Attachment Exhibit-C

This document pretains to SES-LIC-20190411-00503 for License on a Satellite Earth Station filing.

IBFS_SESLIC2019041100503_1651299

Viasat, Inc.                                   Exhibit C

Analysis of Non-Ionizing Radiation for a 0.3 m Earth Station Antenna System

Introduction

This report analyzes the non-ionizing radiation levels for a 0.3 m earth station (ES)
antenna system.

The FCC’s Office of Engineering Technology’s Bulletin No. 65 specifies that there are
two separate tiers of exposure limits that are dependent upon the situation in which the
exposure takes place and/or the status of the individuals who are subject to the exposure.
The two tiers are General Population / Uncontrolled environment, and an Occupational /
Controlled environment.

This ES antenna is mounted on the fuselage or vertical stabilizer on aircraft, well above
head height of people working in the area and is covered by a radome which prevents
access to the area between feed and reflector and reflector surface and which is clearly
marked with RF warnings. Due to its location on top of the aircraft, the antenna is
inaccessible to ground crew during normal gate operations when the antenna is active.
The antenna will be turned off during maintenance windows where personnel may have
access to areas near the antenna. Additionally, as discussed below, when maintenance
occurs inside a hanger, the system will not transmit because receive communications (a
precursor to transmit operations) with the satellite will be blocked.

Because the environment is controlled and any potential exposure of a transitory nature,
the limits for Occupational/Controlled Exposures are assumed to apply. Accordingly, this
analysis discusses only the Maximum Permissible Exposure (MPE) limit for those types
of exposures, which is a power density equal to five milliwatts per centimeter squared
averaged over a six minute period.

As described in the definitional section of this document, this report considers the
maximum power density levels in the vicinity of an ES antenna in several regions: (1) the
far field, (2) the near field, (3) the transition region between near field and far field, and (4)
the surface of the radiating aperture. These radiation regions were analyzed using the
definitions and formulas in Bulletin 65 for aperture antennas. The results of this analysis
are summarized at the end of this document.

Terminal Description

The ES terminal transmits bursts of information at designated times that are assigned to the
terminal by the network. The length and carrier frequency of each transmission burst
depend on the ES terminal's traffic requirements. In normal operation, the ES terminal
transmits burst traffic to the network with a nominal duty cycle of less than 5%.

 The ES terminal incorporates two “fail safe" features that limit the potential for human
exposure. First, the transmitter is not enabled until the receive down link connection to the
satellite has been established and an acceptable down link bit error rate has been achieved.
The transmitter is disabled very quickly, in less than 40 milliseconds, if a loss of down
connectivity occurs. This includes the case where human interference causes degradation


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in the link. Transmissions will not resume until approximately 10 seconds after downlink
communications have been reestablished. Secondly, the terminal's transmitter is not
capable of operating in a continuous transmit mode of operation. The ES terminal's power
amplifier unit prevents the transmitter from remaining in a continuous transmit state for
more than a few seconds. Under these conditions, the transmitter will be turned off briefly
then resume normal operation after an internal reset has occurred.

Analysis of Occupational/Controlled Environment

The calculated values in the analysis show the exposure rates calculated using the formulae
from the Office of Engineering and Technology Bulletin Number 65 (Edition 97-01) for
the peak RF power output during transmission as reduced by the effect of duty cycle. This
is because the Viasat network is based on a Time Division Multiple Access (TDMA)
scheme using so-called “shared pipes". Viasat terminals transmit short bursts of data
periodically as instructed by the network and are neither designed for nor capable of
continuous transmission. Therefore, in order to compute the effective radiated energy of a
Viasat ES terminal, the terminal’s transmitter duty cycle has been used to adjust the values
calculated in accordance with Bulletin Number 65. To do this, the average power during
the averaging period is calculated as the maximum transmitter peak transmit power output
adjusted by the nominal duty cycle of 5%.

An important aspect of the Viasat ES terminal is the “fail safe" feature. When the receive
signal is lost due to signal blockage, the transmitter is shut down until the receive downlink
is restored. The transmitter is shutdown in less than 40 milliseconds of the loss of the
downlink. Since the areas of high field strength near the antenna aperture are very sensitive
to blockage of the down link, this “fail safe" feature minimizes the potential for human
exposure in the area between the feed and reflector. If the blockage due to human exposure
occurs in these areas, the down link will be interrupted causing the transmitter to turn off
almost immediately and it will remain off until the blockage is removed. After the blockage
is removed, the ES terminal will have to reacquire the receive downlink and wait to be
invited back into the network before the transmitter will be enabled. The complete
downlink recovery time is 10 seconds. Accordingly, the average power value would be
multiplied by 0.004 because the transmitter cannot transmit more than 0.4% of any rolling
six minute period (the period over which the power density is averaged) with significant
blockage near the aperture.


