstrates printed circuit board RF signal distribution.

Figure 7. Microstrip Line Electromagnetic Field

Figure 8. Integrated Circuit Measurement

Figure 8 shows the upper integrated circuit (IC) package (32 mm x 32 mm) electric and magnetic field distribution magnitude and phase measurement results (~1 GHz). The left side shows electric field distribution, and the right side shows magnetic field distribution. Magnitude distribution is shown on top, and phase on the bottom.

The IC package electromagnetic field is distributed from the center of the IC block to the IC lead frames. In addition, IC lead phase data is different because there are different signal flows on the lead frames. As a result, measuring electromagnetic field distribution with phase data as well as magnitude provides more information.

Performing EMI Evaluation in the Design Phase

Sometimes it is impractical to evaluate noise or electromagnetic interference (EMI) in the electronic equipment design phase because it typically requires a large evaluation facility, such as an expensive anechoic chamber. To deal with noise, designers are forced to add additional electric component such as EMI filters, which causes the finished-products (circuits) to be larger.  Traditionally, developers took measures to reduce EMI at the end of the product development cycle, which led to development delays and rising costs.

Today, we can perform EMI evaluation in the electronic equipment design phase using the advanced, low-cost, small-scale EMI evaluation instrument we developed. We can design for low EMI early in the development cycle, so design margins are unnecessary. Therefore, the electronic component can be smaller.

Exploring New Market Potential

This compact, low-cost system can make EMI measurements, which traditionally required large, expensive equipment. We plan to further evaluate this system to replace anechoic chambers and initiate an international development standard.

Author Information:
Naoki Hoshino
PERITEC Inc.
peritec@mail.peritec.co.jp

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