EMC and Audio Equipment -

1. EMC and Audio Equipment - EN55103-1 and EN55103-2 Mark Briggs, Elliott Labs (mbriggs@elliottlabs.com)

2. Outline of the presentation The CE Mark The EMC Directive Professional Audio Equipment EN55103-1 - Emissions Standard EN55103-2 Immunity Standard Designing to meet the standards

3. The CE Mark • Required to sell products into Europe. • Used to declare compliance to applicable Directives. (link to directives)

4. The EMC Directive • EMC = Electromagnetic Compatibility. • Two essential requirements: • The product does not interfere with bona fide users of the radio spectrum (Emissions) • The product will operate when subjected to interference from bona fide users of the radio spectrum and to naturally occurring EM phenomena (Immunity)

5. Demonstrating Compliance • Declare compliance to the most applicable standard • Standards are listed in the Official Journal of the European Union • If a standard does not exist or cannot be applied, use a Technical Construction File (TCF) • A “Competent Body” reviews the manufacturers technical file which provides justification to why the product meets the essential requirements. Typically the Competent Body will base their interpretation of “essential requirements” on the most applicable standard

6. Standards Route • Manufacturer declares compliance by stating that the product meets the requirements of the most applicable standard(s) for emissions and immunity • Nowhere does it state that you must test - the actual wording is that you “... apply the standard(s)” • Standards are listed in the Official Journal (OJ) of the European Union(link) • Product specific standards take precedence. There are generic standards for products which do not have a specific standard

7. What about new standards ? • As standards get revised or as new product standards are released, the OJ will list the “Date of cessation” for the superseded standard • Products sold after the cessation date must meet the requirements of the new standard • In the transition period either the new or old standard may be used.

8. Technical Construction File • Manufacturer prepares a technical file which provides justification as to why the product meets the essential requirements. • The file contains • product descriptions, • design details (with emphasis on EMC design techniques) • Results from any EMC tests performed • Description of intended operating environment and the EMC phenomena present in that environment • A Competent Body reviews the file and, if it considers the essential requirements are met, issues a technical certificate.

9. Demonstrating Compliance • A declaration of Conformity (DoC) is produced which details the product name, manufacturer, Directive(s) and standard(s) or Technical certificates. • It is a “good idea” to keep a technical file when using the standards route. This would provide the evidence to a European court if complaints were ever made against a manufacturer. • Apply the CE Mark to the product • Maintain a copy of the DoC with the European distributor for ten years after the last product is sold.

10. Professional Audio Equipment Standards • EN55103-1 (Emissions) • EN55103-2 (Immunity) • Effective as of September 1st 1999 • The scope of the standards covers professional audio, video, audio-visual and entertainment lighting control equipment.

11. Definitions • Professional: Apparatus for use in trades, professions or industries that is not intended for sale to the general public. • Audio, video, audio-visual and entertainment lighting control equipment: • Designed for the purposes of controlling audio, video, audiovisual or entertainment lighting characteristics; • Designed for processing audio, video or lighting control signals in digital form; • Designed to control the intensity, color, nature or direction of light from luminaries with the intention of creating artistic effects in theatrical, televisual or musical productions and visual presentations.

12. Products NOT covered by EN55103 • Consumer apparatus (Sound cards) • These would probably fall under EN55022/EN55024 for PC-based cards. EN55013/EN55020 apply to Broadcast receivers and associated equipment (stereo components) • Apparatus specifically designed for security systems (CCTV video equipment) • These would fall under the standard for alarm systems • Radio communications devices (wireless microphones) • Radio communications equipment have their own specific standards

13. Requirements • The limits on the emissions from products are defined in EN55103-1 • The immunity requirements are detailed in EN55103-2 • Limits and test levels depend on the intended environment of the product

14. Product Environments • E1: Residential environment • E2: Commercial and light industrial (e.g. theatres) • E3: Urban outdoors • E4: controlled EMC environment (e.g. purpose built broadcasting/recording studios, rural outdoors some distance from railways, transmitters, overhead power lines etc.). It should be noted that some studios might be considered as environment E2. • E5: Heavy industrial environment and environments close to broadcast transmitters.

15. EN55103-1 Emissions

16. Emissions Tests

17. Radiated Emissions, 30 - 1000 MHz • Should be tested on an Open Area Test Site (OATS) or a suitable emissions chamber • For FCC testing, the frequency range may extend above 1GHz (1000MHz) : • If the highest frequency generated/used is > 108MHz then test to 2 GHz • If the highest frequency > 500 MHz then test to 5 GHz • If >1 GHz then test to 5x frequency

18. Radiated Emissions, 30 - 1000 MHz • Emissions tend to occur at harmonics of the digital clocks plus power-supply switching harmonics ! • Emissions require an antenna with a length greater than /10 (30m / f in MHz) • Generally the emissions below 300 MHz are due to common mode noise on external interface cables • Above 300 MHz emissions tend to radiate from slots in the enclosure • Best controlled through good circuit layout

19. Radiated Emissions, 50Hz - 50kHz • Tested using a loop antenna as specified in the EN55103-1 standard • Loop can be made (or purchased - it is equivalent to mil Std 461 RE101 Loop antenna) • For rack-mount equipment, test at 10cm. For other, test at 1m • Typically problem frequencies will be • Switching frequency of power supply • Harmonics of AC frequency due to diode switching action

20. AC Conducted Emissions • Limits the rf voltage between line/neutral and ground in the frequency range 0.15 - 30 MHz • Use a LISN to measure the voltage (cost about $3000) with an EMI receiver ($30,000) - however a pre-compliance analyzer may be purchased for about $15,000 (Agilent EM-series)

21. Signal and I/O Conducted Emissions • Limits the common mode current /voltage on signal lines and dc power in the frequency range 150kHz - 30 MHz • For shielded lines, the test is performed with the shield terminated to ground via a 150 ohm resistor • Unshielded cables - common mode termination by tying each signal lead to ground via a 150 ohms x n resistor (n = number of signal lines) • RF current probe is placed around the signal lead to be tested

22. Signal and I/O Conducted Emissions Termination of a shielded cable

23. Signal and I/O Conducted Emissions Termination of a four-wire, unshielded cable

24. AC Current Harmonics • This test restricts the current harmonics that can be produced by a power supply. • If using an external PS vendor, specify that it must meet the EN61000-3-2 standard • Typically a power-factor-corrected (pfc) supply will meet the requirements on harmonic current emissions • Could use vendor data to show compliance with requirements (make sure they tested at power rating of your product)

25. AC Voltage Flicker • “Flicker” is the effect caused when a large load current is switched, creating a short-duration dip in the AC voltage (e.g. refrigerator, when compressor switches on the lights dim momentarily) • Can only be measured with a custom-built test equipment - but could be evaluated using a light bulb connected to the same AC outlet ?

26. Other Emissions Tests • Discontinuous interference • Click interference • In-Rush Current • No limits but must specify the in rush current in the user documentation • Antenna Port Emissions • Required if the device has receiver antenna ports

27. EN55103-2 IMMUNITY

28. Immunity Tests (1)

29. Immunity Tests (2)

30. Performance Criteria During immunity testing the product’s performance has to be assessed against various performance criteria: • Criterion A: • EUT should continue to operate as intended • Criterion B: • Degradation during the test but conformity with product specs after the test • Criterion C: • Degradation during the test and after the test. Conformity with product spec via user-intervention or automatic recovery. Replacement of fuses, or other repairs, does not constitute user-intervention

31. Performance Criteria - Examples Reduced signal-to-noise Increased non-linearity distortion Clicks and pops Pitch variations Intermittent muting Change in gain Change in operating mode (e.g. sample rate changes) Examples of symptoms of lack of immunity for audio equipment are:

32. ESD Immunity • EN61000-4-2 • Performance Criteria B • ESD events create high-speed transients that can: • Permanently damage ICs • Cause false resets or other spurious reactions • The performance criteria is B - so some degradation in performance is permitted during the test but the device MUST recover without user intervention. • ESD events caused by people discharging directly to the product or to nearby objects

33. Radiated Immunity • EN61000-4-3 • Performance Criteria A • The device is subjected to a radiated field from 80 - 1000 MHz • The field is amplitude modulated by a 1kHz tone • Simulates interference from radio (broadcast, walkie-talkie etc) • Products typically demodulate the 1kHz tone, creating interference on audio signal channels or on video displays

34. Conducted Immunity • EN61000-4-6 • Performance Criteria A • Simulates interference on signal leads generated from AM and SW radio • A common mode interference signal is superimposed onto signal and power interface ports from 0.15 - 80 MHz • The signal is amplitude modulated by a 1kHz tone • Shielded signal lines have the noise directly coupled onto the shield

35. Fast Transients • EN61000-4-4 • Performance Criteria B • Fast transients have a rise time of 5nS and width of 50nS • Simulates switching of inductive loads • They are applied in bursts • Bursts are 15mS long • Repetition rate of individual transients is 5kHz • Bursts occur every 330mS

36. Surge • EN61000-4-5 • Performance Criteria B • The surge waveform simulates the transients induced onto the AC power line by lightning events • The wave-shape is 1.2/50 S open circuit voltage through a 2 ohm resistor (line to line) or 12 ohm resistor (line to ground). The short circuit current wave-form is 8/20S

37. Voltage Dips and Interrupts • EN61000-4-11 • Simulates sags and brownouts in the AC supply voltage • Unit must self recover after a single cycle dropout (Criterion B) • Criterion C (user intervention permitted) for the 60%/100mS dip and 100%/5 second interruption

38. Magnetic Field Immunity 50Hz-10kHz • Test methods detailed in Annex A of EN55103-2 • Criterion A • For Rack-Mount equipment, test level equals the limit for the emissions • (so this is to ensure immunity from other equipment) • Test method depends on installation • (rack-mount vs non-rack mount) • Specification details the construction of the loops • Possible to build the loops and perform tests in-house using an audio signal generator

39. Audio Frequency Common Mode • Test methods detailed in Annex B of EN55103-2 • Required only for balanced signal/control ports that connect to cables longer than 10m • Annex B of the standard details the test circuit • Should be possible to test in-house • Performance should be detailed in user-manual

40. Design Techniques Although the next section concentrates on radiated emissions solutions, there is a reciprocity between emissions and immunity design techniques - the techniques that reduce emissions from a circuit can also reduce the amount of energy that is coupled into a circuit

41. Typical Problems • Products with digital circuits typically have problems meeting the emissions requirements • Products with predominantly audio circuitry typically have problems meeting the immunity requirements

42. Good Circuit Layout (1) Be VERY careful when splitting ground planes • Current flows in loops. The actual current path is the path of least IMPEDANCE • Large loops (relative to wavelength) create good radiating mechanisms to couple onto other signal traces • Fortunately at rf frequencies, return currents want to flow as close as possible to the signal current as this gives the path with least inductance and reduce the current loop - so provide the return path by routing fast signals next to power or ground planes. • NEVER let digital clocks cross splits in power planes - it forces current to flow in loops

43. Current Loops • Trace Crosses complete split

44. Current Loops • Trace Crosses split

45. Current Loops • No Split - no loop

46. Good Circuit Layout (2) • Keep clock lines as short as possible • Keep clock lines away from the edge of the board • Provide rf decoupling capacitors (ceramic, 0.01uF) on switching ICs located as close as possible to the IC • Decoupling caps are only effective to 100 MHz or so, above this frequency the best decoupling is achieved by having adjacent power and ground planes. • Clock lines should be terminated when they exceed 3” x tr to prevent ringing on the lines caused by reflections at either end of a line because the impedance of the trace  load/source impedance. tr = rise time in nS

47. Good Circuit Layout (3) • Provide filtering on all interface ports (including AC & DC power ) • RF caps to a “clean” ground (typically chassis), common mode chokes or ferrite beads make ideal circuit elements • Include the filter components on ALL signal lines, including ground (especially where the ground is a digital signal ground)

48. I/O Interfaces • If possible, use PCB connectors with metal back shells as these can prevent high frequency signals radiated from the board from coupling onto the signal lines after the filter • Shields ideally terminate 360 to the enclosure (NOT to digital ground). • Shielded cables should have the shield terminated to the enclosure at the “noisy” end(s) - single ended grounding at rf does not work • Never use pigtails to terminate shields - at best they make a shielded cable ineffective, at worst they can increase emissions. • XLR cables are not designed for effective use of the shields - if you cannot terminate the shield directly to chassis (because of low frequency ground loops) tie to chassis using ceramic capacitors (alternatively create a capacitor on the PCB)

49. Enclosure Design • Required to reduce emissions above 250 MHz • Can help with ESD and other immunity problems • Slots and seams less than /10 (3cm @ 1GHz) • Select /10 based on • Highest clock speed • Preliminary test data • Previous product • Conductive finishes on metals • Good metal-to-metal contact (no paint !) • For low frequency emissions, consider using steel

50. AC Power Supply • Just because a power supply is CE-marked does not indicate that it meets any emissions (or immunity) limits - but it should indicate that it meets an appropriate LVD (electrical safety) standards. • If the vendor specifies that an RFI filter is required, use one • When using filters, make certain that the metal case is bonded to the enclosure. • Do not route the output wiring from the filter past any circuits, the wiring should exit the enclosure immediately to prevent noise coupling back onto the AC wiring.