Misure di pre-compliance EMI · PDF fileEvaluate the conducted and radiated ... Susceptibility...

EMC seminar

Misure di pre-compliance EMI

Roberto Sacchi

Application [email protected]

EMC seminar

Agenda

Introduzione alle misure EMI Terminologia;

Sistema di misura (antenna, LISN, ricevitore, etc.);

Detectors;

Normative europee ed internazionali

Misure di pre-compatibilita’ elettromagnetica Misure di emissioni radiate;

Misure di emissioni condotte

Soluzioni Agilent Introduzione agli analizzatori serie-X;

Software applicativo per le misure di pre-compatibilita’ EMI

EMC seminar

Comparison of precompliance and full compliance

measurements

Precompliance MeasurementsEvaluate the conducted and radiated

emissions of a device using correct

detectors and bandwidths before going

to a test house for compliance testing

Full Compliance measurements

Full compliance testing requires a receiver

that meets all the requirements of CISPR

16-1-1 (response to a CISPR pulse gen),

a qualified open area test site or semi

anechoic chamber and an antenna tower

and turntable to maximize EUT signals.

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What is EMC?

Electromagnetic Compatibility (EMC): The ability of equipment to function

satisfactorily in its electromagnetic environment without introducing intolerable

disturbances into that environment or into other equipment.

Combination of Interference and Immunity.

Electromagnetic Interference (EMI):Electromagnetic energy emanating from one device which causes another device to

have degraded performance.

Electromagnetic Immunity (Susceptibility, EMS): Tolerance in the presence

of electromagnetic energy (Performance degradation due to electromagnetic energy).

Compliance measurements require a receiver that meets the requirements of

CISPR part 16 (for commercial) or MIL-STDd 461 (for military).

All EMI receivers require a pre-selector at lower frequencies to limit the input energy

and maintain sufficient dynamic range to meet the CISPR 16 requirements.

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Definitions

EMC –

ElectroMagnetic Compatibility

EMI –

ElectroMagnetic

Interference

EMS –

ElectroMagnetic

Susceptibility

(aka Immunity)

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OverviewWhat is Signal, Vector and Spectrum Analysis?

•Display and measure amplitude versus frequency for RF & MW signals

•Separate or demodulate complex signals into their base components (sine waves)

Spectrum Analysis

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OverviewTypes of Tests Made

Modulation

Noise

Distortion

EMC

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Architecture of Modern Spectrum/Signal Analyzers

What does “Modern” mean?

Digitize the IF output, not detector output

FFT and swept capability (neither one is optimum for everything)

Digitized data output available

Connectivity

Automated measurement features

What we hope it doesn’t mean

Incompatibility

What can it mean

Ability to use new features to duplicate or expand necessary old ones

Complete spectrum analyzer & vector signal analyzer

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Theory of OperationSwept Spectrum Analyzer Block Diagram

Pre-Selector

Or Low Pass

Input Filter

Crystal

Reference

Oscillator

Log

Amp

RF input

attenuator

mixer

IF filter

(RBW)envelope

detector

video

filterlocal

oscillator

sweep

generator

IF gain

Input

signal

ADC, Display

& Video

Processing

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Traditional Spectrum Analyzer

Scalar analysis

Digitizing the video signal

Classic superheterodyne swept spectrum analyzer

Product detector

loss of phase

information

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Digital IF Spectrum/Signal Analyzer

Vector data CAN be preserved (mag/phase or I/Q)

Digitizing the IF Signal

Some troublesome operations

and conversions are now

fast, accurate DSP

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OverviewDifferent Types of Analyzers

Parallel filters measured

simultaneouslyA

ff1 f2

FFT Analyzer

A

ff1 f2

Filter 'sweeps' over

range of interest

Swept Analyzer

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SpecificationsResolution: RBW Type Determines Sweep Time

