MPE Estimates

FCC ID: S9E-NOMADWF

RF Exposure Info

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FCCID_815659

Compliance with 47 CFR 15.247(i) “Systems operating under the provisions of this section shall be operated in a manner that ensures that the public is not exposed to radio frequency energy levels in excess of the Commission's guidelines. See § 1.1307(b)(1) of this chapter.” The EUT will only be used with a separation distance of 20 centimeters or greater between the antenna and the body of the user or nearby persons and can therefore be considered a mobile transmitter per 47 CFR 2.1091 (b). No body worn accessories are provided with the unit. Two radio modules will be installed in the unit – each operating in the 2.4GHz band. A 802.11(b)/(g) radio module and a Bluetooth EDR radio module. The radios can transmit simultaneously. Each radio transmits through its own antenna. The total transmit power is less than 1.5 W (ERP), therefore the EUT is categorically excluded from routine environmental evaluation per 47 CFR 2.1091(c). The MPE estimates are as follows: Table 1 in 47 CFR 1.1310 defines the maximum permissible exposure (MPE) for the general population. The exposure level at a 20 cm distance from the EUT’s transmitting antenna is calculated using the general equation: S = (PG)/4πR2 Where: S = power density (mW/cm2) P = power input to the antenna (mW) G = numeric power gain relative to an isotropic radiator R = distance to the center of the radiation of the antenna (20 cm = limit for MPE estimates) PG = EIRP Solving for S, the maximum power densities 20 cm from the transmitting antennas are summarized in the tables on the following pages:

MPE Estimates for Self Co-located Device FCC ID: S9E-NOMADBT Bluetooth Radio General Max Peak Minimum Power Ratio of Power Antenna Antenna Part Transmit Population Conducted Antenna Gain Antenna Density @ 20 Density to the Type No. Frequency Exposure Limit Output Power Cable Loss cm Exposure Limit from 1.1310 (MHz) (mW) (dBi) (dB) (mW/cm2) (mW/cm2) Chip ANT-2.45-CHP-x 2400 2.5 0.5 0 0.001 1 0.001 Worst Case Ratio of Power Density to the Exposure Limit = 0.001 FCC ID: S9E-NOMADWF 802.11 (b)/(g) Radio General Max Peak Minimum Power Ratio of Power Antenna Antenna Part Transmit Population Conducted Antenna Gain Antenna Density @ 20 Density to the Type No. Frequency Exposure Limit Output Power Cable Loss cm Exposure Limit from 1.1310 (MHz) (mW) (dBi) (dB) (mW/cm2) (mW/cm2) Chip ANT-2.45-CHP-x 2400 57.94 0.5 0 0.013 1 0.013 Worst Case Ratio of Power Density to the Exposure Limit = 0.013 Worst Case Co-located Exposure Condition Per Note 24 shown below, the Sum of Worst Case Power Ratios cannot exceed 1.0 Bluetooth Radio 802.11b Radio Sum of Worst Worst Case Worst Case Case Ratios FCC Limit for Ratio of Ratio of Power (Power Density Sum of Worst Power Density to the to the Exposure Case Ratios Density to Exposure Limit Limit) the Exposure 0.00100 0.01300 0.01400 1.0 PASS The results shown in the above table are equivalent to the Sum of the EIRP of the Two Co-located Transmitters (EIRP TX1 + EIRP TX2) compared to the exposure limit. The benefit of this method, is that accounts for transmitters operating at different frequencies against different exposure limits. Please note that EIRP = ERP x 1.64, so EIRP is worst case. However, because some parties would prefer to see the calculation as the Sum of the ERP of the Two Co-located Transmitters, the table below shows compliance with ERP TX1 + ERP TX2 General CDMA Radio 802.11b Radio Power Population Sum of Worst Worst Case Worst Case Density @ 20 Exposure Case ERPs ERP ERP cm Limit from 1.1310 2 2 (mW) (mW) (mW) (mW/cm ) (mW/cm ) 1.710393985 39.640091 41.35 0.00823 1.0 PASS

Excerpts from TCB Training, April 3, 2002, “Mobile Transmitters”, Slide 6: “Devices operating in multiple frequency bands When RF exposure evaluation is required for TCB approval o Separate antennas – estimated minimum separation distances may be considered for the frequency bands that do not require evaluation or TCB approval, however, the estimated distance should take into account the effect of co-located transmitters. (Note 24) Note 24 According to multiple frequency exposure criteria, the ratio of field strength or power density to the applicable exposure limit at the exposure location should be determined for each transmitter and the sum of these ratios must not exceed 1.0 for the location to be compliant.” The sum of the ratios (power density to the exposure limit) does not exceed 1.0; therefore, the exposure condition is compliant with FCC rules.


Document Created: 2007-07-13 11:57:54
Document Modified: 2007-07-13 11:57:54
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