Collaboration Meeting at UCI, April 7-9, 2005 EMI Control System Design Kurt Liewer

April 7, 2005Collaboration Meeting at UCI, April 7-9, 2005KML - 1 EMI reduction philosophy Goal is attenuate all locally generated interfering signals by ~100 dB –both radiation and conduction paths to be protected All electronics are enclosed with EMI enclosures –exceptions are telemetry and GPS antennas, rotator and PV arrays –enclosures have copper (or copper plated) walls and soldered or gasketed joints –connectors are either coax or circular connectors with backshells and 360° shielding (mil 33999) –non-coax connectors have additional box-within-a-box filtering and use shielded twisted pair wire Noisy components (power supplies) within the main enclosure will also be within EMI enclosures power will, to the extent possible, have a single ground point that is connected to ground (the gondola) at a single point –the antennas and RF amps prevent this from happening for the RF 12 V supply

April 7, 2005Collaboration Meeting at UCI, April 7-9, 2005KML - 2 Main EMI box construction frame is now stainless steel

April 7, 2005Collaboration Meeting at UCI, April 7-9, 2005KML - 3 Hardware within the main EMI box ADU5 cPCI DC|DC converters instrument power cPCI crate radiator plate

April 7, 2005Collaboration Meeting at UCI, April 7-9, 2005KML - 4 Box-within-a-box concept example of box-within-a-box filtering applied to the RFCM Any signal on the wires or leaking through the connector must pass through the filter –discrete filter components allows leakage past the filter Filter feedthrus would be implemented at both ends of the cable with >65 dB of filter attenuation less than 35 dB of rejection is required in the cable and connector

April 7, 2005Collaboration Meeting at UCI, April 7-9, 2005KML - 5 EMI enclosure to RFCM wiring

April 7, 2005Collaboration Meeting at UCI, April 7-9, 2005KML - 6 Box-within-a-box design for main box

April 7, 2005Collaboration Meeting at UCI, April 7-9, 2005KML - 7 Wiring RF cable –minimal change in attenuation across band –high attenuation of inside to outside fields –candidates heliax (outside of EMI box) LMR-400 (outside of EMI box) semirigid, mini-bend or Coaxicon ultraflex (inside) multiconductor cable –candidate Alpha –twisted pairs –foil/braid –> 40 dB rejection (estimated) Belden (for AD590 temperature sensors) –shielded (foil) twisted pair –> 40 dB rejection (estimated)

April 7, 2005Collaboration Meeting at UCI, April 7-9, 2005KML - 8 AD590 wiring The AD590 outside of the EMI box will have the configuration shown in the diagram The connectors may change from LEMO to something else Shield of twisted pair is connected to the AD590 enclosure but not to the circuit return Resistors are chosen to match the cable impedence

April 7, 2005Collaboration Meeting at UCI, April 7-9, 2005KML - 9 Concerns Very difficult to know if the design will provide the necessary protection without testing The testing is very difficult until the final configuration is in place