Attachment RF Exposure Study

This document pretains to SES-LIC-20170207-00124 for License on a Satellite Earth Station filing.

IBFS_SESLIC2017020700124_1178334

Radiation Hazard Report                                                            Page 1 of 5


     Analysis of Non-Ionizing Radiation for a 1.35-Meter Earth
                         Station System
This report analyzes the non-ionizing radiation levels for a 1.35-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                                     1.35           m
     Antenna Surface Area          Asurface           D2 / 4             1.4314          m2
     Frequency                       F                                    14.25           GHz
     Wavelength                                     300 / F              0.0211          m
     Transmit Power                  P                                      350           W
     Antenna Gain (dBi)             Ges                                    44.5           dBi
     Antenna Gain (factor)           G               10Ges/10           26915.3480
     Pi                                                                  3.1416
     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)
                                                                = 51.94 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)
                                                                = 290.9601 W/m2
                                                                = 29.0960 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)
                                                                = 21.6422 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)
                                                                = 635.7465 W/m2
                                                                = 63.5746 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)
                                                               ≤ 63.5746 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)
                                                                 = 125.2980 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)
                                                                 = 978.0715 W/m2
                                                                 = 97.8072 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)
                                                                 = 0.6357mW/cm2

     Far Field Off-axis Power Density                   Sff(off)   = 0.1 Sff                     (9)
                                                                   = 2.9096 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
Region                                          Level (mW/cm2)             Hazard Assessment
Far Field (Rff = 51.94 m)                       Sff       29.0960             Potential Hazard
Near Field (Rnf = 21.642 m)                     Snf       63.5746             Potential Hazard
Transition Region (Rnf < Rt < Rff)              St        63.5746             Potential Hazard
Safe Distance Region (Dsafe=125.298m)
Main Reflector Surface                          Ssurface 97.8072              Potential Hazard
Near Field Off-axis Region                      Snf(off)   0.6357             Potential Hazard
(Between reflector and ground)
Far Field Off-axis Region                       Sff(off)   2.9096             Potential Hazard


            Table 5. Summary of Expected Radiation levels for Controlled Environment
                                            Calculated Maximum
                                          Radiation Power Density
Region                                          Level (mW/cm2)             Hazard Assessment
Far Field (Rff = 51.94 m)                       Sff      29.0960              Potential Hazard
Near Field (Rnf = 21.642 m)                     Snf      63.5746              Potential Hazard
Transition Region (Rnf < Rt < Rff)              St       63.5746              Potential Hazard
Safe Distance Region (Dsafe=125.298m)
Main Reflector Surface                          Ssurface 97.8072              Potential Hazard
Near Field Off-axis Region                      Snf(off)   0.6357             Potential Hazard
(Between reflector and ground)
Far Field Off-axis Region                       Sff(off)   2.9096             Potential Hazard

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: 2014-07-28 14:29:00
Document Modified: 2014-07-28 14:29:00

© 2024 FCC.report
This site is not affiliated with or endorsed by the FCC