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Summary of expected radiation levels for a Controlled environment


Region                                Maximum Power Density1                        Hazard Assessment

Safe region range ≥ 2.3 m                      2.7 mW/cm2                           Satisfies FCC MPE

Far field (Rff) = 5.6 m                        1.2 mW/cm2                           Satisfies FCC MPE

Near field (Rnf) = 2.3 m                       2.7 mW/cm2                           Satisfies FCC MPE

Transition region (Rt)
(Rt) = Rnf < Rt < Rff                          2.8 mW/cm2                           Satisfies FCC MPE

Main Reflector Surface (Ssurface)              5.5 mW/cm2                           Exceeds FCC MPE*
*
 Note, that the power density level in the area between the feed and the reflector surface
is greater than the reflector surface and is assumed to be a potential hazard. However, as
discussed above, this region and the main reflector surface are covered by a radome,
which prevents access to these areas.


Analysis of General Population/Uncontrolled Environment

The applicable exposure limit for the General Population / Uncontrolled environment,
i.e., areas that people may enter freely, at this frequency of operation is 1 mW/cm^2
average power density over a 30 minute period.

In the case of passengers and other members of the general public, no access is available
near the antenna, and given the minimum operating elevation any area of uncontrolled
access where general population may travel are well removed from the cylinder of RF
projected by the antenna.

Per OET-65, 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 (20 dB) less than the value calculated for the equivalent distance in
the main beam. The expected power density then in any uncontrolled access area would
be at least a factor of 100 below the values in the controlled environment and well below
the 1 mW/cm2 general population limit.




1   Includes duty cycle factor of 5% typical in calculation of average power density over the reference period.


Viasat, Inc.

Analysis

The analysis and calculations that follow in this report are performed in compliance with
the methods described in the OET Bulletin No. 65.

Definition of terms

The terms are used in the formulas here are defined as follows:

Ssurface = maximum power density at the antenna surface
Snf = maximum near-field power density
St = power density in the transition region
Sff = power density (on axis)
Rnf = extent of near-field
Rff = distance to the beginning of the far-field
R = distance to point of interest
Pa = 20 W                      maximum power amplifier output
Lfs = 0 dB                     loss between power amplifier and antenna feed
P = 20 W                       power fed to the antenna in Watts
A = 0.73 m2                    physical area of the aperture antenna
G = 45910                      power gain relative to an isotropic radiator
D = 0.3 m                      diameter of antenna in meters
F = 30.0                       frequency in GHz
l = 0.01 m                     wavelength in meters (300/FMHz)
h = 0.50                       aperture efficiency

Antenna Surface. The maximum power density directly in front of an antenna (e.g., at
the antenna surface) can be approximated by the following equation:

Ssurface = (4 * P) / A                                                     (1.1)

        = (4 * 20 W * 0.05) / 0.073 m2

        = 5.5 mW/cm2


Near Field Region. In the near-field or Fresnel region, of the main beam, the power
density can reach a maximum before it begins to decrease with distance. The extent of
the near field can be described by the following equation (D and l in same units):

Rnf     = D2 / (4 * l)                                                     (1.2)

        = (0.3 m)2 / (4 * 0.01 m)

        = 2.285 m


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The magnitude of the on-axis (main beam) power density varies according to location in
the near field. However, the maximum value of the near-field, on-axis, power density
can be expressed by the following equation:

Snf    = (16 * h * P) / (p * D2)                                              (1.3)

       = (16 * 0.57 * 20 W * 0.05) / (p * (0.3 m)2)

       = 2.7 mW/cm2


Transition Region. Power density in the transition region decreases inversely with
distance from the antenna, while power density in the far field (Fraunhofer region) of the
antenna decreases inversely with the square of the distance. The transition region will
then be the region extending from Rnf to Rff. If the location of interest falls within this
transition region, the on-axis power density can be determined from the following
equation:

St     = (Snf * Rnf) / R                                                      (1.4)

       = (2.7 mW/cm2 * 2.285 m) / R

       = (6.4 m * mW/cm2) / R                 where R is the location of interest in meters


Far-Field Region. The power density in the far-field or Fraunhofer region of the
antenna pattern decreases inversely as the square of the distance. The distance to the start
of the far field can be calculated by the following equation:

Rff    = (0.6 * D2) / l                                                       (1.5)

       = (0.6 * (0.7 m)2) / 0.01 m

       = 5.485 m

The power density at the start of the far-field region of the radiation pattern can be
estimated by the equation:

Sff    = (P * G) / (4 * p * Rff2)                                             (1.6)

       = (20 W * 45910) / (4 * p * (5.485 m)2)

       = 1.7 mW/cm2


Safe Region for Uncontrolled Access. As given above, the power density in the far
field region of the antenna pattern decreases inversely as the square of the distance. The


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distance to the point where the power density equals the 5 mW/cm2 level can be
determined by the equation:

R5 mW = ( (P * G) / (4 * π * 5 mW/cm2 * 10) )0.5                         (1.7)

       = ( ( 20 W * 45910 * 0.05) / (62.8 mW/cm^2) )0.5

       = 2.7 m



Document Created: 0730-04-26 00:00:00
Document Modified: 0730-04-26 00:00:00

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