280 sec

134 sec

13.5 sec

8563E Analog RBW

PSA Digital RBW

PSA FFT RBW

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Speed Improvements

Useful comparisons highly specific, many factors

PXA mode switching typically faster than PSA

Where speed is critical, consider modifying measurement routines to

include features such as list sweep

Benchmark PXA PSASpeed

improvement

Preset (*RST) 28 ms 168 ms 6x

Marker peak search 6.5 ms 78 ms 12x

Local Update 13 ms 17 ms 1.3x

CF Tune and Transfer (4 - 5GHz) 109 ms 186 ms 1.7x

Remote sweep and trace transfer 18 ms 30 ms 1.67x

Nominal speed comparison, PSA example:

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Modern spectrum analyzer

Resolution BW Selectivity or Shape Factor

3 dB

60 dB

60 dBBW

60 dB BW

3 dB BW

3 dB BW

Selectivity =

Determines resolvability of unequal amplitude signals

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Specifications

Resolution: RBW Type and Selectivity

DIGITAL FILTER

ANALOG FILTER

SPAN 3 kHzRES BW 100 Hz

Typical

Selectivity

Analog 15:1

Digital ≤5:1

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Digital Filter Shape

Better shape factor, biggest selectivity benefit for different signal levels

Equivalent selectivity at a wider, faster-sweeping RBW

digital filters swept an additional 3-4x faster

30 kHz Digital Filter

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CISPR Bandwidth Requirements

Measurement Range CISPR Band CISPR Bandwidth

9 KHz – 150KHz A 200 Hz

150 KHz – 30 MHz B 9 KHz

30 MHz – 1 GHz C/D 120 KHz

> 1GHz E 1 MHz

Bandwidth -6dB

-20dB

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MIL-STD-461 Bandwidth Requirements

Measurement Range -6dB Bandwidth

30Hz - 1 KHz 10 Hz

1 KHz -10 KHz 100 Hz

10 KHz - 150 KHz 1 KHz

150 KHz - 30MHz 10 KHz

30 MHz - GHz 100 KHz

> 1GHz 1 MHz

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Some modern analyzers approach accuracy of power meter + sensor

• Even better for low-level signals, with narrower noise bandwidth and

the benefit of frequency selectivity

Some factors determining uncertainty:

• Input connector (mismatch)

• RF input attenuator

• Mixer and input filter (flatness)

• IF gain/attenuation (reference level)

• RBW filters

• Display scale fidelity

• Calibrator

Modern Spectrum Analyzer Accuracy

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Modern Spectrum Analyzer Accuracy Examples

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Line Impedance Stabilization Networks (LISN)

Purpose of a LISN:

1. Isolates the power mains from the

equipment under test. The power

supplied to the EUT must be as clean as

possible. Any noise on the line will be

coupled to the X-Series signal analyzer

and interpreted as noise generated by

the EUT.

2. Isolates any noise generated by the EUT

from being coupled to the power mains.

Excess noise on the power mains can

cause interference with the proper

operation of other devices on the line.

3. The signals generated by the EUT are

coupled to the X-Series analyzer using a

high-pass filter, which is part of the LISN.

Signals that are in the pass band of the

high-pass filter see a 50-Ω load.

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LISN

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LISN

@ Electrical Network Frequency

@ 150 kHz to 30 MHz

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Transient Limiter

The purpose of the limiter is to protect the input of the EMC analyzer from

large transients when connected to a LISN. Switching EUT power on or off

can cause large spikes generated in the LISN.

The Agilent 11947A transient limiter incorporates a limiter, high-pass filter,

and an attenuator. It can withstand 10 kW for 10 μsec and has a frequency

range of 9 kHz to 200 MHz. The high-pass filter reduces the line frequencies

coupled to the EMC analyzer.

DUT

LimiterLISN

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Field Strength and Antenna factors

Radiated EMI emissions tests measure the electric field. The

field strength is calibrated in dBμV/m.

Antenna factors is the ratio of the electric field (V/m) present

at the plane of the antenna versus the voltage out of the

antenna connector.

Log units:

AF(dB/m) = E(dBμV/m) - V(dBμV)

E(dBμV/m) = V(dBμV) + AF(dB/m)

Notes:

Antenna factors are not the same as antenna gain.

dBμV = dBm + 107

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Field Strength Unit

Radiated EMI emissions measurements measure the

electric field. The field strength is calibrated in dBμV/m.

