Attachment Rad Haz report

This document pretains to SES-MOD-20110518-00597 for Modification on a Satellite Earth Station filing.

IBFS_SESMOD2011051800597_889403

Radiation Hazard Study 1.0 Introduction This study analyzes the radiation hazard environment produced by 2.4 meter Ku-band offset antennas with a maximum of 3 Watts into the antenna feed. The antennas may be operated in uncontrolled access areas. The reference document for this study is OET Bulletin No. 65, Edition 97-01, Evaluating Compliance with FCC Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields, August 1997. 2.0 Earth Station Antenna Parameters Antenna diameter (D) = 2.4 meters Wavelength (λ) = 0.021 meters at 14.25 GHz Maximum power to the antenna (P) = 3 Watts 2.4 meter antenna gain (G) = 49.2 dBi at 14.25 GHz 2.4 meter antenna efficiency (η) = 0.65 3.0 Region Definition The limit of the near field (Rnf) and the beginning of the far field (Rff) are calculated as follows: Near Field Extent Rnf = D2 4λ Rnf = 2.42 /(4 * 0.021) = 68.5 m Far Field Extent Rff = 0.6 D2 λ Rff = (0.6)(2.42)/(0.021) = 164.3 m The region between 68.5 m and 164.3 m is designated as the transition region.

4.0 Power Density Calculations 4.1 Near Field Region The on-axis near field power density is calculated as follows: Snf = 16ηP πD2 Snf = (16)(0.65)(3) (3.14)(2.42) Snf = 1.72 W/m2 = 0.172 mW/cm2 The maximum on-axis power density in the far field region is is Snf = 0.172 mW/cm2. This meets the Uncontrolled Exposure limit of 1.0mW/cm2 found in Appendix A or OET Bulletin 65. The off-axis power density in the near field will always be less than the on-axis power density and therefore all volumes within the near field will meet the Uncontrolled Exposure limit of 1.0 mW/cm2. 4.2 Transition Region The on-axis power density in the transition region is calculated as follows: St = SnfRnf R The maximum on-axis power density in the transition region is when R = Rnf at which point the power density is St = Snf = 0.172 mW/cm2. This meets the Uncontrolled Exposure limit of 1.0mW/cm2 found in Appendix A or OET Bulletin 65. The off-axis power density in the transition region will always be less than the on-axis power density and therefore all volumes within the transition region will meet the Uncontrolled Exposure limit of 1.0 mW/cm2 found in Appendix A of OET Bulletin 65.

4.3 Far Field Region The on-axis power density in the far field region is calculated as follows: Sff = PG 4πR2 Sff = (3)(10(49.2/10)) (4)(3.14)(164.3)2 Sff = 0.737 W/m2 = 0.0737 mW/cm2 The maximum on-axis power density in the far field region is is Sff = 0.0737 mW/cm2. This meets the Uncontrolled Exposure limit of 1.0mW/cm2 found in Appendix A of OET Bulletin 65. The off-axis power density in the far field will always be less than the on-axis power density and therefore all volumes within the far field will meet the Uncontrolled Exposure limit of 1.0 mW/cm2. 4.4 Region between the Feed Flange and Main Reflector Transmissions from the feed horn are directed toward the reflector surface. The maximum power density between the feed and reflector surface can be calculated as: Sfl = 4P/A = 16P/(πD2) Sfl = (16)(3)/(3.14 * 0.122) Sfl = 1061 W/m2 = 106.1 mW/cm2 This value exceeds the Uncontrolled Exposure limit of 1.0 mW/cm2 found in Appendix A of OET Bulletin 65 and represents a potential hazard. Therefore, a warning label will be affixed to the surface of the reflector to warn people to avoid the region between the antenna feed and the surface of the reflector. 4.5 Reflector Surface Region The power density at the surface of the reflector is approximated by: Sr = 4P/A = 16P/(πD2) Sr = (16)(3)/(3.14)(2.42)

Sr = 2.65 W/m2 = 0.265 mW/cm2 This value meets the Uncontrolled Exposure limit of 1.0 mW/cm2 found in Appendix A of OET Bulletin 65. 4.5 Region Between Antenna and Ground Assuming uniform illumination of the reflector surface, the power density between the antenna and the ground can be calculated as follows: Sg = P/A = 4P/(πD2) Sg = (4)(3)/(3.14)(2.42) = 0.66 W/m2 = 0.066 mW/cm2 This value meets the Uncontrolled Exposure limit found in Appendix A of OET Bulletin 65. 5.0 Summary Table 1. Summary of Expected Radiation Levels General Occupational/Controlled Population/Uncontrolled Exposure Exposure Maximum Radiation Level Maximum Radiation Level (5.0 mW/cm²) (1.0 mW/cm²) Radiation Region Level Hazard Assessment Hazard Assessment (mW/cm2) Near Field 0.172 Satisfies FCC MPE Satisfies FCC MPE Rnf = 68.5 m Far Field 0.0737 Satisfies FCC MPE Satisfies FCC MPE Rff = 164.3 m Transition Region 0.172 Satisfies FCC MPE Satisfies FCC MPE Rnf < Rt < Rff Region between Feed and 106.1 Potential Hazard Potential Hazard Reflector Reflector Surface 0.265 Satisfies FCC MPE Satisfies FCC MPE Region between Antenna and 0.066 Satisfies FCC MPE Satisfies FCC MPE Ground

6.0 Conclusion Using the methods outlined in OET Bulletin 65, the 2.4 m antennas meet the Uncontrolled and Controlled Exposure limits in all regions except in the region between the antenna feed and the reflector. A warning label will be affixed to the surface of the reflectors to warn people to avoid the region between the antenna's flange and the surface of the reflector.


Document Created: 2011-05-16 11:49:50
Document Modified: 2011-05-16 11:49:50
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