MPE Estimates

FCC ID: S9E-RNGRBTWFR

RF Exposure Info

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FCCID_667059

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 head or torso of the user or nearby persons and can therefore be considered a mobile transmitter per 47 CFR 2.1091 (b). The radio module, FCC ID: S9E- RNGRBTWFR, will be installed in the Recon handheld computer. The 802.11/Bluetooth combo module operates in the 2.4 GHz band. The radios can transmit simultaneously. Each radio transmits through its own antenna. Two Antenna Factor chip antennas, M/N: ANT-2.45-CHP-X, will be installed in the Recon for each type of radio transmission, 802.11 and Bluetooth. The EUT is not subject to routine environmental evaluation per 47 CFR 2.1091. Per 47 CFR 1.1310, the EUT must meet the General Population / Uncontrolled exposure limits listed in Table 1. 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:

FCC ID: S9E-RNGRBTWFR 802.11 (b) Radio Antenna Type Antenna Part No. Transmit Max Peak Antenna Gain Minimum Power General Ratio of Power (MHz) (mW) (dBi) (dB) (mW/cm2) (mW/cm2) Chip ANT-2.45-CHP-X 2400 24.6 0.5 0 0.005 1 0.00549 Worst Case Ratio of Power Density to the Exposure Limit = 0.00549 Bluetooth Radio Antenna Type Antenna Part No. Transmit Max Peak Antenna Gain Minimum Power General Ratio of Power (MHz) (mW) (dBi) (dB) (mW/cm2) (mW/cm2) Chip ANT-2.45-CHP-X 2400 1.92 0.5 0 0.00043 1 0.00043 Worst Case Ratio of Power Density to the Exposure Limit = 0.00043 Worst Case Co-located Exposure Condition Per Note 24 shown below, the Sum of Worst Case Power Ratios cannot exceed 1.0 Bluetooth Sum of Worst Radio 802.11b Radio Case Ratios FCC Limit for Worst Case Worst Case Ratio of (Power Density Sum of Worst Ratio of Power Power Density to the to the Exposure Case Ratios Density to the Exposure Limit Limit) Exposure Limit 0.00043 0.00549 0.00592 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.

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: 2006-06-06 11:15:04
Document Modified: 2006-06-06 11:15:04
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