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Which Frequency Band Is Most Suitable if Passive Inductive Coupling Within 3 Meters Is Required?
To reduce the amount of RF interference within a medical environment, an RFID system should have as low a power density as possible. High-frequency and above are feasible—but which requires the least power to communicate between tags and readers?
I reached out to Victor Vega at NXP Semiconductors, a provider of both passive high-frequency (HF) and ultrahigh-frequency (UHF) technology. According to Victor, inductive coupling with passive low-frequency (LF), HF and UHF can not be accomplished at 3 meters (10 feet). "It is possible with active components," he says. "I designed an LF active tag many years ago that had a read range of about 3 meters, but it required a battery."
Victor notes that some interference tests conducted on medical equipment indicated passive RFID had an impact on older EKG equipment—not that the equipment didn't work, but rather there was noise in the EKG signals. "It turned out that the signal cables were unshielded," he explains, "and they resolved that problem by simply using more updated shielding. To further reduce any potential interference, they simply specified a 'safe' distance (or reader power level), at which they tested and found no interference."
I would add that I have inquired about interference with companies that have used RFID technologies in hospitals—both passive and active—and no one has indicated that they have seen any signs that the technology had an impact on their hospital equipment, though a paper published in the Journal of the American Medical Association (JAMA) did find that passive RFID readers can interfere with equipment (see Researchers Warn RFID May Disrupt Medical Equipment).
AIM Global has been working on guidelines to ensure the safe operation of medical equipment around RFID systems in a hospital setting. If you have any concerns about this, I would suggest choosing the RFID system that best meets your needs, and then testing it with equipment used in the same area.
—Mark Roberti, Founder and Editor, RFID Journal
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