RF Exposure and Modular Equipment. Considerations

Transcription

1 RF Exposure and Modular Equipment Considerations

2 RF Exposure Rules SAR 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

3 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 (c)? If the answer to either of the above is YES than SAR evaluation is required

4 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 , e.g., EMC tested stand-alone (standalone SAR is undefined), FCC ID label on host, etc. A full Modular approval with unlimited SAR configurations is not allowed.

5 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

6 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; a PCMCIA card

7 Safety Rule References on Human Exposure ANSI C95.1 IEEE 1528 OET 65 OET 65-C FCC Part FCC Part Mobile Devices FCC Part Portable Devices FCC Part (b)(4) FCC Part 15E

8 Part 15 and RF Exposure The FCC will require a MPE study (RF estimation) for both Mobile and Fixed devices. (i.e 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.

9 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: key fob Tx do not need SAR test

10 Supplement C: MPE Exposure Limits ( A ) L i m i t s f o r O c c u p a t i o n a l / C o n t r o l l e d E x p o s u r e F r e q u e n c y E l e c t r i c F i e l d M a g n e t i c F i e l d P o w e r D e n s i t y A v e r a g i n g T i m e R a n g e S t r e n g t h ( E ) S t r e n g t h ( H ) ( S ) E 2, H 2 o r S ( M H z ) ( V / m ) ( A / m ) ( m W / c m 2 ) ( m i n u t e s ) ( ) * / f / f ( / f 2 ) * f / , ( B ) L i m i t s f o r G e n e r a l P o p u l a t i o n / U n c o n t r o l l e d E x p o s u r e F r e q u e n c y E l e c t r i c F i e l d M a g n e t i c F i e l d P o w e r D e n s i t y A v e r a g i n g T i m e R a n g e S t r e n g t h ( E ) S t r e n g t h ( H ) ( S ) E 2, H 2 o r S ( M H z ) ( V / m ) ( A / m ) ( m W / c m 2 ) ( m i n u t e s ) ( ) * / f / f ( / f 2 ) * f / , f = f r e q u e n c y i n M H z * P l a n e - w a v e e q u i v a l e n t p o w e r d e n s i t y N O T E 1 : S e e S e c t i o n 1 f o r d i s c u s s i o n o f e x p o s u r e c a t e g o r i e s. N O T E 2 : T h e a v e r a g i n g t i m e f o r G e n e r a l P o p u l a t i o n / U n c o n t r o l l e d e x p o s u r e t o f i x e d t r a n s m i t t e r s i s n o t a p p l i c a b l e f o r m o b i l e a n d p o r t a b l e t r a n s m i t t e r s. S e e 4 7 C F R a n d o n s o u r c e - b a s e d t i m e - a v e r a g i n g r e q u i r e m e n t s f o r m o b i l e a n d p o r t a b l e t r a n s m i t t e r s.

11 Supplement C: SAR Limits (A) Limits for Occupational/Controlled Exposure (W/kg) Whole-Body Partial-Body Hands, Wrists, Feet and Ankles (B) Limits for General Population/Uncontrolled Exposure (W/kg) Whole-Body Partial-Body Hands, Wrists, Feet and Ankles NOTE 1: See Section 1 for discussion of exposure categories. NOTE 2: Whole-Body SAR is averaged over the entire body, partial-body SAR is averaged over any 1 gram of tissue defined as a tissue volume in the shape of a cube. SAR for hands, wrists, feet and ankles is averaged over any 10 grams of tissue defined as a tissue volume in the shape of a cube. NOTE 3: At frequencies above 6.0 GHz, SAR limits are not applicable and MPE limits for power density should be applied at 5 cm or more from the transmitting device. NOTE 4: The time averaging criteria for field strength and power density do not apply to general population SAR limit of 47 CFR

12 MPE Estimation Formula To Determine Power Density (s): S=P x G /4piR 2 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

13 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: 1. RF shielding. 2. Buffered data input/output ports 3. Power supply regulation 4. Permanent antenna or unique connector 5. Tested in stand alone condition 6. Labeled with own ID number 7. Instructions to operator / OEM integrator 8. Must meet RF Exposure requirements.

14 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 b/g card without voltage regulation Example 2: Wireless mini-pci b/g card with SAR results which may apply to a specific chassis or model notebook PC host.

15 Licensed Modules There is officially no such thing as a Licensed Modular Transmitter The Rules of DA do not apply DO NOT ATTEMPT

16 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?

17 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.

18 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.