SEMINARI EMC VOLTA 2016 Ricevitori EMI per misure di prequalifica e full-compliance

Transcription

1 g SEMINARI EMC VOLTA 2016 Ricevitori EMI per misure di prequalifica e full-compliance o 7 Giugno 2016 Osimo (AN) o 8 Giugno 2016 Correggio (RE) o 9 Giugno 2016 Vicenza (VI) o 10 Giugno 2016 Burago Molgora (MI) relatori: Dott Mirko Bombelli Microlease Italia. Ing Angelo Cereser Microlease Italia.

2 Agenda Breve Introduzione alle misure EMI Setup di misura: emissione radiate e condotte CISPR & MIL461F (Cenni) L analisi spettrale per le misure EMI Circuiteria analogica verso nuove tecniche digitali Considerazioni su campo dinamico di misura e piano di rumore Problematiche di Misura Tecniche di scansione diverse ( step, swept, FFT ) Tempi di scansione ed sensibilita : trade-off Preselezione ed overload : trade-off Soluzioni Agilent Introduzione al nuovo ricevitore EMI Full Compliance Agilent MXE Uso degli analizzatori Agilent della Serie-X per misure EMI pre-compliance

3 transducer Measurement Equipment EMISSIONS Radiated Emissions Conducted Emissions EUT EUT Mains Equipment Compliance Receivers Spectrum Analyzers Preamps/Antennas EMSCAN tablets Towers/Turntables Control SW Artificial Mains Networks LISN - (line impedance stabilization network) Conducted Transducers Measurement SW Open Sites (FF and NF) Anechoic Chambers Semi-Anechoic Chambers TEM cells Reverberation chambers EMC Back to Basics 2014

4 transducer ESD source IMMUNITY Radiated Immunity Conducted Immunity ~ ~ EUT EUT AMN transducer RF Sources Power meters Power amps Antennas Measurement SW Control SW Equipment LISN Coupling Transducers - clamps, etc. ESD sources Screen rooms TEM cells GTEM cells EMC Back to Basics 2014

5 Pre-compliance vs. Full compliance Misure di Pre-Compliance measurements Valutazione delle emissioni condotte e radiate di un dispositivo utilizzando detectors, RBW e bande di analisi opportune, prima di andare in test house per le misure di Conformita. Misure di Full Compliance I test di Conformita richiedono Ricevitori che rispettino TUTTE le specifiche richieste dalla pubblicazione tecnica CISPR16-1-1, una area di test qualificata con torre di antenna e tavolo rotante per la massimizzazione dei segnali di interesse.

6 Misure di Pre Qualifica - Stima Unofficial delle performance del DUT prima del Full Compliance test - Tipicamente fatta con un SA negli ambienti aziendali disponibili. - Lo scopo e quello di minimizzare il rischio di Fail nelle successive misure in Test House. Misure di Full Compliance Xseries EMC analyzers, Field Fox, HSA - Test di Pass/Fail in accordo alle Norme - Richiede equippaggiamenti specifici e siti adatti - must comply to specific Mil or Comm l standards - Costose e time consuming Ricevitore MXE EMC Back to Basics 2014

7 EMI measurement system Set Up di misura emissioni radiate

8 Set Up di misura emissioni condotte

9 Tipiche funzionalita di un EMI Receiver CISPR nella banda di Compliance frequenze 9 khz EMI - 18 GHz: receiver requirements 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

10 Receiver requirements above 1 GHz Tipiche funzionalita di un EMI Reciever nella banda di frequenze sopra 1Ghz 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).

11 MIL STD 461F MIL STD 461F Spectrum Analyzer use allowed (and commonly used) - need to ensure measurement linearity (avoid overloads) - need to have sufficient sensitivity (may need preamp) Requires MIL Bandwidths Requires Peak Detector +/- 2dB amp accuracy, +/- 2% frequency accuracy Dwell times specified in document

12 CISPR Product Group CISPR 11 - Industrial, Scientific, and Medical (ISM) Radio-Frequency Equipment CISPR 12 - Vehicles, Motorboats, and Spark-Ignited Engine-Driven Devices CISPR 13 - Sound and Television Broadcast Receivers and Associated Equipment CISPR 14 - Household Appliances, Electric Tools, and Similar Apparatus CISPR 15 - Electrical Lighting and Similar Equipment. CISPR 17 - Suppression Characteristics of Passive Radio Interference Filters and Components. Suppression CISPR 18 - Overhead Power Lines and High-Voltage Equipment CISPR 20 - Sound and Television Broadcast Receivers and Associated Equipment CISPR 21 - Interference to Mobile Radio communications CISPR 22 - Information Technology Equipment Radio Disturbance Characteristics CISPR 24 - Information Technology Equipment Immunity Characteristics CISPR 25 - Receivers Used on Board Vehicles, Boats, and on CISPR 32 Multimedia devices emission testing (under development) CISPR 35 Multimedia devices immunity testing (under development) EMC Back to Basics 2014

