Misure di compatibilita Elettromagnetica

Transcription

1 Misure di compatibilita Elettromagnetica Roberto Sacchi Electronic Measurements Group Agilent Technologies Page 1

2 Agenda Introduzione alle misure EMI Terminologia; Sistema di misura (antenna, LISN, ricevitore, etc.); Detectors; Normative europee ed internazionali Misure di compatibilita elettromagnetica Misure di emissioni radiate Misure di emissioni condotte Misure di immunita (EMS) Setup di misura Camere anecoiche vs. OATS (Open Area Test Site) Soluzioni Agilent Introduzione al nuovo ricevitore EMI Full Compliance Agilent MXE Uso degli analizzatori Agilent della Serie-X per misure EMI pre-compliance. Sorgenti per i test di immunita Software applicativo Soluzioni complete tramite i nostri partners Page 2

3 Pre-compliance vs. Full compliance measurements Pre-compliance 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 (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

4 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-STD-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.

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

6 EMI measurement system Page 6

7 Compliance EMI receiver requirements A CISPR receiver must have the following functionality in the range 9 khz - 18 GHz: A normal +/- 2 db absolute accuracy CISPR-specified resolution bandwidths (-6 db) Peak, quasi-peak, EMI average, and RMS average detectors Specified input impedance with a nominal value of 50 ohms; deviations specified as VSWR Be able to pass product immunity in a 3 V/m field Be able to pass the CISPR pulse test (implies pre-selector below 1 GHz) Other specific harmonic and intermodulation requirements Page 7

8 Receiver requirements above 1 GHz Above 1 GHz regulations require: 1 MHz bandwidth for measurements No quasi-peak detector No CISPR pulse test, meaning no additional pre-selector required excellent sensitivity According to current FCC regulations, the maximum test frequency is the fifth harmonic of the highest clock frequency for an unintentional radiator (for example, computers without wireless connectivity) and the tenth harmonic for an intentional radiator (such as a cellular phone or wireless LAN). Page 8

9 What is an EMI Receiver? Let s begin with a spectrum analyzer Spectrum Analysis Display and measure amplitude versus frequency for RF & MW signals Separate or demodulate complex signals into their base components (sine waves) Page 9

10 Overview Types of Tests Made Modulation EMC Noise Distortion Page 10

11 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 Data output available Connectivity Automated measurement features Ability to use new features and duplicate or expand necessary old ones 11

12 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 12

13 Traditional Spectrum Analyzer Scalar analysis Digitizing the video signal Product detector loss of phase information Classic superheterodyne swept spectrum analyzer 13

14 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 14

15 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 15

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

17 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 17

18 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 18

19 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 19

20 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 20

21 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 21

22 MIL-STD-461 Bandwidth Requirements Measurement Range -6dB Bandwidth 30Hz - 1 KHz 10 Hz 1 KHz -10 KHz 100 Hz 10 KHz KHz 1 KHz 150 KHz - 30MHz 10 KHz 30 MHz - GHz 100 KHz > 1GHz 1 MHz Page 22

23 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 23

24 Modern Spectrum Analyzer Accuracy Examples 24

25 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 25

26 LISN Page 26

27 Electrical Network 150 khz to 30 MHz Page 27

28 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 28 DUT

29 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 29

30 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 Page 30

31 Antennas used in EMI emission measurements Page 31

32 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 32

33 Detectors Most radiated and conducted limits are based on quasi-peak detection mode. Page 33

34 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 34

35 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 35

36 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 36

37 Test example Page 37

38 International emissions regulations (summary) Page 38

39 CISPR changes RMS-Average Preselector-less testing: enables use of spectrum analyzer for specific test cases.(no emissions with PRF < 20 Hz) CISPR 22 to 6 GHz Time Domain: sometimes required for the automotive market APD: soon to be required by CISPR11 Page 39

40 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 40

41 The 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 41

42 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 42

43 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 43

44 Page 44

45 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 MHz MHz MHz 4 - Frequency

46 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). Rotate the DUT to maximize the emissions. 6. Measure all signals above limits with quasi-peak and average detectors Page 46

