Rad Haz Study -Middl

LETTER submitted by Federal Aviation Administration

Rad Haz

2012-05-29

This document pretains to SES-DBE-20120522-00458 for Database Entry on a Satellite Earth Station filing.

IBFS_SESDBE2012052200458_953380

Radiation Hazard Report Page 1 of 5 Analysis of Non-Ionizing Radiation for a 4.5-Meter Earth Station System This report analyzes the non-ionizing radiation levels for a 4.5-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 (MHz) Power Density (mW/cm2) 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 (MHz) Power Density (mW/cm2) 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 4.5 m Antenna Surface Area Asurface π D2 / 4 15.90 m2 Feed Flange Diameter Dfa Input 9.4 cm Area of Feed Flange Afa πDfa2/4 68.96 cm2 Frequency F Input 6175 MHz Wavelength λ 300 / F 0.048583 m Transmit Power P Input 0.83 W Antenna Gain (dBi) Ges Input 46.7 dBi Antenna Gain (factor) G 10Ges/10 44773.5 n/a Pi π Constant 3.1415927 n/a Antenna Efficiency η Gλ2/(π2D2) 0.55 n/a

Radiation Hazard Report Page 2 of 5 1. Far Field Distance Calculation The distance to the beginning of the far field can be determined from the following equation: Distance to the Far Field Region Rff = 0.60 D2 / λ (1) = 250.1 m The maximum main beam power density in the far field can be determined from the following equation: On-Axis Power Density in the Far Field Sff = G P / (4 πRff2) (2) = 0.049 W/m2 = 0.005 mW/cm2 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: Extent of the Near Field Rnf = D2 / (4 λ) (3) = 104.2 m The maximum power density in the Near Field can be determined from the following equation: Near Field Power Density Snf = 16.0 ηP / (πD2) (4) = 0.115 W/m2 = 0.012 mW/cm2 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: Transition Region Power Density St = Snf Rnf / Rt (5) = 0.012 mW/cm2

Radiation Hazard Report Page 3 of 5 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: Power Density at the Feed Flange Sfa = 4000 P / Afa (6) = 48.147 mW/cm2 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: Power Density at the Reflector Surface Ssurface = 4 P / Asurface (7) = 0.209 W/m2 = 0.021 mW/cm2 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: Power Density between Reflector and Ground Sg = P / Asurface (8) = 0.052 W/m2 = 0.005 mW/cm2

Radiation Hazard Report Page 4 of 5 7. Summary of Calculations Table 4. Summary of Expected Radiation levels for Uncontrolled Environment Region Calculated Maximum Hazard Assessment Radiation Power Density Level (mW/cm2) 1. Far Field (Rff = 250.1 m) Sff 0.005 Satisfies FCC MPE 2. Near Field (Rnf = 104.2 m) Snf 0.012 Satisfies FCC MPE 3. Transition Region (Rnf < Rt < Rff) St 0.012 Satisfies FCC MPE 4. Between Feed Assembly and Antenna Reflector Sfa 48.147 Potential Hazard 5. Main Reflector Ssurface 0.021 Satisfies FCC MPE 6. Between Reflector and Ground Sg 0.005 Satisfies FCC MPE Table 5. Summary of Expected Radiation levels for Controlled Environment Region Calculated Maximum Hazard Assessment Radiation Power Density Level (mW/cm2) 1. Far Field (Rff = 250.1 m) Sff 0.005 Satisfies FCC MPE 2. Near Field (Rnf = 104.2 m) Snf 0.012 Satisfies FCC MPE 3. Transition Region (Rnf < Rt < Rff) St 0.012 Satisfies FCC MPE 4. Between Feed Assembly and Antenna Reflector Sfa 48.147 Potential Hazard 5. Main Reflector Ssurface 0.021 Satisfies FCC MPE 6. Between Reflector and Ground Sg 0.005 Satisfies FCC MPE 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 harmful levels of radiation will not exist in regions normally occupied by the public or the earth stations’ operating personnel. The transmitter will be turned off during maintenance.


Document Created: 2012-04-30 11:03:34
Document Modified: 2012-04-30 11:03:34
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