Without knowing anything about your system, RFID and RF bombarders, I will merely offer a SWAG. My guess is that the RFID system is a magnetic loop system? If so, copper will not have significant effect on shielding the system. Ferrous material will. Try a galvanized sheet steel for a shield. This is a commonly available material and will afford much better shielding effectiveness at that frequency than copper will. You will be using the sheet steel to guide the flux from the bombarder around instead of through the RFID system. If the shield is too close to the RFID system, you will warp the field of the intended RFID signal also.
It might also be that you are on the threshold of receiver blocking for the proximity of the 400 kHz bombarder frequency compared to the desired 530 kHz RFID frequency . How sharp can you make a notch filter that is sufficiently stable for your environment? Good luck, Don Umbdenstock Sensormatic > ---------- > From: wmf...@aol.com[SMTP:wmf...@aol.com] > Reply To: wmf...@aol.com > Sent: Monday, October 15, 2001 2:43 PM > To: emc-p...@ieee.org > Cc: jim.gi...@hedus.com > Subject: EMI trouble shoot inquiry > > > Group: > I attach an RF interference inquiry from a customer; I have no 'smarts' > where RF ID is concerned, so I turn to this august body... > > ==paste==We have an OMRON RFID data transfer system operating within the > same room as 12 RF generators (bombarders). The transmission frequency > for the RFID system is 530 kHz and the transmission frequency for the > bombarders is 400 kHz. The RFID system works through an antenna embedded > in a pallet and a stationary read/write head. The bombarders are > positioned on a platform overhead. The normal sequence is for a pallet > containing a bulb to move via conveyor to a read/write station where > information is taken from and added to the pallet. The pallet is conveyed > through several different processes, being read/written on roughly 8 > occasions. One of the processes contains an RF generator. We are > experiencing problems with the RFID system when the RF generators are on. > The read/write system operates properly when the RF generators are off. > We have determined that the RF generators are creating an interference > that does not allow the RFID to operate properly. Initially, w! > e built copper shields in the area of some > of the RFID stationary heads. This did not seem to help. We also placed > EMI suppressors on the RFID cables(near the read heads). This also was > not helpful. I have spoken to a company that suggested the use of Ferrite > tiles to absorb the interfering waves. The problem with these tiles is > that they are very brittle and difficult to use for shields. The concept > sounds good but I don't have much flexibility in where I can place the > shields. I am currently trying to use ferrite magnets attached to the > copper guards. Any help/suggestions you could give me would be greatly > appreciated. > ===end paste== > Thanks for any suggestions; reply as you see fit. > > WmFlanigan > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson: pstc_ad...@garretson.org > Dave Heald davehe...@mediaone.net > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > No longer online until our new server is brought online and the old > messages are imported into the new server. > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
