Supplement.rad haz F

SUPPLEMENT submitted by O3b Limited

Supplement re Radiation Hazard

2014-09-12

This document pretains to SES-STA-20140912-00727 for Special Temporal Authority on a Satellite Earth Station filing.

IBFS_SESSTA2014091200727_1060958

SUPPLEMENT O3b Limited (“O3b”) hereby supplements its request for special temporary authority (“STA”) to demonstrate compliance with the Commission’s RF radiation requirements. O3b is attaching to this supplement a radiation hazard study for the 1.2-m antenna O3b will operate pursuant to the STA. As appropriate, O3b will use fencing, signage, and other measures to limit access to the relevant area. Procedures will be in place requiring that transmit power be turned off before work on the 1.2-m antenna is performed.

Radiation Hazard Study - Orbit AL-7103-Ka, 1.20 m Antenna Radiation Hazard Study The study in this section analyzes the potential RF human exposure levels caused by the Electro Magnetic (EM) fields of an Orbit AL-7103-Ka, 1.20 m antenna, operating with a maximum power at the flange of 20 Watts. The mathematical analysis performed below complies with the methods described in the FCC Office of Engineering and Technology (OET) Bulletin No. 65 (1985 rev. 1997) R&O 96-3 26 in "Evaluating Compliance with FCC Guideliness for Human Exposure to RF EM Fields, OET Bulletin 65 (Edition 97-01), Supplement B, FCC Office of Engineering & Technology, November 1997". Maximum Permissible Exposure There are two separate levels of exposure limits. The first applies to persons in the general population who are in an uncontrolled environment. The second applies to trained personnel in a controlled environment. According to 47 C.F.R. § 1.1310, the Maximum Permissible Exposure (MPE) limits for frequencies above 1.5 GHz are as follows: * General Population / Uncontrolled Exposure: 1.0 mW/cm2 * Occupational / Controlled Exposure: 5.0 mW/cm2 The purpose of this study is to determine the power flux density levels for the earth station under study as compared with the MPE limits. This comparison is done in each of the following regions: 1. Far-field region 2. Near-field region 3. Transition region 4. The region between the feed and the antenna surface 5. The main reflector region 6. The region between the antenna edge and the ground Input Parameters The following input parameters were used in the calculations: Calculated Parameters The following values were calculated using the above input parameters and the corresponding formula: Page - 1 of 4

Radiation Hazard Study - Orbit AL-7103-Ka, 1.20 m Antenna Behavior of EM Fields as a Function of Distance The behavior of the characteristics of EM fields varies depending on the distance from the radiating antenna. These characteristics are analyzed in three primary regions: the near-field region, the far-field region and the transition region. Of interest also are the region between the antenna main reflector and the subreflector, the region of the main reflector area and the region between the main reflector and ground. Figure 1. Electro-Magnetic Fields as a Function of Distance For parabolic aperture antennas with circular cross sections, such as the antenna under study, the near-field, far-field and transition region distances are calculated as follows: Page - 2 of 4

Radiation Hazard Study - Orbit AL-7103-Ka, 1.20 m Antenna The distance in the transition region is between the near and far fields. Thus, Rnf ≤ Rt ≤ Rff . However, the power density in the transition region will not exceed the power density in the near-field. Therefore, for purposes of the present analysis, the distance of the transition region can equate the distance to the near-field. Power Flux Density Calculations The power flux density is considered to be at a maximum through the entire length of the near-field. This region is contained within a cylindrical volume with a diameter, D, equal to the diameter of the antenna. In the transition region and the far-field, the power density decreases inversely with the square of the distance. The following equations are used to calculate power density in these regions: The region between the main reflector and the subreflector is confined to within a conical shape defined by the feed assembly. The most common feed assemblies are waveguide flanges. This energy is determined as follows: The power density in the main reflector is determined similarly to the power density at the feed flange; except that the area of the reflector is used. The power density between the reflector and ground, assuming uniform illumination of the reflector surface, is calculated as follows: Page - 3 of 4

Radiation Hazard Study - Orbit AL-7103-Ka, 1.20 m Antenna Summary of Calculations Table 1 below summarizes the calculated power flux density values for each region. In a controlled environment, the only regions that exceed FCC limitations are the regions between the main reflector and the sub-reflector as well as the main reflector region. These regions are only accessible by trained technicians who, as a matter of procedure, turn off transmit power before performing any work in these areas. Table 1. Power Flux Density for Each Region: In conclusion, the results show that the antenna, in a controlled environment, and under the proper mitigation procedures, meets the guidelines specified in § 1.1310 of the Regulations. Page - 4 of 4


Document Created: 2014-09-12 13:43:08
Document Modified: 2014-09-12 13:43:08
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