Attachment Radiation Study

This document pretains to SES-MOD-20110325-00354 for Modification on a Satellite Earth Station filing.

IBFS_SESMOD2011032500354_878366

Analysis of Non-Ionizing Radiation for a 2.4-Meter Earth Station System This report analyzes the non-ionizing radiation levels for a 2.4-meter earth station system. The analysis and calculations performed in this report comply with the methods described in the FCC Office of Engineering and Technology Bulletin, No. 65 first published in 1985 and revised in 1997 in Edition 97-01. The radiation safety limits used in the analysis are in conformance with the FCC R&O 96-326. Bulletin No. 65 and the FCC R&O specifies that there are two separate tiers of exposure limits that are dependant on the situation in which the exposure takes place and/or the status of the individuals who are subject to the exposure. The Maximum Permissible Exposure (MPE) limits for persons in a General Population/Uncontrolled environment are shown in Table 1. The General Population/Uncontrolled MPE is a function of transmit frequency and is for an exposure period of thirty minutes or less. The MPE limits for persons in an Occupational/Controlled environment are shown in Table 2. The Occupational MPE is a function of transmit frequency and is for an exposure period of six minutes or less. The purpose of the analysis described in this report is to determine the power flux density levels of the earth station in the far-field, near-field, transition region, between the subreflector or feed and main reflector surface, at the main reflector surface, and between the antenna edge and the ground and to compare these levels to the specified MPEs. Table 1. Limits for General Population/Uncontrolled Exposure (MPE) Frequency Range Power Density (mW/cm2) (MHz) 30-300 0.2 300-1500 Frequency (MHz)*(0.8/1200) 1500-100,000 1.0 Table 2. Limits for Occupational/Controlled Exposure (MPE) Frequency Range Power Density (mW/cm2) (MHz) 30-300 1.0 300-1500 Frequency (MHz)*(4.0/1200) 1500-100,000 5.0 Table 3. Formulas and Parameters Used for Determining Power Flux Densities Parameter Symbol Formula Value Units Antenna Diameter D Input 2.4 m Antenna Surface Area Asurface π D2 / 4 4.52 m2 Feed Flange Diameter Dfa Input 9.1 cm Area of Feed Flange Afa π Dfa 2/4 138.59 cm 2 Frequency F Input 14250 MHz Wavelength λ 300 / F 0.0211 m Transmit Power P Input 4.00 W Antenna Gain (dBi) Ges Input 49.2 dBi Antenna Gain (factor) G 10Ges/10 83176 n/a Pi π Constant 3.1415927 n/a Antenna Efficiency η Gλ2/(π2D2) 0.65 n/a

1. Far Field Distance Calculation The distance to the beginning of the far field can be determined from the following equation: 2 Distance to the Far Field Region Rff = 0.60 D / λ = 163.79 m The maximum main beam power density in the far field can be determined from the following equation: 2 2 On-Axis Power Density in the Far Field Sff = G P / (4 π Rff ) = 0.098 mW/cm 2. Near Field Calculation Power flux density is considered to be at a maximum value throughout the entire length of the defined Near Field region. The region is contained within a cylindrical volume having the same diameter as the antenna. Past the boundary of the Near Field region, the power density from the antenna decreases linearly with respect to increasing distance. The distance to the end of the Near Field can be determined from the following equation: 2 Extent of the Near Field Rnf = D / (4 λ) = 68.24 m The maximum power density in the Near Field can be determined from the following equation: 2 2 Near Field Power Density Snf = 16.0 η P/(π D ) = 0.229 mW/cm 3. Transition Region Calculation The Transition region is located between the Near and Far Field regions. The power density begins to decrease linearly with increasing distance in the Transition region. While the power density decreases inversely with distance in the Transition region, the power density decreases inversely with the square of the distance in the Far Field region. The maximum power density in the Transition region will not exceed that calculated for the Near Field region. The power density calculated in Section 1 is the highest power density the antenna can produce in any of the regions away from the antenna. The power density at a distance Rt can be determined from the following equation: 2 Transition Region Power Density St = Snf Rnf / Rt ≤ 0.229 mW/cm

