Attachment Radiation Report

This document pretains to SES-STA-20120515-00442 for Special Temporal Authority on a Satellite Earth Station filing.

IBFS_SESSTA2012051500442_950857

Richard  Sergeant                                                                                                                                                                                         Radiation Hazard Report Gigasat FA-240 C-Band Antenna System The purpose of this report is to examine the potential human exposure to radio frequencies (RF) emitted in the form of electro magnetic (EM) radiation from an Gigasat 2.4m C-Band satellite antenna. The mathematical analysis performed below complies with the methods described in the Federal Communications Commission Office of Engineering and Technology Bulletin No. 65 (1985 rev. 1997) R&O 96-326. 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 1.5GHz 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 values below are used in the calculations detailed in this report Parameter Value Unit Symbol Antenna Diameter 2.4 m D Antenna Transmit Gain 42 dBi G Transmit Frequency 6200 MHz ƒ Feed Flange Diameter 10.1 cm d Power Input to Antenna 260 W P 1                                  

Richard  Sergeant                                                                                                                                                                                     Calculated Parameters The following values are calculated from the input parameters from there corresponding formulas. (All values rounded to two decimal places) Parameter Value Unit Symbol Formula Antenna Surface Area 4.52 m2 A πD2/4 Feed Flange Surface Area 80.12 cm2 a πd2/4 Antenna Efficiency 0.71 η Gλ2/(π2D2) Gain Factor 15848.93 g 10G/10 Wavelength 0.048 m λ 300/∫ Regions of EM fields, Characteristics and there Behavior EM radiation emitting from a parabolic antenna has different behavioral and characteristics depending on the distance from the reflector surface. This distance from the reflector can be catagorised in three regions, Near (Fresnal) Field Region, Transitional Region and Far Field Region. Additional areas of interest are also the area between the feed horn and the reflector, the area between the supporting surface and the reflector, and the main reflector area. Fig. 1 EM regions i eld   r  F Fa D     ld l  F ie a on iti a ns Tr i eld    F al) sn re  (F ar Ne Area  between  reflector   and  feed  horn   2   Area  between  reflector                                   and  supporting  surface  

Richard  Sergeant                                                                                                                                                                                     Parabolic antennas with circular reflectors, such as the dish under analysis in this report, have the Near, Transitional and Far Field distances calculated with the formulas below Parameter Value Unit Formula Near Field Distance 30 m Rnf=D2/(4λ) Distance to Transitional Field 30 m Rt=Rnf Distance to Far Field 72 m Rff=0.60D2/λ The distance within the transition region is between the near and far fields. This allows for the following rule, Rnf ≤ Rt ≤ Rff. However, the power density in the transition region cannot exceed the power density in the near field. Power Flux Density Calculations Power flux density is the rate of transfer the EM moves through space. Flux density is at it strongest through the entire length of the near field and is concentrated through a cylinder proportional to the surface diameter of the reflector (D). Within the transitional and far field, the power density decreases at an opposite rate. Power density with in the three regions is calculated below. Parameter Value Unit Symbol Formula Power Density in the Near Field 1.68 mW/cm2 Snf 16ηP/(πD2) Power Density in the Trans. Field 1.68 mW/cm2 St GP/(4πRff2) Power Density in the Far Field 0.84 mW/cm2 Sff SnfRnf/(Rt) The area between the feed horn and the reflector surface is confined within a conical shape, this is due to the aperture of the feed assembly. The Power density is defined below. Parameter Value Unit Symbol Formula 2 Power Density at Feed Flange 1298.03 mW/cm Sfa 4P/a The above formula also applies when working out the power density at the reflector surface. Parameter Value Unit Symbol Formula 2 Power Density at the Reflector 2.30 mW/cm Ssurface 4P/A Assuming there is uniform spread across the reflector, the power density between the surface and reflector is shown below. Parameter Value Unit Symbol Formula 2 Power Density Between the 1.22 mW/cm Sg P/A Surface and the Reflector 3                                  

Richard  Sergeant                                                                                                                                                                                     The table below shows the results of this report and if they meet the FCC limitations for EM exposure. It can be seen that only the area between the feed horn and the reflector exceeds the limitations set out by the FCC. This area is only accessed by experienced engineers who are trained to cease the transmission before accessing this area. Area of exposure mW/cm2 FCC Limitation (<5 mW/cm2) Power Density in the Near Field 1.68 Within FCC Limitation Power Density in the Trans. Field 1.68 Within FCC Limitation Power Density in the Far Field 0.84 Within FCC Limitation Power Density at Feed Flange 1298.03 Exceeds FCC Limitation Power Density at the Reflector 2.30 Within FCC Limitation Power Density Between the 1.22 Within FCC Limitation Surface and the Reflector In conclusion to this report it can be seen that the antenna, with appropriate controls, and operation by a trained engineer, meet the guidelines set out in 47 C.F.R. § 1.1310. 4                                  

Richard  Sergeant                                                                                                                                                                                     Additional Information Fig. 2. Gigasat FA-240 C-Band Antenna Fig. 3. Gigasat FA-240 off axis gain meets requirement for the following standards Intelsat IESS-601 Eutelsat EESS-502 STANAG 4484 MIL-STD 188-164A 5                                  


Document Created: 2010-04-28 00:00:00
Document Modified: 2010-04-28 00:00:00
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