Attachment RadHaz

This document pretains to SES-MOD-INTR2018-03103 for Modification on a Satellite Earth Station filing.

IBFS_SESMODINTR201803103_1431643

                           RADIATION HAZARD ANALYSIS
                            13.1 meter Ku-band antenna


        This analysis calculates the non-ionizing radiation levels due to transmission
from the earth station. The Office of Engineering and Technology (OET) Bulletin, No. 65
Edition, specifies that the Maximum Permissible Exposure (MPE) limit for persons in a
Controlled environment to non-ionizing radiation averaged over a thirty minute period, is
a power density equal to 5 milli-watt per centimeter squared.

      The analysis estimates the maximum power density levels in the vicinity of the
antenna for six regions: near field; far field; transition zone; near the reflector surface;
between the reflector and the ground; and between the feed mouth and the reflector.

      A brief discussion for each region is given below. The attached table shows the
assumptions, formulae and calculations for all cases.

1. NEAR FIELD REGION

        The near field (or Fresnel region) is essentially an elliptical volume with its axis
co-incident with the antenna boresight. The base of this volume is the same as the
aperture of the antenna. According to OET Bulletin No. 65, its length is equal to the
square of the diameter divided by four times the wavelength. The larger dimension of
the antenna (the width) is used in place of the diameter of a circular aperture as a worst
case approximation. The maximum value of the on-axis power density is calculated
using the equation given in the Bulletin by simply replacing the area of the circular
aperture term with the area of the elliptical aperture antenna.

2. FAR FIELD REGION

        The far field (or Fraunhofer region) extends outwards from a distance equal to
0.6 times the square of the reflector diameter divided by the wavelength, according to
OET Bulletin No. 65. The larger dimension of the antenna (the width) is used in place of
the diameter of a circular aperture. Power density varies inversely as the square of the
distance. The maximum value of the power density is calculated using the equation
given in the Bulletin.

3. TRANSITION REGION

        The transition region between the near field and the far field regions will have a
power density that essentially decreases inversely with increasing distance. In any
case, the maximum power density will not exceed the maximum value calculated for the
near field region, for the purpose of evaluating potential exposure.

4. REGION NEAR REFLECTOR SURFACE

        The power density in the region near the reflector surface can be estimated as
equal to four times the power divided by the area of the reflector surface, assuming that
the illumination is uniform and that it would be possible to intercept equal amounts of
energy radiated towards and reflected from the reflector surface.


5.   REGION BETWEEN REFLECTOR AND GROUND

       The power density in the region between the reflector and the ground can be
estimated as equal to the power divided by the area of the reflector surface, assuming
uniform illumination over the surface of the reflector.

6. REGION BETWEEN THE FEED MOUTH AND REFLECTOR

        The radiation from the feed is essentially confined to a conical region whose
vertex is located at the feed mouth and extends to the reflector. Power density is
maximum at the feed mouth, and can be estimated as four times the output power
divided by the area of the feed mouth.

7. RESULTS OF ANALYSIS

The radiation analyses in the following Tables were performed using the definitions from
the previous sections and assuming worst case operating conditions. The radiation
analysis for this worst case (see Table below) shows that the MPE Level is exceeded
between the feed mouth and the reflector. This antenna will be mounted in a controlled
area such that the area between the main reflector and sub-reflector. The applicant will
comply with the MPE limits by one or more of the following methods:
     Radiation hazard signs will be posted while this earth station is in operation.
     The earth station is located in a secured teleport facility with secured access.
     All individuals having access to the teleport will be aware of the Radiation Hazard
       from the antenna, thus creating a controlled environment.
     The earth station’s operational staff 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


                                          RADIATION HAZARD ANALYSIS

                Nomenclature                      Formula              Value                       Unit


          INPUT PARAMETERS


D = Antenna Diameter                                                              13.1            meters

d = Diameter of Subreflector                                                      1.33            meters

P = Max Power into Antenna                                                        320              Watts

η = Apperture Efficiency                                                          60.7              %

F = Frequency                                                                14000                 MHz

λ = Wavelength                                       300/F                   0.0214               meters


         CALCULATED VALUES


A = Area of Reflector                               pi*D^2/4                 134.78              meters^2

a = Area of Subreflector                            pi*d^2/4                      1.39           meters^2

l = Length of Near Field                            D^2/4λ                 2002.12                meters

L = Beginning of Far Field                         0.6D^2/λ                4805.08                meters

G = Antenna Gain @ F (n=100% max value)           η(pi*D/λ)^2           2238712.19                 linear

Antenna Gain in dB                                 10*log(G)                  63.50                 dBi


                                         POWER DENSITY CALCULATIONS

                                                    Max Power Density In Region              Hazard Assessment
                        Region                      Formula        Value (mW/cm^2)       (FCC MPE Limit=1 mW/cm^2)

1. Snf = Max Near Field Power Density               4*η*P/A                       0.58        <FCC MPE Limit

2. Sff = Max Far Field Power Density             G*P/(4*pi*L^2)                   0.25        <FCC MPE Limit

3. Max Transition Region Power Density          <= Nr Fld Region                  0.58        <FCC MPE Limit

4. Near Main Reflector Surface                       4*P/A                        0.95        <FCC MPE Limit

5. Between Main Reflector and Subreflector           4*P/a                    92.13      >FCC MPE Limit (See Text)

6. Between Main Reflector and Ground                  P/A                         0.24        <FCC MPE Limit



Document Created: 2018-05-21 16:09:24
Document Modified: 2018-05-21 16:09:24

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