Attachment Exhibit D SES-MOD-20150911-00584

Attachment Exhibit D

This document pretains to SES-MOD-20150911-00584 for Modification on a Satellite Earth Station filing.

IBFS_SESMOD2015091100584_1102279

Exhibit D

Radiation Hazard Analysis

Introduction

This analysis calculates the non-ionizing radiation levels for a ViaSat, Inc. (“ViaSat”) M32
aeronautical mobile earth station terminal (“AES terminal”). The calculations performed in this
analysis comply with the methods described in FCC Office of Engineering and Technology Bulletin,
Number 65 (Edition 97-01) (“Bulletin 65”). This analysis demonstrates that ViaSat AES terminals
are compliant and will not result in exposure levels exceeding the applicable radiation hazard limits.

Bulletin 65 and Section 1.1310 of the Commission’s rules specify two separate tiers of exposure
limits: one for Occupational/Controlled Exposures and one for General Population/Uncontrolled
Exposures. Limits for Occupational/Controlled Exposures apply in situations when persons are
exposed as a consequence of their employment and are fully aware of and can control their exposure.
These limits also apply in situations when a person is transient through a location where such limits
would otherwise apply provided the person is made aware of the potential for exposure. The limits
for General Population/Uncontrolled Exposure apply in situations in which the general public may
be exposed, or in which persons that are exposed as a consequence of their employment may not be
fully aware of the potential for exposure or cannot exercise control over their exposure. ViaSat will
typically deploy its AES terminals on commercial airliners where access to the area around the
aircraft is a Controlled Environment, but not all personnel may be aware of the exposure risk.
Accordingly, this analysis discusses the Maximum Permissible Exposure (“MPE”) limit for both of
these types of exposures. The MPE limit for Occupational/Controlled Environments is a power
density equal to 5 milliwatts per centimeter squared averaged over a six minute period. The MPE
for General Population/Uncontrolled Environments is a power density equal to 1 milliwatt per
centimeter squared averaged over a thirty minute period.

As described in the definitional section of Appendix A, this report analyzes the maximum power
density levels in the vicinity of an AES terminal antenna in four regions: (1) the far field, (2) the near
field, (3) the transition region between near field and far field, and (4) near the main radiator surface.
These radiation regions were analyzed using the definitions and formulas in Bulletin 65 for aperture
antennas. The results of this analysis are summarized in Table 1.

AES Terminal Description

The AES terminal uses the same Exede modem technology as the blanket license terminals currently
authorized under license call signs E100143 and E120075. It 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 AES terminal’s mode of operation. There are three modes
of operation: (a) Idle Mode, during which the AES terminal is not in active use; (b) Normal Mode,
when there terminal is actively used under typical network loading conditions; and (c) High Capacity
Mode, when the terminal is actively used under maximum uplink data transfer conditions.

In Idle Mode, the AES terminal transmits only timing and system information to the network for 0.4
millisecond every 640 ms seconds. The average duty cycle (ratio of transmitter on to transmitter off

time) in Idle Mode is 0.06%. In Normal Mode, the AES terminal transmits burst traffic to the
network with a nominal duty cycle of 10%. To support heavy data upload requirements such as file
transfer, current network configuration allows AES terminals to increase their transmit duty cycle to
30% in High Capacity Mode. In practice, operation at 100% duty cycle will not happen due to
network configuration and operational loading of the shared return channel.

Table 1 provides a summary of the radiation exposure analysis for each of the three ViaSat operating
modes.

The AES terminal uses a transmitter power control system to reduce uplink interference and mitigate
the effects of changing atmospheric conditions. At maximum power output, the ViaSat M32 AES
terminals will transmit at a power level of 4.4 watts or less.

The AES 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. Transmissions will
not resume until approximately 10 seconds after downlink communications have been reestablished.
Second, the terminal’s transmitter is not capable of operating in a continuous transmit mode of
operation. The AES terminal’s outdoor unit incorporates a watchdog timer that will shut down the
transmitter if it remains in a continuous transmit state for more than 10 seconds. Under these
conditions, the transmitter will be turned off for 3 ms then resume normal operation after an internal
reset has occurred.