47 Open Area Test Site (OATS) EUTs are measured in an open area test site (OATS) or anechoic chamber. ANSI C63.4 and CISPR specify the requirements for an OATS, including: Preferred measurement distances of 3, 10, and 30 meters Antenna positioning at 1 to 4 meter Heights An area called the CISPR ellipse of major diameter 2X and minor diameter 3 X, where X is the measurement distance; the ellipse must be free of any reflecting objects A metal ground plane for the measurement area Note: 10 meter anechoic chambers and GTEM cells can also be used for radiated compliance measurements. Page 47

48 1. Select the measurement range Page 48

49 2. Load Corrections factors Amplitude at point circled Amplitude referenced to blue line Page 49

50 3. Load Limit line Circle indicates the position of the amplitude frequency pair Page 50

51 4. Scan for signals above the limits with peak detector Page 51

52 5. Quasi-peak and average measurements Page 52

53 Troubleshooting Use the close-field probe to locate the sources of the radiated signals exceeding the limit lines Page 53

54 Immunity test setup Amplifiers Radiated Immunity 30 MHz 18 GHz HF-Switch Conducted Immunity 100 khz 1 GHz

55 Agilent Solutions Page 55

56 What is a CISPR Compliant Receiver CISPR is a subcommittee of the IEC CISPR is the document that defines the functionality of an EMI receiver Detectors Frequency response N9038A MXE EMI receiver is CISPR Compliant

57 What is the MXE EMI Receiver? The Agilent MXE is more than a CISPR compliant EMI receiver It is also an X-Series signal analyzer that can run a variety of measurement applications The MXE can evolve as technology changes X-Series signal analyzer CISPR 16 compliant EMI receiver

58 N9038A MXE EMI Receiver in 30 seconds CISPR Compliant EMI Receiver Compliant Preselection 20 Hz to 3.6 GHz in both EMI Receiver Mode and SA Mode on Both Inputs 20 Hz to 1 GHz for Conducted Emissions (built-in limiter) Run X-Series applications 20 Hz to 26.5 GHz for Radiated Emissions

59 LB 20 Hz -1GHz CFB INB DDS RFB Noise Source

60 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

61 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

62 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

63 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

64 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 64

65 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 65

66 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 66

67 Noise Subtraction, Noise Floor Extension New 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 67

68 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 ( db) error 68

69 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 69

70 EMC Features standard in all X-Series Spectrum analyzers Limit Lines (2000 pts) Amplitude correction (2000 pts) sweep points Page 70 EMI Roadmap 6/28/2011

71 Option EMC in X-Series spectrum analyzer CISPR 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 71

72 W/N6141A EMC measurement application Full Featured Pre-compliance Application Available in all X-Series models Page 72

73 Auto-detect peaks Log Display Realtime Meters with any 3 Simultaneous Detectors Peak List Limit Delta Page 75

74 N6141A measurement: Frequency Scan with Log Display - same functionality as E7400 Signal List Meters tune to selected signal Page 76

75 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 77 EMI Roadmap 6/28/2011

76 Option EDP (Enhanced Display Package) for the SA Spectrogram Trace Zoom Zone Span Page 78 Group/Presentation Title Agilent Restricted

77 N6141A EMI Measurement Application PXA MXA Pre-compliance EXA Compliance CXA Agilent MXE N9038A

78 Agilent products for Immunity test (EMS) Signal generator Signal generator 9 khz 3 GHz, AM, FM, Phase, Pulse IQ Modulator, 40 MHz Mod.-BW N5182, N5182, N khz- 1,3, 6, 20, 40 GHz, AM, FM, Phase, Pulse, optional vector, 120 MHz Mod.-BW, step, sweep, USB-Power meter included Power meter/ Power sensors E441x, E191x, N8262, U200x 100 khz 40 GHz single channel, dual channel, USB, peak, envelope, pulse Accessories Directional Couplers, cables, Adapters, Switches etc.

79 Solution partners for EMC Complete solution: 1. Automation software 2. Chambers 3. GTEM 4. Antennas 5. Power amplifiers 6. Accessories Page 81

80 Per documentazione su prodotti ed applicazioni EMI/EMC visitare il sito Contatti: Agilent Technologies Italia Roberto Sacchi Application Engineer Giuseppe Savoia Signal Analysis and Generation Sales Specialist Agilent Contact Center Tel: