safety for electronic systems High-frequency Filtering of DC Power Lines Technical, constructional and practical issues with filtering on dc power lines Wolfgang L. Klampfer Manager Training Center

safety for electronic systems Contents EMC issues for base stations Filtering at high frequencies Contacting under high load Conventional solutions A new approach

safety for electronic systems Basestations and EMC Standard requirements in Europe Noise sources and distribution

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Requirements for Base Stations AC Mains DC Supply Antenna Other lines Radio Interface Enclosure

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Requirements for Base Stations Emission EN CISPR 16-1 Immunity EN EN AC Mains DC Supply Antenna Other lines Radio Interface Enclosure

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Conducted Emission according to EN 55022, CISPR 16-1 EUT Supply PE EMI Receiver DC LISN

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Differential mode noise R L L N PE

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Parasitic components as cause for differential mode noise ESL ESR

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Characteristics for differential mode noise Current through ESL and ESR Lower frequencies Switching frequency and harmonics Loop structures ESL ESR

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Common mode noise R L L N PE

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Insulation as cause for common mode noise ~ = I CM

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Characteristics of common mode noise Usually high frequency problems, e.g. switching/oscillating at higher frequencies Affected by circuit layout, e.g. heat sinks Cables

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Differential to common mode conversion Perfectly balanced only differential mode no radiation Slight unbalance differential to common mode conversion conducted and radiated noise at high frequencies

safety for electronic systems Filtering at high frequencies Problems with resonances and solutions Special filter requirements for base stations

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Capacitors and chokes for noise suppression Two metal plates, separated by insulation Often realised by 2 metallized plastic foils Wire wound to a coil Usually winding is placed on magnetic material (core)

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Frequency response of capacitors and chokes

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Use of capacitors and chokes in circuits C Load ~ AC mains pathRF path Load ~ L

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Resonances of capacitors and chokes Connection leads of capacitors work like small series inductances Inductors can have significant capacitance between windings

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Frequency response of feedthrough capacitors

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Filters for Base Stations Special Requirements: Customized power requirements Mixed AC and DC configurations Environmental stress High attenuation Special enclosure forms AC Mains

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Power Layout Filter Circuit Line Load L1 L2 GND L1 L2 GND L1 L2 GND L1 L2 GND 60A 20A

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Environmental Requirements Corrosion resistance Thermal shock Vibration Impact resistance Transportation shock and vibration Earthquakes

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Attenuation Requirements Insertion Loss, Line to GND, MHz – 5.0 MHz 20 dB 5.0 MHz – 10.0 MHz 30 dB 10.0 MHz – 30.0 MHz 40 dB 30.0 MHz – 4.0 GHz 40 dB

safety for electronic systems Contacting at high loads Special issues and requirements for contacts

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Requirements for dc power connections Reliable contact Easy connect/disconnect Low contact resistance High number of connect-disconnect cycles Hot-pluggable

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Potential threats and problems Reliable contact Force of contacts over time Easy connect/disconnect Installation/maintenance time Low contact resistance Risk of overheating High number of connect-disconnect cycles Wear-out of contact surface Hot-pluggable Arcing between male and female connector; destruction of contacts

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Specialties about a proper contact Fixed beams Surround spring (Activates only cantilevered beams) Cantilevered beams Crimp barrel

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Function of the surround spring assists cantilevered beams at operating temperatures > 80 °C provides high mechanical shock/vibration stability with no contact bounce Male pin engaging fixed beams – hot plug surface Male pin engaging cantilevered beams

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Function of the beams Fixed beams provide mechanical guidance thermal conductivity sacrificial hot plug / hot swap location Cantilevered beams low contact resistance low current density optimum insertion force

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Contact material selection for power connectors n High conductivity copper = low temperature rise n Good manufacturing process n Copper with good spring properties at contact interface = normal force n Copper with good formability for crimping to finely stranded copper conductors

safety for electronic systems Conventional solution Standard approach for dc filtering and connecting

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems DC Power to Filter Filter to Bus Bar Traditional installation until today

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Some considerations for the conventional solution 8 parts with 10 (!) connection points Necessary extra provisions for capacitor grounding Overall attenuation relies on quality of connection Work- and cost-intensive installation Many connections means many potential failure sources

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Relation between attenuation and earth resistance

safety for electronic systems A new approach Advanced filtering and contacting solution

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Requirements for a contacting-filtering solution Easy connect and disconnect under full-load Easy and quick installation Reduced number of connection points Reliable filtering up to several GHz Protection against reverse polarity Protection against wrong connections in case of several power lines

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems The solution: ACARA 2 parts with 2 connection points High-quality contacts for connection and disconnection under full-load Time/cost/space saving solution

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Frequency response of ACARA

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Reverse polarity protection and code keying Protection against reverse polarity Pins for keying of connector pairs6 positions for keying pins

IEEE Dallas EMC SocietyJanuary 20, 2004 safety for electronic systems Thank you very much for your attention Any questions?