RF Exposure and Modular Equipment Considerations

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RF Exposure and Modular Equipment Considerations
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RF Exposure RulesSAR and MPE Estimation Summary

• Based on current interpretations of US radio law
  by FCC
• Based upon the TCB Exclusion List and various
  interpretations by FCC
• Based upon experience of ATCB

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RF Exposure SAR or MPE ?

• Questions to ask
• Is device used at less than 20cm to the body? And
  is the device above the Low Threshold
  conditions in the TCB exclusion list of July 17,
  2002?
• Is the device listed in 2.1093(c)?
• If the answer to either of the above is YES than
  SAR evaluation is required

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Definitions and Nomenclature

• Host-independent certification for device to be
  installed and expected to comply in any
  applicable host unfeasible for portable
  exposure conditions
• Module Transmitter operating (usually)
  internally as part of another device or product
• Full Modular Approval Part 15 Tx module that
  meets eight criteria of DA 00-1407, e.g., EMC
  tested stand-alone (stand-alone SAR is
  undefined), FCC ID label on host, etc. A full
  Modular approval with unlimited SAR
  configurations is not allowed.

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Definitions and Nomenclature

• Limited Modular Approval (LMA) LMA is used with
  SAR testing on an Unlicensed module to allow SAR
  tests to be applied to more than one model.
• Licensed module Certification for Licensed Tx
  daughter-board or Tx box, installed in RF
  category Mobile or Fixed conditions only. Antenna
  might be specified with limit on gain.
• Dedicated host Tx intended for OEM integration
  or permanent installation into a specific host
  product also covered by 3-host method for
  integral-antenna plug-in cards. Applies
  specifically to Part 15 modules above 100mW

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Portable Devices

• Operate less then 20cm from any user or bystander
• Usually involves body worn or ear or face held
  devices
• SAR Testing required if above the low threshold
  limit in July 17, 2002 TCB Exclusion List
• Some devices are specifically required by law to
  have SAR testing as a condition of Certification,
  regardless of RF Pout.
• Example Cellphones 802.11a PCMCIA card

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Safety Rule References on Human Exposure

• ANSI C95.1
• IEEE 1528
• OET 65
• OET 65-C
• FCC Part 1.1037
• FCC Part 2.1091 Mobile Devices
• FCC Part 2.1093 Portable Devices
• FCC Part 15.247(b)(4)
• FCC Part 15E

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Part 15 and RF Exposure

• The FCC will require a MPE study (RF estimation)
  for both Mobile and Fixed devices. (i.e.15.247
  and UNII devices).
• Estimation should be performed with highest gain
  antenna of each antenna type.
• For SAR and MPE evaluation, the default limits
  are the Uncontrolled Environment. It is assumed
  that users of Part 15 devices have no
  understanding of radio principals.
• You cannot evaluate any Part 15 device to the
  Controlled/Occupational limits.

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Part 15 and RF Exposure

• The vast majority of Low Power Part 15
  Intentional Radiators are categorically excluded
  from Routine Evaluation under the FCC rules.
  However, the FCC will require a SAR test for RF
  category Portable devices if the power exceeds
  60/f(GHz) if contact with antenna is allowed, or
  120mW/f(GHz) if 2.5cm is maintained to the
  antenna.
• Example 15.231 key fob Tx do not need SAR test

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Supplement C MPE Exposure Limits
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Supplement C SAR Limits
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MPE Estimation Formula

• To Determine Power Density (s)
• SP x G /4piR2
• FCC requires that RF category Mobile devices
  calculate power density for 20cm.
• Calculation of power density at other distances
  for Mobile products not allowed.
• Calculation of power density for Fixed devices
  is allowed, as long as distance not shown less
  than 20cm

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Full Modular Approvals (Part 15)

• By Definition, these transmitters must have own
  reference oscillator. In addition a separate
  letter on Applicant letterhead addressing all
  these items must accompany the filing
• RF shielding.
• Buffered data input/output ports
• Power supply regulation
• Permanent antenna or unique connector
• Tested in stand alone condition
• Labeled with own ID number
• Instructions to operator / OEM integrator
• Must meet RF Exposure requirements.

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Limited Modular Approval (LMA) Part 15

• If any of the 8 elements on the preceding slide
  cannot be met, a limited modular approval may be
  obtained in some circumstances. LMAs define
  special circumstances where Certification is
  valid
• Example 1 Wireless mini-PCI 802.11b/g card
  without voltage regulation
• Example 2 Wireless mini-PCI 802.11b/g card with
  SAR results which may apply to a specific chassis
  or model notebook PC host.

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Licensed Modules

• There is officially no such thing as a Licensed
  Modular Transmitter
• The Rules of DA 00-1407 do not apply DO NOT
  ATTEMPT

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Complex Example

• Notebook PC with built-in Bluetooth, WiFi, and
  GPRS
• Are Part 15 transmitters separately Certified?
• Are Part 15 transmitters Modular Approved?
• Are any transmitters capable of co-location?
• Is BT below 5mw?
• Are any transmitters end-user installable?
• Labeling?

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SAR Testing Updates.

• SAR Probes must be calibrated on a yearly basis.
  The only allowed exception is when the probe
  manufacturer specifically permits different
  calibration intervals.
• Tolerance between RF conducted power measured at
  the EMC lab and SAR lab must be within 5. Common
  spectrum analyzers are good to only 1dB (25)
• TCBs now allowed to do SAR approval work from
  300MHz to 6GHz.

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Additional Documents

• FCC has released specific guidance for SAR
  testing of WiFi products.
• FCC is now specifying specific combinations of
  channel, power, and data rates.
• FCC has released SAR review to TCBs to
  frequencies of 6GHz.

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Contact Information

• William H. Graff
• President and Director of Engineering
• AmericanTCB, Inc.
• 6731 Whittier Ave.
• McLean, VA 22101
• mailto whgraff_at_ATCB.com
• Corporate Phone [phone]
• Corporate FAX [phone]
• Direct Mobile [phone]
• SKYPE whgraff