Misure di pre-compliance EMI

Misure di pre-compliance EMI Roberto Sacchi Application Engineer Roberto_sacchi@agilent.com Page 1

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 Page 2

Comparison of precompliance and full compliance measurements Precompliance Measurements Evaluate 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. Page 3

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.

Definitions EMI ElectroMagnetic Interference EMC ElectroMagnetic Compatibility EMS ElectroMagnetic Susceptibility (aka Immunity)

Page 6

Overview What is Signal, Vector and Spectrum Analysis? Spectrum Analysis Display and measure amplitude versus frequency for RF & MW signals Separate or demodulate complex signals into their base components (sine waves) Page 7

Overview Types of Tests Made Modulation EMC Noise Distortion Page 8

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) Complete spectrum analyzer & vector signal analyzer 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 9

Theory of Operation Swept Spectrum Analyzer Block Diagram RF input attenuator mixer IF gain IF filter (RBW) envelope detector Input signal Pre-Selector Or Low Pass Input Filter local oscillator Log Amp video filter sweep generator Crystal Reference Oscillator ADC, Display & Video Processing Page 10

Traditional Spectrum Analyzer Scalar analysis Digitizing the video signal Product detector loss of phase information Classic superheterodyne swept spectrum analyzer 11

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 12

Overview Different Types of Analyzers FFT Analyzer Swept Analyzer A Parallel filters measured simultaneously A Filter 'sweeps' over range of interest f 1 f2 f f1 f2 f Page 13

Specifications Resolution: RBW Type Determines Sweep Time 8563E Analog RBW PSA Digital RBW PSA FFT RBW 280 sec 134 sec 13.5 sec

Speed Improvements Nominal speed comparison, PSA example: Benchmark PXA PSA Useful comparisons highly specific, many factors PXA mode switching typically faster than PSA Speed 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 Where speed is critical, consider modifying measurement routines to include features such as list sweep 15

Modern spectrum analyzer Resolution BW Selectivity or Shape Factor 3 db 3 db BW 60 db 60 db BW Selectivity = 60 db BW 3 db BW Determines resolvability of unequal amplitude signals Page 16

Specifications Resolution: RBW Type and Selectivity ANALOG FILTER Typical Selectivity Analog 15:1 Digital 5:1 DIGITAL FILTER RES BW 100 Hz SPAN 3 khz Page 17

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 18

CISPR Bandwidth Requirements Bandwidth -6dB -20dB 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 Page 19

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 Page 20

Modern Spectrum Analyzer Accuracy 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 21

Modern Spectrum Analyzer Accuracy Examples 22

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. Page 23

LISN Page 24

LISN @ Electrical Network Frequency @ 150 khz to 30 MHz Page 25

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. Limiter 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. Page 26 DUT

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 Page 27

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) P d Pt 4 r 2 E R 2 Pt 4 r 2 R 120 [ohm] 2 E P d R E Pt 30 r [V/m] Page 28

Antennas used in EMI emission measurements Page 29

Detectors: Convert IF Samples to Display Bins or Buckets Multiple simultaneous detectors Peak, Neg Peak, Sample Display points or buckets Peak Normal, Average, Neg Peak Volts Sample Neg Peak Screen Shot Detector 3types Time 30

Detectors Most radiated and conducted limits are based on quasi-peak detection mode. Page 31

Peak vs. Quasi-peak vs. Average V Peak Detection Quasi-Peak Detection Average Detection V time Peak Detection time Quasi-Peak Detection Average Detection Page 32

Peak QP Average Peak 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 Page 33

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 Page 34

Test example Page 35

Emissions Regulations (Summary) Page 36

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. Page 37

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. Page 38

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. Page 39

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 Page 40

Page 41

The challenge of measuring radiated emissions Radiated Emissions are difficult to measure because of multiple dimensions (five) and the use of quasi-peak detection below 1GHz 5 -Time 1 - Azimuth 2 - Antenna Height 3 - Field Strength 1500.260MHz 218.120MHz 41.2563MHz 4 - Frequency