4. Region between the Feed Assembly and the Antenna Reflector Transmissions from the feed assembly are directed toward the antenna reflector surface, and are confined within a conical shape defined by the type of feed assembly. The most common feed assemblies are waveguide flanges, horns or subreflectors. The energy between the feed assembly and reflector surface can be calculated by determining the power density at the feed assembly surface. This can be determined from the following equation: 2 Power Density at the Feed Flange Sfa = 4000 P / Afa = 115.44 mW/cm 5. Main Reflector Region The power density in the main reflector is determined in the same manner as the power density at the feed assembly. The area is now the area of the reflector aperture and can be determined from the following equation: 2 Power Density at the Reflector Surface Ssurface = 4 P / Asurface = 0.353 mW/cm 6. Region between the Reflector and the Ground Assuming uniform illumination of the reflector surface, the power density between the antenna and the ground can be determined from the following equation: 2 Power Density between Reflector and Ground Sg = P / Asurface = 0.088 mW/cm

7. Summary of Calculations Table 4. Summary of Expected Radiation Levels for Uncontrolled Environment Region !"#$ulated%& "’. Radiation Hazard Assesment ()* +, Density Level (mW/cm2)% 1. Far Field (Rff = 163.79 m) Sff = 0.098 Meets Ansi Standard 2. Near Field (Rnf = 68.24 m) Snf = 0.229 Meets Ansi Standard 3. Transition Region (Rnf < Rt < Rff) St ≤ 0.229 Meets Ansi Standard 4. Between Feed Assembly and Potential Hazard Antenna Reflector Sfa = 115.44 5. Main Reflector Surface Ssurface = 0.353 Meets Ansi Standard 6. Between Reflector and Ground Sg = 0.088 Meets Ansi Standard Table 5. Summary of Expected Radiation Levels for Controlled Environment Region !"#$ulated%& "’. Radiation Hazard Assesment ()* +, Density Level (mW/cm2)% 1. Far Field (Rff = 163.79 m) Sff = 0.098 Meets Ansi Standard 2. Near Field (Rnf = 68.24 m) Snf = 0.229 Meets Ansi Standard 3. Transition Region (Rnf < Rt < Rff) St ≤ 0.229 Meets Ansi Standard 4. Between Feed Assembly and Potential Hazard Antenna Reflector Sfa = 115.44 5. Main Reflector Surface Ssurface = 0.353 Meets Ansi Standard 6. Between Reflector and Ground Sg = 0.088 Meets Ansi Standard It is the applicant's responsibility to ensure that the public and operational personnel are not exposed to harmful levels of radiation. 8. Conclusions Based on this analysis it is concluded that the FCC RF Guidelines have been exceeded in the specific regions of Tables 4 and 5. The applicant proposes to comply with the Maximum Permissible Exposure (MPE) limits of 1 mW/cm2 for the uncontrolled areas and the MPE limits of 5 mW/cm2 for the Controlled areas by one or more of the following methods: Means of Compliance Uncontrolled Areas The antenna will be located in a fenced area. The area will be sufficient to prohibit access to the areas that exceed the MPE limits. The general public will not have access to areas within ½ diameters from the edge of the antenna.

Since one diameter removed from the main beam of the antenna or ½ diameters removed from the edge of the antenna the RF levels are reduced by a factor of 100 or 20 dB. None of the areas exceeding the MPE levels will be accessible by the general public. Radiation hazard signs will be posted while this earth station is in operation. The applicant will ensure that no buildings or other obstacles will be in the areas that exceed the MPE levels. Means of Compliance Controlled Areas The earth stationʼs operational personnel will not have access to the areas that exceed the MPE levels while the earth station is in operation. The transmitters will be turned off during antenna maintenance.


Document Created: 2011-03-23 17:26:05
Document Modified: 2011-03-23 17:26:05
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