Attachment Rad Hazard study

This document pretains to SES-LIC-20091130-01644 for License on a Satellite Earth Station filing.

IBFS_SESLIC2009113001644_784301

Radiation Hazard Report Page 1 of 5 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 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 2.4 m Antenna Surface Area Asurface  D2 / 4 4.5239 m2 Frequency F 14.25 GHz Wavelength  300 / F 0.0211 m Transmit Power P 300 W Antenna Gain (dBi) Ges 48.9 dBi Antenna Gain (factor) G 10Ges/10 77624.7117 Pi  3.1415927 Antenna Efficiency  0.65

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 /  (1) = 164.16 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  Rff 2) (2) = 68.766 W/m2 = 6.876 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 ) (3) = 68.4 m The maximum power density in the Near Field can be determined from the following equation: Near Field Power Density Snf = 16.0  P / ( D2) (4) = 172.418 W/m2 = 17.242 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 2 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) ≤ 17.242 mW/cm2

Radiation Hazard Report Page 3 of 5 4. Distance to Safe Region Calculation Since the power density decreases inversely with the square of the distance in the Far Field region, the distance to the On-axis Power Density of 5 mW/cm2 can be determined from the following equation: Distance to ANSI 5 mW/cm2 Dsafe = Rff ((Sff / 5) 0.5) (6) = 192.5177 meters 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) = 265.258 W/m2 = 26.526 mW/cm2 6. Off-axis Evaluation For off-axis calculations in the Near Field and in the Transition region, it can be assumed that, if the point of interest is at least one antenna diameter removed from the center of the main beam, the power density at that point would be at least a factor of 100 (20dB) less than the value calculated for the equivalent distance in the main beam. For off-axis calculations in the Far Field, the calculated main-beam power density can be multiplied by the appropriate relative power density factor obtained from the antenna gain pattern. Since the proposed antenna meets or exceeds the performance specifications under Part 25.209 of the FCC rules, the off-axis gain for this antenna is equal to or greater than 10dBi less than the on-axis gain in any direction of 48 degrees or more removed from the centerline of the main beam. Near Field Off-axis Power Density Snf(off) = 0.01 Snf (8) = 0.172 mW/cm2 Far Field Off-axis Power Density Sff(off) = 0.1 Sff (9) = 0.688 mW/cm2

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/cm2) Hazard Assessment Far Field (Rff = 164.16 m) Sff 6.877 Potential Hazard Near Field (Rnf = 68.4 m) Snf 17.242 Potential Hazard Transition Region (Rnf < Rt < Rff) St 17.242 Potential Hazard Safe Distance Region (Dsafe = 192.518 m) Main Reflector Surface Ssurface 26.526 Potential Hazard Far Field Off-axis Region Sff(off) 0.172 Potential Hazard Near Field Off-axis Region Snf(off) 0.688 Potential Hazard (Between reflector and ground) Table 5. Summary of Expected Radiation levels for Controlled Environment Calculated Maximum Radiation Power Density Level Region (mW/cm2) Hazard Assessment Far Field (Rff = 164.16 m) Sff 6.877 Potential Hazard Near Field (Rnf = 68.4 m) Snf 17.242 Potential Hazard Transition Region (Rnf < Rt < Rff) St 17.242 Potential Hazard Safe Distance Region (Dsafe = 192.5177 m) Main Reflector Surface Ssurface 26.526 Potential Hazard Far Field Off-axis Region Sff(off) 0.172 Potential Hazard Near Field Off-axis Region Snf(off) 0.688 Potential Hazard (Between reflector and ground) It is the applicant's responsibility to ensure that the public and operational personnel are not exposed to harmful levels of radiation.

Radiation Hazard Report Page 5 of 5 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 This antenna will be located on a vehicle rooftop. The distance from the ground to the center of the antenna is approximately 4.0 meters. The location 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 diameter removed from the edge of the antenna. Radiation hazard signs will be posted at any rooftop access location. The signs will be completely visible from the ground. 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 station’s 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. Means of Compliance – Safety in General This antenna system is located on a mobile unit and conditions will vary from operating site to operating site. Because of this, the licensee will establish procedures for the operational personnel to verify that the antenna is not pointing in the direction of populated areas, and that access to hazardous areas are restricted while the unit is in operation. In addition, the transmit power used in these calculations is greater than that which will typically be utilized by the earth station. During normal operation, the typical power level would generally not exceed more than 50 to 75 percent of the indicated transmitter power. Maximum transmit power would generally only occur in conditions of extreme inclement weather.


Document Created: 2009-11-30 13:24:06
Document Modified: 2009-11-30 13:24:06
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