Attachment Rad Haz

This document pretains to SES-STA-20190815-01100 for Special Temporal Authority on a Satellite Earth Station filing.

IBFS_SESSTA2019081501100_1850101

                                           Radiation Hazard Study

                                                    Sailor 900B

This study analyzes the potential Radio Frequency (RF) human exposure levels caused by the Electro Magnetic
(EM) fields of the above-captioned antenna. The mathematical analysis performed below complies with the
methods described in the Federal Communications Commission Office of Engineering and Technology Bulletin
No. 65 (1985 rev. 1997) R&O 96-326.

Maximum Permisible Exposure
There are two separate levels of exposure limits. The first applies to persons in the general population who are
in an uncontrolled environment. The second applies to trained personnel in a controlled environment. According
to 47 C.F.R. § 1.1310, the Maximum Permissible Exposure (MPE) limits for frequencies above 1.5 GHz are as
follows:
            • General Population / Uncontrolled Exposure 1.0 mW/cm2
            • Occupational / Controlled Exposure 5.0 mW/cm2
The purpose of this study is to determine the power flux density levels for the earth station under study as
compared with the MPE limits. This comparison is done in each of the following regions:
            1. Far-field region
            2. Near-field region
            3. Transition region
            4. The region between the feed and the antenna surface
            5. The main reflector region
            6. The region between the antenna edge and the ground


Input Parameters
The following input parameters were used in the calculations:

Parameter                                           Value         Unit      Symbol
Atenna Diameter:                                    1.03           m          D
Antenna Transmit Gain:                              41.60         dBi         G
Trasmit Frequency:                                  14250         MHz         f
Feed Flange Diameter:                                5.30         cm          d
Power Input to the Antenna:                          8.00         W           P

Calculated Parameters
The following values were calculated using the above input parameters and the corresponding formulas.

Parameter                                           Value         Unit      Symbol        Formula
                                                                      2                   2
Anenna Surface Area:                                 0.83         m            A      πD /4
                                                                       2                  2
Area of Feed Flange:                                22.06         cm           a      πd /4
                                                                                          2      2   2
Antenna Efficiency:                                  0.58                      η      Gλ /( π D )
                                                                                         G /10
Gain Factor:                                      13803.84                     g      10
Wavelength:                                        0.0211         m            λ      300/ f




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Behavior of EM Fields as a Function of Distance
The behavior of the characteristics of EM fields varies depending on the distance from the radiating antenna.
These characteristics are analyzed in three primary regions: the near-field region, the far-field region and the
transition region. Of interest also are the region between the antenna main reflector and the subreflector, the
region of the main reflector area and the region between the main reflector and ground.




Figure 1. EM Fields as a Function of Distance

For parabolic aperture antennas with circular cross sections, such as the antenna under study, the near-field, far-
field and transition region distances are calculated as follows:

Parameter                                           Value         Unit    Formula
Near Field Distance:                                12.598         m      Rnf = D2/(4λ)
Distance to Far Field:                              30.236         m      Rff = 0.60D2/(λ)
Distance of Trasition Region                        12.598         m      Rt = Rnf

The distance in the transition region is between the near and far fields. Thus, Rnf ≤ Rt ≤ Rff . However, the
power density in the transition region will not exceed the power density in the near-field. Therefore, for purposes
of the present analysis, the distance of the transition region can equate the distance to the near-field.


Power Flux Density Calculations
The power flux density is considered to be at a maximum through the entire length of the near-field. This region
is contained within a cylindrical volume with a diameter, D, equal to the diameter of the antenna. In the transition
region and the far-field, the power density decreases inversely with the square of the distance. The following
equations are used to calculate power density in these regions.




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Parameter                                           Value        Unit       Symbol      Formula
                                                                        2
Power Density in the Near-Field                     2.244      mW/cm          S nf      16.0 η P /(πD 2)
Power Density in the Far-Field                      0.961      mW/cm2         S ff
                                                                                                     2
                                                                                        GP /(4π R ff )
Power Density in the Trans. Region                  2.244      mW/cm2          St       Snf R nf /(R t)

The region between the main reflector and the subreflector is confined within a conical shape defined by the feed
assembly. The most common feed assemblies are waveguide flanges. This energy is determined as follows:



Parameter                                           Value        Unit       Symbol      Formula
Power Density at the Feed Flange                   1450.5      mW/cm2         S fa      4P / a

The power density in the main reflector is determined similarly to the power density at the feed flange; except that
the area of the reflector is used.

Parameter                                           Value        Unit       Symbol      Formula
                                                                        2
Power Density at Main Reflector                     3.840      mW/cm        S surface   4P / A

The power density between the reflector and ground, assuming uniform illumination of the reflector surface, is
calculated as follows:

Parameter                                           Value        Unit       Symbol      Formula
Power Density between Reflector and Ground          0.960      mW/cm2         Sg        P /A

Table 1 summarizes the calculated power flux density values for each region. In a controlled environment, the
only regions that exceed FCC limitations are shown below. These regions are only accessible by trained
technicians who, as a matter of procedure, turn off transmit power before performing any work in these areas.


                                                                    Controlled Environment
Power Densities                                   mW/cm2
                                                                           (5 mW/cm2)
Far Field Calculation                               0.961          Satisfies FCC Requirements
Near Field Calculation                              2.244          Satisfies FCC Requirements
Transition Region                                   2.244          Satisfies FCC Requirements
Region between Main and Subreflector               1450.5              Exceeds Limitations
Main Reflector Region                               3.840          Satisfies FCC Requirements
Region between Main Reflector and Ground            0.960          Satisfies FCC Requirements
Table 1. Power Flux Density for Each Region

In conclusion, the results show that the antenna, in a controlled environment, and under the proper mitigation
procedures, meets the guidelines specified in 47 C.F.R. § 1.1310.




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Document Created: 2019-08-15 15:31:07
Document Modified: 2019-08-15 15:31:07

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