RF Exposure

FCC ID: Q87-WRT54GH

RF Exposure Info

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FCCID_1137694

RF EXPOSURE REPORT REPORT NO.: SA980618H03 MODEL NO.: WRT54GH ACCORDING: FCC Guidelines for Human Exposure IEEE C95.1 APPLICANT: Cisco-Linksys LLC ADDRESS: 121 Theory Drive, Irvine, CA 92617, USA ISSUED BY: Bureau Veritas Consumer Products Services (H.K.) Ltd., Taoyuan Branch LAB LOCATION: No. 81-1, Lu Liao Keng, 9th Ling,Wu Lung Tsuen, Chiung Lin Hsiang, Hsin Chu Hsien 307, Taiwan Report No.: SA980618H03 1 Report Format Version 3.0.0

RF Exposure Measurement 1. Introduction In this document, we try to prove the safety of radiation harmfulness to the human body for our product. The limit for Maximum Permissible Exposure (MPE) specified in FCC 1.1310 is followed. The Gain of the antenna used in this product is measured in a Fully Anechoic Chamber (FAC) calibrated for antenna measurement in our lab, and also the maximum total power input to the antenna is measured. Through the Friis transmission formula and the maximum gain of the antenna, we can calculate the distance, away from the product, where the limit of MPE is reached. Although the Friis transmission formula is a far field assumption, the calculated result of that is an over-prediction for near field power density. We will take that as the worst case to specify the safety range. 2. RF Exposure Limit According to FCC 1.1310: The criteria listed in the following table shall be used to evaluate the environmental impact of human exposure to radio-frequency (RF) radiation as specified in 1.1307(b) LIMITS FOR MAXIMUM PERMISSIBLE EXPOSURE (MPE) Frequency Electric Field Magnetic Field Power Density Average Time Range Strength (V/m) Strength (A/m) (mW/cm2) (minutes) (MHz) (A)Limits For Occupational / Control Exposures 300-1500 … … F/300 6 1500-100,000 … … 5 6 (B)Limits For General Population / Uncontrolled Exposure 300-1500 … … F/1500 30 1500-100,000 … … 1.0 30 F = Frequency in MHz Report No.: SA980618H03 2 Report Format Version 3.0.0

3. Friis Formula Friis transmission formula : Pd = (Pout*G) / (4*pi*r2) where Pd = power density in mW/cm2 Pout = output power to antenna in mW G = gain of antenna in linear scale Pi = 3.1416 R = distance between observation point and center of the radiator in cm Pd is the limit of MPE, 1 mW/cm2. If we know the maximum Gain of the antenna and the total power input to the antenna, through the calculation, we will know the MPE value at distance 20cm. Ref. : David K. Cheng, Field and Wave Electromagnetics, Second Edition, Page 640, Eq. (11-133). 4. EUT Operating condition The software provided by Manufacturer enabled the EUT to transmit and receive data at lowest, middle and highest channel individually. 5. Classification The antenna of this product, under normal use condition, is at least 20cm away from the body of the user. Warning statement to the user for keeping at least 20cm or more separation distance with the antenna should be included in users manual. So, this device is classified as Mobile Device Report No.: SA980618H03 3 Report Format Version 3.0.0

6. Test Results 6.1 Antenna Gain The maximum Gain measured in Fully Anechoic Chamber is 3dBi or 1.995262 (numeric) 6.2 Output Power Into Antenna & RF Exposure value at distance 20cm: For Part 802.11b: Channel Limit of Output Power to Power Density Channel Frequency Power Density Antenna (mW) (mW/cm2) (MHz) (mW/cm2) 1 2412 120.226 0.048 1.0 6 2437 106.660 0.042 1.0 11 2462 90.157 0.036 1.0 For Part 802.11g: Channel Limit of Output Power to Power Density Channel Frequency Power Density Antenna (mW) (mW/cm2) (MHz) (mW/cm2) 1 2412 359.749 0.143 1.0 6 2437 331.894 0.132 1.0 11 2462 288.403 0.114 1.0 Report No.: SA980618H03 4 Report Format Version 3.0.0


Document Created: 2009-07-09 13:58:25
Document Modified: 2009-07-09 13:58:25
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