Radiation Hazard

0202-EX-PL-2006 Text Documents

General Dynamics SATCOM Technologies

2006-04-18ELS_75592

Radiation Hazard Report Page 1 of 5 Analysis of Non—lonizing Radiation for a 1.0—Meter Earth Station System This report analyzes the non—ionizing radiation levels for a 1.0—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 Builletin, 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 limitsthat 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/iem*) 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/ecm") 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 1.0 m Antenna Surface Area Asurtace 1 D/ 4 0.79 m* Feed Flange Diameter Di Input 9.1 cm Area of Feed Flange Afa x Di °/4 65.04 cm* Frequency F Input 14250 MHz Wavelength A 300 /F 0.021053 m Transmit Power P Input 15.00 W Antenna Gain (dBi) CGies Input 41.7 dBi Antenna Gain (factor) 6 10ce"° 14791.1 n/a Pi T Constant 3.1415927 n/a Antenna Efficiency n GA/(RD") 0.66 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 R; = 0.60 D@ /A (1) = 28.5 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 S; =GP/(4 1 Ry") (2) = 21.7837 W/im" = 2.174 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: Extent of the Near Field Ry = D/ (4 A) (3) = 11.9 m The maximum power density in the Near Field can be determined from the following equation: Near Field Power Density Sar =16.01nP/(x D) (4) = 50.743 W/m* = 5.074 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 R, can be determined from the following equation: Transition Region Power Density S =Su Ru/R (5) = 5.074 mW/icm*

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 Sia = 4000 P / Afj (6) = 922.526 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: Power Density at the Reflector Surface Ssurtace = 4 P / Asurtace (7) = 76.394 W/m* = 7.639 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: Power Density between Reflector and Ground Sg =P / Asurtace (8) = 19.099 W/m* = 1.910 mW/cm*

Radiation Hazard Report Page 4 of 5 7. Summary of Calculations Table 4. Summary of Expected Radiation levels for Uncontrolled Environment Calculated Maximum Radiation Power Density Level Region (mW/iecm?) Hazard Assessment 1. Far Field (Ry = 28.5 m) Sy 2.174 Potential Hazard 2. Near Field (Ry; =11.9 m) Sn 5.074 Potential Hazard 3. Transition Region (Ry; < R;< Ryg) S, 5.074 Potential Hazard 4. Between Feed Assembly and S 922.526 Potential Hazard Antenna Reflector 5. Main Reflector Scurtace 7.639 Potential Hazard 6. Between Reflector and Ground Sy 1.910 Potential Hazard Table 5. Summary of Expected Radiation levels for Controlled Environment Calculated Maximum Radiation Power Density Region Level (mW/cm*) Hazard Assessment 1. Far Field (R; = 28.5 m) of 2.174 Satisfies FCC MPE 2. Near Field (Ry;=11.9 m) Sar 5.074 Potential Hazard 3. Transition Region (Ry; < R< Ry) S, 5.074 Potential Hazard 4. Between Feed Assembly and Sia 922.526 Potential Hazard Antenna Reflector 5. Main Reflector Ssurtace 7.639 Potential Hazard 6. Between Reflector and Ground Sy 1.910 Satisfies FCC MPE t 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 area around this antenna will be roped off while this antenna is in operation. The roped off 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 1 diameter removed from the edge of the antenna. Since one diameter removed from the main beam of the antenna or % diameter 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.


Document Created: 2006-04-18 15:22:28
Document Modified: 2006-04-18 15:22:28
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