Explanation of the Analysis

The “Calculated Values” in Table 1 are the on-axis exposure rates calculated using the formulae
from the Office of Engineering and Technology Bulletin Number 65 (Edition 97-01) for a system
with continuous (100% transmit duty cycle) transmission. The ViaSat network, however, is based on
so-called “shared pipes.” ViaSat terminals transmit short bursts of data periodically as instructed by
the network and do not operate using continuous transmission. Therefore, in order to compute the
effective radiated energy of a ViaSat AES terminal, the terminal’s transmitter duty cycle has been
used to adjust the values calculated from Bulletin Number 65.

The columns in the tables labeled “Idle Mode,” “Normal Mode,” and “High Capacity Mode” reflect
the total potential for human exposure based on the length of time that the AES terminal transmits
energy during a rolling 30 minute period. In Idle Mode, the maximum transmitter duty cycle is
0.06% and therefore the values in the column labeled “Idle Mode” are equal to the calculated values
multiplied by 0.0006. Similarly, in Normal Mode the maximum transmitter duty cycle is 10% and
the values in the column labeled “Normal Mode” are equal to the Calculated Values multiplied by
0.1. And finally, in High Capacity Mode the transmitter duty cycle is 30% and the values in the
column labeled “High Capacity Mode” are equal to the Calculated Values multiplied by 0.3.

The MPE level calculations for each of the three operating modes for conditions labeled “Aperture”
are calculated based on the “fail safe” features of the ViaSat AES terminal. 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 reflector and the feed are very sensitive to blockage of the down link, this
“fail safe” feature minimizes the potential for human exposure. If the blockage due to human

exposure occurs in these areas, the downlink 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 AES 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. The values in the column labeled “Idle,” “Normal,” and “Worst Case” are multiplied by
0.004 because the transmitter cannot transmit more than 0.4% of any rolling 30 minute period with
significant blockage near the sub-reflector and between the sub-reflector and the feed.

Results of Analysis

This analysis demonstrates that the ViaSat M32 AES terminal satisfies the requirements and
guidelines in Section 1.1310 of the FCC’s rules. The terminal does not exceed the MPE limit of 1
milliwatt per centimeter squared averaged over a thirty minute period in the far field and transition
regions, as well as in the near-field under typical operating conditions. As demonstrated in Table 1,
the area with the greatest field concentrations is the Near Field. The area in which these high field
concentrations exist is very small in size, located on the top of the aircraft fuselage, and pointing
upward. Proximity to the antenna will also be limited by the radome. Therefore, it is highly
unlikely that the general population will have access to the Near Field. However, if the down link
(receive signal) is interrupted by an object in an area of high field concentration, the uplink (transmit
signal) is shut down in less than 40 milliseconds and the receiver down link recovery time is 10
seconds. The uplink will remain off until the blockage is removed and the downlink recovery is
complete. This feature, coupled with the terminal’s use of uplink power control and non-continuous
operation, ensures that the general population will not be exposed to levels of radiation that exceed
FCC limits. Furthermore, the MPE limit for occupational environments is met in all regions.
Moreover, in the remote event that maintenance personnel are located above the aircraft and directly
in front of the aperture, they will be protected by the fail-safe features described above.

Conclusion

This radiation hazard analysis demonstrates that ViaSat AES terminals will not result in exposure
levels exceeding the applicable radiation hazard limits for either the Occupational/Controlled
Environment or General Population/Uncontrolled Environments.

Definitions

1) Far Field Region

2
0.6 ⋅ Dmaj
The far field region extends outward from the antenna, beginning at a distance of
λ
meters where the larger diameter of the array antenna is Dmaj. The maximum power density is
calculated using the equation recommended in Bulletin 65.

2) Near Field Region

The near field region is a volume co-incident with the boresight of the main beam extending
2
D maj
outward from the radiator surface. The length of the near field meters. The larger dimension
4⋅ λ
(Dmaj) of the array is used in place of the diameter of a circular antenna to calculate the worst case
length of the near field.

3) Transition Region

The transition region is located between the near field region and the far field region. This
region has a power density that decreases inversely with increasing distance. Therefore the power
density in the transition region will be less than the power density in the near field for the purpose of
evaluating potential exposure.

4) Region Near the Array Surface

The power density near the array’s radiating surface can be estimated as equal to four times
the power divided by the area of the radiator surface, assuming that the illumination is uniform and
that it would be possible to intercept equal amounts of energy radiating towards and reflected from
the antenna surface.

Document Created: 1350-05-29 00:00:00
Document Modified: 1350-05-29 00:00:00

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