13 Swept Spectrum Analyzer Block Diagram Theory of Operation 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

14 Traditional Spectrum Analyzer ( add scalar analysis with TG) Digitizing the video signal Product detector loss of phase information Classic superheterodyne swept spectrum analyzer

15 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

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

17 Input Connector RF Input Attenuator 2 db Steps Pre-selector Componenti che contribuiscono alla incertezza di misura Downconversion ADC DSP Input connector (mismatch) Calibrator RF input attenuator flatness and switching Mixer and input filter frequency response Frequency Dependent Frequency Independent Digital IF improves Amplitude Accuracy: Ref Level switching uncertainty (IF gain) Level correction digitally synthesized RBW filter switching uncertainty RBWs all digitally synthesized Display scale fidelity (Log Amp) Log response & display scaling digitally synthesized IF Filter IF Gain Log Amp Video Filter Log ADC

18 Input Connector RF Input Attenuator 2 db Steps Pre-selector Componenti che contribuiscono alla incertezza di misura Downconversion ADC DSP Amplitude Uncertainty Input connector (mismatch) Ref Level Switching Calibrator N9038A Receiver 0dB RF input attenuator RBW flatness and +/- Switching switching.05db <= +/-.5dB Mixer and input filter Frequency Dependent Analog IF (older receivers) <= +/- 1dB Display Scale +/-.15dB <= +/-.85dB Fidelity frequency response Frequency Independent Digital IF improves Amplitude Accuracy: Ref Level switching uncertainty (IF gain) Level correction digitally synthesized RBW filter switching uncertainty RBWs all digitally synthesized Display scale fidelity (Log Amp) Log response & display scaling digitally synthesized IF Filter IF Gain Log Amp Video Filter Log ADC

19 EMI Reciever Block DiagramrBlock Diagram Input 2 Pre-amp Transient Limiter Input 1 Attenuation RF Preselector Digital IF Filter Digital Detectors MXE Analog IF Filter FFT Swept vs. FFT Digital Log Amp ADC

20 Purpose of RF pre-selection RF Help Pre-selection to prevent overload by reducing (RF total input energy at input filtering) mixer RF preselector tracks the center frequency of the EMI receiver The bandwidth of the RF preselector is wider than the widest RBW used Useful in measuring broadband signals Types of filters used in RF pre-selectors Low-pass, Band-pass and High-pass Fixed and Tracking Narrow band signals Broadband signals

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

22 Detectors Most radiated and conducted limits are based on quasi-peak detection mode. P a

23 V Peak Detection Quasi-Peak Detection Average Detection time V Peak Detection time Quasi-Peak Detection Average Detection P a

24 Peak Detector QP Average Initially used QP Faster than QP and Average modes If all signals fall below the limit, then the product passes and no future testing is needed. 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 Average the higher repetition rate of the signal, the higher QP reading Radiated emissions measurements above 1 GHz are performed using average detection

25 Some important concepts for EMI measurements: for EMI Sensitivity Amplitude Accuracy Scan Speed Others.

26 Specifications: Sensitivity/DANL Sensitivity is the Smallest Signal That Can Be Measured Signal Equals Noise 2.2 db

27 Specifications: Sensitivity/DANL Effective Level of Displayed Noise is a Function of RF Input Attenuation signal level 10 db Attenuation = 10 db Attenuation = 20 db Signal To Noise Ratio Decreases as RF Input Attenuation is Increased

28 Sensitivity/DANL: IF Filter (RBW) Displayed Noise is a Function of IF Filter Bandwidth 100 khz RBW 10 db 10 db 10 khz RBW 1 khz RBW Decreased BW = Decreased Noise

29 Techniques for Reducing DANL, Improving Dynamic Range and Amplitude Accuracy for Reducing DANL, Improving Dynamic Range and Amplitude Accuracy Reduce attenuation Add preamp Reduce RBW Good performance for preselection ( add external filters ) 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 Noise floor extension (NFE) leverages deep knowledge of analyzer/circuit behavior

30 Specifications: dobbiamo accelerare Scan i tempi Speed di misura, come si fa? I tempi di misura dipendono da: Tipo di scansione (Stepped, Swept, Time Domain) Resolution Bandwidth Dwell Time RF Preselector Others

31 Methods to EMI Scanning: Stepped Scan Methods Slowest method to EMI Scanning LO moves for every bin Must re-tune LO each time Swept Scan Slow (slightly faster than Stepped) LO re-tunes once each sweep Time Domain Scan (TDS) Very fast Highly overlapped FFT (>90%) Alternate scan method allowed by CISPR 16