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 Page 43

1. Select the measurement range Page 44

2. Load Corrections factors Amplitude at point circled Amplitude referenced to blue line Page 45

3. Load Limit line Circle indicates the position of the amplitude frequency pair Page 46

4. Scan for signals above the limits with peak detector Page 47

5. Quasi-peak and average measurements Page 48

Troubleshooting Use the close-field probe to locate the sources of the radiated signals exceeding the limit lines Page 49

Agilent Solutions Page 50

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 Architecture Modern Spectrum Analyzers Architecture (PSA, X-Series) RF Section ADC IF Section BB Section IF/BB Section on ASIC Attenuation Filtering Downconversion RBW Filtering Envelope Detection Log Conversion VBW Filtering Peak/sample/rms detection Averaging All Digital IF Architecture

Modern Spectrum Analyzer Block Diagram Pre-amp Analog IF Filter Digital IF Filter Digital Detectors FFT Attenuation Swept vs. FFT Digital Log Amp YIG AD C Replaced by

All Digital IF Advantages RF Section ADC FFT IF/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

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 55

CW Signal Measured Near Analyzer Noise Floor Example: No noise subtraction or near noise correction Apparent Signal Actual S/N Displayed S/N CW Signal Ampl & Freq Axes Expanded This is fundamental, and often missed 56

Noise Subtraction, Noise Floor Extension New PXA technique NFE improves D.A.N.L. analyzer noise power calculated/subtracted real time No error 3 db error without NFE Improved noise floor or displayed average noise level 57

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 58

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 59

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 60

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 61

A Closer Look Source noise Level, no NFE Source Noise Level, with NFE Analyzer Noise, no NFE Analyzer Noise with NFE 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 62

Signal Type vs. Effectiveness Signal/Noise Variation with RBW SNR (db) Noise-like Real signals can be one type or combination Amplitude envelope vs. time Best RBW is one matched to signal Best ability to separate analyzer noise from signal RBW (log) 63

Noise Floor Enhancement CW Example 95% confidence interval, 2 db tolerance 3.5 db improvement for CW signal 64

Noise Floor Enhancement Noise-Like Signal Example 95% confidence interval, 1 db tolerance 9.1 db improvement for noise-like signal 65

Noise Floor Enhancement Pulsed RF Example 95% confidence interval, 3 db tolerance 10.8 db improvement for pulsed-rf signal 66

Low Noise Path To μw Converters To Low Band 67

Alternate Low Noise Path 3 db @ 3.6 GHz 10 db @ 26 GHz Example: Spur Search 20-50x faster at 18 GHz 68

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 69

NF uncertainty (db) 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 Uncertainty vs. Cal Type 70

Noise Floor Subtraction P obss+n = P obsn + P S P S = P obss+n P obsn 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 71

EMC Features standard in X-Series: (today) Limit Lines (2000 pts) Amplitude correction (2000 pts) 40001 sweep points Page 72 EMI Roadmap 10/25/2010

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 Page 73

W/N6141A EMC measurement application Full Featured Pre-compliance Application Ship Nov 2010 Available in all X-Series models Page 74

Corrections factors edit display Amplitude at point circled Amplitude referenced to blue line Page 75

Limit line edit display Circle indicates the position of the amplitude frequency pair Page 76

Auto-detect peaks Log Display Realtime Meters with any 3 Simultaneous Detectors Peak List Limit Delta Page 77

N6141A measurement: Frequency Scan with Log Display - same functionality as E7400 Signal List Meters tune to selected signal Page 78

N6141A measurement: Strip Chart Time record of zero span data scrolls to left Up to three different detectors Can be used to make click measurements Patent Applied For Click measurements are made on home appliances Page 79 EMI Roadmap 10/25/2010

Option EDP (Enhanced Display Package) for the SA - available November 2010 Spectrogram Trace Zoom Zone Span Page 80 Group/Presentation Title Agilent Restricted

Summary PXA, MXA, EXA,CXA Pre-compliance solutions N6141A EMC advanced measurement application Page 81

Per documentazione su prodotti ed applicazioni EMI/EMC visitare il sito Contatti: http://www.agilent.com/find/emc Agilent Technologies Italia Giuseppe Savoia Signal Analysis and Generation Specialist E-mail: giuseppe_savoia@agilent.com Agilent Contact Center E-mail: contactcenter_italy@agilent.com Tel: 02 9260 8484

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}