Pt = total power radiated from an isotropic radiator

Pd = the power density at a distance from the isotropic radiator

(far field >λ/2π)

24 r

PP t

d

120R

R

EPd

2

2

2

4 r

P

R

E t

r

PE

t 30 [V/m]

[ohm]

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Antennas used in EMI emission measurements

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Detectors: Convert IF Samples to Display Bins or

“Buckets”

Multiple simultaneous detectors

Screen Shot “Detector 3types”

Time

Volts

Peak

Neg Peak

Sample

Display points or

buckets

Normal, Average, Neg Peak

Peak, Neg Peak, Sample

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Detectors

Most radiated and conducted limits are based on quasi-peak

detection mode.

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Peak vs. Quasi-peak vs. Average

time

VPeak Detection

Quasi-Peak Detection

Average Detection

time

VPeak Detection

Quasi-Peak DetectionAverage Detection

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Peak ≧ QP ≧AveragePeak Detector

• Initially used

• Faster than QP and Average modes

• If all signals fall below the limit, then the product passes and no future

testing is needed.

QP

• For CW signal, Peak = QP

• Much slower by 2 or 3 order magnitude compared to using Peak detector

• Charge rate much faster than discharge rate

– the higher repetition rate of the signal, the higher QP reading

Average

• Radiated emissions measurements above 1 GHz are performed using

average detection

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Close field probe

Measures the magnetic field H strength at the center

of its sense loop. The plane of the probe tip loops

must be perpendicular to the radiating magnetic field

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Test example

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Emissions Regulations (Summary)

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European Norms example

EN55014 (CISPR 14)

This standard applies to electric motor-operated and thermal

appliances for household and similar purposes, electric tools

and electric apparatus.

Limit line use depends upon the power rating of the item.

EN55014 distinguishes between household appliances, motors

less than 700W, less than 1000W and greater than 1000W.

Limits for conducted emissions are 150 kHz to 30 MHz, and

limits for radiated emissions are 30 MHz to 300 MHz.

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The pre-compliance measurement process

Before making measurements on your product, some

preliminary questions must be answered.

1. Where will the product be sold (for example, Europe, United

States, Japan)?

2. What is the classification of the product?a. Information technology equipment (ITE)

b. Industrial, scientific or medical equipment (ISM)

c. Automotive or communication

d. Generic (equipment not found in other standards)

3. Where will the product be used (for example home,

commercial, light industry or heavy industry)?

With the answers to these questions, you can determine

which standard your product must be tested against.

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General Process for Making EMI Measurements

Determine the country or countries in which the product

will be sold which in turn identifies the regulator agency.

Select the limit lines to be tested to (conducted/radiated).

Select the band to be used.

Correct for transducer loses and amplifiers gains.

Identify signals above the limit that must be evaluated.

Zoom in on failed signal and perform quasi-peak or

average measurements.

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Conducted Emissions Measurements

1. Connect DUT to the test system

2. Set the proper frequency range

3. Load limit lines and correction factors for LISN and limiter

4. View the ambient emissions with DUT OFF

5. Switch on the DUT and find signals above limits by using peak detector

6. Measure all signals above limits with quasi-peak and average detectors

EMC seminar

Radiated Emissions are difficult to

measure because of multiple

dimensions (five) and the use of

quasi-peak detection below 1GHz

41.2563MHz

218.120MHz

1500.260MHz

1 - Azimuth

2 - Antenna Height

3 - Field Strength

4 - Frequency

5 -Time

The challenge of measuring radiated emissions

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Radiated Emissions Measurements

1. Connect the antenna to the EMI receiver and separate the antenna from

the DUT as specified by the regulation requirements

2. Set the proper frequency range and bandwidth

3. Load limit lines and correction factors for antenna and cable.

4. With DUT OFF, measure the ambient emissions and store them

5. Switch on the DUT and find signals above limits by using peak detector

(only those not present during the ambient scan)

6. Measure all signals above limits with quasi-peak and average detectors

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1. Select the measurement range

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2. Load Corrections factors

Amplitude at

point circled

Amplitude

referenced to

blue line

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3. Load Limit line

Circle indicates

the position of

the amplitude

frequency pair

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4. Scan for signals above the limits with peak

detector

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5. Quasi-peak and average measurements

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Troubleshooting

Use the close-field probe to locate the sources of the radiated signals

exceeding the limit lines

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Agilent Solutions

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Agilent X-Series Signal Analyzers

Multiple instruments in one box: Swept spectrum analyzer;

FFT analyzer;

RF and Baseband Vector Signal analyzer;

Noise Figure analyzer.

Fastest signal analysis measurements

Broadest set of applications and demodulation capabilities

Upgradeable HW

Most advanced user interface & world-class connectivity

Instrument ArchitectureModern Spectrum Analyzers Architecture (PSA, X-Series)

RF Section IF Section BB Section

•Attenuation

•Filtering

•Downconversion• RBW Filtering

• Envelope Detection

• Log Conversion

• VBW Filtering

• Peak/sample/rms

detection

• Averaging

ADCIF/BB Section

on ASIC

“All Digital” IF Architecture

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Modern Spectrum Analyzer Block Diagram

YIG ADC

Analog IF

FilterDigital IF Filter

Digital Log Amp

Digital Detectors

FFT

Swept vs. FFTAttenuation

Pre-amp

Replaced

by

“All Digital IF” Advantages

RF Section ADCIF/BB Section

on ASIC

Flexibility:

RBW filtering in 10% steps

Filters with better selectivity

Multiple operation modes (Swept, FFT, VSA, NFA)

Accuracy:

Log conversion practically ideal

No drift errors; increased repeatability

Speed:

When Swept mode is slow, go FFT

FFT

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Techniques for Reducing DANL, Improving Dynamic

Range

Reduce attenuation

Add preamp

Reduce RBW

Add external filtering

Better/shorter cables, connectors

Move analyzer closer

Time averaging (where possible, not measurement avg.)

Measurement processing (take advantage of Moore’s Law)

• Noise power subtraction/noise correction/NNC

• Noise floor extension (NFE) leverages deep knowledge of

analyzer/circuit behavior

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CW Signal Measured Near Analyzer Noise Floor

Actual S/N

Displayed

S/N

CW Signal

Apparent

Signal

This is

fundamental, and

often missedAmpl & Freq

Axes Expanded

Example: No noise subtraction or near noise correction

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Noise Subtraction, “Noise Floor Extension”

New PXA technique “NFE” improves D.A.N.L.

analyzer noise power calculated/subtracted real time

3 dB error

without NFE

“No” error

Improved noise floor

or displayed average

noise level

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Noise-Like Signal and Noise

1 MSymbol/sec QPSK, 1.9 GHz

Signal accurately measured, but noise biased higher by analyzer

noise power (no NFE)

Average detector, slower sweep to measure signal and noise,

reduce variance

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Result from Noise Subtraction

Implemented in the Agilent PXA Signal Analyzer

Blue trace shows more accurate measurement due to removal of analyzer noise power

Note increased variance of result

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Analyzer Noise Floor without NFE

Source switched off, pink trace shows analyzer noise level, no NFE

Other measurement conditions unchanged

PXA DANL (pink) adds to source power (blue) for first meas. result (yellow)

Note that noise level variance (pink trace) is smaller without NFE

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Analyzer Noise Floor with NFE

Source still off, green trace shows analyzer noise level with NFE

Other measurement conditions unchanged

Note high variance result from subtraction of small, noisy numbers

Analyzer DANL now far enough below source for minimal(0.2 - 0.4 dB) error

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A Closer Look

Pink trace adds to blue trace; result is yellow trace (NFE not used)

Green trace is included in blue trace but resulting error very small

Source noise Level, no NFE

Source Noise Level, with NFE

Analyzer Noise, no NFE

Analyzer Noise with NFE

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Signal Type vs. EffectivenessSignal/Noise Variation with RBW

Amplitude envelope vs. time

Best RBW is one matched to signal

Best ability to separate analyzer noise from signal

RBW (log)

SNR

(dB)

Noise-like

Real signals

can be one

type or

combination

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Noise Floor EnhancementCW Example

95% confidence interval, 2 dB tolerance

3.5 dB improvement for CW signal

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Noise Floor EnhancementNoise-Like Signal Example


9.1 dB improvement for noise-like signal

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Noise Floor EnhancementPulsed RF Example


10.8 dB improvement for pulsed-RF signal

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Low Noise Path

To μW

Converters

To Low Band

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Alternate “Low Noise Path”

3 dB

@ 3.6 GHz

10 dB

@ 26 GHz

Example:

Spur Search

20-50x faster

at 18 GHz

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Combining Noise Floor Extension and Low Noise Path

3.6 - 26.5 GHz, preamplifier off

Low noise path incompatible with preamp, >3.6 GHz only

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Noise Figure Measurements with a Spectrum/Signal

Analyzer and NFE

Noise Figure Measurement Application

Perf. Comparable to Dedicated Noise Figure Analyzer

NFE Offers an Additional Calibration Type

Faster/easier but less precise

NF

un

ce

rta

inty

(d

B)

NF Uncertainty vs. Cal Type

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Noise Floor Subtraction

Analyzer noise adds incoherently to any signal to be measured

Power calculations are performed on a linear power scale

(watts, not dBm) and results typically are shown in dBm

PobsS+N = PobsN + PS

PS = PobsS+N − PobsN

EMI Roadmap

10/25/2010

EMC Features standard in X-Series:(today)

• Limit Lines (2000 pts)

• Amplitude correction (2000 pts)

• 40001 sweep points

Option EMC in X-Series:(available today)

CISPR 16-1-1 detectors

(to latest spec)

Quasi Peak

EMI Average (“CISPR-AVG”)

RMS Average (“CISPR-RMS”)

EMI Bandwidths (CISPR & MIL STD)

EMI Presets

Tune & Listen

Measure at Marker

EMI Peak, EMI Average, and

Quasi Peak measurements

displayed together

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Full Featured Pre-compliance Application

Ship Nov 2010

Available in all X-Series models

W/N6141A EMC measurement application

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Corrections factors edit display

Amplitude at

point circled

Amplitude

referenced to

blue line

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Limit line edit display

Circle indicates

the position of

the amplitude

frequency pair

Log Display

Peak List

Auto-detect peaks

Limit Delta

Realtime

Meters

with any 3

Simultaneous

Detectors

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N6141A measurement: Frequency Scan with Log Display

- same functionality as E7400 Signal List

Meters tune

to selected

signal

EMI Roadmap

10/25/2010

N6141A measurement: Strip Chart

• Time record

of zero span

data scrolls

to left

• Up to three

different

detectors

• Can be used

to make

“click”

measure-

ments

Click measurements are made on home appliances

Patent

Applied

For

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Option EDP (Enhanced Display Package)

for the SA- available November 2010 • Spectrogram

• Trace Zoom

• Zone Span

Group/Presentation Title

Agilent Restricted

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Summary

Pre-compliance

solutions

PXA, MXA, EXA,CXA

N6141A EMC advanced

measurement application

EMC seminar

Per documentazione su prodotti ed applicazioni EMI/EMC visitare il sito

http://www.agilent.com/find/EMC

Contatti:

Agilent Technologies ItaliaGiuseppe SavoiaSignal Analysis and Generation SpecialistE-mail: [email protected]

Agilent Contact CenterE-mail: [email protected]: 02 9260 8484

http://www.agilent.com/find/EMC

mailto:[email protected]





EMC seminar

Setup instructions for the N6141A EMC

measurement application

Press [Mode], more, {EMI Receiver}

Press [Meas], {Frequency Scan}

Press [Meas Setup], {Scan Table}, {Range 3 on}, {Range 5 off}

[Return] {Signal list}, {Delete Signals}, {Delete all} OK

Press [Mode Setup], {meter control},{meters}, {Select meter 1},

{Meter on}, {Select meter 2}, {Meter on}

Press [Meas Setup], {Scan Sequence}, {Scan only}, more

{Search criteria}, {Peak criteria and limits}, {Limits}, {Limits

on}, {Margin -6 dB}

Misure di pre-compliance EMI · PDF fileEvaluate the conducted and radiated ... Susceptibility...

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Transcript of Misure di pre-compliance EMI · PDF fileEvaluate the conducted and radiated ... Susceptibility...