32 Amplitude and Frequency error in step and swept mode worst case

33 What is Time Domain Scan Time Domain Scan (TDS) A new way to do Frequency scanning. Swept scans, Stepped scans, now Time Domain scans FFT-based scan - uses ~ 90% overlap (in time) to ensure amplitude accuracy for measurements of both CW and Impulsive signals Allowed by CISPR 16, but not required. - Internal Automotive industry testing specifications require Time Domain 33

34 Overview FFT Analyzer Different Types of Analyzers Swept Analyzer A Parallel filters measured simultaneously A Filter 'sweeps' over range of interest f 1 f 2 f f 1 f 2 f

35 amplitude amplitude How time domain sweep save time.. How Time Domain Sweep Saves Time Have to dwell at each RBW Receiver Resolution BW Only have to dwell for each FFT BW (multiple RBWs) Receiver FFT BW frequency Swept or Stepped Frequency Scan Time Domain Frequency Scan frequency 35

36 Window Effects and Sample Rate Classic FFT is critically sampled windows are contiguous What happens to impulsive signals? Signals that fall between windows are attenuated by window edges Impulsive signals not detected or detected with amplitude scalloping How to solve this problem? P a

37 ..oversampling before FFT Answer is to add overlap windowing Equivalent to increasing sampling rate out of the decimated downconverters Impulsive signals no longer can fall between widows Amplitude scalloping reduced More overlapping => less amplitude errors

38 Wider RF Preselector Filter BW = Reduced Impulse Overload Protectionced Impulse Overload Protection Input pulse Receiver RF Section Vp Impulse BW BW i Vmax = Vp Τ BW i Max Pulse voltage into mixer is proportional to RFPS filter impulse BW (BW i ) Τ= pulse width RF Input Attenuator RF Preselector Downconversion Examples* 20 log (35MHz/9.5MHz) = 500MHz: 20 log (200MHz/ 50MHz) = 12dB *Note: Above calculations using 6dB BW ratios, not impulse BW ratios Results provide approximate values of required input attenuation

39 RF Preselector Bands for MXE RF Preselector Bands

40 Portfolio of Solutions PXA MXA EXA Pre-compliance with N/W6141A CXA Compliance Agilent MXE N9038A

41 Existing Solutions for Emission Tests:xisti Solutions Anechoic chambers Slow testing High CAPEX (in-house) / OPEX (third party) Real-estate Qualified technicians Probes Automated Slow Resolution mm Handheld Slow Resolution at pin level Simulation software Extensive training required Time consuming to customize per PCB

42 misure di emissioni a campo vicino su PCB facili economiche ed immediate : tovoletta EMxpert! Directly addresses the challenges Real-time measurements( <1 sec) Compact tabletop instrument Cost effective solution

43 Per documentazione su prodotti ed applicazioni EMI/EMC visitare il sito THANK YOU!!

44 APPENDIX

45 Specifications Resolution: RBW Type Determines Sweep Time 8563E Analog RBW MXA Swept RBW (w/ FS1*) MXA FFT RBW 280 sec 2.3 sec *: FS1 is fast sweep capability comes standard for MXA if the MXA has option DP2, MPB, or 40 MHz BW option and wider BW. It improves the sweep speed by ~50x 1.9 sec

46 Modern spectrum analyzer RBW Selectivity 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 P a

47 RBW Selectivity ecific Resolution: RBW Type and Selectivity Typical Selectivity ANALOG FILTER Analog 15:1 Digital 5:1 DIGITAL FILTER RES BW 100 Hz SPAN 3 khz P a

48 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

49 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

50 Measurement Range -6dB Bandwidth MIL - STD Bandwidth Requirements 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 P a

51 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 P a

52 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 P obss+n = P obsn + P S P S = P obss+n P obsn

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

54 2dB Step Attenuation: Improves Accuracy in the Presence of Large Ambient Signals e Ambient Signals 2dB/division. 3-4 db diff. 10dB/division. Large ambient signal Input Attn. 10dB Message is strong because customers: - are focused on measurement accuracy - struggle with ambient signals when making measurements on open sites. 6dB 2dB 0dB

55 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.

56 Emissions 1. Connect DUT Measurements 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 P a

57 Purpose of a LISN: Line Impedance Stabilization Networks (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. P a

58 Electrical Network 150 khz to 30 MHz P a

59 The purpose of the limiter is to protect the input of the EMC Transient Limiter 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 DUT

60 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] P a

61 Radiated EMI emissions tests measure the electric field. The Field Strength and Antenna factors 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. P a

62 Antenna Factor (db/m) Understanding Antenna Factors Ratio of the electric field to the voltage out of the antenna Linear Units AF = E in V out AF = Antenna Factor (1/m) 20 Typical biconical antenna factors E = Electric Field units (V/m) V = Voltage output from antenna (V) 10 Log Units AF(dB/m) = E(dBµV/m) V(dBµV) Frequency (MHz)

