Test sites for EMC measurements

Transcription

1 Test sites for EMC measurements EMV Fachtagung 21. Januar 2014 Christophe Perrenoud montena emc Route de Montena 75 CH Rossens Tel Fax office.emc@montenaemc.ch

2 Programm Definition and standards Measurement of radiated emission Anechoic chambers advantage/disadvantage Site validation between 30 MHz and 1 GHz Site validation above 1 GHz 2

3 Definition and standards Radiated emission according to CISPR: The quantity to be measured is the maximum E field strength emitted by the EUT as a function of H and V polarization at heights between 1 and 4 m, and at a distance of 10 m, over all angles and in the azimuth plane With following provisions: 3

4 Definition and standards With following provisions among others : - Frequency range of interest 30 MHz 1 GHz - Compliant measuring receiver (CISPR ) - Other measurement distance (3 m) shall be considered as alternative methods 4

5 Definition and standards OATS: Open Area Test Site SAC : FAR: Fully Anechoic Room 5

6 6 Definition and standards

7 Definition and standards CISPR : CISPR : ANSI 63.4: 7

8 Programm Definition and standards Measurement of radiated emission Anechoic chambers advantage/disadvantage Site validation between 30 MHz and 1 GHz Site validation above 1 GHz 8

9 Measurement of radiated emissions 3 or 10 (30) m in max hold mode 1 to 4 (6) m 9

10 10 Measurement of radiated emissions

11 Programm Definition and standards Measurement of radiated emission Anechoic chambers advantage/disadvantage Site validation between 30 MHz and 1 GHz Site validation above 1 GHz 11

12 Chamber vs OATS Ambiant noise measurement in an OATS 12

13 Chamber vs OATS Noise floor in an anechoic chamber 13

14 Chamber vs OATS Advantages of a chamber Independant of the weather conditions Not disturbed from other sender (FM radio, DAB, mobile phone, ) Protection of measuring equipment Disadvantages of a chamber Wall and ceiling reflexions Test volume 14

15 Programm Definition and standards Measurement of radiated emission Anechoic chambers Advantage/disadvantage Site validation between 30 MHz and 1 GHz Site validation above 1 GHz 15

16 Definition and method 3 different methods are defined in the norm NSA method with tuned dipoles (OATS) NSA method with broadband antennas (OATS and SAC) RSM (Reference Site Method) with broadband antennas 16

17 Definition and method An OATS or SAC is conform if : the difference between the NSA (A N ) and the SA EUT is < 4 db in all measured positions of the test volume 17

18 Material (1 GHz technology) A network analyser (VNA) A couple of tuned dipoles (λ/2) 30 MHz 300 MHz 300 MHz 1 GHz or A couple of biconical antennas (30 MHz 300 MHz) A couple of logperiodic antennas (300 MHz 1 GHz) 18

19 19 Site validation methods

20 Tuned dipoles NSA The SA is measured with a couple of tunable dipoles, which antenna factors are calibrated 20

21 Schema of NSA in a 50 Ω system AF send Propagation in the air AF receive V1 SA EUT = V2-V1-AF S -AF R [db] SA EUT -NSA < 4 db V2 Cable adapter Normalisation Cable P1 P2 VNA 21

22 Broadband antennas RSM V1 AF send Propagation in the air AF receive SA REF = V2-V1 [db] V2 Cable Cable V1 AF send Propagation in the air AF receive SA EUT = V2-V1 [db] V2 22 Cable => SA = SA EUT - SA REF <4 [db] Cable

23 23 Broadband antennas RSM: Reference

24 Broadband antennas RSM: Reference The site attenuation (SA) is measured on the OATS with couples of antennas in In the horizontal polarization with a sending antenna at 1 and 2 m height In the vertical polarization with a sending antenna at 1 and 1.5 m height At distances of 3 and 10 m It means 8 measurements for 3 m 24

25 Broadband antennas RSM: Site EUT The same setup is repeated several times in the test volume of the site to be calibrated 25

26 Broadband antennas RSM: Site EUT In the horizontal polarization 26

27 Broadband antennas RSM: Site EUT In the vertical polarization 27

28 Broadband antennas RSM: Site EUT For a total of 40 measurements 5 positions 2 polarizations 2 heights 2 antenna couples (2 frequency bands) Some conditions allow to skip some measurements and reduce it to 26 (28) 28

29 SA of the site to be calibrated Example of Site Attenuation: SA C (Norm) SA C ±4 db SA Mes SA Ref + SA C 29

30 Programm Definition and standards Measurement of radiated emission Anechoic chambers Advantage/disadvantage Site validation between 30 MHz and 1 GHz Site validation between 1 GHz and 18 GHz 30

31 Definition The test site shall rely on reflection free conditions Absorbing material is used on the floor to achieve free-space conditions (FAR) 31

32 Definition The site validation is performed by measuring the S VSWR Site Voltage Sanding-Wave Ratio S VSWR is the ratio of maximum and minimum received signal caused by interference between direct (intended) and reflected (undesired) waves The acceptance criterion is S VSWR 6 db 32

33 Material (18 GHz technology) A signal generator A spectrum analyzer A sending antenna with specific patern charactristics A receive antenna, the one used for EMI measurements 33

34 Sending antenna characteristics 34 Source: Seibersdorf laboratories

35 35 Validation test setup

36 S VSWR measurement h= 1 m h= 1 m h= 1 & 2 m D REF h= 1 m 36

37 S VSWR measurement F6 = D REF 2.25 m F5 = D REF + 2 cm F4 = D REF + 10 cm F3 = D REF + 18 cm F2 = D REF + 30 cm F1 = D REF + 40 cm 2.65 m Each measurement is reported to Dref to ideally have the same value = +20log ( = E db 37

38 S VSWR result Freq [GHz] F1 brute [dbm] F2 brute [dbm] F3 brute [dbm] F4 brute [dbm] db F5 brute [dbm] F6 brute [dbm] F1 corr [dbm] F2 corr [dbm] F3 corr [dbm] F4 corr [dbm] F5 corr [dbm] F6 corr [dbm] VSWR [db] S =[max 1 : 6 min 1 : 6 ] = ( )= 0.92 db 38

39 Thank you for your attention Danke für Ihre Aufmerksamkeit Merci de votre attention Christophe Perrenoud / Christophe.perrenoud@montenaemc.ch 39