63 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

64 Test example P a

65 Why are Click Measurements Important to Manufacturers? could be relaxed.. If an emission is classified as a click, the emission limit.your product can be sold! Discontinuous Disturbance (Click) Limit line Continuous Disturbance Limit line Click Limit relaxation Continuous Disturbance Emission 6 6

66 amplitude A click is a conducted emission with: Definition of a Click - a peak-detected duration less than or equal to 200 msec. - a separation of at least 200 msec. from a following emission - a QP amplitude exceeding the Continuous Disturbance limit.. measured 250 ms after falling edge of disturbance Continuous Disturbance Limit Line 200 msec. 250 msec. QP response time 200 msec. 6 7

67 Clicks are Not Necessarily Well-Defined Pulses Examples of Clicks from CISPR 14: Single Clicks: Two Clicks: 6 8

68 Target Customers for Click Measurements EMC Test Laboratories Test a variety of products for compliance Manufacturers Build and self-certify products covered by CISPR

69 Typical Click Measurement measurements setup are conducted emissions measurements EUT Emissions signal AC Power LISN (Line Impedance Stabilization Network) Mains connection 7 0

70 Click Measurements are Overview made at four specified frequencies 150kHz, 500 khz, 1.4 MHz and 30 MHz testing run until 40 clicks/switching operations are registered or for 2 hours, whichever is shorter Quasi-Peak limits Limit relaxation determined by the Click Rate N N = measured clicks per minute Determined at 2 frequencies 150 khz for 150 khz f 500 khz 500 khz for 500 khz f 30 MHz 7 1

71 Click Limit Relaxation Rules: Limit Relaxation Lq = L continuous + 44dB for N < 0.2 = L continuous + 20 log (30/N) for 0.2 N < 30 = L continuous for N 30 Click Limit relaxation where: Lq = Click limit L continuous = Continuous Disturbance limit as defined in CISPR 14 N = Click Rate (# of clicks per minute over measurement time) 7 2

72 Click Limit Relaxation Rules: Lq = L continuous + 44dB for N < 0.2 = L continuous + 20 log (30/N) for 0.2 N < 30 = L continuous for N 30 Upper Quartile Rule Applies to Clicks Click Limit relaxation EUTs are listed as non-compliant if: > 25% of the total measured clicks exceed Lq 73

73 Individual switching operations CISPR 14 Exceptions to the Click Definitions - E.g., single on/off switching. These are not counted when testing for compliance - Combinations of clicks in less than 600 ms - Allowed once in an operating cycle Instantaneous switching - Click rate < 5 - Number of clicks > 20 ms duration - 90% of all clicks with < 10 ms duration Separation of Clicks less than 200ms - If Click rate < 5, two disturbances < 200ms, separation < 200ms, then the disturbances are counted as 2 clicks Mentioned here because Click Measurements need to address 2 through 4 7 4

74 EMC Features standard in all X-Series Spectrum analyzers Limit Lines (2000 pts) Amplitude correction (2000 pts) sweep points EMI Roadmap 6/1/2016 P a

75 Option Spectrogram EDP (Enhanced Display Package) for the SA Trace Zoom Zone Span P a

76 Time record N6141A of zero span measurement: Strip Chart 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 EMI Roadmap 6/1/2016 P a

77 Making an emissions measurement Recommended by CISPR Measurement methodology found in CISPR Fastest way to make the measurement Pre-scan Data Reduction MIL Measurements* Maximization Final Measurement Report Generation

78 Preview spectrum using Peak detector Measurement Parameters Frequency range Limit lines Margins Antenna Factors Scan Type Scan Types Stepped Swept Time Domain Prescan Pre-scan Data Reduction Maximization Final Measurement Report Generation

79 Signals exceeding the limit are automatically: Marked in red Peaks are marked with white X added to signal list Only do final measurement on signals exceeding the limit and Margin. Don t measure unnecessary Signals saves time Signal List Pre-scan Data Reduction Maximization Final Measurement Report Generation 8 0

80 Maximization Techniques Maximize signal amplitude before final measurement Receiver mode Spectrum Analyzer Mode Monitor Spectrum Simultaneous spectrum and meter measurements Access to signal (suspect) list Meter max hold Spectrum Analyzer mode Switch between EMI receiver and SA modes using global center frequency Powerful analyzer mode Pre-scan Data Reduction Maximization Final Measurement Report Generation 8 1

81 Signals in list are automatically measured Measure suspect signals with Quasipeak, EMI average detector, etc. Suspect signals still failing? Start troubleshooting? Pre-scan Data Reduction Maximization Final Measurement Report Generation 8 2

82 Report Generation Report Generator Settings Screenshots Tables Pre-scan Data Reduction Maximization Report Format: PDF or HTML Final Measurement Report Generation